ScrollView.java revision a174d7a0d5475dbae2b48f7359abf1637a882896
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 android.view.ViewDebug; 20import com.android.internal.R; 21 22import android.content.Context; 23import android.content.res.Resources; 24import android.content.res.TypedArray; 25import android.graphics.Canvas; 26import android.graphics.Rect; 27import android.graphics.drawable.Drawable; 28import android.os.StrictMode; 29import android.util.AttributeSet; 30import android.view.FocusFinder; 31import android.view.KeyEvent; 32import android.view.MotionEvent; 33import android.view.VelocityTracker; 34import android.view.View; 35import android.view.ViewConfiguration; 36import android.view.ViewGroup; 37import android.view.ViewParent; 38import android.view.animation.AnimationUtils; 39 40import java.util.List; 41 42/** 43 * Layout container for a view hierarchy that can be scrolled by the user, 44 * allowing it to be larger than the physical display. A ScrollView 45 * is a {@link FrameLayout}, meaning you should place one child in it 46 * containing the entire contents to scroll; this child may itself be a layout 47 * manager with a complex hierarchy of objects. A child that is often used 48 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 49 * array of top-level items that the user can scroll through. 50 * 51 * <p>The {@link TextView} class also 52 * takes care of its own scrolling, so does not require a ScrollView, but 53 * using the two together is possible to achieve the effect of a text view 54 * within a larger container. 55 * 56 * <p>ScrollView only supports vertical scrolling. 57 * 58 * @attr ref android.R.styleable#ScrollView_fillViewport 59 */ 60public class ScrollView extends FrameLayout { 61 static final int ANIMATED_SCROLL_GAP = 250; 62 63 static final float MAX_SCROLL_FACTOR = 0.5f; 64 65 66 private long mLastScroll; 67 68 private final Rect mTempRect = new Rect(); 69 private OverScroller mScroller; 70 private EdgeGlow mEdgeGlowTop; 71 private EdgeGlow mEdgeGlowBottom; 72 73 /** 74 * Flag to indicate that we are moving focus ourselves. This is so the 75 * code that watches for focus changes initiated outside this ScrollView 76 * knows that it does not have to do anything. 77 */ 78 private boolean mScrollViewMovedFocus; 79 80 /** 81 * Position of the last motion event. 82 */ 83 private float mLastMotionY; 84 85 /** 86 * True when the layout has changed but the traversal has not come through yet. 87 * Ideally the view hierarchy would keep track of this for us. 88 */ 89 private boolean mIsLayoutDirty = true; 90 91 /** 92 * The child to give focus to in the event that a child has requested focus while the 93 * layout is dirty. This prevents the scroll from being wrong if the child has not been 94 * laid out before requesting focus. 95 */ 96 private View mChildToScrollTo = null; 97 98 /** 99 * True if the user is currently dragging this ScrollView around. This is 100 * not the same as 'is being flinged', which can be checked by 101 * mScroller.isFinished() (flinging begins when the user lifts his finger). 102 */ 103 private boolean mIsBeingDragged = false; 104 105 /** 106 * Determines speed during touch scrolling 107 */ 108 private VelocityTracker mVelocityTracker; 109 110 /** 111 * When set to true, the scroll view measure its child to make it fill the currently 112 * visible area. 113 */ 114 @ViewDebug.ExportedProperty(category = "layout") 115 private boolean mFillViewport; 116 117 /** 118 * Whether arrow scrolling is animated. 119 */ 120 private boolean mSmoothScrollingEnabled = true; 121 122 private int mTouchSlop; 123 private int mMinimumVelocity; 124 private int mMaximumVelocity; 125 126 private int mOverscrollDistance; 127 private int mOverflingDistance; 128 129 /** 130 * ID of the active pointer. This is used to retain consistency during 131 * drags/flings if multiple pointers are used. 132 */ 133 private int mActivePointerId = INVALID_POINTER; 134 135 /** 136 * The StrictMode "critical time span" objects to catch animation 137 * stutters. Non-null when a time-sensitive animation is 138 * in-flight. Must call finish() on them when done animating. 139 * These are no-ops on user builds. 140 */ 141 private StrictMode.Span mScrollStrictSpan = null; // aka "drag" 142 private StrictMode.Span mFlingStrictSpan = null; 143 144 /** 145 * Sentinel value for no current active pointer. 146 * Used by {@link #mActivePointerId}. 147 */ 148 private static final int INVALID_POINTER = -1; 149 150 public ScrollView(Context context) { 151 this(context, null); 152 } 153 154 public ScrollView(Context context, AttributeSet attrs) { 155 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 156 } 157 158 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 159 super(context, attrs, defStyle); 160 initScrollView(); 161 162 TypedArray a = 163 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 164 165 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 166 167 a.recycle(); 168 } 169 170 @Override 171 protected float getTopFadingEdgeStrength() { 172 if (getChildCount() == 0) { 173 return 0.0f; 174 } 175 176 final int length = getVerticalFadingEdgeLength(); 177 if (mScrollY < length) { 178 return mScrollY / (float) length; 179 } 180 181 return 1.0f; 182 } 183 184 @Override 185 protected float getBottomFadingEdgeStrength() { 186 if (getChildCount() == 0) { 187 return 0.0f; 188 } 189 190 final int length = getVerticalFadingEdgeLength(); 191 final int bottomEdge = getHeight() - mPaddingBottom; 192 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 193 if (span < length) { 194 return span / (float) length; 195 } 196 197 return 1.0f; 198 } 199 200 /** 201 * @return The maximum amount this scroll view will scroll in response to 202 * an arrow event. 