ScrollView.java revision 82e236d72ac197d6673d0b4d484fe5f0b9436731
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 final float y = ev.getY(index); 646 mLastMotionY = y; 647 mActivePointerId = ev.getPointerId(index); 648 break; 649 } 650 case MotionEvent.ACTION_POINTER_UP: 651 onSecondaryPointerUp(ev); 652 mLastMotionY = ev.getY(ev.findPointerIndex(mActivePointerId)); 653 break; 654 } 655 return true; 656 } 657 658 private void onSecondaryPointerUp(MotionEvent ev) { 659 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 660 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 661 final int pointerId = ev.getPointerId(pointerIndex); 662 if (pointerId == mActivePointerId) { 663 // This was our active pointer going up. Choose a new 664 // active pointer and adjust accordingly. 665 // TODO: Make this decision more intelligent. 666 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 667 mLastMotionY = ev.getY(newPointerIndex); 668 mActivePointerId = ev.getPointerId(newPointerIndex); 669 if (mVelocityTracker != null) { 670 mVelocityTracker.clear(); 671 } 672 } 673 } 674 675 @Override 676 public boolean onGenericMotionEvent(MotionEvent event) { 677 if ((event.getSource() & InputDevice.SOURCE_CLASS_POINTER) != 0) { 678 switch (event.getAction()) { 679 case MotionEvent.ACTION_SCROLL: { 680 if (!mIsBeingDragged) { 681 final float vscroll = event.getAxisValue(MotionEvent.AXIS_VSCROLL); 682 if (vscroll != 0) { 683 final int delta = (int) (vscroll * getVerticalScrollFactor()); 684 final int range = getScrollRange(); 685 int oldScrollY = mScrollY; 686 int newScrollY = oldScrollY - delta; 687 if (newScrollY < 0) { 688 newScrollY = 0; 689 } else if (newScrollY > range) { 690 newScrollY = range; 691 } 692 if (newScrollY != oldScrollY) { 693 super.scrollTo(mScrollX, newScrollY); 694 return true; 695 } 696 } 697 } 698 } 699 } 700 } 701 return super.onGenericMotionEvent(event); 702 } 703 704 @Override 705 protected void onOverScrolled(int scrollX, int scrollY, 706 boolean clampedX, boolean clampedY) { 707 // Treat animating scrolls differently; see #computeScroll() for why. 708 if (!mScroller.isFinished()) { 709 mScrollX = scrollX; 710 mScrollY = scrollY; 711 invalidateParentIfNeeded(); 712 if (clampedY) { 713 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 714 } 715 } else { 716 super.scrollTo(scrollX, scrollY); 717 } 718 awakenScrollBars(); 719 } 720 721 @Override 722 public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) { 723 super.onInitializeAccessibilityNodeInfo(info); 724 info.setScrollable(true); 725 } 726 727 @Override 728 public void onInitializeAccessibilityEvent(AccessibilityEvent event) { 729 super.onInitializeAccessibilityEvent(event); 730 event.setScrollable(true); 731 } 732 733 private int getScrollRange() { 734 int scrollRange = 0; 735 if (getChildCount() > 0) { 736 View child = getChildAt(0); 737 scrollRange = Math.max(0, 738 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); 739 } 740 return scrollRange; 741 } 742 743 /** 744 * <p> 745 * Finds the next focusable component that fits in this View's bounds 746 * (excluding fading edges) pretending that this View's top is located at 747 * the parameter top. 748 * </p> 749 * 750 * @param topFocus look for a candidate at the top of the bounds if topFocus is true, 751 * or at the bottom of the bounds if topFocus is false 752 * @param top the top offset of the bounds in which a focusable must be 753 * found (the fading edge is assumed to start at this position) 754 * @param preferredFocusable the View that has highest priority and will be 755 * returned if it is within my bounds (null is valid) 756 * @return the next focusable component in the bounds or null if none can be found 757 */ 758 private View findFocusableViewInMyBounds(final boolean topFocus, 759 final int top, View preferredFocusable) { 760 /* 761 * The fading edge's transparent side should be considered for focus 762 * since it's mostly visible, so we divide the actual fading edge length 763 * by 2. 