NestedScrollView.java revision bd9c35d6db58b5c9b075d751a2c64203eccc6cd7
1/* 2 * Copyright (C) 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 18package androidx.core.widget; 19 20import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP; 21 22import android.content.Context; 23import android.content.res.TypedArray; 24import android.graphics.Canvas; 25import android.graphics.Rect; 26import android.os.Build; 27import android.os.Bundle; 28import android.os.Parcel; 29import android.os.Parcelable; 30import android.util.AttributeSet; 31import android.util.Log; 32import android.util.TypedValue; 33import android.view.FocusFinder; 34import android.view.KeyEvent; 35import android.view.MotionEvent; 36import android.view.VelocityTracker; 37import android.view.View; 38import android.view.ViewConfiguration; 39import android.view.ViewGroup; 40import android.view.ViewParent; 41import android.view.accessibility.AccessibilityEvent; 42import android.view.animation.AnimationUtils; 43import android.widget.EdgeEffect; 44import android.widget.FrameLayout; 45import android.widget.OverScroller; 46import android.widget.ScrollView; 47 48import androidx.annotation.NonNull; 49import androidx.annotation.Nullable; 50import androidx.annotation.RestrictTo; 51import androidx.core.view.AccessibilityDelegateCompat; 52import androidx.core.view.InputDeviceCompat; 53import androidx.core.view.NestedScrollingChild2; 54import androidx.core.view.NestedScrollingChildHelper; 55import androidx.core.view.NestedScrollingParent2; 56import androidx.core.view.NestedScrollingParentHelper; 57import androidx.core.view.ScrollingView; 58import androidx.core.view.ViewCompat; 59import androidx.core.view.accessibility.AccessibilityNodeInfoCompat; 60import androidx.core.view.accessibility.AccessibilityRecordCompat; 61 62import java.util.List; 63 64/** 65 * NestedScrollView is just like {@link android.widget.ScrollView}, but it supports acting 66 * as both a nested scrolling parent and child on both new and old versions of Android. 67 * Nested scrolling is enabled by default. 68 */ 69public class NestedScrollView extends FrameLayout implements NestedScrollingParent2, 70 NestedScrollingChild2, ScrollingView { 71 static final int ANIMATED_SCROLL_GAP = 250; 72 73 static final float MAX_SCROLL_FACTOR = 0.5f; 74 75 private static final String TAG = "NestedScrollView"; 76 77 /** 78 * Interface definition for a callback to be invoked when the scroll 79 * X or Y positions of a view change. 80 * 81 * <p>This version of the interface works on all versions of Android, back to API v4.</p> 82 * 83 * @see #setOnScrollChangeListener(OnScrollChangeListener) 84 */ 85 public interface OnScrollChangeListener { 86 /** 87 * Called when the scroll position of a view changes. 88 * 89 * @param v The view whose scroll position has changed. 90 * @param scrollX Current horizontal scroll origin. 91 * @param scrollY Current vertical scroll origin. 92 * @param oldScrollX Previous horizontal scroll origin. 93 * @param oldScrollY Previous vertical scroll origin. 94 */ 95 void onScrollChange(NestedScrollView v, int scrollX, int scrollY, 96 int oldScrollX, int oldScrollY); 97 } 98 99 private long mLastScroll; 100 101 private final Rect mTempRect = new Rect(); 102 private OverScroller mScroller; 103 private EdgeEffect mEdgeGlowTop; 104 private EdgeEffect mEdgeGlowBottom; 105 106 /** 107 * Position of the last motion event. 108 */ 109 private int mLastMotionY; 110 111 /** 112 * True when the layout has changed but the traversal has not come through yet. 113 * Ideally the view hierarchy would keep track of this for us. 114 */ 115 private boolean mIsLayoutDirty = true; 116 private boolean mIsLaidOut = false; 117 118 /** 119 * The child to give focus to in the event that a child has requested focus while the 120 * layout is dirty. This prevents the scroll from being wrong if the child has not been 121 * laid out before requesting focus. 122 */ 123 private View mChildToScrollTo = null; 124 125 /** 126 * True if the user is currently dragging this ScrollView around. This is 127 * not the same as 'is being flinged', which can be checked by 128 * mScroller.isFinished() (flinging begins when the user lifts his finger). 129 */ 130 private boolean mIsBeingDragged = false; 131 132 /** 133 * Determines speed during touch scrolling 134 */ 135 private VelocityTracker mVelocityTracker; 136 137 /** 138 * When set to true, the scroll view measure its child to make it fill the currently 139 * visible area. 140 */ 141 private boolean mFillViewport; 142 143 /** 144 * Whether arrow scrolling is animated. 145 */ 146 private boolean mSmoothScrollingEnabled = true; 147 148 private int mTouchSlop; 149 private int mMinimumVelocity; 150 private int mMaximumVelocity; 151 152 /** 153 * ID of the active pointer. This is used to retain consistency during 154 * drags/flings if multiple pointers are used. 155 */ 156 private int mActivePointerId = INVALID_POINTER; 157 158 /** 159 * Used during scrolling to retrieve the new offset within the window. 160 */ 161 private final int[] mScrollOffset = new int[2]; 162 private final int[] mScrollConsumed = new int[2]; 163 private int mNestedYOffset; 164 165 private int mLastScrollerY; 166 167 /** 168 * Sentinel value for no current active pointer. 169 * Used by {@link #mActivePointerId}. 170 */ 171 private static final int INVALID_POINTER = -1; 172 173 private SavedState mSavedState; 174 175 private static final AccessibilityDelegate ACCESSIBILITY_DELEGATE = new AccessibilityDelegate(); 176 177 private static final int[] SCROLLVIEW_STYLEABLE = new int[] { 178 android.R.attr.fillViewport 179 }; 180 181 private final NestedScrollingParentHelper mParentHelper; 182 private final NestedScrollingChildHelper mChildHelper; 183 184 private float mVerticalScrollFactor; 185 186 private OnScrollChangeListener mOnScrollChangeListener; 187 188 public NestedScrollView(@NonNull Context context) { 189 this(context, null); 190 } 191 192 public NestedScrollView(@NonNull Context context, @Nullable AttributeSet attrs) { 193 this(context, attrs, 0); 194 } 195 196 public NestedScrollView(@NonNull Context context, @Nullable AttributeSet attrs, 197 int defStyleAttr) { 198 super(context, attrs, defStyleAttr); 199 initScrollView(); 200 201 final TypedArray a = context.obtainStyledAttributes( 202 attrs, SCROLLVIEW_STYLEABLE, defStyleAttr, 0); 203 204 setFillViewport(a.getBoolean(0, false)); 205 206 a.recycle(); 207 208 mParentHelper = new NestedScrollingParentHelper(this); 209 mChildHelper = new NestedScrollingChildHelper(this); 210 211 // ...because why else would you be using this widget? 212 setNestedScrollingEnabled(true); 213 214 ViewCompat.setAccessibilityDelegate(this, ACCESSIBILITY_DELEGATE); 215 } 216 217 // NestedScrollingChild2 218 219 @Override 220 public boolean startNestedScroll(int axes, int type) { 221 return mChildHelper.startNestedScroll(axes, type); 222 } 223 224 @Override 225 public void stopNestedScroll(int type) { 226 mChildHelper.stopNestedScroll(type); 227 } 228 229 @Override 230 public boolean hasNestedScrollingParent(int type) { 231 return mChildHelper.hasNestedScrollingParent(type); 232 } 233 234 @Override 235 public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, 236 int dyUnconsumed, int[] offsetInWindow, int type) { 237 return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, 238 offsetInWindow, type); 239 } 240 241 @Override 242 public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow, 243 int type) { 244 return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type); 245 } 246 247 // NestedScrollingChild 248 249 @Override 250 public void setNestedScrollingEnabled(boolean enabled) { 251 mChildHelper.setNestedScrollingEnabled(enabled); 252 } 253 254 @Override 255 public boolean isNestedScrollingEnabled() { 256 return mChildHelper.isNestedScrollingEnabled(); 257 } 258 259 @Override 260 public boolean startNestedScroll(int axes) { 261 return startNestedScroll(axes, ViewCompat.TYPE_TOUCH); 262 } 263 264 @Override 265 public void