203 */ 204 public int getMaxScrollAmount() { 205 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 206 } 207 208 209 private void initScrollView() { 210 mScroller = new OverScroller(getContext()); 211 setFocusable(true); 212 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 213 setWillNotDraw(false); 214 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 215 mTouchSlop = configuration.getScaledTouchSlop(); 216 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 217 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 218 mOverscrollDistance = configuration.getScaledOverscrollDistance(); 219 mOverflingDistance = configuration.getScaledOverflingDistance(); 220 } 221 222 @Override 223 public void addView(View child) { 224 if (getChildCount() > 0) { 225 throw new IllegalStateException("ScrollView can host only one direct child"); 226 } 227 228 super.addView(child); 229 } 230 231 @Override 232 public void addView(View child, int index) { 233 if (getChildCount() > 0) { 234 throw new IllegalStateException("ScrollView can host only one direct child"); 235 } 236 237 super.addView(child, index); 238 } 239 240 @Override 241 public void addView(View child, ViewGroup.LayoutParams params) { 242 if (getChildCount() > 0) { 243 throw new IllegalStateException("ScrollView can host only one direct child"); 244 } 245 246 super.addView(child, params); 247 } 248 249 @Override 250 public void addView(View child, int index, ViewGroup.LayoutParams params) { 251 if (getChildCount() > 0) { 252 throw new IllegalStateException("ScrollView can host only one direct child"); 253 } 254 255 super.addView(child, index, params); 256 } 257 258 /** 259 * @return Returns true this ScrollView can be scrolled 260 */ 261 private boolean canScroll() { 262 View child = getChildAt(0); 263 if (child != null) { 264 int childHeight = child.getHeight(); 265 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 266 } 267 return false; 268 } 269 270 /** 271 * Indicates whether this ScrollView's content is stretched to fill the viewport. 272 * 273 * @return True if the content fills the viewport, false otherwise. 274 * 275 * @attr ref android.R.styleable#ScrollView_fillViewport 276 */ 277 public boolean isFillViewport() { 278 return mFillViewport; 279 } 280 281 /** 282 * Indicates this ScrollView whether it should stretch its content height to fill 283 * the viewport or not. 284 * 285 * @param fillViewport True to stretch the content's height to the viewport's 286 * boundaries, false otherwise. 287 * 288 * @attr ref android.R.styleable#ScrollView_fillViewport 289 */ 290 public void setFillViewport(boolean fillViewport) { 291 if (fillViewport != mFillViewport) { 292 mFillViewport = fillViewport; 293 requestLayout(); 294 } 295 } 296 297 /** 298 * @return Whether arrow scrolling will animate its transition. 299 */ 300 public boolean isSmoothScrollingEnabled() { 301 return mSmoothScrollingEnabled; 302 } 303 304 /** 305 * Set whether arrow scrolling will animate its transition. 306 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 307 */ 308 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 309 mSmoothScrollingEnabled = smoothScrollingEnabled; 310 } 311 312 @Override 313 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 314 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 315 316 if (!mFillViewport) { 317 return; 318 } 319 320 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 321 if (heightMode == MeasureSpec.UNSPECIFIED) { 322 return; 323 } 324 325 if (getChildCount() > 0) { 326 final View child = getChildAt(0); 327 int height = getMeasuredHeight(); 328 if (child.getMeasuredHeight() < height) { 329 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 330 331 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, 332 mPaddingLeft + mPaddingRight, lp.width); 333 height -= mPaddingTop; 334 height -= mPaddingBottom; 335 int childHeightMeasureSpec = 336 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 337 338 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 339 } 340 } 341 } 342 343 @Override 344 public boolean dispatchKeyEvent(KeyEvent event) { 345 // Let the focused view and/or our descendants get the key first 346 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 347 } 348 349 /** 350 * You can call this function yourself to have the scroll view perform 351 * scrolling from a key event, just as if the event had been dispatched to 352 * it by the view hierarchy. 353 * 354 * @param event The key event to execute. 355 * @return Return true if the event was handled, else false. 356 */ 357 public boolean executeKeyEvent(KeyEvent event) { 358 mTempRect.setEmpty(); 359 360 if (!canScroll()) { 361 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { 362 View currentFocused = findFocus(); 363 if (currentFocused == this) currentFocused = null; 364 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 365 currentFocused, View.FOCUS_DOWN); 366 return nextFocused != null 367 && nextFocused != this 368 && nextFocused.requestFocus(View.FOCUS_DOWN); 369 } 370 return false; 371 } 372 373 boolean handled = false; 374 if (event.getAction() == KeyEvent.ACTION_DOWN) { 375 switch (event.getKeyCode()) { 376 case KeyEvent.KEYCODE_DPAD_UP: 377 if (!event.isAltPressed()) { 378 handled = arrowScroll(View.FOCUS_UP); 379 } else { 380 handled = fullScroll(View.FOCUS_UP); 381 } 382 break; 383 case KeyEvent.KEYCODE_DPAD_DOWN: 384 if (!event.isAltPressed()) { 385 handled = arrowScroll(View.FOCUS_DOWN); 386 } else { 387 handled = fullScroll(View.FOCUS_DOWN); 388 } 389 break; 390 case KeyEvent.KEYCODE_SPACE: 391 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 392 break; 393 } 394 } 395 396 return handled; 397 } 398 399 private boolean inChild(int x, int y) { 400 if (getChildCount() > 0) { 401 final int scrollY = mScrollY; 402 final View child = getChildAt(0); 403 return !