ScrollView.java revision e0a799a2ac1ca78e30fbac9e4e12a063425c08d3
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.Resources; 23import android.content.res.TypedArray; 24import android.graphics.Canvas; 25import android.graphics.Rect; 26import android.graphics.drawable.Drawable; 27import android.os.StrictMode; 28import android.util.AttributeSet; 29import android.view.FocusFinder; 30import android.view.InputDevice; 31import android.view.KeyEvent; 32import android.view.MotionEvent; 33import android.view.VelocityTracker; 34import android.view.View; 35import android.view.ViewConfiguration; 36import android.view.ViewDebug; 37import android.view.ViewGroup; 38import android.view.ViewParent; 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 67 private long mLastScroll; 68 69 private final Rect mTempRect = new Rect(); 70 private OverScroller mScroller; 71 private EdgeGlow mEdgeGlowTop; 72 private EdgeGlow mEdgeGlowBottom; 73 74 /** 75 * Position of the last motion event. 76 */ 77 private float mLastMotionY; 78 79 /** 80 * True when the layout has changed but the traversal has not come through yet. 81 * Ideally the view hierarchy would keep track of this for us. 82 */ 83 private boolean mIsLayoutDirty = true; 84 85 /** 86 * The child to give focus to in the event that a child has requested focus while the 87 * layout is dirty. This prevents the scroll from being wrong if the child has not been 88 * laid out before requesting focus. 89 */ 90 private View mChildToScrollTo = null; 91 92 /** 93 * True if the user is currently dragging this ScrollView around. This is 94 * not the same as 'is being flinged', which can be checked by 95 * mScroller.isFinished() (flinging begins when the user lifts his finger). 96 */ 97 private boolean mIsBeingDragged = false; 98 99 /** 100 * Determines speed during touch scrolling 101 */ 102 private VelocityTracker mVelocityTracker; 103 104 /** 105 * When set to true, the scroll view measure its child to make it fill the currently 106 * visible area. 107 */ 108 @ViewDebug.ExportedProperty(category = "layout") 109 private boolean mFillViewport; 110 111 /** 112 * Whether arrow scrolling is animated. 113 */ 114 private boolean mSmoothScrollingEnabled = true; 115 116 private int mTouchSlop; 117 private int mMinimumVelocity; 118 private int mMaximumVelocity; 119 120 private int mOverscrollDistance; 121 private int mOverflingDistance; 122 123 /** 124 * ID of the active pointer. This is used to retain consistency during 125 * drags/flings if multiple pointers are used. 126 */ 127 private int mActivePointerId = INVALID_POINTER; 128 129 /** 130 * The StrictMode "critical time span" objects to catch animation 131 * stutters. Non-null when a time-sensitive animation is 132 * in-flight. Must call finish() on them when done animating. 133 * These are no-ops on user builds. 134 */ 135 private StrictMode.Span mScrollStrictSpan = null; // aka "drag" 136 private StrictMode.Span mFlingStrictSpan = null; 137 138 /** 139 * Sentinel value for no current active pointer. 140 * Used by {@link #mActivePointerId}. 141 */ 142 private static final int INVALID_POINTER = -1; 143 144 public ScrollView(Context context) { 145 this(context, null); 146 } 147 148 public ScrollView(Context context, AttributeSet attrs) { 149 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 150 } 151 152 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 153 super(context, attrs, defStyle); 154 initScrollView(); 155 156 TypedArray a = 157 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 158 159 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 160 161 a.recycle(); 162 } 163 164 @Override 165 public boolean shouldDelayChildPressedState() { 166 return true; 167 } 168 169 @Override 170 protected float getTopFadingEdgeStrength() { 171 if (getChildCount() == 0) { 172 return 0.0f; 173 } 174 175 final int length = getVerticalFadingEdgeLength(); 176 if (mScrollY < length) { 177 return mScrollY / (float) length; 178 } 179 180 return 1.0f; 181 } 182 183 @Override 184 protected float getBottomFadingEdgeStrength() { 185 if (getChildCount() == 0) { 186 return 0.0f; 187 } 188 189 final int length = getVerticalFadingEdgeLength(); 190 final int bottomEdge = getHeight() - mPaddingBottom; 191 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 192 if (span < length) { 193 return span / (float) length; 194 } 195 196 return 1.0f; 197 } 198 199 /** 200 * @return The maximum amount this scroll view will scroll in response to 201 * an arrow event. 