ScrollView.java revision e72cf7341a608402309ce894fc12d050cc7c0e14
1/* 2 * Copyright (C) 2006 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 17package android.widget; 18 19import com.android.internal.R; 20 21import android.content.Context; 22import android.content.res.TypedArray; 23import android.graphics.Canvas; 24import android.graphics.Rect; 25import android.os.StrictMode; 26import android.util.AttributeSet; 27import android.view.FocusFinder; 28import android.view.InputDevice; 29import android.view.KeyEvent; 30import android.view.MotionEvent; 31import android.view.VelocityTracker; 32import android.view.View; 33import android.view.ViewConfiguration; 34import android.view.ViewDebug; 35import android.view.ViewGroup; 36import android.view.ViewParent; 37import android.view.accessibility.AccessibilityEvent; 38import android.view.accessibility.AccessibilityNodeInfo; 39import android.view.animation.AnimationUtils; 40 41import java.util.List; 42 43/** 44 * Layout container for a view hierarchy that can be scrolled by the user, 45 * allowing it to be larger than the physical display. A ScrollView 46 * is a {@link FrameLayout}, meaning you should place one child in it 47 * containing the entire contents to scroll; this child may itself be a layout 48 * manager with a complex hierarchy of objects. A child that is often used 49 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 50 * array of top-level items that the user can scroll through. 51 * 52 * <p>The {@link TextView} class also 53 * takes care of its own scrolling, so does not require a ScrollView, but 54 * using the two together is possible to achieve the effect of a text view 55 * within a larger container. 56 * 57 * <p>ScrollView only supports vertical scrolling. 58 * 59 * @attr ref android.R.styleable#ScrollView_fillViewport 60 */ 61public class ScrollView extends FrameLayout { 62 static final int ANIMATED_SCROLL_GAP = 250; 63 64 static final float MAX_SCROLL_FACTOR = 0.5f; 65 66 private long mLastScroll; 67 68 private final Rect mTempRect = new Rect(); 69 private OverScroller mScroller; 70 private EdgeEffect mEdgeGlowTop; 71 private EdgeEffect mEdgeGlowBottom; 72 73 /** 74 * Position of the last motion event. 75 */ 76 private float mLastMotionY; 77 78 /** 79 * True when the layout has changed but the traversal has not come through yet. 80 * Ideally the view hierarchy would keep track of this for us. 81 */ 82 private boolean mIsLayoutDirty = true; 83 84 /** 85 * The child to give focus to in the event that a child has requested focus while the 86 * layout is dirty. This prevents the scroll from being wrong if the child has not been 87 * laid out before requesting focus. 88 */ 89 private View mChildToScrollTo = null; 90 91 /** 92 * True if the user is currently dragging this ScrollView around. This is 93 * not the same as 'is being flinged', which can be checked by 94 * mScroller.isFinished() (flinging begins when the user lifts his finger). 95 */ 96 private boolean mIsBeingDragged = false; 97 98 /** 99 * Determines speed during touch scrolling 100 */ 101 private VelocityTracker mVelocityTracker; 102 103 /** 104 * When set to true, the scroll view measure its child to make it fill the currently 105 * visible area. 106 */ 107 @ViewDebug.ExportedProperty(category = "layout") 108 private boolean mFillViewport; 109 110 /** 111 * Whether arrow scrolling is animated. 112 */ 113 private boolean mSmoothScrollingEnabled = true; 114 115 private int mTouchSlop; 116 private int mMinimumVelocity; 117 private int mMaximumVelocity; 118 119 private int mOverscrollDistance; 120 private int mOverflingDistance; 121 122 /** 123 * ID of the active pointer. This is used to retain consistency during 124 * drags/flings if multiple pointers are used. 125 */ 126 private int mActivePointerId = INVALID_POINTER; 127 128 /** 129 * The StrictMode "critical time span" objects to catch animation 130 * stutters. Non-null when a time-sensitive animation is 131 * in-flight. Must call finish() on them when done animating. 132 * These are no-ops on user builds. 133 */ 134 private StrictMode.Span mScrollStrictSpan = null; // aka "drag" 135 private StrictMode.Span mFlingStrictSpan = null; 136 137 /** 138 * Sentinel value for no current active pointer. 139 * Used by {@link #mActivePointerId}. 140 */ 141 private static final int INVALID_POINTER = -1; 142 143 public ScrollView(Context context) { 144 this(context, null); 145 } 146 147 public ScrollView(Context context, AttributeSet attrs) { 148 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 149 } 150 151 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 152 super(context, attrs, defStyle); 153 initScrollView(); 154 155 TypedArray a = 156 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 157 158 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 159 160 a.recycle(); 161 } 162 163 @Override 164 public boolean shouldDelayChildPressedState() { 165 return true; 166 } 167 168 @Override 169 protected float getTopFadingEdgeStrength() { 170 if (getChildCount() == 0) { 171 return 0.0f; 172 } 173 174 final int length = getVerticalFadingEdgeLength(); 175 if (mScrollY < length) { 176 return mScrollY / (float) length; 177 } 178 179 return 1.0f; 180 } 181 182 @Override 183 protected float getBottomFadingEdgeStrength() { 184 if (getChildCount() == 0) { 185 return 0.0f; 186 } 187 188 final int length = getVerticalFadingEdgeLength(); 189 final int bottomEdge = getHeight() - mPaddingBottom; 190 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 191 if (span < length) { 192 return span / (float) length; 193 } 194 195 return 1.0f; 196 } 197 198 /** 199 * @return The maximum amount this scroll view will scroll in response to 200 * an arrow event. 