764 */ 765 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 766 final int topWithoutFadingEdge = top + fadingEdgeLength; 767 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 768 769 if ((preferredFocusable != null) 770 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 771 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 772 return preferredFocusable; 773 } 774 775 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 776 bottomWithoutFadingEdge); 777 } 778 779 /** 780 * <p> 781 * Finds the next focusable component that fits in the specified bounds. 782 * </p> 783 * 784 * @param topFocus look for a candidate is the one at the top of the bounds 785 * if topFocus is true, or at the bottom of the bounds if topFocus is 786 * false 787 * @param top the top offset of the bounds in which a focusable must be 788 * found 789 * @param bottom the bottom offset of the bounds in which a focusable must 790 * be found 791 * @return the next focusable component in the bounds or null if none can 792 * be found 793 */ 794 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 795 796 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 797 View focusCandidate = null; 798 799 /* 800 * A fully contained focusable is one where its top is below the bound's 801 * top, and its bottom is above the bound's bottom. A partially 802 * contained focusable is one where some part of it is within the 803 * bounds, but it also has some part that is not within bounds. A fully contained 804 * focusable is preferred to a partially contained focusable. 805 */ 806 boolean foundFullyContainedFocusable = false; 807 808 int count = focusables.size(); 809 for (int i = 0; i < count; i++) { 810 View view = focusables.get(i); 811 int viewTop = view.getTop(); 812 int viewBottom = view.getBottom(); 813 814 if (top < viewBottom && viewTop < bottom) { 815 /* 816 * the focusable is in the target area, it is a candidate for 817 * focusing 818 */ 819 820 final boolean viewIsFullyContained = (top < viewTop) && 821 (viewBottom < bottom); 822 823 if (focusCandidate == null) { 824 /* No candidate, take this one */ 825 focusCandidate = view; 826 foundFullyContainedFocusable = viewIsFullyContained; 827 } else { 828 final boolean viewIsCloserToBoundary = 829 (topFocus && viewTop < focusCandidate.getTop()) || 830 (!topFocus && viewBottom > focusCandidate 831 .getBottom()); 832 833 if (foundFullyContainedFocusable) { 834 if (viewIsFullyContained && viewIsCloserToBoundary) { 835 /* 836 * We're dealing with only fully contained views, so 837 * it has to be closer to the boundary to beat our 838 * candidate 839 */ 840 focusCandidate = view; 841 } 842 } else { 843 if (viewIsFullyContained) { 844 /* Any fully contained view beats a partially contained view */ 845 focusCandidate = view; 846 foundFullyContainedFocusable = true; 847 } else if (viewIsCloserToBoundary) { 848 /* 849 * Partially contained view beats another partially 850 * contained view if it's closer 851 */ 852 focusCandidate = view; 853 } 854 } 855 } 856 } 857 } 858 859 return focusCandidate; 860 } 861 862 /** 863 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 864 * method will scroll the view by one page up or down and give the focus 865 * to the topmost/bottommost component in the new visible area. If no 866 * component is a good candidate for focus, this scrollview reclaims the 867 * focus.</p> 868 * 869 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 870 * to go one page up or 871 * {@link android.view.View#FOCUS_DOWN} to go one page down 872 * @return true if the key event is consumed by this method, false otherwise 873 */ 874 public boolean pageScroll(int direction) { 875 boolean down = direction == View.FOCUS_DOWN; 876 int height = getHeight(); 877 878 if (down) { 879 mTempRect.top = getScrollY() + height; 880 int count = getChildCount(); 881 if (count > 0) { 882 View view = getChildAt(count - 1); 883 if (mTempRect.top + height > view.getBottom()) { 884 mTempRect.top = view.getBottom() - height; 885 } 886 } 887 } else { 888 mTempRect.top = getScrollY() - height; 889 if (mTempRect.top < 0) { 890 mTempRect.top = 0; 891 } 892 } 893 mTempRect.bottom = mTempRect.top + height; 894 895 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 896 } 897 898 /** 899 * <p>Handles scrolling in response to a "home/end" shortcut press. This 900 * method will scroll the view to the top or bottom and give the focus 901 * to the topmost/bottommost component in the new visible area. If no 902 * component is a good candidate for focus, this scrollview reclaims the 903 * focus.