202 */ 203 public int getMaxScrollAmount() { 204 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 205 } 206 207 208 private void initScrollView() { 209 mScroller = new OverScroller(getContext()); 210 setFocusable(true); 211 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 212 setWillNotDraw(false); 213 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 214 mTouchSlop = configuration.getScaledTouchSlop(); 215 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 216 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 217 mOverscrollDistance = configuration.getScaledOverscrollDistance(); 218 mOverflingDistance = configuration.getScaledOverflingDistance(); 219 } 220 221 @Override 222 public void addView(View child) { 223 if (getChildCount() > 0) { 224 throw new IllegalStateException("ScrollView can host only one direct child"); 225 } 226 227 super.addView(child); 228 } 229 230 @Override 231 public void addView(View child, int index) { 232 if (getChildCount() > 0) { 233 throw new IllegalStateException("ScrollView can host only one direct child"); 234 } 235 236 super.addView(child, index); 237 } 238 239 @Override 240 public void addView(View child, ViewGroup.LayoutParams params) { 241 if (getChildCount() > 0) { 242 throw new IllegalStateException("ScrollView can host only one direct child"); 243 } 244 245 super.addView(child, params); 246 } 247 248 @Override 249 public void addView(View child, int index, ViewGroup.LayoutParams params) { 250 if (getChildCount() > 0) { 251 throw new IllegalStateException("ScrollView can host only one direct child"); 252 } 253 254 super.addView(child, index, params); 255 } 256 257 /** 258 * @return Returns true this ScrollView can be scrolled 259 */ 260 private boolean canScroll() { 261 View child = getChildAt(0); 262 if (child != null) { 263 int childHeight = child.getHeight(); 264 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 265 } 266 return false; 267 } 268 269 /** 270 * Indicates whether this ScrollView's content is stretched to fill the viewport. 271 * 272 * @return True if the content fills the viewport, false otherwise. 273 * 274 * @attr ref android.R.styleable#ScrollView_fillViewport 275 */ 276 public boolean isFillViewport() { 277 return mFillViewport; 278 } 279 280 /** 281 * Indicates this ScrollView whether it should stretch its content height to fill 282 * the viewport or not. 283 * 284 * @param fillViewport True to stretch the content's height to the viewport's 285 * boundaries, false otherwise. 286 * 287 * @attr ref android.R.styleable#ScrollView_fillViewport 288 */ 289 public void setFillViewport(boolean fillViewport) { 290 if (fillViewport != mFillViewport) { 291 mFillViewport = fillViewport; 292 requestLayout(); 293 } 294 } 295 296 /** 297 * @return Whether arrow scrolling will animate its transition. 298 */ 299 public boolean isSmoothScrollingEnabled() { 300 return mSmoothScrollingEnabled; 301 } 302 303 /** 304 * Set whether arrow scrolling will animate its transition. 305 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 306 */ 307 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 308 mSmoothScrollingEnabled = smoothScrollingEnabled; 309 } 310 311 @Override 312 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 313 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 314 315 if (!mFillViewport) { 316 return; 317 } 318 319 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 320 if (heightMode == MeasureSpec.UNSPECIFIED) { 321 return; 322 } 323 324 if (getChildCount() > 0) { 325 final View child = getChildAt(0); 326 int height = getMeasuredHeight(); 327 if (child.getMeasuredHeight() < height) { 328 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 329 330 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, 331 mPaddingLeft + mPaddingRight, lp.width); 332 height -= mPaddingTop; 333 height -= mPaddingBottom; 334 int childHeightMeasureSpec = 335 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 336 337 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 338 } 339 } 340 } 341 342 @Override 343 public boolean dispatchKeyEvent(KeyEvent event) { 344 // Let the focused view and/or our descendants get the key first 345 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 346 } 347 348 /** 349 * You can call this function yourself to have the scroll view perform 350 * scrolling from a key event, just as if the event had been dispatched to 351 * it by the view hierarchy. 352 * 353 * @param event The key event to execute. 