201 */ 202 public int getMaxScrollAmount() { 203 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 204 } 205 206 207 private void initScrollView() { 208 mScroller = new OverScroller(getContext()); 209 setFocusable(true); 210 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 211 setWillNotDraw(false); 212 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 213 mTouchSlop = configuration.getScaledTouchSlop(); 214 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 215 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 216 mOverscrollDistance = configuration.getScaledOverscrollDistance(); 217 mOverflingDistance = configuration.getScaledOverflingDistance(); 218 } 219 220 @Override 221 public void addView(View child) { 222 if (getChildCount() > 0) { 223 throw new IllegalStateException("ScrollView can host only one direct child"); 224 } 225 226 super.addView(child); 227 } 228 229 @Override 230 public void addView(View child, int index) { 231 if (getChildCount() > 0) { 232 throw new IllegalStateException("ScrollView can host only one direct child"); 233 } 234 235 super.addView(child, index); 236 } 237 238 @Override 239 public void addView(View child, ViewGroup.LayoutParams params) { 240 if (getChildCount() > 0) { 241 throw new IllegalStateException("ScrollView can host only one direct child"); 242 } 243 244 super.addView(child, params); 245 } 246 247 @Override 248 public void addView(View child, int index, ViewGroup.LayoutParams params) { 249 if (getChildCount() > 0) { 250 throw new IllegalStateException("ScrollView can host only one direct child"); 251 } 252 253 super.addView(child, index, params); 254 } 255 256 /** 257 * @return Returns true this ScrollView can be scrolled 258 */ 259 private boolean canScroll() { 260 View child = getChildAt(0); 261 if (child != null) { 262 int childHeight = child.getHeight(); 263 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 264 } 265 return false; 266 } 267 268 /** 269 * Indicates whether this ScrollView's content is stretched to fill the viewport. 270 * 271 * @return True if the content fills the viewport, false otherwise. 272 * 273 * @attr ref android.R.styleable#ScrollView_fillViewport 274 */ 275 public boolean isFillViewport() { 276 return mFillViewport; 277 } 278 279 /** 280 * Indicates this ScrollView whether it should stretch its content height to fill 281 * the viewport or not. 282 * 283 * @param fillViewport True to stretch the content's height to the viewport's 284 * boundaries, false otherwise. 285 * 286 * @attr ref android.R.styleable#ScrollView_fillViewport 287 */ 288 public void setFillViewport(boolean fillViewport) { 289 if (fillViewport != mFillViewport) { 290 mFillViewport = fillViewport; 291 requestLayout(); 292 } 293 } 294 295 /** 296 * @return Whether arrow scrolling will animate its transition. 297 */ 298 public boolean isSmoothScrollingEnabled() { 299 return mSmoothScrollingEnabled; 300 } 301 302 /** 303 * Set whether arrow scrolling will animate its transition. 304 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 305 */ 306 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 307 mSmoothScrollingEnabled = smoothScrollingEnabled; 308 } 309 310 @Override 311 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 312 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 313 314 if (!mFillViewport) { 315 return; 316 } 317 318 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 319 if (heightMode == MeasureSpec.UNSPECIFIED) { 320 return; 321 } 322 323 if (getChildCount() > 0) { 324 final View child = getChildAt(0); 325 int height = getMeasuredHeight(); 326 if (child.getMeasuredHeight() < height) { 327 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 328 329 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, 330 mPaddingLeft + mPaddingRight, lp.width); 331 height -= mPaddingTop; 332 height -= mPaddingBottom; 333 int childHeightMeasureSpec = 334 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 335 336 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 337 } 338 } 339 } 340 341 @Override 342 public boolean dispatchKeyEvent(KeyEvent event) { 343 // Let the focused view and/or our descendants get the key first 344 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 345 } 346 347 /** 348 * You can call this function yourself to have the scroll view perform 349 * scrolling from a key event, just as if the event had been dispatched to 350 * it by the view hierarchy. 351 * 352 * @param event The key event to execute. 353 * @return Return true if the event was handled, else false. 354 */ 355 public boolean executeKeyEvent(KeyEvent event) { 356 mTempRect.setEmpty(); 357 358 if (!canScroll()) { 359 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { 360 View currentFocused = findFocus(); 361 if (currentFocused == this) currentFocused = null; 362 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 363 currentFocused, View.FOCUS_DOWN); 364 return nextFocused != null 365 && nextFocused != this 366 && nextFocused.requestFocus(View.FOCUS_DOWN); 367 } 368 return false; 369 } 370 371 boolean handled = false; 372 if (event.getAction() == KeyEvent.ACTION_DOWN) { 373 switch (event.getKeyCode()) { 374 case KeyEvent.KEYCODE_DPAD_UP: 375 if (!event.isAltPressed()) { 376 handled = arrowScroll(View.FOCUS_UP); 377 } else { 378 handled = fullScroll(View.FOCUS_UP); 379 } 380 break; 381 case KeyEvent.KEYCODE_DPAD_DOWN: 382 if (!event.isAltPressed()) { 383 handled = arrowScroll(View.FOCUS_DOWN); 384 } else { 385 handled = fullScroll(View.FOCUS_DOWN); 386 } 387 break; 388 case KeyEvent.KEYCODE_SPACE: 389 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 390 break; 391 } 392 } 393 394 return handled; 395 } 396 397 private boolean inChild(int x, int y) { 398 if (getChildCount() > 0) { 399 final int scrollY = mScrollY; 400 final View child = getChildAt(0); 401 return !