</p> 904 * 905 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 906 * to go the top of the view or 907 * {@link android.view.View#FOCUS_DOWN} to go the bottom 908 * @return true if the key event is consumed by this method, false otherwise 909 */ 910 public boolean fullScroll(int direction) { 911 boolean down = direction == View.FOCUS_DOWN; 912 int height = getHeight(); 913 914 mTempRect.top = 0; 915 mTempRect.bottom = height; 916 917 if (down) { 918 int count = getChildCount(); 919 if (count > 0) { 920 View view = getChildAt(count - 1); 921 mTempRect.bottom = view.getBottom() + mPaddingBottom; 922 mTempRect.top = mTempRect.bottom - height; 923 } 924 } 925 926 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 927 } 928 929 /** 930 * <p>Scrolls the view to make the area defined by <code>top</code> and 931 * <code>bottom</code> visible. This method attempts to give the focus 932 * to a component visible in this area. If no component can be focused in 933 * the new visible area, the focus is reclaimed by this ScrollView.</p> 934 * 935 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 936 * to go upward, {@link android.view.View#FOCUS_DOWN} to downward 937 * @param top the top offset of the new area to be made visible 938 * @param bottom the bottom offset of the new area to be made visible 939 * @return true if the key event is consumed by this method, false otherwise 940 */ 941 private boolean scrollAndFocus(int direction, int top, int bottom) { 942 boolean handled = true; 943 944 int height = getHeight(); 945 int containerTop = getScrollY(); 946 int containerBottom = containerTop + height; 947 boolean up = direction == View.FOCUS_UP; 948 949 View newFocused = findFocusableViewInBounds(up, top, bottom); 950 if (newFocused == null) { 951 newFocused = this; 952 } 953 954 if (top >= containerTop && bottom <= containerBottom) { 955 handled = false; 956 } else { 957 int delta = up ? (top - containerTop) : (bottom - containerBottom); 958 doScrollY(delta); 959 } 960 961 if (newFocused != findFocus()) newFocused.requestFocus(direction); 962 963 return handled; 964 } 965 966 /** 967 * Handle scrolling in response to an up or down arrow click. 968 * 969 * @param direction The direction corresponding to the arrow key that was 970 * pressed 971 * @return True if we consumed the event, false otherwise 972 */ 973 public boolean arrowScroll(int direction) { 974 975 View currentFocused = findFocus(); 976 if (currentFocused == this) currentFocused = null; 977 978 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 979 980 final int maxJump = getMaxScrollAmount(); 981 982 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 983 nextFocused.getDrawingRect(mTempRect); 984 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 985 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 986 doScrollY(scrollDelta); 987 nextFocused.requestFocus(direction); 988 } else { 989 // no new focus 990 int scrollDelta = maxJump; 991 992 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 993 scrollDelta = getScrollY(); 994 } else if (direction == View.FOCUS_DOWN) { 995 if (getChildCount() > 0) { 996 int daBottom = getChildAt(0).getBottom(); 997 int screenBottom = getScrollY() + getHeight() - mPaddingBottom; 998 if (daBottom - screenBottom < maxJump) { 999 scrollDelta = daBottom - screenBottom; 1000 } 1001 } 1002 } 1003 if (scrollDelta == 0) { 1004 return false; 1005 } 1006 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 1007 } 1008 1009 if (currentFocused != null && currentFocused.isFocused() 1010 && isOffScreen(currentFocused)) { 1011 // previously focused item still has focus and is off screen, give 1012 // it up (take it back to ourselves) 1013 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 1014 // sure to 1015 // get it) 1016 final int descendantFocusability = getDescendantFocusability(); // save 1017 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 1018 requestFocus(); 1019 setDescendantFocusability(descendantFocusability); // restore 1020 } 1021 return true; 1022 } 1023 1024 /** 1025 * @return whether the descendant of this scroll view is scrolled off 1026 * screen. 