(y < child.getTop() - scrollY 404 || y >= child.getBottom() - scrollY 405 || x < child.getLeft() 406 || x >= child.getRight()); 407 } 408 return false; 409 } 410 411 @Override 412 public boolean onInterceptTouchEvent(MotionEvent ev) { 413 /* 414 * This method JUST determines whether we want to intercept the motion. 415 * If we return true, onMotionEvent will be called and we do the actual 416 * scrolling there. 417 */ 418 419 /* 420 * Shortcut the most recurring case: the user is in the dragging 421 * state and he is moving his finger. We want to intercept this 422 * motion. 423 */ 424 final int action = ev.getAction(); 425 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 426 return true; 427 } 428 429 switch (action & MotionEvent.ACTION_MASK) { 430 case MotionEvent.ACTION_MOVE: { 431 /* 432 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 433 * whether the user has moved far enough from his original down touch. 434 */ 435 436 /* 437 * Locally do absolute value. mLastMotionY is set to the y value 438 * of the down event. 439 */ 440 final int activePointerId = mActivePointerId; 441 if (activePointerId == INVALID_POINTER) { 442 // If we don't have a valid id, the touch down wasn't on content. 443 break; 444 } 445 446 final int pointerIndex = ev.findPointerIndex(activePointerId); 447 final float y = ev.getY(pointerIndex); 448 final int yDiff = (int) Math.abs(y - mLastMotionY); 449 if (yDiff > mTouchSlop) { 450 mIsBeingDragged = true; 451 mLastMotionY = y; 452 if (mScrollStrictSpan == null) { 453 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 454 } 455 } 456 break; 457 } 458 459 case MotionEvent.ACTION_DOWN: { 460 final float y = ev.getY(); 461 if (!inChild((int) ev.getX(), (int) y)) { 462 mIsBeingDragged = false; 463 break; 464 } 465 466 /* 467 * Remember location of down touch. 468 * ACTION_DOWN always refers to pointer index 0. 469 */ 470 mLastMotionY = y; 471 mActivePointerId = ev.getPointerId(0); 472 473 /* 474 * If being flinged and user touches the screen, initiate drag; 475 * otherwise don't. mScroller.isFinished should be false when 476 * being flinged. 477 */ 478 mIsBeingDragged = !mScroller.isFinished(); 479 if (mIsBeingDragged && mScrollStrictSpan == null) { 480 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 481 } 482 break; 483 } 484 485 case MotionEvent.ACTION_CANCEL: 486 case MotionEvent.ACTION_UP: 487 /* Release the drag */ 488 mIsBeingDragged = false; 489 mActivePointerId = INVALID_POINTER; 490 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 491 invalidate(); 492 } 493 break; 494 case MotionEvent.ACTION_POINTER_UP: 495 onSecondaryPointerUp(ev); 496 break; 497 } 498 499 /* 500 * The only time we want to intercept motion events is if we are in the 501 * drag mode. 502 */ 503 return mIsBeingDragged; 504 } 505 506 @Override 507 public boolean onTouchEvent(MotionEvent ev) { 508 509 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 510 // Don't handle edge touches immediately -- they may actually belong to one of our 511 // descendants. 512 return false; 513 } 514 515 if (mVelocityTracker == null) { 516 mVelocityTracker = VelocityTracker.obtain(); 517 } 518 mVelocityTracker.addMovement(ev); 519 520 final int action = ev.getAction(); 521 522 switch (action & MotionEvent.ACTION_MASK) { 523 case MotionEvent.ACTION_DOWN: { 524 final float y = ev.getY(); 525 mIsBeingDragged = true; 526 527 /* 528 * If being flinged and user touches, stop the fling. isFinished 529 * will be false if being flinged. 530 */ 531 if (!mScroller.isFinished()) { 532 mScroller.abortAnimation(); 533 if (mFlingStrictSpan != null) { 534 mFlingStrictSpan.finish(); 535 mFlingStrictSpan = null; 536 } 537 } 538 539 // Remember where the motion event started 540 mLastMotionY = y; 541 mActivePointerId = ev.getPointerId(0); 542 break; 543 } 544 case MotionEvent.ACTION_MOVE: 545 if (mIsBeingDragged) { 546 // Scroll to follow the motion event 547 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 548 final float y = ev.getY(activePointerIndex); 549 final int deltaY = (int) (mLastMotionY - y); 550 mLastMotionY = y; 551 552 final int oldX = mScrollX; 553 final int oldY = mScrollY; 554 final int range = getScrollRange(); 555 if (overScrollBy(0, deltaY, 0, mScrollY, 0, range, 556 0, mOverscrollDistance, true)) { 557 // Break our velocity if we hit a scroll barrier. 558 mVelocityTracker.clear(); 559 } 560 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 561 562 final int overscrollMode = getOverScrollMode(); 563 if (overscrollMode == OVER_SCROLL_ALWAYS || 564 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { 565 final int pulledToY = oldY + deltaY; 566 if (pulledToY < 0) { 567 mEdgeGlowTop.onPull((float) deltaY / getHeight()); 568 if (!mEdgeGlowBottom.isFinished()) { 569 mEdgeGlowBottom.onRelease(); 570 } 571 } else if (pulledToY > range) { 572 mEdgeGlowBottom.onPull((float) deltaY / getHeight()); 573 if (!mEdgeGlowTop.isFinished()) { 574 mEdgeGlowTop.onRelease(); 575 } 576 } 577 if (mEdgeGlowTop != null 578 && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) { 579 invalidate(); 580 } 581 } 582 } 583 break; 584 case MotionEvent.ACTION_UP: 585 if (mIsBeingDragged) { 586 final VelocityTracker velocityTracker = mVelocityTracker; 587 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 588 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 589 590 if (getChildCount() > 0) { 591 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 592 fling(-initialVelocity); 593 } else { 594 final int bottom = getScrollRange(); 595 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, bottom)) { 596 invalidate(); 597 } 598 } 599 } 600 601 mActivePointerId = INVALID_POINTER; 602 endDrag(); 603 } 604 break; 605 case MotionEvent.ACTION_CANCEL: 606 if (mIsBeingDragged && getChildCount() > 0) { 607 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 608 invalidate(); 609 } 610 mActivePointerId = INVALID_POINTER; 611 endDrag(); 612 } 613 break; 614 case MotionEvent.ACTION_POINTER_UP: 615 onSecondaryPointerUp(ev); 616 break; 617 } 618 return true; 619 } 620 621 private void onSecondaryPointerUp(MotionEvent ev) { 622 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 623 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 624 final int pointerId = ev.getPointerId(pointerIndex); 625 if (pointerId == mActivePointerId) { 626 // This was our active pointer going up. Choose a new 627 // active pointer and adjust accordingly. 