(y < child.getTop() - scrollY 402 || y >= child.getBottom() - scrollY 403 || x < child.getLeft() 404 || x >= child.getRight()); 405 } 406 return false; 407 } 408 409 private void initOrResetVelocityTracker() { 410 if (mVelocityTracker == null) { 411 mVelocityTracker = VelocityTracker.obtain(); 412 } else { 413 mVelocityTracker.clear(); 414 } 415 } 416 417 private void initVelocityTrackerIfNotExists() { 418 if (mVelocityTracker == null) { 419 mVelocityTracker = VelocityTracker.obtain(); 420 } 421 } 422 423 private void recycleVelocityTracker() { 424 if (mVelocityTracker != null) { 425 mVelocityTracker.recycle(); 426 mVelocityTracker = null; 427 } 428 } 429 430 @Override 431 public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) { 432 if (disallowIntercept) { 433 recycleVelocityTracker(); 434 } 435 super.requestDisallowInterceptTouchEvent(disallowIntercept); 436 } 437 438 439 @Override 440 public boolean onInterceptTouchEvent(MotionEvent ev) { 441 /* 442 * This method JUST determines whether we want to intercept the motion. 443 * If we return true, onMotionEvent will be called and we do the actual 444 * scrolling there. 445 */ 446 447 /* 448 * Shortcut the most recurring case: the user is in the dragging 449 * state and he is moving his finger. We want to intercept this 450 * motion. 451 */ 452 final int action = ev.getAction(); 453 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 454 return true; 455 } 456 457 switch (action & MotionEvent.ACTION_MASK) { 458 case MotionEvent.ACTION_MOVE: { 459 /* 460 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 461 * whether the user has moved far enough from his original down touch. 462 */ 463 464 /* 465 * Locally do absolute value. mLastMotionY is set to the y value 466 * of the down event. 467 */ 468 final int activePointerId = mActivePointerId; 469 if (activePointerId == INVALID_POINTER) { 470 // If we don't have a valid id, the touch down wasn't on content. 471 break; 472 } 473 474 final int pointerIndex = ev.findPointerIndex(activePointerId); 475 final float y = ev.getY(pointerIndex); 476 final int yDiff = (int) Math.abs(y - mLastMotionY); 477 if (yDiff > mTouchSlop) { 478 mIsBeingDragged = true; 479 mLastMotionY = y; 480 initVelocityTrackerIfNotExists(); 481 mVelocityTracker.addMovement(ev); 482 if (mScrollStrictSpan == null) { 483 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 484 } 485 } 486 break; 487 } 488 489 case MotionEvent.ACTION_DOWN: { 490 final float y = ev.getY(); 491 if (!inChild((int) ev.getX(), (int) y)) { 492 mIsBeingDragged = false; 493 recycleVelocityTracker(); 494 break; 495 } 496 497 /* 498 * Remember location of down touch. 499 * ACTION_DOWN always refers to pointer index 0. 500 */ 501 mLastMotionY = y; 502 mActivePointerId = ev.getPointerId(0); 503 504 initOrResetVelocityTracker(); 505 mVelocityTracker.addMovement(ev); 506 /* 507 * If being flinged and user touches the screen, initiate drag; 508 * otherwise don't. mScroller.isFinished should be false when 509 * being flinged. 510 */ 511 mIsBeingDragged = !mScroller.isFinished(); 512 if (mIsBeingDragged && mScrollStrictSpan == null) { 513 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 514 } 515 break; 516 } 517 518 case MotionEvent.ACTION_CANCEL: 519 case MotionEvent.ACTION_UP: 520 /* Release the drag */ 521 mIsBeingDragged = false; 522 mActivePointerId = INVALID_POINTER; 523 recycleVelocityTracker(); 524 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 525 invalidate(); 526 } 527 break; 528 case MotionEvent.ACTION_POINTER_UP: 529 onSecondaryPointerUp(ev); 530 break; 531 } 532 533 /* 534 * The only time we want to intercept motion events is if we are in the 535 * drag mode. 536 */ 537 return mIsBeingDragged; 538 } 539 540 @Override 541 public boolean onTouchEvent(MotionEvent ev) { 542 initVelocityTrackerIfNotExists(); 543 mVelocityTracker.addMovement(ev); 544 545 final int action = ev.getAction(); 546 547 switch (action & MotionEvent.ACTION_MASK) { 548 case MotionEvent.ACTION_DOWN: { 549 mIsBeingDragged = getChildCount() != 0; 550 if (!mIsBeingDragged) { 551 return false; 552 } 553 554 /* 555 * If being flinged and user touches, stop the fling. isFinished 556 * will be false if being flinged. 557 */ 558 if (!mScroller.isFinished()) { 559 mScroller.abortAnimation(); 560 if (mFlingStrictSpan != null) { 561 mFlingStrictSpan.finish(); 562 mFlingStrictSpan = null; 563 } 564 } 565 566 // Remember where the motion event started 567 mLastMotionY = ev.getY(); 568 mActivePointerId = ev.getPointerId(0); 569 break; 570 } 571 case MotionEvent.ACTION_MOVE: 572 if (mIsBeingDragged) { 573 // Scroll to follow the motion event 574 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 575 final float y = ev.getY(activePointerIndex); 576 final int deltaY = (int) (mLastMotionY - y); 577 mLastMotionY = y; 578 579 final int oldX = mScrollX; 580 final int oldY = mScrollY; 581 final int range = getScrollRange(); 582 final int overscrollMode = getOverScrollMode(); 583 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || 584 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 585 586 if (overScrollBy(0, deltaY, 0, mScrollY, 587 0, range, 0, mOverscrollDistance, true)) { 588 // Break our velocity if we hit a scroll barrier. 