stopNestedScroll() { 266 stopNestedScroll(ViewCompat.TYPE_TOUCH); 267 } 268 269 @Override 270 public boolean hasNestedScrollingParent() { 271 return hasNestedScrollingParent(ViewCompat.TYPE_TOUCH); 272 } 273 274 @Override 275 public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, 276 int dyUnconsumed, int[] offsetInWindow) { 277 return dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, 278 offsetInWindow, ViewCompat.TYPE_TOUCH); 279 } 280 281 @Override 282 public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) { 283 return dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, ViewCompat.TYPE_TOUCH); 284 } 285 286 @Override 287 public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) { 288 return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed); 289 } 290 291 @Override 292 public boolean dispatchNestedPreFling(float velocityX, float velocityY) { 293 return mChildHelper.dispatchNestedPreFling(velocityX, velocityY); 294 } 295 296 // NestedScrollingParent2 297 298 @Override 299 public boolean onStartNestedScroll(@NonNull View child, @NonNull View target, int axes, 300 int type) { 301 return (axes & ViewCompat.SCROLL_AXIS_VERTICAL) != 0; 302 } 303 304 @Override 305 public void onNestedScrollAccepted(@NonNull View child, @NonNull View target, int axes, 306 int type) { 307 mParentHelper.onNestedScrollAccepted(child, target, axes, type); 308 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, type); 309 } 310 311 @Override 312 public void onStopNestedScroll(@NonNull View target, int type) { 313 mParentHelper.onStopNestedScroll(target, type); 314 stopNestedScroll(type); 315 } 316 317 @Override 318 public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, 319 int dyUnconsumed, int type) { 320 final int oldScrollY = getScrollY(); 321 scrollBy(0, dyUnconsumed); 322 final int myConsumed = getScrollY() - oldScrollY; 323 final int myUnconsumed = dyUnconsumed - myConsumed; 324 dispatchNestedScroll(0, myConsumed, 0, myUnconsumed, null, 325 type); 326 } 327 328 @Override 329 public void onNestedPreScroll(@NonNull View target, int dx, int dy, @NonNull int[] consumed, 330 int type) { 331 dispatchNestedPreScroll(dx, dy, consumed, null, type); 332 } 333 334 // NestedScrollingParent 335 336 @Override 337 public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) { 338 return onStartNestedScroll(child, target, nestedScrollAxes, ViewCompat.TYPE_TOUCH); 339 } 340 341 @Override 342 public void onNestedScrollAccepted(View child, View target, int nestedScrollAxes) { 343 onNestedScrollAccepted(child, target, nestedScrollAxes, ViewCompat.TYPE_TOUCH); 344 } 345 346 @Override 347 public void onStopNestedScroll(View target) { 348 onStopNestedScroll(target, ViewCompat.TYPE_TOUCH); 349 } 350 351 @Override 352 public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, 353 int dyUnconsumed) { 354 onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, 355 ViewCompat.TYPE_TOUCH); 356 } 357 358 @Override 359 public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) { 360 onNestedPreScroll(target, dx, dy, consumed, ViewCompat.TYPE_TOUCH); 361 } 362 363 @Override 364 public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) { 365 if (!consumed) { 366 flingWithNestedDispatch((int) velocityY); 367 return true; 368 } 369 return false; 370 } 371 372 @Override 373 public boolean onNestedPreFling(View target, float velocityX, float velocityY) { 374 return dispatchNestedPreFling(velocityX, velocityY); 375 } 376 377 @Override 378 public int getNestedScrollAxes() { 379 return mParentHelper.getNestedScrollAxes(); 380 } 381 382 // ScrollView import 383 384 @Override 385 public boolean shouldDelayChildPressedState() { 386 return true; 387 } 388 389 @Override 390 protected float getTopFadingEdgeStrength() { 391 if (getChildCount() == 0) { 392 return 0.0f; 393 } 394 395 final int length = getVerticalFadingEdgeLength(); 396 final int scrollY = getScrollY(); 397 if (scrollY < length) { 398 return scrollY / (float) length; 399 } 400 401 return 1.0f; 402 } 403 404 @Override 405 protected float getBottomFadingEdgeStrength() { 406 if (getChildCount() == 0) { 407 return 0.0f; 408 } 409 410 final int length = getVerticalFadingEdgeLength(); 411 final int bottomEdge = getHeight() - getPaddingBottom(); 412 final int span = getChildAt(0).getBottom() - getScrollY() - bottomEdge; 413 if (span < length) { 414 return span / (float) length; 415 } 416 417 return 1.0f; 418 } 419 420 /** 421 * @return The maximum amount this scroll view will scroll in response to 422 * an arrow event. 423 */ 424 public int getMaxScrollAmount() { 425 return (int) (MAX_SCROLL_FACTOR * getHeight()); 426 } 427 428 private void initScrollView() { 429 mScroller = new OverScroller(getContext()); 430 setFocusable(true); 431 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 432 setWillNotDraw(false); 433 final ViewConfiguration configuration = ViewConfiguration.get(getContext()); 434 mTouchSlop = configuration.getScaledTouchSlop(); 435 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 436 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 437 } 438 439 @Override 440 public void addView(View child) { 441 if (getChildCount() > 0) { 442 throw new IllegalStateException("ScrollView can host only one direct child"); 443 } 444 445 super.addView(child); 446 } 447 448 @Override 449 public void addView(View child, int index) { 450 if (getChildCount() > 0) { 451 throw new IllegalStateException("ScrollView can host only one direct child"); 452 } 453 454 super.addView(child, index); 455 } 456 457 @Override 458 public void addView(View child, ViewGroup.LayoutParams params) { 459 if (getChildCount() > 0) { 460 throw new IllegalStateException("ScrollView can host only one direct child"); 461 } 462 463 super.addView(child, params); 464 } 465 466 @Override 467 public void addView(View child, int index, ViewGroup.LayoutParams params) { 468 if (getChildCount() > 0) { 469 throw new IllegalStateException("ScrollView can host only one direct child"); 470 } 471 472 super.addView(child, index, params); 473 } 474 475 /** 476 * Register a callback to be invoked when the scroll X or Y positions of 477 * this view change. 478 * <p>This version of the method works on all versions of Android, back to API v4.</p> 479 * 480 * @param l The listener to notify when the scroll X or Y position changes. 481 * @see android.view.View#getScrollX() 482 * @see android.view.View#getScrollY() 483 */ 484 public void setOnScrollChangeListener(@Nullable OnScrollChangeListener l) { 485 mOnScrollChangeListener = l; 486 } 487 488 /** 489 * @return Returns true this ScrollView can be scrolled 490 */ 491 private boolean canScroll() { 492 View child = getChildAt(0); 493 if (child != null) { 494 int childHeight = child.getHeight(); 495 return getHeight() < childHeight + getPaddingTop() + getPaddingBottom(); 496 } 497 return false; 498 } 499 500 /** 501 * Indicates whether this ScrollView's content is stretched to fill the viewport. 502 * 503 * @return True if the content fills the viewport, false otherwise. 504 * 505 * @attr name android:fillViewport 506 */ 507 public boolean isFillViewport() { 508 return mFillViewport; 509 } 510 511 /** 512 * Set whether this ScrollView should stretch its content height to fill the viewport or not. 513 * 514 * @param fillViewport True to stretch the content's height to the viewport's 515 * boundaries, false otherwise. 516 * 517 * @attr name android:fillViewport 518 */ 519 public void setFillViewport(boolean fillViewport) { 520 if (fillViewport != mFillViewport) { 521 mFillViewport = fillViewport; 522 requestLayout(); 523 } 524 } 525 526 /** 527 * @return Whether arrow scrolling will animate its transition. 528 */ 529 public boolean isSmoothScrollingEnabled() { 530 return mSmoothScrollingEnabled; 531 } 532 533 /** 534 * Set whether arrow scrolling will animate its transition. 