1027 */ 1028 private boolean isOffScreen(View descendant) { 1029 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 1030 } 1031 1032 /** 1033 * @return whether the descendant of this scroll view is within delta 1034 * pixels of being on the screen. 1035 */ 1036 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 1037 descendant.getDrawingRect(mTempRect); 1038 offsetDescendantRectToMyCoords(descendant, mTempRect); 1039 1040 return (mTempRect.bottom + delta) >= getScrollY() 1041 && (mTempRect.top - delta) <= (getScrollY() + height); 1042 } 1043 1044 /** 1045 * Smooth scroll by a Y delta 1046 * 1047 * @param delta the number of pixels to scroll by on the Y axis 1048 */ 1049 private void doScrollY(int delta) { 1050 if (delta != 0) { 1051 if (mSmoothScrollingEnabled) { 1052 smoothScrollBy(0, delta); 1053 } else { 1054 scrollBy(0, delta); 1055 } 1056 } 1057 } 1058 1059 /** 1060 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 1061 * 1062 * @param dx the number of pixels to scroll by on the X axis 1063 * @param dy the number of pixels to scroll by on the Y axis 1064 */ 1065 public final void smoothScrollBy(int dx, int dy) { 1066 if (getChildCount() == 0) { 1067 // Nothing to do. 1068 return; 1069 } 1070 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 1071 if (duration > ANIMATED_SCROLL_GAP) { 1072 final int height = getHeight() - mPaddingBottom - mPaddingTop; 1073 final int bottom = getChildAt(0).getHeight(); 1074 final int maxY = Math.max(0, bottom - height); 1075 final int scrollY = mScrollY; 1076 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 1077 1078 mScroller.startScroll(mScrollX, scrollY, 0, dy); 1079 invalidate(); 1080 } else { 1081 if (!mScroller.isFinished()) { 1082 mScroller.abortAnimation(); 1083 if (mFlingStrictSpan != null) { 1084 mFlingStrictSpan.finish(); 1085 mFlingStrictSpan = null; 1086 } 1087 } 1088 scrollBy(dx, dy); 1089 } 1090 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1091 } 1092 1093 /** 1094 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1095 * 1096 * @param x the position where to scroll on the X axis 1097 * @param y the position where to scroll on the Y axis 1098 */ 1099 public final void smoothScrollTo(int x, int y) { 1100 smoothScrollBy(x - mScrollX, y - mScrollY); 1101 } 1102 1103 /** 1104 * <p>The scroll range of a scroll view is the overall height of all of its 1105 * children.</p> 1106 */ 1107 @Override 1108 protected int computeVerticalScrollRange() { 1109 final int count = getChildCount(); 1110 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1111 if (count == 0) { 1112 return contentHeight; 1113 } 1114 1115 int scrollRange = getChildAt(0).getBottom(); 1116 final int scrollY = mScrollY; 1117 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1118 if (scrollY < 0) { 1119 scrollRange -= scrollY; 1120 } else if (scrollY > overscrollBottom) { 1121 scrollRange += scrollY - overscrollBottom; 1122 } 1123 1124 return scrollRange; 1125 } 1126 1127 @Override 1128 protected int computeVerticalScrollOffset() { 1129 return Math.max(0, super.computeVerticalScrollOffset()); 1130 } 1131 1132 @Override 1133 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1134 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1135 1136 int childWidthMeasureSpec; 1137 int childHeightMeasureSpec; 1138 1139 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1140 + mPaddingRight, lp.width); 1141 1142 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1143 1144 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1145 } 1146 1147 @Override 1148 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1149 int parentHeightMeasureSpec, int heightUsed) { 1150 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1151 1152 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1153 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1154 + widthUsed, lp.width); 1155 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1156 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1157 1158 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1159 } 1160 1161 @Override 1162 public void computeScroll() { 1163 if (mScroller.computeScrollOffset()) { 1164 // This is called at drawing time by ViewGroup. We don't want to 1165 // re-show the scrollbars at this point, which scrollTo will do, 1166 // so we replicate most of scrollTo here. 1167 // 1168 // It's a little odd to call onScrollChanged from inside the drawing. 