589 mVelocityTracker.clear(); 590 } 591 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 592 593 if (canOverscroll) { 594 final int pulledToY = oldY + deltaY; 595 if (pulledToY < 0) { 596 mEdgeGlowTop.onPull((float) deltaY / getHeight()); 597 if (!mEdgeGlowBottom.isFinished()) { 598 mEdgeGlowBottom.onRelease(); 599 } 600 } else if (pulledToY > range) { 601 mEdgeGlowBottom.onPull((float) deltaY / getHeight()); 602 if (!mEdgeGlowTop.isFinished()) { 603 mEdgeGlowTop.onRelease(); 604 } 605 } 606 if (mEdgeGlowTop != null 607 && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) { 608 invalidate(); 609 } 610 } 611 } 612 break; 613 case MotionEvent.ACTION_UP: 614 if (mIsBeingDragged) { 615 final VelocityTracker velocityTracker = mVelocityTracker; 616 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 617 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 618 619 if (getChildCount() > 0) { 620 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 621 fling(-initialVelocity); 622 } else { 623 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, 624 getScrollRange())) { 625 invalidate(); 626 } 627 } 628 } 629 630 mActivePointerId = INVALID_POINTER; 631 endDrag(); 632 } 633 break; 634 case MotionEvent.ACTION_CANCEL: 635 if (mIsBeingDragged && getChildCount() > 0) { 636 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 637 invalidate(); 638 } 639 mActivePointerId = INVALID_POINTER; 640 endDrag(); 641 } 642 break; 643 case MotionEvent.ACTION_POINTER_DOWN: { 644 final int index = ev.getActionIndex(); 645 mLastMotionY = ev.getY(index); 646 mActivePointerId = ev.getPointerId(index); 647 break; 648 } 649 case MotionEvent.ACTION_POINTER_UP: 650 onSecondaryPointerUp(ev); 651 mLastMotionY = ev.getY(ev.findPointerIndex(mActivePointerId)); 652 break; 653 } 654 return true; 655 } 656 657 private void onSecondaryPointerUp(MotionEvent ev) { 658 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 659 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 660 final int pointerId = ev.getPointerId(pointerIndex); 661 if (pointerId == mActivePointerId) { 662 // This was our active pointer going up. Choose a new 663 // active pointer and adjust accordingly. 664 // TODO: Make this decision more intelligent. 665 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 666 mLastMotionY = ev.getY(newPointerIndex); 667 mActivePointerId = ev.getPointerId(newPointerIndex); 668 if (mVelocityTracker != null) { 669 mVelocityTracker.clear(); 670 } 671 } 672 } 673 674 @Override 675 public boolean onGenericMotionEvent(MotionEvent event) { 676 if ((event.getSource() & InputDevice.SOURCE_CLASS_POINTER) != 0) { 677 switch (event.getAction()) { 678 case MotionEvent.ACTION_SCROLL: { 679 if (!mIsBeingDragged) { 680 final float vscroll = event.getAxisValue(MotionEvent.AXIS_VSCROLL); 681 if (vscroll != 0) { 682 final int delta = (int) (vscroll * getVerticalScrollFactor()); 683 final int range = getScrollRange(); 684 int oldScrollY = mScrollY; 685 int newScrollY = oldScrollY - delta; 686 if (newScrollY < 0) { 687 newScrollY = 0; 688 } else if (newScrollY > range) { 689 newScrollY = range; 690 } 691 if (newScrollY != oldScrollY) { 692 super.scrollTo(mScrollX, newScrollY); 693 return true; 694 } 695 } 696 } 697 } 698 } 699 } 700 return super.onGenericMotionEvent(event); 701 } 702 703 @Override 704 protected void onOverScrolled(int scrollX, int scrollY, 705 boolean clampedX, boolean clampedY) { 706 // Treat animating scrolls differently; see #computeScroll() for why. 707 if (!mScroller.isFinished()) { 708 mScrollX = scrollX; 709 mScrollY = scrollY; 710 invalidateParentIfNeeded(); 711 if (clampedY) { 712 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 713 } 714 } else { 715 super.scrollTo(scrollX, scrollY); 716 } 717 718 awakenScrollBars(); 719 } 720 721 @Override 722 public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) { 723 super.onInitializeAccessibilityNodeInfo(info); 724 info.setClassName(ScrollView.class.getName()); 725 info.setScrollable(getScrollRange() > 0); 726 } 727 728 @Override 729 public void onInitializeAccessibilityEvent(AccessibilityEvent event) { 730 super.onInitializeAccessibilityEvent(event); 731 event.setClassName(ScrollView.class.getName()); 732 final boolean scrollable = getScrollRange() > 0; 733 event.setScrollable(scrollable); 734 event.setScrollX(mScrollX); 735 event.setScrollY(mScrollY); 736 event.setMaxScrollX(mScrollX); 737 event.setMaxScrollY(getScrollRange()); 738 } 739 740 private int getScrollRange() { 741 int scrollRange = 0; 742 if (getChildCount() > 0) { 743 View child = getChildAt(0); 744 scrollRange = Math.max(0, 745 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); 746 } 747 return scrollRange; 748 } 749 750 /** 751 * <p> 752 * Finds the next focusable component that fits in the specified bounds. 753 * </p> 754 * 755 * @param topFocus look for a candidate is the one at the top of the bounds 756 * if topFocus is true, or at the bottom of the bounds if topFocus is 757 * false 758 * @param top the top offset of the bounds in which a focusable must be 759 * found 760 * @param bottom the bottom offset of the bounds in which a focusable must 761 * be found 762 * @return the next focusable component in the bounds or null if none can 763 * be found 764 */ 765 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 766 767 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 768 View focusCandidate = null; 769 770 /* 771 * A fully contained focusable is one where its top is below the bound's 772 * top, and its bottom is above the bound's bottom. A partially 773 * contained focusable is one where some part of it is within the 774 * bounds, but it also has some part that is not within bounds. A fully contained 775 * focusable is preferred to a partially contained focusable. 