535 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 536 */ 537 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 538 mSmoothScrollingEnabled = smoothScrollingEnabled; 539 } 540 541 @Override 542 protected void onScrollChanged(int l, int t, int oldl, int oldt) { 543 super.onScrollChanged(l, t, oldl, oldt); 544 545 if (mOnScrollChangeListener != null) { 546 mOnScrollChangeListener.onScrollChange(this, l, t, oldl, oldt); 547 } 548 } 549 550 @Override 551 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 552 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 553 554 if (!mFillViewport) { 555 return; 556 } 557 558 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 559 if (heightMode == MeasureSpec.UNSPECIFIED) { 560 return; 561 } 562 563 if (getChildCount() > 0) { 564 final View child = getChildAt(0); 565 int height = getMeasuredHeight(); 566 if (child.getMeasuredHeight() < height) { 567 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 568 569 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, 570 getPaddingLeft() + getPaddingRight(), lp.width); 571 height -= getPaddingTop(); 572 height -= getPaddingBottom(); 573 int childHeightMeasureSpec = 574 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 575 576 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 577 } 578 } 579 } 580 581 @Override 582 public boolean dispatchKeyEvent(KeyEvent event) { 583 // Let the focused view and/or our descendants get the key first 584 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 585 } 586 587 /** 588 * You can call this function yourself to have the scroll view perform 589 * scrolling from a key event, just as if the event had been dispatched to 590 * it by the view hierarchy. 591 * 592 * @param event The key event to execute. 593 * @return Return true if the event was handled, else false. 594 */ 595 public boolean executeKeyEvent(@NonNull KeyEvent event) { 596 mTempRect.setEmpty(); 597 598 if (!canScroll()) { 599 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { 600 View currentFocused = findFocus(); 601 if (currentFocused == this) currentFocused = null; 602 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 603 currentFocused, View.FOCUS_DOWN); 604 return nextFocused != null 605 && nextFocused != this 606 && nextFocused.requestFocus(View.FOCUS_DOWN); 607 } 608 return false; 609 } 610 611 boolean handled = false; 612 if (event.getAction() == KeyEvent.ACTION_DOWN) { 613 switch (event.getKeyCode()) { 614 case KeyEvent.KEYCODE_DPAD_UP: 615 if (!event.isAltPressed()) { 616 handled = arrowScroll(View.FOCUS_UP); 617 } else { 618 handled = fullScroll(View.FOCUS_UP); 619 } 620 break; 621 case KeyEvent.KEYCODE_DPAD_DOWN: 622 if (!event.isAltPressed()) { 623 handled = arrowScroll(View.FOCUS_DOWN); 624 } else { 625 handled = fullScroll(View.FOCUS_DOWN); 626 } 627 break; 628 case KeyEvent.KEYCODE_SPACE: 629 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 630 break; 631 } 632 } 633 634 return handled; 635 } 636 637 private boolean inChild(int x, int y) { 638 if (getChildCount() > 0) { 639 final int scrollY = getScrollY(); 640 final View child = getChildAt(0); 641 return !(y < child.getTop() - scrollY 642 || y >= child.getBottom() - scrollY 643 || x < child.getLeft() 644 || x >= child.getRight()); 645 } 646 return false; 647 } 648 649 private void initOrResetVelocityTracker() { 650 if (mVelocityTracker == null) { 651 mVelocityTracker = VelocityTracker.obtain(); 652 } else { 653 mVelocityTracker.clear(); 654 } 655 } 656 657 private void initVelocityTrackerIfNotExists() { 658 if (mVelocityTracker == null) { 659 mVelocityTracker = VelocityTracker.obtain(); 660 } 661 } 662 663 private void recycleVelocityTracker() { 664 if (mVelocityTracker != null) { 665 mVelocityTracker.recycle(); 666 mVelocityTracker = null; 667 } 668 } 669 670 @Override 671 public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) { 672 if (disallowIntercept) { 673 recycleVelocityTracker(); 674 } 675 super.requestDisallowInterceptTouchEvent(disallowIntercept); 676 } 677 678 @Override 679 public boolean onInterceptTouchEvent(MotionEvent ev) { 680 /* 681 * This method JUST determines whether we want to intercept the motion. 682 * If we return true, onMotionEvent will be called and we do the actual 683 * scrolling there. 684 */ 685 686 /* 687 * Shortcut the most recurring case: the user is in the dragging 688 * state and he is moving his finger. We want to intercept this 689 * motion. 690 */ 691 final int action = ev.getAction(); 692 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 693 return true; 694 } 695 696 switch (action & MotionEvent.ACTION_MASK) { 697 case MotionEvent.ACTION_MOVE: { 698 /* 699 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 700 * whether the user has moved far enough from his original down touch. 701 */ 702 703 /* 704 * Locally do absolute value. mLastMotionY is set to the y value 705 * of the down event. 706 */ 707 final int activePointerId = mActivePointerId; 708 if (activePointerId == INVALID_POINTER) { 709 // If we don't have a valid id, the touch down wasn't on content. 710 break; 711 } 712 713 final int pointerIndex = ev.findPointerIndex(activePointerId); 714 if (pointerIndex == -1) { 715 Log.e(TAG, "Invalid pointerId=" + activePointerId 716 + " in onInterceptTouchEvent"); 717 break; 718 } 719 720 final int y = (int) ev.getY(pointerIndex); 721 final int yDiff = Math.abs(y - mLastMotionY); 722 if (yDiff > mTouchSlop 723 && (getNestedScrollAxes() & ViewCompat.SCROLL_AXIS_VERTICAL) == 0) { 724 mIsBeingDragged = true; 725 mLastMotionY = y; 726 initVelocityTrackerIfNotExists(); 727 mVelocityTracker.addMovement(ev); 728 mNestedYOffset = 0; 729 final ViewParent parent = getParent(); 730 if (parent != null) { 731 parent.requestDisallowInterceptTouchEvent(true); 732 } 733 } 734 break; 735 } 736 737 case MotionEvent.ACTION_DOWN: { 738 final int y = (int) ev.getY(); 739 if (!inChild((int) ev.getX(), y)) { 740 mIsBeingDragged = false; 741 recycleVelocityTracker(); 742 break; 743 } 744 745 /* 746 * Remember location of down touch. 747 * ACTION_DOWN always refers to pointer index 0. 748 */ 749 mLastMotionY = y; 750 mActivePointerId = ev.getPointerId(0); 751 752 initOrResetVelocityTracker(); 753 mVelocityTracker.addMovement(ev); 754 /* 755 * If being flinged and user touches the screen, initiate drag; 756 * otherwise don't. mScroller.isFinished should be false when 757 * being flinged. We need to call computeScrollOffset() first so that 758 * isFinished() is correct. 759 */ 760 mScroller.computeScrollOffset(); 761 mIsBeingDragged = !mScroller.isFinished(); 762 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_TOUCH); 763 break; 764 } 765 766 case MotionEvent.ACTION_CANCEL: 767 case MotionEvent.ACTION_UP: 768 /* Release the drag */ 769 mIsBeingDragged = false; 770 mActivePointerId = INVALID_POINTER; 771 recycleVelocityTracker(); 772 if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0, getScrollRange())) { 773 ViewCompat.postInvalidateOnAnimation(this); 774 } 775 stopNestedScroll(ViewCompat.TYPE_TOUCH); 776 break; 777 case MotionEvent.ACTION_POINTER_UP: 778 onSecondaryPointerUp(ev); 779 break; 780 } 781 782 /* 783 * The only time we want to intercept motion events is if we are in the 784 * drag mode. 785 */ 786 return mIsBeingDragged; 787 } 788 789 @Override 790 public boolean onTouchEvent(MotionEvent ev) { 791 initVelocityTrackerIfNotExists(); 792 793 MotionEvent vtev = MotionEvent.obtain(ev); 794 795 final int actionMasked = ev.getActionMasked(); 796 797 if (actionMasked == MotionEvent.ACTION_DOWN) { 798 mNestedYOffset = 0; 799 } 800 vtev.offsetLocation(0, mNestedYOffset); 801 802 switch (actionMasked) { 803 case MotionEvent.ACTION_DOWN: { 804 if (getChildCount() == 0) { 805 return false; 806 } 807 if ((mIsBeingDragged = !mScroller.isFinished())) { 808 final ViewParent parent = getParent(); 809 if (parent != null) { 810 parent.requestDisallowInterceptTouchEvent(true); 811 } 812 } 813 814 /* 815 * If being flinged and user touches, stop the fling. isFinished 816 * will be false if being flinged. 