628 // TODO: Make this decision more intelligent. 629 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 630 mLastMotionY = ev.getY(newPointerIndex); 631 mActivePointerId = ev.getPointerId(newPointerIndex); 632 if (mVelocityTracker != null) { 633 mVelocityTracker.clear(); 634 } 635 } 636 } 637 638 @Override 639 protected void onOverScrolled(int scrollX, int scrollY, 640 boolean clampedX, boolean clampedY) { 641 // Treat animating scrolls differently; see #computeScroll() for why. 642 if (!mScroller.isFinished()) { 643 mScrollX = scrollX; 644 mScrollY = scrollY; 645 if (clampedY) { 646 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 647 } 648 } else { 649 super.scrollTo(scrollX, scrollY); 650 } 651 awakenScrollBars(); 652 } 653 654 private int getScrollRange() { 655 int scrollRange = 0; 656 if (getChildCount() > 0) { 657 View child = getChildAt(0); 658 scrollRange = Math.max(0, 659 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); 660 } 661 return scrollRange; 662 } 663 664 /** 665 * <p> 666 * Finds the next focusable component that fits in this View's bounds 667 * (excluding fading edges) pretending that this View's top is located at 668 * the parameter top. 669 * </p> 670 * 671 * @param topFocus look for a candidate is the one at the top of the bounds 672 * if topFocus is true, or at the bottom of the bounds if topFocus is 673 * false 674 * @param top the top offset of the bounds in which a focusable must be 675 * found (the fading edge is assumed to start at this position) 676 * @param preferredFocusable the View that has highest priority and will be 677 * returned if it is within my bounds (null is valid) 678 * @return the next focusable component in the bounds or null if none can be 679 * found 680 */ 681 private View findFocusableViewInMyBounds(final boolean topFocus, 682 final int top, View preferredFocusable) { 683 /* 684 * The fading edge's transparent side should be considered for focus 685 * since it's mostly visible, so we divide the actual fading edge length 686 * by 2. 687 */ 688 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 689 final int topWithoutFadingEdge = top + fadingEdgeLength; 690 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 691 692 if ((preferredFocusable != null) 693 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 694 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 695 return preferredFocusable; 696 } 697 698 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 699 bottomWithoutFadingEdge); 700 } 701 702 /** 703 * <p> 704 * Finds the next focusable component that fits in the specified bounds. 705 * </p> 706 * 707 * @param topFocus look for a candidate is the one at the top of the bounds 708 * if topFocus is true, or at the bottom of the bounds if topFocus is 709 * false 710 * @param top the top offset of the bounds in which a focusable must be 711 * found 712 * @param bottom the bottom offset of the bounds in which a focusable must 713 * be found 714 * @return the next focusable component in the bounds or null if none can 715 * be found 716 */ 717 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 718 719 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 720 View focusCandidate = null; 721 722 /* 723 * A fully contained focusable is one where its top is below the bound's 724 * top, and its bottom is above the bound's bottom. A partially 725 * contained focusable is one where some part of it is within the 726 * bounds, but it also has some part that is not within bounds. A fully contained 727 * focusable is preferred to a partially contained focusable. 728 */ 729 boolean foundFullyContainedFocusable = false; 730 731 int count = focusables.size(); 732 for (int i = 0; i < count; i++) { 733 View view = focusables.get(i); 734 int viewTop = view.getTop(); 735 int viewBottom = view.getBottom(); 736 737 if (top < viewBottom && viewTop < bottom) { 738 /* 739 * the focusable is in the target area, it is a candidate for 740 * focusing 741 */ 742 743 final boolean viewIsFullyContained = (top < viewTop) && 744 (viewBottom < bottom); 745 746 if (focusCandidate == null) { 747 /* No candidate, take this one */ 748 focusCandidate = view; 749 foundFullyContainedFocusable = viewIsFullyContained; 750 } else { 751 final boolean viewIsCloserToBoundary = 752 (topFocus && viewTop < focusCandidate.getTop()) || 753 (!topFocus && viewBottom > focusCandidate 754 .getBottom()); 755 756 if (foundFullyContainedFocusable) { 757 if (viewIsFullyContained && viewIsCloserToBoundary) { 758 /* 759 * We're dealing with only fully contained views, so 760 * it has to be closer to the boundary to beat our 761 * candidate 762 */ 763 focusCandidate = view; 764 } 765 } else { 766 if (viewIsFullyContained) { 767 /* Any fully contained view beats a partially contained view */ 768 focusCandidate = view; 769 foundFullyContainedFocusable = true; 770 } else if (viewIsCloserToBoundary) { 771 /* 772 * Partially contained view beats another partially 773 * contained view if it's closer 774 */ 775 focusCandidate = view; 776 } 777 } 778 } 779 } 780 } 781 782 return focusCandidate; 783 } 784 785 /** 786 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 787 * method will scroll the view by one page up or down and give the focus 788 * to the topmost/bottommost component in the new visible area. If no 789 * component is a good candidate for focus, this scrollview reclaims the 790 * focus.