1169 // 1170 // It is, except when you remember that computeScroll() is used to 1171 // animate scrolling. So unless we want to defer the onScrollChanged() 1172 // until the end of the animated scrolling, we don't really have a 1173 // choice here. 1174 // 1175 // I agree. The alternative, which I think would be worse, is to post 1176 // something and tell the subclasses later. This is bad because there 1177 // will be a window where mScrollX/Y is different from what the app 1178 // thinks it is. 1179 // 1180 int oldX = mScrollX; 1181 int oldY = mScrollY; 1182 int x = mScroller.getCurrX(); 1183 int y = mScroller.getCurrY(); 1184 1185 if (oldX != x || oldY != y) { 1186 final int range = getScrollRange(); 1187 final int overscrollMode = getOverScrollMode(); 1188 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || 1189 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 1190 1191 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, range, 1192 0, mOverflingDistance, false); 1193 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1194 1195 if (canOverscroll) { 1196 if (y < 0 && oldY >= 0) { 1197 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1198 } else if (y > range && oldY <= range) { 1199 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1200 } 1201 } 1202 } 1203 1204 awakenScrollBars(); 1205 1206 // Keep on drawing until the animation has finished. 1207 postInvalidate(); 1208 } else { 1209 if (mFlingStrictSpan != null) { 1210 mFlingStrictSpan.finish(); 1211 mFlingStrictSpan = null; 1212 } 1213 } 1214 } 1215 1216 /** 1217 * Scrolls the view to the given child. 1218 * 1219 * @param child the View to scroll to 1220 */ 1221 private void scrollToChild(View child) { 1222 child.getDrawingRect(mTempRect); 1223 1224 /* Offset from child's local coordinates to ScrollView coordinates */ 1225 offsetDescendantRectToMyCoords(child, mTempRect); 1226 1227 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1228 1229 if (scrollDelta != 0) { 1230 scrollBy(0, scrollDelta); 1231 } 1232 } 1233 1234 /** 1235 * If rect is off screen, scroll just enough to get it (or at least the 1236 * first screen size chunk of it) on screen. 1237 * 1238 * @param rect The rectangle. 1239 * @param immediate True to scroll immediately without animation 1240 * @return true if scrolling was performed 1241 */ 1242 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1243 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1244 final boolean scroll = delta != 0; 1245 if (scroll) { 1246 if (immediate) { 1247 scrollBy(0, delta); 1248 } else { 1249 smoothScrollBy(0, delta); 1250 } 1251 } 1252 return scroll; 1253 } 1254 1255 /** 1256 * Compute the amount to scroll in the Y direction in order to get 1257 * a rectangle completely on the screen (or, if taller than the screen, 1258 * at least the first screen size chunk of it). 1259 * 1260 * @param rect The rect. 1261 * @return The scroll delta. 1262 */ 1263 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1264 if (getChildCount() == 0) return 0; 1265 1266 int height = getHeight(); 1267 int screenTop = getScrollY(); 1268 int screenBottom = screenTop + height; 1269 1270 int fadingEdge = getVerticalFadingEdgeLength(); 1271 1272 // leave room for top fading edge as long as rect isn't at very top 1273 if (rect.top > 0) { 1274 screenTop += fadingEdge; 1275 } 1276 1277 // leave room for bottom fading edge as long as rect isn't at very bottom 1278 if (rect.bottom < getChildAt(0).getHeight()) { 1279 screenBottom -= fadingEdge; 1280 } 1281 1282 int scrollYDelta = 0; 1283 1284 if (rect.bottom > screenBottom && rect.top > screenTop) { 1285 // need to move down to get it in view: move down just enough so 1286 // that the entire rectangle is in view (or at least the first 1287 // screen size chunk). 