817 */ 818 if (!mScroller.isFinished()) { 819 mScroller.abortAnimation(); 820 } 821 822 // Remember where the motion event started 823 mLastMotionY = (int) ev.getY(); 824 mActivePointerId = ev.getPointerId(0); 825 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_TOUCH); 826 break; 827 } 828 case MotionEvent.ACTION_MOVE: 829 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 830 if (activePointerIndex == -1) { 831 Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent"); 832 break; 833 } 834 835 final int y = (int) ev.getY(activePointerIndex); 836 int deltaY = mLastMotionY - y; 837 if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset, 838 ViewCompat.TYPE_TOUCH)) { 839 deltaY -= mScrollConsumed[1]; 840 vtev.offsetLocation(0, mScrollOffset[1]); 841 mNestedYOffset += mScrollOffset[1]; 842 } 843 if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) { 844 final ViewParent parent = getParent(); 845 if (parent != null) { 846 parent.requestDisallowInterceptTouchEvent(true); 847 } 848 mIsBeingDragged = true; 849 if (deltaY > 0) { 850 deltaY -= mTouchSlop; 851 } else { 852 deltaY += mTouchSlop; 853 } 854 } 855 if (mIsBeingDragged) { 856 // Scroll to follow the motion event 857 mLastMotionY = y - mScrollOffset[1]; 858 859 final int oldY = getScrollY(); 860 final int range = getScrollRange(); 861 final int overscrollMode = getOverScrollMode(); 862 boolean canOverscroll = overscrollMode == View.OVER_SCROLL_ALWAYS 863 || (overscrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 864 865 // Calling overScrollByCompat will call onOverScrolled, which 866 // calls onScrollChanged if applicable. 867 if (overScrollByCompat(0, deltaY, 0, getScrollY(), 0, range, 0, 868 0, true) && !hasNestedScrollingParent(ViewCompat.TYPE_TOUCH)) { 869 // Break our velocity if we hit a scroll barrier. 870 mVelocityTracker.clear(); 871 } 872 873 final int scrolledDeltaY = getScrollY() - oldY; 874 final int unconsumedY = deltaY - scrolledDeltaY; 875 if (dispatchNestedScroll(0, scrolledDeltaY, 0, unconsumedY, mScrollOffset, 876 ViewCompat.TYPE_TOUCH)) { 877 mLastMotionY -= mScrollOffset[1]; 878 vtev.offsetLocation(0, mScrollOffset[1]); 879 mNestedYOffset += mScrollOffset[1]; 880 } else if (canOverscroll) { 881 ensureGlows(); 882 final int pulledToY = oldY + deltaY; 883 if (pulledToY < 0) { 884 EdgeEffectCompat.onPull(mEdgeGlowTop, (float) deltaY / getHeight(), 885 ev.getX(activePointerIndex) / getWidth()); 886 if (!mEdgeGlowBottom.isFinished()) { 887 mEdgeGlowBottom.onRelease(); 888 } 889 } else if (pulledToY > range) { 890 EdgeEffectCompat.onPull(mEdgeGlowBottom, (float) deltaY / getHeight(), 891 1.f - ev.getX(activePointerIndex) 892 / getWidth()); 893 if (!mEdgeGlowTop.isFinished()) { 894 mEdgeGlowTop.onRelease(); 895 } 896 } 897 if (mEdgeGlowTop != null 898 && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) { 899 ViewCompat.postInvalidateOnAnimation(this); 900 } 901 } 902 } 903 break; 904 case MotionEvent.ACTION_UP: 905 final VelocityTracker velocityTracker = mVelocityTracker; 906 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 907 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 908 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 909 flingWithNestedDispatch(-initialVelocity); 910 } else if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0, 911 getScrollRange())) { 912 ViewCompat.postInvalidateOnAnimation(this); 913 } 914 mActivePointerId = INVALID_POINTER; 915 endDrag(); 916 break; 917 case MotionEvent.ACTION_CANCEL: 918 if (mIsBeingDragged && getChildCount() > 0) { 919 if (mScroller.springBack(getScrollX(), getScrollY(), 0, 0, 0, 920 getScrollRange())) { 921 ViewCompat.postInvalidateOnAnimation(this); 922 } 923 } 924 mActivePointerId = INVALID_POINTER; 925 endDrag(); 926 break; 927 case MotionEvent.ACTION_POINTER_DOWN: { 928 final int index = ev.getActionIndex(); 929 mLastMotionY = (int) ev.getY(index); 930 mActivePointerId = ev.getPointerId(index); 931 break; 932 } 933 case MotionEvent.ACTION_POINTER_UP: 934 onSecondaryPointerUp(ev); 935 mLastMotionY = (int) ev.getY(ev.findPointerIndex(mActivePointerId)); 936 break; 937 } 938 939 if (mVelocityTracker != null) { 940 mVelocityTracker.addMovement(vtev); 941 } 942 vtev.recycle(); 943 return true; 944 } 945 946 private void onSecondaryPointerUp(MotionEvent ev) { 947 final int pointerIndex = ev.getActionIndex(); 948 final int pointerId = ev.getPointerId(pointerIndex); 949 if (pointerId == mActivePointerId) { 950 // This was our active pointer going up. Choose a new 951 // active pointer and adjust accordingly. 952 // TODO: Make this decision more intelligent. 953 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 954 mLastMotionY = (int) ev.getY(newPointerIndex); 955 mActivePointerId = ev.getPointerId(newPointerIndex); 956 if (mVelocityTracker != null) { 957 mVelocityTracker.clear(); 958 } 959 } 960 } 961 962 @Override 963 public boolean onGenericMotionEvent(MotionEvent event) { 964 if ((event.getSource() & InputDeviceCompat.SOURCE_CLASS_POINTER) != 0) { 965 switch (event.getAction()) { 966 case MotionEvent.ACTION_SCROLL: { 967 if (!mIsBeingDragged) { 968 final float vscroll = event.getAxisValue(MotionEvent.AXIS_VSCROLL); 969 if (vscroll != 0) { 970 final int delta = (int) (vscroll * getVerticalScrollFactorCompat()); 971 final int range = getScrollRange(); 972 int oldScrollY = getScrollY(); 973 int newScrollY = oldScrollY - delta; 974 if (newScrollY < 0) { 975 newScrollY = 0; 976 } else if (newScrollY > range) { 977 newScrollY = range; 978 } 979 if (newScrollY != oldScrollY) { 980 super.scrollTo(getScrollX(), newScrollY); 981 return true; 982 } 983 } 984 } 985 } 986 } 987 } 988 return false; 989 } 990 991 private float getVerticalScrollFactorCompat() { 992 if (mVerticalScrollFactor == 0) { 993 TypedValue outValue = new TypedValue(); 994 final Context context = getContext(); 995 if (!context.getTheme().resolveAttribute( 996 android.R.attr.listPreferredItemHeight, outValue, true)) { 997 throw new IllegalStateException( 998 "Expected theme to define listPreferredItemHeight."); 999 } 1000 mVerticalScrollFactor = outValue.getDimension( 1001 context.getResources().getDisplayMetrics()); 1002 } 1003 return mVerticalScrollFactor; 1004 } 1005 1006 @Override 1007 protected void onOverScrolled(int scrollX, int scrollY, 1008 boolean clampedX, boolean clampedY) { 1009 super.scrollTo(scrollX, scrollY); 1010 } 1011 1012 boolean overScrollByCompat(int deltaX, int deltaY, 1013 int scrollX, int scrollY, 1014 int scrollRangeX, int scrollRangeY, 1015 int maxOverScrollX, int maxOverScrollY, 1016 boolean isTouchEvent) { 1017 final int overScrollMode = getOverScrollMode(); 1018 final boolean canScrollHorizontal = 1019 computeHorizontalScrollRange() > computeHorizontalScrollExtent(); 1020 final boolean canScrollVertical = 1021 computeVerticalScrollRange() > computeVerticalScrollExtent(); 1022 final boolean overScrollHorizontal = overScrollMode == View.OVER_SCROLL_ALWAYS 1023 || (overScrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS && canScrollHorizontal); 1024 final boolean overScrollVertical = overScrollMode == View.OVER_SCROLL_ALWAYS 1025 || (overScrollMode == View.OVER_SCROLL_IF_CONTENT_SCROLLS && canScrollVertical); 1026 1027 int newScrollX = scrollX + deltaX; 1028 if (!overScrollHorizontal) { 1029 maxOverScrollX = 0; 1030 } 1031 1032 int newScrollY = scrollY + deltaY; 1033 if (!overScrollVertical) { 1034 maxOverScrollY = 0; 1035 } 1036 1037 // Clamp values if at the limits and record 1038 final int left = -maxOverScrollX; 1039 final int right = maxOverScrollX + scrollRangeX; 1040 final int top = -maxOverScrollY; 1041 final int bottom = maxOverScrollY + scrollRangeY; 1042 1043 boolean clampedX = false; 1044 if (newScrollX > right) { 1045 newScrollX = right; 1046 clampedX = true; 1047 } else if (newScrollX < left) { 1048 newScrollX = left; 1049 clampedX = true; 1050 } 1051 1052 boolean clampedY = false; 1053 if (newScrollY > bottom) { 1054 newScrollY = bottom; 1055 clampedY = true; 1056 } else if (newScrollY < top) { 1057 newScrollY = top; 1058 clampedY = true; 1059 } 1060 1061 if (clampedY && !hasNestedScrollingParent(ViewCompat.TYPE_NON_TOUCH)) { 1062 mScroller.springBack(newScrollX, newScrollY, 0, 0, 0, getScrollRange()); 1063 } 1064 1065 onOverScrolled(newScrollX, newScrollY, clampedX, clampedY); 1066 1067 return clampedX || clampedY; 1068 } 1069 1070 int getScrollRange() { 1071 int scrollRange = 0; 1072 if (getChildCount() > 0) { 1073 View child = getChildAt(0); 1074 scrollRange = Math.max(0, 1075 child.getHeight() - (getHeight() - getPaddingBottom() - getPaddingTop())); 1076 } 1077 return scrollRange; 1078 } 1079 1080 /** 1081 * <p> 1082 * Finds the next focusable component that fits in the specified bounds. 