776 */ 777 boolean foundFullyContainedFocusable = false; 778 779 int count = focusables.size(); 780 for (int i = 0; i < count; i++) { 781 View view = focusables.get(i); 782 int viewTop = view.getTop(); 783 int viewBottom = view.getBottom(); 784 785 if (top < viewBottom && viewTop < bottom) { 786 /* 787 * the focusable is in the target area, it is a candidate for 788 * focusing 789 */ 790 791 final boolean viewIsFullyContained = (top < viewTop) && 792 (viewBottom < bottom); 793 794 if (focusCandidate == null) { 795 /* No candidate, take this one */ 796 focusCandidate = view; 797 foundFullyContainedFocusable = viewIsFullyContained; 798 } else { 799 final boolean viewIsCloserToBoundary = 800 (topFocus && viewTop < focusCandidate.getTop()) || 801 (!topFocus && viewBottom > focusCandidate 802 .getBottom()); 803 804 if (foundFullyContainedFocusable) { 805 if (viewIsFullyContained && viewIsCloserToBoundary) { 806 /* 807 * We're dealing with only fully contained views, so 808 * it has to be closer to the boundary to beat our 809 * candidate 810 */ 811 focusCandidate = view; 812 } 813 } else { 814 if (viewIsFullyContained) { 815 /* Any fully contained view beats a partially contained view */ 816 focusCandidate = view; 817 foundFullyContainedFocusable = true; 818 } else if (viewIsCloserToBoundary) { 819 /* 820 * Partially contained view beats another partially 821 * contained view if it's closer 822 */ 823 focusCandidate = view; 824 } 825 } 826 } 827 } 828 } 829 830 return focusCandidate; 831 } 832 833 /** 834 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 835 * method will scroll the view by one page up or down and give the focus 836 * to the topmost/bottommost component in the new visible area. If no 837 * component is a good candidate for focus, this scrollview reclaims the 838 * focus.</p> 839 * 840 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 841 * to go one page up or 842 * {@link android.view.View#FOCUS_DOWN} to go one page down 843 * @return true if the key event is consumed by this method, false otherwise 844 */ 845 public boolean pageScroll(int direction) { 846 boolean down = direction == View.FOCUS_DOWN; 847 int height = getHeight(); 848 849 if (down) { 850 mTempRect.top = getScrollY() + height; 851 int count = getChildCount(); 852 if (count > 0) { 853 View view = getChildAt(count - 1); 854 if (mTempRect.top + height > view.getBottom()) { 855 mTempRect.top = view.getBottom() - height; 856 } 857 } 858 } else { 859 mTempRect.top = getScrollY() - height; 860 if (mTempRect.top < 0) { 861 mTempRect.top = 0; 862 } 863 } 864 mTempRect.bottom = mTempRect.top + height; 865 866 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 867 } 868 869 /** 870 * <p>Handles scrolling in response to a "home/end" shortcut press. This 871 * method will scroll the view to the top or bottom and give the focus 872 * to the topmost/bottommost component in the new visible area. If no 873 * component is a good candidate for focus, this scrollview reclaims the 874 * focus.</p> 875 * 876 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 877 * to go the top of the view or 878 * {@link android.view.View#FOCUS_DOWN} to go the bottom 879 * @return true if the key event is consumed by this method, false otherwise 880 */ 881 public boolean fullScroll(int direction) { 882 boolean down = direction == View.FOCUS_DOWN; 883 int height = getHeight(); 884 885 mTempRect.top = 0; 886 mTempRect.bottom = height; 887 888 if (down) { 889 int count = getChildCount(); 890 if (count > 0) { 891 View view = getChildAt(count - 1); 892 mTempRect.bottom = view.getBottom() + mPaddingBottom; 893 mTempRect.top = mTempRect.bottom - height; 894 } 895 } 896 897 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 898 } 899 900 /** 901 * <p>Scrolls the view to make the area defined by <code>top</code> and 902 * <code>bottom</code> visible. This method attempts to give the focus 903 * to a component visible in this area. If no component can be focused in 904 * the new visible area, the focus is reclaimed by this ScrollView.</p> 905 * 906 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 907 * to go upward, {@link android.view.View#FOCUS_DOWN} to downward 908 * @param top the top offset of the new area to be made visible 909 * @param bottom the bottom offset of the new area to be made visible 910 * @return true if the key event is consumed by this method, false otherwise 911 */ 912 private boolean scrollAndFocus(int direction, int top, int bottom) { 913 boolean handled = true; 914 915 int height = getHeight(); 916 int containerTop = getScrollY(); 917 int containerBottom = containerTop + height; 918 boolean up = direction == View.FOCUS_UP; 919 920 View newFocused = findFocusableViewInBounds(up, top, bottom); 921 if (newFocused == null) { 922 newFocused = this; 923 } 924 925 if (top >= containerTop && bottom <= containerBottom) { 926 handled = false; 927 } else { 928 int delta = up ? (top - containerTop) : (bottom - containerBottom); 929 doScrollY(delta); 930 } 931 932 if (newFocused != findFocus()) newFocused.requestFocus(direction); 933 934 return handled; 935 } 936 937 /** 938 * Handle scrolling in response to an up or down arrow click. 939 * 940 * @param direction The direction corresponding to the arrow key that was 941 * pressed 942 * @return True if we consumed the event, false otherwise 943 */ 944 public boolean arrowScroll(int direction) { 945 946 View currentFocused = findFocus(); 947 if (currentFocused == this) currentFocused = null; 948 949 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 950 951 final int maxJump = getMaxScrollAmount(); 952 953 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 954 nextFocused.getDrawingRect(mTempRect); 955 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 956 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 957 doScrollY(scrollDelta); 958 nextFocused.requestFocus(direction); 959 } else { 960 // no new focus 961 int scrollDelta = maxJump; 962 963 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 964 scrollDelta = getScrollY(); 965 } else if (direction == View.FOCUS_DOWN) { 966 if (getChildCount() > 0) { 967 int daBottom = getChildAt(0).getBottom(); 968 int screenBottom = getScrollY() + getHeight() - mPaddingBottom; 969 if (daBottom - screenBottom < maxJump) { 970 scrollDelta = daBottom - screenBottom; 971 } 972 } 973 } 974 if (scrollDelta == 0) { 975 return false; 976 } 977 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 978 } 979 980 if (currentFocused != null && currentFocused.isFocused() 981 && isOffScreen(currentFocused)) { 982 // previously focused item still has focus and is off screen, give 983 // it up (take it back to ourselves) 984 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 985 // sure to 986 // get it) 987 final int descendantFocusability = getDescendantFocusability(); // save 988 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 989 requestFocus(); 990 setDescendantFocusability(descendantFocusability); // restore 991 } 992 return true; 993 } 994 995 /** 996 * @return whether the descendant of this scroll view is scrolled off 997 * screen. 