1288 1289 if (rect.height() > height) { 1290 // just enough to get screen size chunk on 1291 scrollYDelta += (rect.top - screenTop); 1292 } else { 1293 // get entire rect at bottom of screen 1294 scrollYDelta += (rect.bottom - screenBottom); 1295 } 1296 1297 // make sure we aren't scrolling beyond the end of our content 1298 int bottom = getChildAt(0).getBottom(); 1299 int distanceToBottom = bottom - screenBottom; 1300 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1301 1302 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1303 // need to move up to get it in view: move up just enough so that 1304 // entire rectangle is in view (or at least the first screen 1305 // size chunk of it). 1306 1307 if (rect.height() > height) { 1308 // screen size chunk 1309 scrollYDelta -= (screenBottom - rect.bottom); 1310 } else { 1311 // entire rect at top 1312 scrollYDelta -= (screenTop - rect.top); 1313 } 1314 1315 // make sure we aren't scrolling any further than the top our content 1316 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1317 } 1318 return scrollYDelta; 1319 } 1320 1321 @Override 1322 public void requestChildFocus(View child, View focused) { 1323 if (!mIsLayoutDirty) { 1324 scrollToChild(focused); 1325 } else { 1326 // The child may not be laid out yet, we can't compute the scroll yet 1327 mChildToScrollTo = focused; 1328 } 1329 super.requestChildFocus(child, focused); 1330 } 1331 1332 1333 /** 1334 * When looking for focus in children of a scroll view, need to be a little 1335 * more careful not to give focus to something that is scrolled off screen. 1336 * 1337 * This is more expensive than the default {@link android.view.ViewGroup} 1338 * implementation, otherwise this behavior might have been made the default. 1339 */ 1340 @Override 1341 protected boolean onRequestFocusInDescendants(int direction, 1342 Rect previouslyFocusedRect) { 1343 1344 // convert from forward / backward notation to up / down / left / right 1345 // (ugh). 1346 if (direction == View.FOCUS_FORWARD) { 1347 direction = View.FOCUS_DOWN; 1348 } else if (direction == View.FOCUS_BACKWARD) { 1349 direction = View.FOCUS_UP; 1350 } 1351 1352 final View nextFocus = previouslyFocusedRect == null ? 1353 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1354 FocusFinder.getInstance().findNextFocusFromRect(this, 1355 previouslyFocusedRect, direction); 1356 1357 if (nextFocus == null) { 1358 return false; 1359 } 1360 1361 if (isOffScreen(nextFocus)) { 1362 return false; 1363 } 1364 1365 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1366 } 1367 1368 @Override 1369 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1370 boolean immediate) { 1371 // offset into coordinate space of this scroll view 1372 rectangle.offset(child.getLeft() - child.getScrollX(), 1373 child.getTop() - child.getScrollY()); 1374 1375 return scrollToChildRect(rectangle, immediate); 1376 } 1377 1378 @Override 1379 public void requestLayout() { 1380 mIsLayoutDirty = true; 1381 super.requestLayout(); 1382 } 1383 1384 @Override 1385 protected void onDetachedFromWindow() { 1386 super.onDetachedFromWindow(); 1387 1388 if (mScrollStrictSpan != null) { 1389 mScrollStrictSpan.finish(); 1390 mScrollStrictSpan = null; 1391 } 1392 if (mFlingStrictSpan != null) { 1393 mFlingStrictSpan.finish(); 1394 mFlingStrictSpan = null; 1395 } 1396 } 1397 1398 @Override 1399 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1400 super.onLayout(changed, l, t, r, b); 1401 mIsLayoutDirty = false; 1402 // Give a child focus if it needs it 1403 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1404 scrollToChild(mChildToScrollTo); 1405 } 1406 mChildToScrollTo = null; 1407 1408 // Calling this with the present values causes it to re-clam them 1409 scrollTo(mScrollX, mScrollY); 1410 } 1411 1412 @Override 1413 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1414 super.onSizeChanged(w, h, oldw, oldh); 1415 1416 View currentFocused = findFocus(); 1417 if (null == currentFocused || this == currentFocused) 1418 return; 1419 1420 // If the currently-focused view was visible on the screen when the 1421 // screen was at the old height, then scroll the screen to make that 1422 // view visible with the new screen height. 