1083 * </p> 1084 * 1085 * @param topFocus look for a candidate is the one at the top of the bounds 1086 * if topFocus is true, or at the bottom of the bounds if topFocus is 1087 * false 1088 * @param top the top offset of the bounds in which a focusable must be 1089 * found 1090 * @param bottom the bottom offset of the bounds in which a focusable must 1091 * be found 1092 * @return the next focusable component in the bounds or null if none can 1093 * be found 1094 */ 1095 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 1096 1097 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 1098 View focusCandidate = null; 1099 1100 /* 1101 * A fully contained focusable is one where its top is below the bound's 1102 * top, and its bottom is above the bound's bottom. A partially 1103 * contained focusable is one where some part of it is within the 1104 * bounds, but it also has some part that is not within bounds. A fully contained 1105 * focusable is preferred to a partially contained focusable. 1106 */ 1107 boolean foundFullyContainedFocusable = false; 1108 1109 int count = focusables.size(); 1110 for (int i = 0; i < count; i++) { 1111 View view = focusables.get(i); 1112 int viewTop = view.getTop(); 1113 int viewBottom = view.getBottom(); 1114 1115 if (top < viewBottom && viewTop < bottom) { 1116 /* 1117 * the focusable is in the target area, it is a candidate for 1118 * focusing 1119 */ 1120 1121 final boolean viewIsFullyContained = (top < viewTop) && (viewBottom < bottom); 1122 1123 if (focusCandidate == null) { 1124 /* No candidate, take this one */ 1125 focusCandidate = view; 1126 foundFullyContainedFocusable = viewIsFullyContained; 1127 } else { 1128 final boolean viewIsCloserToBoundary = 1129 (topFocus && viewTop < focusCandidate.getTop()) 1130 || (!topFocus && viewBottom > focusCandidate.getBottom()); 1131 1132 if (foundFullyContainedFocusable) { 1133 if (viewIsFullyContained && viewIsCloserToBoundary) { 1134 /* 1135 * We're dealing with only fully contained views, so 1136 * it has to be closer to the boundary to beat our 1137 * candidate 1138 */ 1139 focusCandidate = view; 1140 } 1141 } else { 1142 if (viewIsFullyContained) { 1143 /* Any fully contained view beats a partially contained view */ 1144 focusCandidate = view; 1145 foundFullyContainedFocusable = true; 1146 } else if (viewIsCloserToBoundary) { 1147 /* 1148 * Partially contained view beats another partially 1149 * contained view if it's closer 1150 */ 1151 focusCandidate = view; 1152 } 1153 } 1154 } 1155 } 1156 } 1157 1158 return focusCandidate; 1159 } 1160 1161 /** 1162 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 1163 * method will scroll the view by one page up or down and give the focus 1164 * to the topmost/bottommost component in the new visible area. If no 1165 * component is a good candidate for focus, this scrollview reclaims the 1166 * focus.</p> 1167 * 1168 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 1169 * to go one page up or 1170 * {@link android.view.View#FOCUS_DOWN} to go one page down 1171 * @return true if the key event is consumed by this method, false otherwise 1172 */ 1173 public boolean pageScroll(int direction) { 1174 boolean down = direction == View.FOCUS_DOWN; 1175 int height = getHeight(); 1176 1177 if (down) { 1178 mTempRect.top = getScrollY() + height; 1179 int count = getChildCount(); 1180 if (count > 0) { 1181 View view = getChildAt(count - 1); 1182 if (mTempRect.top + height > view.getBottom()) { 1183 mTempRect.top = view.getBottom() - height; 1184 } 1185 } 1186 } else { 1187 mTempRect.top = getScrollY() - height; 1188 if (mTempRect.top < 0) { 1189 mTempRect.top = 0; 1190 } 1191 } 1192 mTempRect.bottom = mTempRect.top + height; 1193 1194 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 1195 } 1196 1197 /** 1198 * <p>Handles scrolling in response to a "home/end" shortcut press. This 1199 * method will scroll the view to the top or bottom and give the focus 1200 * to the topmost/bottommost component in the new visible area. If no 1201 * component is a good candidate for focus, this scrollview reclaims the 1202 * focus.</p> 1203 * 1204 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 1205 * to go the top of the view or 1206 * {@link android.view.View#FOCUS_DOWN} to go the bottom 1207 * @return true if the key event is consumed by this method, false otherwise 1208 */ 1209 public boolean fullScroll(int direction) { 1210 boolean down = direction == View.FOCUS_DOWN; 1211 int height = getHeight(); 1212 1213 mTempRect.top = 0; 1214 mTempRect.bottom = height; 1215 1216 if (down) { 1217 int count = getChildCount(); 1218 if (count > 0) { 1219 View view = getChildAt(count - 1); 1220 mTempRect.bottom = view.getBottom() + getPaddingBottom(); 1221 mTempRect.top = mTempRect.bottom - height; 1222 } 1223 } 1224 1225 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 1226 } 1227 1228 /** 1229 * <p>Scrolls the view to make the area defined by <code>top</code> and 1230 * <code>bottom</code> visible. This method attempts to give the focus 1231 * to a component visible in this area. If no component can be focused in 1232 * the new visible area, the focus is reclaimed by this ScrollView.</p> 1233 * 1234 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 1235 * to go upward, {@link android.view.View#FOCUS_DOWN} to downward 1236 * @param top the top offset of the new area to be made visible 1237 * @param bottom the bottom offset of the new area to be made visible 1238 * @return true if the key event is consumed by this method, false otherwise 1239 */ 1240 private boolean scrollAndFocus(int direction, int top, int bottom) { 1241 boolean handled = true; 1242 1243 int height = getHeight(); 1244 int containerTop = getScrollY(); 1245 int containerBottom = containerTop + height; 1246 boolean up = direction == View.FOCUS_UP; 1247 1248 View newFocused = findFocusableViewInBounds(up, top, bottom); 1249 if (newFocused == null) { 1250 newFocused = this; 1251 } 1252 1253 if (top >= containerTop && bottom <= containerBottom) { 1254 handled = false; 1255 } else { 1256 int delta = up ? (top - containerTop) : (bottom - containerBottom); 1257 doScrollY(delta); 1258 } 1259 1260 if (newFocused != findFocus()) newFocused.requestFocus(direction); 1261 1262 return handled; 1263 } 1264 1265 /** 1266 * Handle scrolling in response to an up or down arrow click. 1267 * 1268 * @param direction The direction corresponding to the arrow key that was 1269 * pressed 1270 * @return True if we consumed the event, false otherwise 1271 */ 1272 public boolean arrowScroll(int direction) { 1273 1274 View currentFocused = findFocus(); 1275 if (currentFocused == this) currentFocused = null; 1276 1277 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 1278 1279 final int maxJump = getMaxScrollAmount(); 1280 1281 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 1282 nextFocused.getDrawingRect(mTempRect); 1283 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 1284 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1285 doScrollY(scrollDelta); 1286 nextFocused.requestFocus(direction); 1287 } else { 1288 // no new focus 1289 int scrollDelta = maxJump; 1290 1291 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 1292 scrollDelta = getScrollY(); 1293 } else if (direction == View.FOCUS_DOWN) { 1294 if (getChildCount() > 0) { 1295 int daBottom = getChildAt(0).getBottom(); 1296 int screenBottom = getScrollY() + getHeight() - getPaddingBottom(); 1297 if (daBottom - screenBottom < maxJump) { 1298 scrollDelta = daBottom - screenBottom; 1299 } 1300 } 1301 } 1302 if (scrollDelta == 0) { 1303 return false; 1304 } 1305 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 1306 } 1307 1308 if (currentFocused != null && currentFocused.isFocused() 1309 && isOffScreen(currentFocused)) { 1310 // previously focused item still has focus and is off screen, give 1311 // it up (take it back to ourselves) 1312 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 1313 // sure to 1314 // get it) 1315 final int descendantFocusability = getDescendantFocusability(); // save 1316 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 1317 requestFocus(); 1318 setDescendantFocusability(descendantFocusability); // restore 1319 } 1320 return true; 1321 } 1322 1323 /** 1324 * @return whether the descendant of this scroll view is scrolled off 1325 * screen. 