998 */ 999 private boolean isOffScreen(View descendant) { 1000 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 1001 } 1002 1003 /** 1004 * @return whether the descendant of this scroll view is within delta 1005 * pixels of being on the screen. 1006 */ 1007 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 1008 descendant.getDrawingRect(mTempRect); 1009 offsetDescendantRectToMyCoords(descendant, mTempRect); 1010 1011 return (mTempRect.bottom + delta) >= getScrollY() 1012 && (mTempRect.top - delta) <= (getScrollY() + height); 1013 } 1014 1015 /** 1016 * Smooth scroll by a Y delta 1017 * 1018 * @param delta the number of pixels to scroll by on the Y axis 1019 */ 1020 private void doScrollY(int delta) { 1021 if (delta != 0) { 1022 if (mSmoothScrollingEnabled) { 1023 smoothScrollBy(0, delta); 1024 } else { 1025 scrollBy(0, delta); 1026 } 1027 } 1028 } 1029 1030 /** 1031 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 1032 * 1033 * @param dx the number of pixels to scroll by on the X axis 1034 * @param dy the number of pixels to scroll by on the Y axis 1035 */ 1036 public final void smoothScrollBy(int dx, int dy) { 1037 if (getChildCount() == 0) { 1038 // Nothing to do. 1039 return; 1040 } 1041 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 1042 if (duration > ANIMATED_SCROLL_GAP) { 1043 final int height = getHeight() - mPaddingBottom - mPaddingTop; 1044 final int bottom = getChildAt(0).getHeight(); 1045 final int maxY = Math.max(0, bottom - height); 1046 final int scrollY = mScrollY; 1047 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 1048 1049 mScroller.startScroll(mScrollX, scrollY, 0, dy); 1050 invalidate(); 1051 } else { 1052 if (!mScroller.isFinished()) { 1053 mScroller.abortAnimation(); 1054 if (mFlingStrictSpan != null) { 1055 mFlingStrictSpan.finish(); 1056 mFlingStrictSpan = null; 1057 } 1058 } 1059 scrollBy(dx, dy); 1060 } 1061 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1062 } 1063 1064 /** 1065 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1066 * 1067 * @param x the position where to scroll on the X axis 1068 * @param y the position where to scroll on the Y axis 1069 */ 1070 public final void smoothScrollTo(int x, int y) { 1071 smoothScrollBy(x - mScrollX, y - mScrollY); 1072 } 1073 1074 /** 1075 * <p>The scroll range of a scroll view is the overall height of all of its 1076 * children.</p> 1077 */ 1078 @Override 1079 protected int computeVerticalScrollRange() { 1080 final int count = getChildCount(); 1081 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1082 if (count == 0) { 1083 return contentHeight; 1084 } 1085 1086 int scrollRange = getChildAt(0).getBottom(); 1087 final int scrollY = mScrollY; 1088 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1089 if (scrollY < 0) { 1090 scrollRange -= scrollY; 1091 } else if (scrollY > overscrollBottom) { 1092 scrollRange += scrollY - overscrollBottom; 1093 } 1094 1095 return scrollRange; 1096 } 1097 1098 @Override 1099 protected int computeVerticalScrollOffset() { 1100 return Math.max(0, super.computeVerticalScrollOffset()); 1101 } 1102 1103 @Override 1104 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1105 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1106 1107 int childWidthMeasureSpec; 1108 int childHeightMeasureSpec; 1109 1110 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1111 + mPaddingRight, lp.width); 1112 1113 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1114 1115 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1116 } 1117 1118 @Override 1119 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1120 int parentHeightMeasureSpec, int heightUsed) { 1121 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1122 1123 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1124 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1125 + widthUsed, lp.width); 1126 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1127 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1128 1129 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1130 } 1131 1132 @Override 1133 public void computeScroll() { 1134 if (mScroller.computeScrollOffset()) { 1135 // This is called at drawing time by ViewGroup. We don't want to 1136 // re-show the scrollbars at this point, which scrollTo will do, 1137 // so we replicate most of scrollTo here. 1138 // 1139 // It's a little odd to call onScrollChanged from inside the drawing. 1140 // 1141 // It is, except when you remember that computeScroll() is used to 1142 // animate scrolling. So unless we want to defer the onScrollChanged() 1143 // until the end of the animated scrolling, we don't really have a 1144 // choice here. 1145 // 1146 // I agree. The alternative, which I think would be worse, is to post 1147 // something and tell the subclasses later. This is bad because there 1148 // will be a window where mScrollX/Y is different from what the app 1149 // thinks it is. 1150 // 1151 int oldX = mScrollX; 1152 int oldY = mScrollY; 1153 int x = mScroller.getCurrX(); 1154 int y = mScroller.getCurrY(); 1155 1156 if (oldX != x || oldY != y) { 1157 final int range = getScrollRange(); 1158 final int overscrollMode = getOverScrollMode(); 1159 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || 1160 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 1161 1162 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, range, 1163 0, mOverflingDistance, false); 1164 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1165 1166 if (canOverscroll) { 1167 if (y < 0 && oldY >= 0) { 1168 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1169 } else if (y > range && oldY <= range) { 1170 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1171 } 1172 } 1173 } 1174 1175 if (!awakenScrollBars()) { 1176 // Keep on drawing until the animation has finished. 