</p> 791 * 792 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 793 * to go one page up or 794 * {@link android.view.View#FOCUS_DOWN} to go one page down 795 * @return true if the key event is consumed by this method, false otherwise 796 */ 797 public boolean pageScroll(int direction) { 798 boolean down = direction == View.FOCUS_DOWN; 799 int height = getHeight(); 800 801 if (down) { 802 mTempRect.top = getScrollY() + height; 803 int count = getChildCount(); 804 if (count > 0) { 805 View view = getChildAt(count - 1); 806 if (mTempRect.top + height > view.getBottom()) { 807 mTempRect.top = view.getBottom() - height; 808 } 809 } 810 } else { 811 mTempRect.top = getScrollY() - height; 812 if (mTempRect.top < 0) { 813 mTempRect.top = 0; 814 } 815 } 816 mTempRect.bottom = mTempRect.top + height; 817 818 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 819 } 820 821 /** 822 * <p>Handles scrolling in response to a "home/end" shortcut press. This 823 * method will scroll the view to the top or bottom and give the focus 824 * to the topmost/bottommost component in the new visible area. If no 825 * component is a good candidate for focus, this scrollview reclaims the 826 * focus.</p> 827 * 828 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 829 * to go the top of the view or 830 * {@link android.view.View#FOCUS_DOWN} to go the bottom 831 * @return true if the key event is consumed by this method, false otherwise 832 */ 833 public boolean fullScroll(int direction) { 834 boolean down = direction == View.FOCUS_DOWN; 835 int height = getHeight(); 836 837 mTempRect.top = 0; 838 mTempRect.bottom = height; 839 840 if (down) { 841 int count = getChildCount(); 842 if (count > 0) { 843 View view = getChildAt(count - 1); 844 mTempRect.bottom = view.getBottom(); 845 mTempRect.top = mTempRect.bottom - height; 846 } 847 } 848 849 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 850 } 851 852 /** 853 * <p>Scrolls the view to make the area defined by <code>top</code> and 854 * <code>bottom</code> visible. This method attempts to give the focus 855 * to a component visible in this area. If no component can be focused in 856 * the new visible area, the focus is reclaimed by this scrollview.</p> 857 * 858 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 859 * to go upward 860 * {@link android.view.View#FOCUS_DOWN} to downward 861 * @param top the top offset of the new area to be made visible 862 * @param bottom the bottom offset of the new area to be made visible 863 * @return true if the key event is consumed by this method, false otherwise 864 */ 865 private boolean scrollAndFocus(int direction, int top, int bottom) { 866 boolean handled = true; 867 868 int height = getHeight(); 869 int containerTop = getScrollY(); 870 int containerBottom = containerTop + height; 871 boolean up = direction == View.FOCUS_UP; 872 873 View newFocused = findFocusableViewInBounds(up, top, bottom); 874 if (newFocused == null) { 875 newFocused = this; 876 } 877 878 if (top >= containerTop && bottom <= containerBottom) { 879 handled = false; 880 } else { 881 int delta = up ? (top - containerTop) : (bottom - containerBottom); 882 doScrollY(delta); 883 } 884 885 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 886 mScrollViewMovedFocus = true; 887 mScrollViewMovedFocus = false; 888 } 889 890 return handled; 891 } 892 893 /** 894 * Handle scrolling in response to an up or down arrow click. 895 * 896 * @param direction The direction corresponding to the arrow key that was 897 * pressed 898 * @return True if we consumed the event, false otherwise 899 */ 900 public boolean arrowScroll(int direction) { 901 902 View currentFocused = findFocus(); 903 if (currentFocused == this) currentFocused = null; 904 905 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 906 907 final int maxJump = getMaxScrollAmount(); 908 909 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 910 nextFocused.getDrawingRect(mTempRect); 911 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 912 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 913 doScrollY(scrollDelta); 914 nextFocused.requestFocus(direction); 915 } else { 916 // no new focus 917 int scrollDelta = maxJump; 918 919 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 920 scrollDelta = getScrollY(); 921 } else if (direction == View.FOCUS_DOWN) { 922 if (getChildCount() > 0) { 923 int daBottom = getChildAt(0).getBottom(); 924 925 int screenBottom = getScrollY() + getHeight(); 926 927 if (daBottom - screenBottom < maxJump) { 928 scrollDelta = daBottom - screenBottom; 929 } 930 } 931 } 932 if (scrollDelta == 0) { 933 return false; 934 } 935 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 936 } 937 938 if (currentFocused != null && currentFocused.isFocused() 939 && isOffScreen(currentFocused)) { 940 // previously focused item still has focus and is off screen, give 941 // it up (take it back to ourselves) 942 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 943 // sure to 944 // get it) 945 final int descendantFocusability = getDescendantFocusability(); // save 946 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 947 requestFocus(); 948 setDescendantFocusability(descendantFocusability); // restore 949 } 950 return true; 951 } 952 953 /** 954 * @return whether the descendant of this scroll view is scrolled off 955 * screen. 