1326 */ 1327 private boolean isOffScreen(View descendant) { 1328 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 1329 } 1330 1331 /** 1332 * @return whether the descendant of this scroll view is within delta 1333 * pixels of being on the screen. 1334 */ 1335 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 1336 descendant.getDrawingRect(mTempRect); 1337 offsetDescendantRectToMyCoords(descendant, mTempRect); 1338 1339 return (mTempRect.bottom + delta) >= getScrollY() 1340 && (mTempRect.top - delta) <= (getScrollY() + height); 1341 } 1342 1343 /** 1344 * Smooth scroll by a Y delta 1345 * 1346 * @param delta the number of pixels to scroll by on the Y axis 1347 */ 1348 private void doScrollY(int delta) { 1349 if (delta != 0) { 1350 if (mSmoothScrollingEnabled) { 1351 smoothScrollBy(0, delta); 1352 } else { 1353 scrollBy(0, delta); 1354 } 1355 } 1356 } 1357 1358 /** 1359 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 1360 * 1361 * @param dx the number of pixels to scroll by on the X axis 1362 * @param dy the number of pixels to scroll by on the Y axis 1363 */ 1364 public final void smoothScrollBy(int dx, int dy) { 1365 if (getChildCount() == 0) { 1366 // Nothing to do. 1367 return; 1368 } 1369 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 1370 if (duration > ANIMATED_SCROLL_GAP) { 1371 final int height = getHeight() - getPaddingBottom() - getPaddingTop(); 1372 final int bottom = getChildAt(0).getHeight(); 1373 final int maxY = Math.max(0, bottom - height); 1374 final int scrollY = getScrollY(); 1375 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 1376 1377 mScroller.startScroll(getScrollX(), scrollY, 0, dy); 1378 ViewCompat.postInvalidateOnAnimation(this); 1379 } else { 1380 if (!mScroller.isFinished()) { 1381 mScroller.abortAnimation(); 1382 } 1383 scrollBy(dx, dy); 1384 } 1385 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1386 } 1387 1388 /** 1389 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1390 * 1391 * @param x the position where to scroll on the X axis 1392 * @param y the position where to scroll on the Y axis 1393 */ 1394 public final void smoothScrollTo(int x, int y) { 1395 smoothScrollBy(x - getScrollX(), y - getScrollY()); 1396 } 1397 1398 /** 1399 * <p>The scroll range of a scroll view is the overall height of all of its 1400 * children.</p> 1401 * @hide 1402 */ 1403 @RestrictTo(LIBRARY_GROUP) 1404 @Override 1405 public int computeVerticalScrollRange() { 1406 final int count = getChildCount(); 1407 final int contentHeight = getHeight() - getPaddingBottom() - getPaddingTop(); 1408 if (count == 0) { 1409 return contentHeight; 1410 } 1411 1412 int scrollRange = getChildAt(0).getBottom(); 1413 final int scrollY = getScrollY(); 1414 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1415 if (scrollY < 0) { 1416 scrollRange -= scrollY; 1417 } else if (scrollY > overscrollBottom) { 1418 scrollRange += scrollY - overscrollBottom; 1419 } 1420 1421 return scrollRange; 1422 } 1423 1424 /** @hide */ 1425 @RestrictTo(LIBRARY_GROUP) 1426 @Override 1427 public int computeVerticalScrollOffset() { 1428 return Math.max(0, super.computeVerticalScrollOffset()); 1429 } 1430 1431 /** @hide */ 1432 @RestrictTo(LIBRARY_GROUP) 1433 @Override 1434 public int computeVerticalScrollExtent() { 1435 return super.computeVerticalScrollExtent(); 1436 } 1437 1438 /** @hide */ 1439 @RestrictTo(LIBRARY_GROUP) 1440 @Override 1441 public int computeHorizontalScrollRange() { 1442 return super.computeHorizontalScrollRange(); 1443 } 1444 1445 /** @hide */ 1446 @RestrictTo(LIBRARY_GROUP) 1447 @Override 1448 public int computeHorizontalScrollOffset() { 1449 return super.computeHorizontalScrollOffset(); 1450 } 1451 1452 /** @hide */ 1453 @RestrictTo(LIBRARY_GROUP) 1454 @Override 1455 public int computeHorizontalScrollExtent() { 1456 return super.computeHorizontalScrollExtent(); 1457 } 1458 1459 @Override 1460 protected void measureChild(View child, int parentWidthMeasureSpec, 1461 int parentHeightMeasureSpec) { 1462 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1463 1464 int childWidthMeasureSpec; 1465 int childHeightMeasureSpec; 1466 1467 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, getPaddingLeft() 1468 + getPaddingRight(), lp.width); 1469 1470 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1471 1472 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1473 } 1474 1475 @Override 1476 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1477 int parentHeightMeasureSpec, int heightUsed) { 1478 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1479 1480 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1481 getPaddingLeft() + getPaddingRight() + lp.leftMargin + lp.rightMargin 1482 + widthUsed, lp.width); 1483 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1484 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1485 1486 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1487 } 1488 1489 @Override 1490 public void computeScroll() { 1491 if (mScroller.computeScrollOffset()) { 1492 final int x = mScroller.getCurrX(); 1493 final int y = mScroller.getCurrY(); 1494 1495 int dy = y - mLastScrollerY; 1496 1497 // Dispatch up to parent 1498 if (dispatchNestedPreScroll(0, dy, mScrollConsumed, null, ViewCompat.TYPE_NON_TOUCH)) { 1499 dy -= mScrollConsumed[1]; 1500 } 1501 1502 if (dy != 0) { 1503 final int range = getScrollRange(); 1504 final int oldScrollY = getScrollY(); 1505 1506 overScrollByCompat(0, dy, getScrollX(), oldScrollY, 0, range, 0, 0, false); 1507 1508 final int scrolledDeltaY = getScrollY() - oldScrollY; 1509 final int unconsumedY = dy - scrolledDeltaY; 1510 1511 if (!dispatchNestedScroll(0, scrolledDeltaY, 0, unconsumedY, null, 1512 ViewCompat.TYPE_NON_TOUCH)) { 1513 final int mode = getOverScrollMode(); 1514 final boolean canOverscroll = mode == OVER_SCROLL_ALWAYS 1515 || (mode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 1516 if (canOverscroll) { 1517 ensureGlows(); 1518 if (y <= 0 && oldScrollY > 0) { 1519 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1520 } else if (y >= range && oldScrollY < range) { 1521 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1522 } 1523 } 1524 } 1525 } 1526 1527 // Finally update the scroll positions and post an invalidation 1528 mLastScrollerY = y; 1529 ViewCompat.postInvalidateOnAnimation(this); 1530 } else { 1531 // We can't scroll any more, so stop any indirect scrolling 1532 if (hasNestedScrollingParent(ViewCompat.TYPE_NON_TOUCH)) { 1533 stopNestedScroll(ViewCompat.TYPE_NON_TOUCH); 1534 } 1535 // and reset the scroller y 1536 mLastScrollerY = 0; 1537 } 1538 } 1539 1540 /** 1541 * Scrolls the view to the given child. 1542 * 1543 * @param child the View to scroll to 1544 */ 1545 private void scrollToChild(View child) { 1546 child.getDrawingRect(mTempRect); 1547 1548 /* Offset from child's local coordinates to ScrollView coordinates */ 1549 offsetDescendantRectToMyCoords(child, mTempRect); 1550 1551 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1552 1553 if (scrollDelta != 0) { 1554 scrollBy(0, scrollDelta); 1555 } 1556 } 1557 1558 /** 1559 * If rect is off screen, scroll just enough to get it (or at least the 1560 * first screen size chunk of it) on screen. 