1177 invalidate(); 1178 } 1179 } else { 1180 if (mFlingStrictSpan != null) { 1181 mFlingStrictSpan.finish(); 1182 mFlingStrictSpan = null; 1183 } 1184 } 1185 } 1186 1187 /** 1188 * Scrolls the view to the given child. 1189 * 1190 * @param child the View to scroll to 1191 */ 1192 private void scrollToChild(View child) { 1193 child.getDrawingRect(mTempRect); 1194 1195 /* Offset from child's local coordinates to ScrollView coordinates */ 1196 offsetDescendantRectToMyCoords(child, mTempRect); 1197 1198 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1199 1200 if (scrollDelta != 0) { 1201 scrollBy(0, scrollDelta); 1202 } 1203 } 1204 1205 /** 1206 * If rect is off screen, scroll just enough to get it (or at least the 1207 * first screen size chunk of it) on screen. 1208 * 1209 * @param rect The rectangle. 1210 * @param immediate True to scroll immediately without animation 1211 * @return true if scrolling was performed 1212 */ 1213 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1214 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1215 final boolean scroll = delta != 0; 1216 if (scroll) { 1217 if (immediate) { 1218 scrollBy(0, delta); 1219 } else { 1220 smoothScrollBy(0, delta); 1221 } 1222 } 1223 return scroll; 1224 } 1225 1226 /** 1227 * Compute the amount to scroll in the Y direction in order to get 1228 * a rectangle completely on the screen (or, if taller than the screen, 1229 * at least the first screen size chunk of it). 1230 * 1231 * @param rect The rect. 1232 * @return The scroll delta. 1233 */ 1234 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1235 if (getChildCount() == 0) return 0; 1236 1237 int height = getHeight(); 1238 int screenTop = getScrollY(); 1239 int screenBottom = screenTop + height; 1240 1241 int fadingEdge = getVerticalFadingEdgeLength(); 1242 1243 // leave room for top fading edge as long as rect isn't at very top 1244 if (rect.top > 0) { 1245 screenTop += fadingEdge; 1246 } 1247 1248 // leave room for bottom fading edge as long as rect isn't at very bottom 1249 if (rect.bottom < getChildAt(0).getHeight()) { 1250 screenBottom -= fadingEdge; 1251 } 1252 1253 int scrollYDelta = 0; 1254 1255 if (rect.bottom > screenBottom && rect.top > screenTop) { 1256 // need to move down to get it in view: move down just enough so 1257 // that the entire rectangle is in view (or at least the first 1258 // screen size chunk). 1259 1260 if (rect.height() > height) { 1261 // just enough to get screen size chunk on 1262 scrollYDelta += (rect.top - screenTop); 1263 } else { 1264 // get entire rect at bottom of screen 1265 scrollYDelta += (rect.bottom - screenBottom); 1266 } 1267 1268 // make sure we aren't scrolling beyond the end of our content 1269 int bottom = getChildAt(0).getBottom(); 1270 int distanceToBottom = bottom - screenBottom; 1271 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1272 1273 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1274 // need to move up to get it in view: move up just enough so that 1275 // entire rectangle is in view (or at least the first screen 1276 // size chunk of it). 1277 1278 if (rect.height() > height) { 1279 // screen size chunk 1280 scrollYDelta -= (screenBottom - rect.bottom); 1281 } else { 1282 // entire rect at top 1283 scrollYDelta -= (screenTop - rect.top); 1284 } 1285 1286 // make sure we aren't scrolling any further than the top our content 1287 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1288 } 1289 return scrollYDelta; 1290 } 1291 1292 @Override 1293 public void requestChildFocus(View child, View focused) { 1294 if (!mIsLayoutDirty) { 1295 scrollToChild(focused); 1296 } else { 1297 // The child may not be laid out yet, we can't compute the scroll yet 1298 mChildToScrollTo = focused; 1299 } 1300 super.requestChildFocus(child, focused); 1301 } 1302 1303 1304 /** 1305 * When looking for focus in children of a scroll view, need to be a little 1306 * more careful not to give focus to something that is scrolled off screen. 1307 * 1308 * This is more expensive than the default {@link android.view.ViewGroup} 1309 * implementation, otherwise this behavior might have been made the default. 1310 */ 1311 @Override 1312 protected boolean onRequestFocusInDescendants(int direction, 1313 Rect previouslyFocusedRect) { 1314 1315 // convert from forward / backward notation to up / down / left / right 1316 // (ugh). 1317 if (direction == View.FOCUS_FORWARD) { 1318 direction = View.FOCUS_DOWN; 1319 } else if (direction == View.FOCUS_BACKWARD) { 1320 direction = View.FOCUS_UP; 1321 } 1322 1323 final View nextFocus = previouslyFocusedRect == null ? 