956 */ 957 private boolean isOffScreen(View descendant) { 958 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 959 } 960 961 /** 962 * @return whether the descendant of this scroll view is within delta 963 * pixels of being on the screen. 964 */ 965 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 966 descendant.getDrawingRect(mTempRect); 967 offsetDescendantRectToMyCoords(descendant, mTempRect); 968 969 return (mTempRect.bottom + delta) >= getScrollY() 970 && (mTempRect.top - delta) <= (getScrollY() + height); 971 } 972 973 /** 974 * Smooth scroll by a Y delta 975 * 976 * @param delta the number of pixels to scroll by on the Y axis 977 */ 978 private void doScrollY(int delta) { 979 if (delta != 0) { 980 if (mSmoothScrollingEnabled) { 981 smoothScrollBy(0, delta); 982 } else { 983 scrollBy(0, delta); 984 } 985 } 986 } 987 988 /** 989 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 990 * 991 * @param dx the number of pixels to scroll by on the X axis 992 * @param dy the number of pixels to scroll by on the Y axis 993 */ 994 public final void smoothScrollBy(int dx, int dy) { 995 if (getChildCount() == 0) { 996 // Nothing to do. 997 return; 998 } 999 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 1000 if (duration > ANIMATED_SCROLL_GAP) { 1001 final int height = getHeight() - mPaddingBottom - mPaddingTop; 1002 final int bottom = getChildAt(0).getHeight(); 1003 final int maxY = Math.max(0, bottom - height); 1004 final int scrollY = mScrollY; 1005 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 1006 1007 mScroller.startScroll(mScrollX, scrollY, 0, dy); 1008 invalidate(); 1009 } else { 1010 if (!mScroller.isFinished()) { 1011 mScroller.abortAnimation(); 1012 if (mFlingStrictSpan != null) { 1013 mFlingStrictSpan.finish(); 1014 mFlingStrictSpan = null; 1015 } 1016 } 1017 scrollBy(dx, dy); 1018 } 1019 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1020 } 1021 1022 /** 1023 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1024 * 1025 * @param x the position where to scroll on the X axis 1026 * @param y the position where to scroll on the Y axis 1027 */ 1028 public final void smoothScrollTo(int x, int y) { 1029 smoothScrollBy(x - mScrollX, y - mScrollY); 1030 } 1031 1032 /** 1033 * <p>The scroll range of a scroll view is the overall height of all of its 1034 * children.</p> 1035 */ 1036 @Override 1037 protected int computeVerticalScrollRange() { 1038 final int count = getChildCount(); 1039 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1040 if (count == 0) { 1041 return contentHeight; 1042 } 1043 1044 int scrollRange = getChildAt(0).getBottom(); 1045 final int scrollY = mScrollY; 1046 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1047 if (scrollY < 0) { 1048 scrollRange -= scrollY; 1049 } else if (scrollY > overscrollBottom) { 1050 scrollRange += scrollY - overscrollBottom; 1051 } 1052 1053 return scrollRange; 1054 } 1055 1056 @Override 1057 protected int computeVerticalScrollOffset() { 1058 return Math.max(0, super.computeVerticalScrollOffset()); 1059 } 1060 1061 @Override 1062 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1063 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1064 1065 int childWidthMeasureSpec; 1066 int childHeightMeasureSpec; 1067 1068 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1069 + mPaddingRight, lp.width); 1070 1071 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1072 1073 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1074 } 1075 1076 @Override 1077 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1078 int parentHeightMeasureSpec, int heightUsed) { 1079 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1080 1081 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1082 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1083 + widthUsed, lp.width); 1084 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1085 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1086 1087 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1088 } 1089 1090 @Override 1091 public void computeScroll() { 1092 if (mScroller.computeScrollOffset()) { 1093 // This is called at drawing time by ViewGroup. We don't want to 1094 // re-show the scrollbars at this point, which scrollTo will do, 1095 // so we replicate most of scrollTo here. 1096 // 1097 // It's a little odd to call onScrollChanged from inside the drawing. 1098 // 1099 // It is, except when you remember that computeScroll() is used to 1100 // animate scrolling. So unless we want to defer the onScrollChanged() 1101 // until the end of the animated scrolling, we don't really have a 1102 // choice here. 1103 // 1104 // I agree. The alternative, which I think would be worse, is to post 1105 // something and tell the subclasses later. This is bad because there 1106 // will be a window where mScrollX/Y is different from what the app 1107 // thinks it is. 1108 // 1109 int oldX = mScrollX; 1110 int oldY = mScrollY; 1111 int x = mScroller.getCurrX(); 1112 int y = mScroller.getCurrY(); 1113 1114 if (oldX != x || oldY != y) { 1115 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 1116 0, mOverflingDistance, false); 1117 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1118 1119 final int range = getScrollRange(); 1120 final int overscrollMode = getOverScrollMode(); 1121 if (overscrollMode == OVER_SCROLL_ALWAYS || 1122 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { 1123 if (y < 0 && oldY >= 0) { 1124 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1125 } else if (y > range && oldY <= range) { 1126 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1127 } 1128 } 1129 } 1130 awakenScrollBars(); 1131 1132 // Keep on drawing until the animation has finished. 