1561 * 1562 * @param rect The rectangle. 1563 * @param immediate True to scroll immediately without animation 1564 * @return true if scrolling was performed 1565 */ 1566 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1567 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1568 final boolean scroll = delta != 0; 1569 if (scroll) { 1570 if (immediate) { 1571 scrollBy(0, delta); 1572 } else { 1573 smoothScrollBy(0, delta); 1574 } 1575 } 1576 return scroll; 1577 } 1578 1579 /** 1580 * Compute the amount to scroll in the Y direction in order to get 1581 * a rectangle completely on the screen (or, if taller than the screen, 1582 * at least the first screen size chunk of it). 1583 * 1584 * @param rect The rect. 1585 * @return The scroll delta. 1586 */ 1587 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1588 if (getChildCount() == 0) return 0; 1589 1590 int height = getHeight(); 1591 int screenTop = getScrollY(); 1592 int screenBottom = screenTop + height; 1593 1594 int fadingEdge = getVerticalFadingEdgeLength(); 1595 1596 // leave room for top fading edge as long as rect isn't at very top 1597 if (rect.top > 0) { 1598 screenTop += fadingEdge; 1599 } 1600 1601 // leave room for bottom fading edge as long as rect isn't at very bottom 1602 if (rect.bottom < getChildAt(0).getHeight()) { 1603 screenBottom -= fadingEdge; 1604 } 1605 1606 int scrollYDelta = 0; 1607 1608 if (rect.bottom > screenBottom && rect.top > screenTop) { 1609 // need to move down to get it in view: move down just enough so 1610 // that the entire rectangle is in view (or at least the first 1611 // screen size chunk). 1612 1613 if (rect.height() > height) { 1614 // just enough to get screen size chunk on 1615 scrollYDelta += (rect.top - screenTop); 1616 } else { 1617 // get entire rect at bottom of screen 1618 scrollYDelta += (rect.bottom - screenBottom); 1619 } 1620 1621 // make sure we aren't scrolling beyond the end of our content 1622 int bottom = getChildAt(0).getBottom(); 1623 int distanceToBottom = bottom - screenBottom; 1624 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1625 1626 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1627 // need to move up to get it in view: move up just enough so that 1628 // entire rectangle is in view (or at least the first screen 1629 // size chunk of it). 1630 1631 if (rect.height() > height) { 1632 // screen size chunk 1633 scrollYDelta -= (screenBottom - rect.bottom); 1634 } else { 1635 // entire rect at top 1636 scrollYDelta -= (screenTop - rect.top); 1637 } 1638 1639 // make sure we aren't scrolling any further than the top our content 1640 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1641 } 1642 return scrollYDelta; 1643 } 1644 1645 @Override 1646 public void requestChildFocus(View child, View focused) { 1647 if (!mIsLayoutDirty) { 1648 scrollToChild(focused); 1649 } else { 1650 // The child may not be laid out yet, we can't compute the scroll yet 1651 mChildToScrollTo = focused; 1652 } 1653 super.requestChildFocus(child, focused); 1654 } 1655 1656 1657 /** 1658 * When looking for focus in children of a scroll view, need to be a little 1659 * more careful not to give focus to something that is scrolled off screen. 1660 * 1661 * This is more expensive than the default {@link android.view.ViewGroup} 1662 * implementation, otherwise this behavior might have been made the default. 1663 */ 1664 @Override 1665 protected boolean onRequestFocusInDescendants(int direction, 1666 Rect previouslyFocusedRect) { 1667 1668 // convert from forward / backward notation to up / down / left / right 1669 // (ugh). 1670 if (direction == View.FOCUS_FORWARD) { 1671 direction = View.FOCUS_DOWN; 1672 } else if (direction == View.FOCUS_BACKWARD) { 1673 direction = View.FOCUS_UP; 1674 } 1675 1676 final View nextFocus = previouslyFocusedRect == null 1677 ? FocusFinder.getInstance().findNextFocus(this, null, direction) 1678 : FocusFinder.getInstance().findNextFocusFromRect( 1679 this, previouslyFocusedRect, direction); 1680 1681 if (nextFocus == null) { 1682 return false; 1683 } 1684 1685 if (isOffScreen(nextFocus)) { 1686 return false; 1687 } 1688 1689 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1690 } 1691 1692 @Override 1693 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1694 boolean immediate) { 1695 // offset into coordinate space of this scroll view 1696 rectangle.offset(child.getLeft() - child.getScrollX(), 1697 child.getTop() - child.getScrollY()); 1698 1699 return scrollToChildRect(rectangle, immediate); 1700 } 1701 1702 @Override 1703 public void requestLayout() { 1704 mIsLayoutDirty = true; 1705 super.requestLayout(); 1706 } 1707 1708 @Override 1709 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1710 super.onLayout(changed, l, t, r, b); 1711 mIsLayoutDirty = false; 1712 // Give a child focus if it needs it 1713 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1714 scrollToChild(mChildToScrollTo); 1715 } 1716 mChildToScrollTo = null; 1717 1718 if (!mIsLaidOut) { 1719 if (mSavedState != null) { 1720 scrollTo(getScrollX(), mSavedState.scrollPosition); 1721 mSavedState = null; 1722 } // mScrollY default value is "0" 1723 1724 final int childHeight = (getChildCount() > 0) ? getChildAt(0).getMeasuredHeight() : 0; 1725 final int scrollRange = Math.max(0, 1726 childHeight - (b - t - getPaddingBottom() - getPaddingTop())); 1727 1728 // Don't forget to clamp 1729 if (getScrollY() > scrollRange) { 1730 scrollTo(getScrollX(), scrollRange); 1731 } else if (getScrollY() < 0) { 1732 scrollTo(getScrollX(), 0); 1733 } 1734 } 1735 1736 // Calling this with the present values causes it to re-claim them 1737 scrollTo(getScrollX(), getScrollY()); 1738 mIsLaidOut = true; 1739 } 1740 1741 @Override 1742 public void onAttachedToWindow() { 1743 super.onAttachedToWindow(); 1744 1745 mIsLaidOut = false; 1746 } 1747 1748 @Override 1749 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1750 super.onSizeChanged(w, h, oldw, oldh); 1751 1752 View currentFocused = findFocus(); 1753 if (null == currentFocused || this == currentFocused) { 1754 return; 1755 } 1756 1757 // If the currently-focused view was visible on the screen when the 1758 // screen was at the old height, then scroll the screen to make that 1759 // view visible with the new screen height. 1760 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1761 currentFocused.getDrawingRect(mTempRect); 1762 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1763 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1764 doScrollY(scrollDelta); 1765 } 1766 } 1767 1768 /** 1769 * Return true if child is a descendant of parent, (or equal to the parent). 1770 */ 1771 private static boolean isViewDescendantOf(View child, View parent) { 1772 if (child == parent) { 1773 return true; 1774 } 1775 1776 final ViewParent theParent = child.getParent(); 1777 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1778 } 1779 1780 /** 1781 * Fling the scroll view 1782 * 1783 * @param velocityY The initial velocity in the Y direction. Positive 1784 * numbers mean that the finger/cursor is moving down the screen, 1785 * which means we want to scroll towards the top. 1786 */ 1787 public void fling(int velocityY) { 1788 if (getChildCount() > 0) { 1789 startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL, ViewCompat.TYPE_NON_TOUCH); 1790 mScroller.fling(getScrollX(), getScrollY(), // start 1791 0, velocityY, // velocities 1792 0, 0, // x 1793 Integer.MIN_VALUE, Integer.MAX_VALUE, // y 1794 0, 0); // overscroll 1795 mLastScrollerY = getScrollY(); 1796 ViewCompat.postInvalidateOnAnimation(this); 1797 } 1798 } 1799 1800 private void flingWithNestedDispatch(int velocityY) { 1801 final int scrollY = getScrollY(); 1802 final boolean canFling = (scrollY > 0 || velocityY > 0) 1803 && (scrollY < getScrollRange() || velocityY < 0); 1804 if (!dispatchNestedPreFling(0, velocityY)) { 1805 dispatchNestedFling(0, velocityY, canFling); 1806 fling(velocityY); 1807 } 1808 } 1809 1810 private void endDrag() { 1811 mIsBeingDragged = false; 1812 1813 recycleVelocityTracker(); 1814 stopNestedScroll(ViewCompat.TYPE_TOUCH); 1815 1816 if (mEdgeGlowTop != null) { 1817 mEdgeGlowTop.onRelease(); 1818 mEdgeGlowBottom.onRelease(); 1819 } 1820 } 1821 1822 /** 1823 * {@inheritDoc} 1824 * 1825 * <p>This version also clamps the scrolling to the bounds of our child. 