1423 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1424 currentFocused.getDrawingRect(mTempRect); 1425 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1426 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1427 doScrollY(scrollDelta); 1428 } 1429 } 1430 1431 /** 1432 * Return true if child is an descendant of parent, (or equal to the parent). 1433 */ 1434 private boolean isViewDescendantOf(View child, View parent) { 1435 if (child == parent) { 1436 return true; 1437 } 1438 1439 final ViewParent theParent = child.getParent(); 1440 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1441 } 1442 1443 /** 1444 * Fling the scroll view 1445 * 1446 * @param velocityY The initial velocity in the Y direction. Positive 1447 * numbers mean that the finger/cursor is moving down the screen, 1448 * which means we want to scroll towards the top. 1449 */ 1450 public void fling(int velocityY) { 1451 if (getChildCount() > 0) { 1452 int height = getHeight() - mPaddingBottom - mPaddingTop; 1453 int bottom = getChildAt(0).getHeight(); 1454 1455 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1456 Math.max(0, bottom - height), 0, height/2); 1457 1458 final boolean movingDown = velocityY > 0; 1459 1460 if (mFlingStrictSpan == null) { 1461 mFlingStrictSpan = StrictMode.enterCriticalSpan("ScrollView-fling"); 1462 } 1463 1464 invalidate(); 1465 } 1466 } 1467 1468 private void endDrag() { 1469 mIsBeingDragged = false; 1470 1471 recycleVelocityTracker(); 1472 1473 if (mEdgeGlowTop != null) { 1474 mEdgeGlowTop.onRelease(); 1475 mEdgeGlowBottom.onRelease(); 1476 } 1477 1478 if (mScrollStrictSpan != null) { 1479 mScrollStrictSpan.finish(); 1480 mScrollStrictSpan = null; 1481 } 1482 } 1483 1484 /** 1485 * {@inheritDoc} 1486 * 1487 * <p>This version also clamps the scrolling to the bounds of our child. 1488 */ 1489 @Override 1490 public void scrollTo(int x, int y) { 1491 // we rely on the fact the View.scrollBy calls scrollTo. 1492 if (getChildCount() > 0) { 1493 View child = getChildAt(0); 1494 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1495 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1496 if (x != mScrollX || y != mScrollY) { 1497 super.scrollTo(x, y); 1498 } 1499 } 1500 } 1501 1502 @Override 1503 public void setOverScrollMode(int mode) { 1504 if (mode != OVER_SCROLL_NEVER) { 1505 if (mEdgeGlowTop == null) { 1506 Context context = getContext(); 1507 mEdgeGlowTop = new EdgeEffect(context); 1508 mEdgeGlowBottom = new EdgeEffect(context); 1509 } 1510 } else { 1511 mEdgeGlowTop = null; 1512 mEdgeGlowBottom = null; 1513 } 1514 super.setOverScrollMode(mode); 1515 } 1516 1517 @Override 1518 public void draw(Canvas canvas) { 1519 super.draw(canvas); 1520 if (mEdgeGlowTop != null) { 1521 final int scrollY = mScrollY; 1522 if (!mEdgeGlowTop.isFinished()) { 1523 final int restoreCount = canvas.save(); 1524 final int width = getWidth() - mPaddingLeft - mPaddingRight; 1525 1526 canvas.translate(mPaddingLeft, Math.min(0, scrollY)); 1527 mEdgeGlowTop.setSize(width, getHeight()); 1528 if (mEdgeGlowTop.draw(canvas)) { 1529 invalidate(); 1530 } 1531 canvas.restoreToCount(restoreCount); 1532 } 1533 if (!mEdgeGlowBottom.isFinished()) { 1534 final int restoreCount = canvas.save(); 1535 final int width = getWidth() - mPaddingLeft - mPaddingRight; 1536 final int height = getHeight(); 1537 1538 canvas.translate(-width + mPaddingLeft, 1539 Math.max(getScrollRange(), scrollY) + height); 1540 canvas.rotate(180, width, 0); 1541 mEdgeGlowBottom.setSize(width, height); 1542 if (mEdgeGlowBottom.draw(canvas)) { 1543 invalidate(); 1544 } 1545 canvas.restoreToCount(restoreCount); 1546 } 1547 } 1548 } 1549 1550 private int clamp(int n, int my, int child) { 1551 if (my >= child || n < 0) { 1552 /* my >= child is this case: 1553 * |--------------- me ---------------| 1554 * |------ child ------| 1555 * or 1556 * |--------------- me ---------------| 1557 * |------ child ------| 1558 * or 1559 * |--------------- me ---------------| 1560 * |------ child ------| 1561 * 1562 * n < 0 is this case: 1563 * |------ me ------| 1564 * |-------- child --------| 1565 * |-- mScrollX --| 1566 */ 1567 return 0; 1568 } 1569 if ((my+n) > child) { 1570 /* this case: 1571 * |------ me ------| 1572 * |------ child ------| 1573 * |-- mScrollX --| 1574 */ 1575 return child-my; 1576 } 1577 return n; 1578 } 1579} 1580