1133 postInvalidate(); 1134 } else { 1135 if (mFlingStrictSpan != null) { 1136 mFlingStrictSpan.finish(); 1137 mFlingStrictSpan = null; 1138 } 1139 } 1140 } 1141 1142 /** 1143 * Scrolls the view to the given child. 1144 * 1145 * @param child the View to scroll to 1146 */ 1147 private void scrollToChild(View child) { 1148 child.getDrawingRect(mTempRect); 1149 1150 /* Offset from child's local coordinates to ScrollView coordinates */ 1151 offsetDescendantRectToMyCoords(child, mTempRect); 1152 1153 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1154 1155 if (scrollDelta != 0) { 1156 scrollBy(0, scrollDelta); 1157 } 1158 } 1159 1160 /** 1161 * If rect is off screen, scroll just enough to get it (or at least the 1162 * first screen size chunk of it) on screen. 1163 * 1164 * @param rect The rectangle. 1165 * @param immediate True to scroll immediately without animation 1166 * @return true if scrolling was performed 1167 */ 1168 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1169 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1170 final boolean scroll = delta != 0; 1171 if (scroll) { 1172 if (immediate) { 1173 scrollBy(0, delta); 1174 } else { 1175 smoothScrollBy(0, delta); 1176 } 1177 } 1178 return scroll; 1179 } 1180 1181 /** 1182 * Compute the amount to scroll in the Y direction in order to get 1183 * a rectangle completely on the screen (or, if taller than the screen, 1184 * at least the first screen size chunk of it). 1185 * 1186 * @param rect The rect. 1187 * @return The scroll delta. 1188 */ 1189 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1190 if (getChildCount() == 0) return 0; 1191 1192 int height = getHeight(); 1193 int screenTop = getScrollY(); 1194 int screenBottom = screenTop + height; 1195 1196 int fadingEdge = getVerticalFadingEdgeLength(); 1197 1198 // leave room for top fading edge as long as rect isn't at very top 1199 if (rect.top > 0) { 1200 screenTop += fadingEdge; 1201 } 1202 1203 // leave room for bottom fading edge as long as rect isn't at very bottom 1204 if (rect.bottom < getChildAt(0).getHeight()) { 1205 screenBottom -= fadingEdge; 1206 } 1207 1208 int scrollYDelta = 0; 1209 1210 if (rect.bottom > screenBottom && rect.top > screenTop) { 1211 // need to move down to get it in view: move down just enough so 1212 // that the entire rectangle is in view (or at least the first 1213 // screen size chunk). 1214 1215 if (rect.height() > height) { 1216 // just enough to get screen size chunk on 1217 scrollYDelta += (rect.top - screenTop); 1218 } else { 1219 // get entire rect at bottom of screen 1220 scrollYDelta += (rect.bottom - screenBottom); 1221 } 1222 1223 // make sure we aren't scrolling beyond the end of our content 1224 int bottom = getChildAt(0).getBottom(); 1225 int distanceToBottom = bottom - screenBottom; 1226 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1227 1228 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1229 // need to move up to get it in view: move up just enough so that 1230 // entire rectangle is in view (or at least the first screen 1231 // size chunk of it). 1232 1233 if (rect.height() > height) { 1234 // screen size chunk 1235 scrollYDelta -= (screenBottom - rect.bottom); 1236 } else { 1237 // entire rect at top 1238 scrollYDelta -= (screenTop - rect.top); 1239 } 1240 1241 // make sure we aren't scrolling any further than the top our content 1242 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1243 } 1244 return scrollYDelta; 1245 } 1246 1247 @Override 1248 public void requestChildFocus(View child, View focused) { 1249 if (!mScrollViewMovedFocus) { 1250 if (!mIsLayoutDirty) { 1251 scrollToChild(focused); 1252 } else { 1253 // The child may not be laid out yet, we can't compute the scroll yet 1254 mChildToScrollTo = focused; 1255 } 1256 } 1257 super.requestChildFocus(child, focused); 1258 } 1259 1260 1261 /** 1262 * When looking for focus in children of a scroll view, need to be a little 1263 * more careful not to give focus to something that is scrolled off screen. 1264 * 1265 * This is more expensive than the default {@link android.view.ViewGroup} 1266 * implementation, otherwise this behavior might have been made the default. 1267 */ 1268 @Override 1269 protected boolean onRequestFocusInDescendants(int direction, 1270 Rect previouslyFocusedRect) { 1271 1272 // convert from forward / backward notation to up / down / left / right 1273 // (ugh). 1274 if (direction == View.FOCUS_FORWARD) { 1275 direction = View.FOCUS_DOWN; 1276 } else if (direction == View.FOCUS_BACKWARD) { 1277 direction = View.FOCUS_UP; 1278 } 1279 1280 final View nextFocus = previouslyFocusedRect == null ? 1281 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1282 FocusFinder.getInstance().findNextFocusFromRect(this, 1283 previouslyFocusedRect, direction); 1284 1285 if (nextFocus == null) { 1286 return false; 1287 } 1288 1289 if (isOffScreen(nextFocus)) { 1290 return false; 1291 } 1292 1293 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1294 } 1295 1296 @Override 1297 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1298 boolean immediate) { 1299 // offset into coordinate space of this scroll view 1300 rectangle.offset(child.getLeft() - child.getScrollX(), 1301 child.getTop() - child.getScrollY()); 1302 1303 return scrollToChildRect(rectangle, immediate); 1304 } 1305 1306 @Override 1307 public void requestLayout() { 1308 mIsLayoutDirty = true; 1309 super.requestLayout(); 1310 } 1311 1312 @Override 1313 protected void onDetachedFromWindow() { 1314 super.onDetachedFromWindow(); 1315 1316 if (mScrollStrictSpan != null) { 1317 mScrollStrictSpan.finish(); 1318 mScrollStrictSpan = null; 1319 } 1320 if (mFlingStrictSpan != null) { 1321 mFlingStrictSpan.finish(); 1322 mFlingStrictSpan = null; 1323 } 