1826 */ 1827 @Override 1828 public void scrollTo(int x, int y) { 1829 // we rely on the fact the View.scrollBy calls scrollTo. 1830 if (getChildCount() > 0) { 1831 View child = getChildAt(0); 1832 x = clamp(x, getWidth() - getPaddingRight() - getPaddingLeft(), child.getWidth()); 1833 y = clamp(y, getHeight() - getPaddingBottom() - getPaddingTop(), child.getHeight()); 1834 if (x != getScrollX() || y != getScrollY()) { 1835 super.scrollTo(x, y); 1836 } 1837 } 1838 } 1839 1840 private void ensureGlows() { 1841 if (getOverScrollMode() != View.OVER_SCROLL_NEVER) { 1842 if (mEdgeGlowTop == null) { 1843 Context context = getContext(); 1844 mEdgeGlowTop = new EdgeEffect(context); 1845 mEdgeGlowBottom = new EdgeEffect(context); 1846 } 1847 } else { 1848 mEdgeGlowTop = null; 1849 mEdgeGlowBottom = null; 1850 } 1851 } 1852 1853 @Override 1854 public void draw(Canvas canvas) { 1855 super.draw(canvas); 1856 if (mEdgeGlowTop != null) { 1857 final int scrollY = getScrollY(); 1858 if (!mEdgeGlowTop.isFinished()) { 1859 final int restoreCount = canvas.save(); 1860 int width = getWidth(); 1861 int height = getHeight(); 1862 int xTranslation = 0; 1863 int yTranslation = Math.min(0, scrollY); 1864 if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP || getClipToPadding()) { 1865 width -= getPaddingLeft() + getPaddingRight(); 1866 xTranslation += getPaddingLeft(); 1867 } 1868 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && getClipToPadding()) { 1869 height -= getPaddingTop() + getPaddingBottom(); 1870 yTranslation += getPaddingTop(); 1871 } 1872 canvas.translate(xTranslation, yTranslation); 1873 mEdgeGlowTop.setSize(width, height); 1874 if (mEdgeGlowTop.draw(canvas)) { 1875 ViewCompat.postInvalidateOnAnimation(this); 1876 } 1877 canvas.restoreToCount(restoreCount); 1878 } 1879 if (!mEdgeGlowBottom.isFinished()) { 1880 final int restoreCount = canvas.save(); 1881 int width = getWidth(); 1882 int height = getHeight(); 1883 int xTranslation = 0; 1884 int yTranslation = Math.max(getScrollRange(), scrollY) + height; 1885 if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP || getClipToPadding()) { 1886 width -= getPaddingLeft() + getPaddingRight(); 1887 xTranslation += getPaddingLeft(); 1888 } 1889 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && getClipToPadding()) { 1890 height -= getPaddingTop() + getPaddingBottom(); 1891 yTranslation -= getPaddingBottom(); 1892 } 1893 canvas.translate(xTranslation - width, yTranslation); 1894 canvas.rotate(180, width, 0); 1895 mEdgeGlowBottom.setSize(width, height); 1896 if (mEdgeGlowBottom.draw(canvas)) { 1897 ViewCompat.postInvalidateOnAnimation(this); 1898 } 1899 canvas.restoreToCount(restoreCount); 1900 } 1901 } 1902 } 1903 1904 private static int clamp(int n, int my, int child) { 1905 if (my >= child || n < 0) { 1906 /* my >= child is this case: 1907 * |--------------- me ---------------| 1908 * |------ child ------| 1909 * or 1910 * |--------------- me ---------------| 1911 * |------ child ------| 1912 * or 1913 * |--------------- me ---------------| 1914 * |------ child ------| 1915 * 1916 * n < 0 is this case: 1917 * |------ me ------| 1918 * |-------- child --------| 1919 * |-- mScrollX --| 1920 */ 1921 return 0; 1922 } 1923 if ((my + n) > child) { 1924 /* this case: 1925 * |------ me ------| 1926 * |------ child ------| 1927 * |-- mScrollX --| 1928 */ 1929 return child - my; 1930 } 1931 return n; 1932 } 1933 1934 @Override 1935 protected void onRestoreInstanceState(Parcelable state) { 1936 if (!(state instanceof SavedState)) { 1937 super.onRestoreInstanceState(state); 1938 return; 1939 } 1940 1941 SavedState ss = (SavedState) state; 1942 super.onRestoreInstanceState(ss.getSuperState()); 1943 mSavedState = ss; 1944 requestLayout(); 1945 } 1946 1947 @Override 1948 protected Parcelable onSaveInstanceState() { 1949 Parcelable superState = super.onSaveInstanceState(); 1950 SavedState ss = new SavedState(superState); 1951 ss.scrollPosition = getScrollY(); 1952 return ss; 1953 } 1954 1955 static class SavedState extends BaseSavedState { 1956 public int scrollPosition; 1957 1958 SavedState(Parcelable superState) { 1959 super(superState); 1960 } 1961 1962 SavedState(Parcel source) { 1963 super(source); 1964 scrollPosition = source.readInt(); 1965 } 1966 1967 @Override 1968 public void writeToParcel(Parcel dest, int flags) { 1969 super.writeToParcel(dest, flags); 1970 dest.writeInt(scrollPosition); 1971 } 1972 1973 @Override 1974 public String toString() { 1975 return "HorizontalScrollView.SavedState{" 1976 + Integer.toHexString(System.identityHashCode(this)) 1977 + " scrollPosition=" + scrollPosition + "}"; 1978 } 1979 1980 public static final Parcelable.Creator<SavedState> CREATOR = 1981 new Parcelable.Creator<SavedState>() { 1982 @Override 1983 public SavedState createFromParcel(Parcel in) { 1984 return new SavedState(in); 1985 } 1986 1987 @Override 1988 public SavedState[] newArray(int size) { 1989 return new SavedState[size]; 1990 } 1991 }; 1992 } 1993 1994 static class AccessibilityDelegate extends AccessibilityDelegateCompat { 1995 @Override 1996 public boolean performAccessibilityAction(View host, int action, Bundle arguments) { 1997 if (super.performAccessibilityAction(host, action, arguments)) { 1998 return true; 1999 } 2000 final NestedScrollView nsvHost = (NestedScrollView) host; 2001 if (!nsvHost.isEnabled()) { 2002 return false; 2003 } 2004 switch (action) { 2005 case AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD: { 2006 final int viewportHeight = nsvHost.getHeight() - nsvHost.getPaddingBottom() 2007 - nsvHost.getPaddingTop(); 2008 final int targetScrollY = Math.min(nsvHost.getScrollY() + viewportHeight, 2009 nsvHost.getScrollRange()); 2010 if (targetScrollY != nsvHost.getScrollY()) { 2011 nsvHost.smoothScrollTo(0, targetScrollY); 2012 return true; 2013 } 2014 } 2015 return false; 2016 case AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD: { 2017 final int viewportHeight = nsvHost.getHeight() - nsvHost.getPaddingBottom() 2018 - nsvHost.getPaddingTop(); 2019 final int targetScrollY = Math.max(nsvHost.getScrollY() - viewportHeight, 0); 2020 if (targetScrollY != nsvHost.getScrollY()) { 2021 nsvHost.smoothScrollTo(0, targetScrollY); 2022 return true; 2023 } 2024 } 2025 return false; 2026 } 2027 return false; 2028 } 2029 2030 @Override 2031 public void onInitializeAccessibilityNodeInfo(View host, AccessibilityNodeInfoCompat info) { 2032 super.onInitializeAccessibilityNodeInfo(host, info); 2033 final NestedScrollView nsvHost = (NestedScrollView) host; 2034 info.setClassName(ScrollView.class.getName()); 2035 if (nsvHost.isEnabled()) { 2036 final int scrollRange = nsvHost.getScrollRange(); 2037 if (scrollRange > 0) { 2038 info.setScrollable(true); 2039 if (nsvHost.getScrollY() > 0) { 2040 info.addAction(AccessibilityNodeInfoCompat.ACTION_SCROLL_BACKWARD); 2041 } 2042 if (nsvHost.getScrollY() < scrollRange) { 2043 info.addAction(AccessibilityNodeInfoCompat.ACTION_SCROLL_FORWARD); 2044 } 2045 } 2046 } 2047 } 2048 2049 @Override 2050 public void onInitializeAccessibilityEvent(View host, AccessibilityEvent event) { 2051 super.onInitializeAccessibilityEvent(host, event); 2052 final NestedScrollView nsvHost = (NestedScrollView) host; 2053 event.setClassName(ScrollView.class.getName()); 2054 final boolean scrollable = nsvHost.getScrollRange() > 0; 2055 event.setScrollable(scrollable); 2056 event.setScrollX(nsvHost.getScrollX()); 2057 event.setScrollY(nsvHost.getScrollY()); 2058 AccessibilityRecordCompat.setMaxScrollX(event, nsvHost.getScrollX()); 2059 AccessibilityRecordCompat.setMaxScrollY(event, nsvHost.getScrollRange()); 2060 } 2061 } 2062} 2063