1324 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1325 FocusFinder.getInstance().findNextFocusFromRect(this, 1326 previouslyFocusedRect, direction); 1327 1328 if (nextFocus == null) { 1329 return false; 1330 } 1331 1332 if (isOffScreen(nextFocus)) { 1333 return false; 1334 } 1335 1336 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1337 } 1338 1339 @Override 1340 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1341 boolean immediate) { 1342 // offset into coordinate space of this scroll view 1343 rectangle.offset(child.getLeft() - child.getScrollX(), 1344 child.getTop() - child.getScrollY()); 1345 1346 return scrollToChildRect(rectangle, immediate); 1347 } 1348 1349 @Override 1350 public void requestLayout() { 1351 mIsLayoutDirty = true; 1352 super.requestLayout(); 1353 } 1354 1355 @Override 1356 protected void onDetachedFromWindow() { 1357 super.onDetachedFromWindow(); 1358 1359 if (mScrollStrictSpan != null) { 1360 mScrollStrictSpan.finish(); 1361 mScrollStrictSpan = null; 1362 } 1363 if (mFlingStrictSpan != null) { 1364 mFlingStrictSpan.finish(); 1365 mFlingStrictSpan = null; 1366 } 1367 } 1368 1369 @Override 1370 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1371 super.onLayout(changed, l, t, r, b); 1372 mIsLayoutDirty = false; 1373 // Give a child focus if it needs it 1374 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1375 scrollToChild(mChildToScrollTo); 1376 } 1377 mChildToScrollTo = null; 1378 1379 // Calling this with the present values causes it to re-claim them 1380 scrollTo(mScrollX, mScrollY); 1381 } 1382 1383 @Override 1384 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1385 super.onSizeChanged(w, h, oldw, oldh); 1386 1387 View currentFocused = findFocus(); 1388 if (null == currentFocused || this == currentFocused) 1389 return; 1390 1391 // If the currently-focused view was visible on the screen when the 1392 // screen was at the old height, then scroll the screen to make that 1393 // view visible with the new screen height. 1394 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1395 currentFocused.getDrawingRect(mTempRect); 1396 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1397 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1398 doScrollY(scrollDelta); 1399 } 1400 } 1401 1402 /** 1403 * Return true if child is a descendant of parent, (or equal to the parent). 1404 */ 1405 private static boolean isViewDescendantOf(View child, View parent) { 1406 if (child == parent) { 1407 return true; 1408 } 1409 1410 final ViewParent theParent = child.getParent(); 1411 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1412 } 1413 1414 /** 1415 * Fling the scroll view 1416 * 1417 * @param velocityY The initial velocity in the Y direction. Positive 1418 * numbers mean that the finger/cursor is moving down the screen, 1419 * which means we want to scroll towards the top. 1420 */ 1421 public void fling(int velocityY) { 1422 if (getChildCount() > 0) { 1423 int height = getHeight() - mPaddingBottom - mPaddingTop; 1424 int bottom = getChildAt(0).getHeight(); 1425 1426 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1427 Math.max(0, bottom - height), 0, height/2); 1428 1429 if (mFlingStrictSpan == null) { 1430 mFlingStrictSpan = StrictMode.enterCriticalSpan("ScrollView-fling"); 1431 } 1432 1433 invalidate(); 1434 } 1435 } 1436 1437 private void endDrag() { 1438 mIsBeingDragged = false; 1439 1440 recycleVelocityTracker(); 1441 1442 if (mEdgeGlowTop != null) { 1443 mEdgeGlowTop.onRelease(); 1444 mEdgeGlowBottom.onRelease(); 1445 } 1446 1447 if (mScrollStrictSpan != null) { 1448 mScrollStrictSpan.finish(); 1449 mScrollStrictSpan = null; 1450 } 1451 } 1452 1453 /** 1454 * {@inheritDoc} 1455 * 1456 * <p>This version also clamps the scrolling to the bounds of our child. 1457 */ 1458 @Override 1459 public void scrollTo(int x, int y) { 1460 // we rely on the fact the View.scrollBy calls scrollTo. 1461 if (getChildCount() > 0) { 1462 View child = getChildAt(0); 1463 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1464 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1465 if (x != mScrollX || y != mScrollY) { 1466 super.scrollTo(x, y); 1467 } 1468 } 1469 } 1470 1471 @Override 1472 public void setOverScrollMode(int mode) { 1473 if (mode != OVER_SCROLL_NEVER) { 1474 if (mEdgeGlowTop == null) { 1475 Context context = getContext(); 1476 mEdgeGlowTop = new EdgeEffect(context); 1477 mEdgeGlowBottom = new EdgeEffect(context); 1478 } 1479 } else { 1480 mEdgeGlowTop = null; 1481 mEdgeGlowBottom = null; 1482 } 1483 super.setOverScrollMode(mode); 1484 } 1485 1486 @Override 1487 public void draw(Canvas canvas) { 1488 super.draw(canvas); 1489 if (mEdgeGlowTop != null) { 1490 final int scrollY = mScrollY; 1491 if (!mEdgeGlowTop.isFinished()) { 1492 final int restoreCount = canvas.save(); 1493 final int width = getWidth() - mPaddingLeft - mPaddingRight; 1494 1495 canvas.translate(mPaddingLeft, Math.min(0, scrollY)); 1496 mEdgeGlowTop.setSize(width, getHeight()); 1497 if (mEdgeGlowTop.draw(canvas)) { 1498 invalidate(); 1499 } 1500 canvas.restoreToCount(restoreCount); 1501 } 1502 if (!mEdgeGlowBottom.isFinished()) { 1503 final int restoreCount = canvas.save(); 1504 final int width = getWidth() - mPaddingLeft - mPaddingRight; 1505 final int height = getHeight(); 1506 1507 canvas.translate(-width + mPaddingLeft, 1508 Math.max(getScrollRange(), scrollY) + height); 1509 canvas.rotate(180, width, 0); 1510 mEdgeGlowBottom.setSize(width, height); 1511 if (mEdgeGlowBottom.draw(canvas)) { 1512 invalidate(); 1513 } 1514 canvas.restoreToCount(restoreCount); 1515 } 1516 } 1517 } 1518 1519 private static int clamp(int n, int my, int child) { 1520 if (my >= child || n < 0) { 1521 /* my >= child is this case: 1522 * |--------------- me ---------------| 1523 * |------ child ------| 1524 * or 1525 * |--------------- me ---------------| 1526 * |------ child ------| 1527 * or 1528 * |--------------- me ---------------| 1529 * |------ child ------| 1530 * 1531 * n < 0 is this case: 1532 * |------ me ------| 1533 * |-------- child --------| 1534 * |-- mScrollX --| 1535 */ 1536 return 0; 1537 } 1538 if ((my+n) > child) { 1539 /* this case: 1540 * |------ me ------| 1541 * |------ child ------| 1542 * |-- mScrollX --| 1543 */ 1544 return child-my; 1545 } 1546 return n; 1547 } 1548} 1549