1324 } 1325 1326 @Override 1327 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1328 super.onLayout(changed, l, t, r, b); 1329 mIsLayoutDirty = false; 1330 // Give a child focus if it needs it 1331 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1332 scrollToChild(mChildToScrollTo); 1333 } 1334 mChildToScrollTo = null; 1335 1336 // Calling this with the present values causes it to re-clam them 1337 scrollTo(mScrollX, mScrollY); 1338 } 1339 1340 @Override 1341 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1342 super.onSizeChanged(w, h, oldw, oldh); 1343 1344 View currentFocused = findFocus(); 1345 if (null == currentFocused || this == currentFocused) 1346 return; 1347 1348 // If the currently-focused view was visible on the screen when the 1349 // screen was at the old height, then scroll the screen to make that 1350 // view visible with the new screen height. 1351 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1352 currentFocused.getDrawingRect(mTempRect); 1353 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1354 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1355 doScrollY(scrollDelta); 1356 } 1357 } 1358 1359 /** 1360 * Return true if child is an descendant of parent, (or equal to the parent). 1361 */ 1362 private boolean isViewDescendantOf(View child, View parent) { 1363 if (child == parent) { 1364 return true; 1365 } 1366 1367 final ViewParent theParent = child.getParent(); 1368 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1369 } 1370 1371 /** 1372 * Fling the scroll view 1373 * 1374 * @param velocityY The initial velocity in the Y direction. Positive 1375 * numbers mean that the finger/cursor is moving down the screen, 1376 * which means we want to scroll towards the top. 1377 */ 1378 public void fling(int velocityY) { 1379 if (getChildCount() > 0) { 1380 int height = getHeight() - mPaddingBottom - mPaddingTop; 1381 int bottom = getChildAt(0).getHeight(); 1382 1383 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1384 Math.max(0, bottom - height), 0, height/2); 1385 1386 final boolean movingDown = velocityY > 0; 1387 1388 View newFocused = 1389 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1390 if (newFocused == null) { 1391 newFocused = this; 1392 } 1393 1394 if (newFocused != findFocus() 1395 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1396 mScrollViewMovedFocus = true; 1397 mScrollViewMovedFocus = false; 1398 } 1399 1400 if (mFlingStrictSpan == null) { 1401 mFlingStrictSpan = StrictMode.enterCriticalSpan("ScrollView-fling"); 1402 } 1403 1404 invalidate(); 1405 } 1406 } 1407 1408 private void endDrag() { 1409 mIsBeingDragged = false; 1410 1411 if (mVelocityTracker != null) { 1412 mVelocityTracker.recycle(); 1413 mVelocityTracker = null; 1414 } 1415 1416 if (mEdgeGlowTop != null) { 1417 mEdgeGlowTop.onRelease(); 1418 mEdgeGlowBottom.onRelease(); 1419 } 1420 1421 if (mScrollStrictSpan != null) { 1422 mScrollStrictSpan.finish(); 1423 mScrollStrictSpan = null; 1424 } 1425 } 1426 1427 /** 1428 * {@inheritDoc} 1429 * 1430 * <p>This version also clamps the scrolling to the bounds of our child. 1431 */ 1432 @Override 1433 public void scrollTo(int x, int y) { 1434 // we rely on the fact the View.scrollBy calls scrollTo. 1435 if (getChildCount() > 0) { 1436 View child = getChildAt(0); 1437 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1438 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1439 if (x != mScrollX || y != mScrollY) { 1440 super.scrollTo(x, y); 1441 } 1442 } 1443 } 1444 1445 @Override 1446 public void setOverScrollMode(int mode) { 1447 if (mode != OVER_SCROLL_NEVER) { 1448 if (mEdgeGlowTop == null) { 1449 Context context = getContext(); 1450 final Resources res = context.getResources(); 1451 final Drawable edge = res.getDrawable(R.drawable.overscroll_edge); 1452 final Drawable glow = res.getDrawable(R.drawable.overscroll_glow); 1453 mEdgeGlowTop = new EdgeGlow(context, edge, glow); 1454 mEdgeGlowBottom = new EdgeGlow(context, edge, glow); 1455 } 1456 } else { 1457 mEdgeGlowTop = null; 1458 mEdgeGlowBottom = null; 1459 } 1460 super.setOverScrollMode(mode); 1461 } 1462 1463 @Override 1464 public void draw(Canvas canvas) { 1465 super.draw(canvas); 1466 if (mEdgeGlowTop != null) { 1467 final int scrollY = mScrollY; 1468 if (!mEdgeGlowTop.isFinished()) { 1469 final int restoreCount = canvas.save(); 1470 final int width = getWidth(); 1471 1472 canvas.translate(0, Math.min(0, scrollY)); 1473 mEdgeGlowTop.setSize(width, getHeight()); 1474 if (mEdgeGlowTop.draw(canvas)) { 1475 invalidate(); 1476 } 1477 canvas.restoreToCount(restoreCount); 1478 } 1479 if (!mEdgeGlowBottom.isFinished()) { 1480 final int restoreCount = canvas.save(); 1481 final int width = getWidth(); 1482 final int height = getHeight(); 1483 1484 canvas.translate(-width, Math.max(getScrollRange(), scrollY) + height); 1485 canvas.rotate(180, width, 0); 1486 mEdgeGlowBottom.setSize(width, height); 1487 if (mEdgeGlowBottom.draw(canvas)) { 1488 invalidate(); 1489 } 1490 canvas.restoreToCount(restoreCount); 1491 } 1492 } 1493 } 1494 1495 private int clamp(int n, int my, int child) { 1496 if (my >= child || n < 0) { 1497 /* my >= child is this case: 1498 * |--------------- me ---------------| 1499 * |------ child ------| 1500 * or 1501 * |--------------- me ---------------| 1502 * |------ child ------| 1503 * or 1504 * |--------------- me ---------------| 1505 * |------ child ------| 1506 * 1507 * n < 0 is this case: 1508 * |------ me ------| 1509 * |-------- child --------| 1510 * |-- mScrollX --| 1511 */ 1512 return 0; 1513 } 1514 if ((my+n) > child) { 1515 /* this case: 1516 * |------ me ------| 1517 * |------ child ------| 1518 * |-- mScrollX --| 1519 */ 1520 return child-my; 1521 } 1522 return n; 1523 } 1524} 1525