354 * @return Return true if the event was handled, else false. 355 */ 356 public boolean executeKeyEvent(KeyEvent event) { 357 mTempRect.setEmpty(); 358 359 if (!canScroll()) { 360 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { 361 View currentFocused = findFocus(); 362 if (currentFocused == this) currentFocused = null; 363 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 364 currentFocused, View.FOCUS_DOWN); 365 return nextFocused != null 366 && nextFocused != this 367 && nextFocused.requestFocus(View.FOCUS_DOWN); 368 } 369 return false; 370 } 371 372 boolean handled = false; 373 if (event.getAction() == KeyEvent.ACTION_DOWN) { 374 switch (event.getKeyCode()) { 375 case KeyEvent.KEYCODE_DPAD_UP: 376 if (!event.isAltPressed()) { 377 handled = arrowScroll(View.FOCUS_UP); 378 } else { 379 handled = fullScroll(View.FOCUS_UP); 380 } 381 break; 382 case KeyEvent.KEYCODE_DPAD_DOWN: 383 if (!event.isAltPressed()) { 384 handled = arrowScroll(View.FOCUS_DOWN); 385 } else { 386 handled = fullScroll(View.FOCUS_DOWN); 387 } 388 break; 389 case KeyEvent.KEYCODE_SPACE: 390 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 391 break; 392 } 393 } 394 395 return handled; 396 } 397 398 private boolean inChild(int x, int y) { 399 if (getChildCount() > 0) { 400 final int scrollY = mScrollY; 401 final View child = getChildAt(0); 402 return !(y < child.getTop() - scrollY 403 || y >= child.getBottom() - scrollY 404 || x < child.getLeft() 405 || x >= child.getRight()); 406 } 407 return false; 408 } 409 410 @Override 411 public boolean onInterceptTouchEvent(MotionEvent ev) { 412 /* 413 * This method JUST determines whether we want to intercept the motion. 414 * If we return true, onMotionEvent will be called and we do the actual 415 * scrolling there. 416 */ 417 418 /* 419 * Shortcut the most recurring case: the user is in the dragging 420 * state and he is moving his finger. We want to intercept this 421 * motion. 422 */ 423 final int action = ev.getAction(); 424 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 425 return true; 426 } 427 428 switch (action & MotionEvent.ACTION_MASK) { 429 case MotionEvent.ACTION_MOVE: { 430 /* 431 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 432 * whether the user has moved far enough from his original down touch. 433 */ 434 435 /* 436 * Locally do absolute value. mLastMotionY is set to the y value 437 * of the down event. 438 */ 439 final int activePointerId = mActivePointerId; 440 if (activePointerId == INVALID_POINTER) { 441 // If we don't have a valid id, the touch down wasn't on content. 442 break; 443 } 444 445 final int pointerIndex = ev.findPointerIndex(activePointerId); 446 final float y = ev.getY(pointerIndex); 447 final int yDiff = (int) Math.abs(y - mLastMotionY); 448 if (yDiff > mTouchSlop) { 449 mIsBeingDragged = true; 450 mLastMotionY = y; 451 if (mScrollStrictSpan == null) { 452 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 453 } 454 } 455 break; 456 } 457 458 case MotionEvent.ACTION_DOWN: { 459 final float y = ev.getY(); 460 if (!inChild((int) ev.getX(), (int) y)) { 461 mIsBeingDragged = false; 462 break; 463 } 464 465 /* 466 * Remember location of down touch. 467 * ACTION_DOWN always refers to pointer index 0. 468 */ 469 mLastMotionY = y; 470 mActivePointerId = ev.getPointerId(0); 471 472 /* 473 * If being flinged and user touches the screen, initiate drag; 474 * otherwise don't. mScroller.isFinished should be false when 475 * being flinged. 476 */ 477 mIsBeingDragged = !mScroller.isFinished(); 478 if (mIsBeingDragged && mScrollStrictSpan == null) { 479 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 480 } 481 break; 482 } 483 484 case MotionEvent.ACTION_CANCEL: 485 case MotionEvent.ACTION_UP: 486 /* Release the drag */ 487 mIsBeingDragged = false; 488 mActivePointerId = INVALID_POINTER; 489 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 490 invalidate(); 491 } 492 break; 493 case MotionEvent.ACTION_POINTER_UP: 494 onSecondaryPointerUp(ev); 495 break; 496 } 497 498 /* 499 * The only time we want to intercept motion events is if we are in the 500 * drag mode. 501 */ 502 return mIsBeingDragged; 503 } 504 505 @Override 506 public boolean onTouchEvent(MotionEvent ev) { 507 508 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 509 // Don't handle edge touches immediately -- they may actually belong to one of our 510 // descendants. 511 return false; 512 } 513 514 if (mVelocityTracker == null) { 515 mVelocityTracker = VelocityTracker.obtain(); 516 } 517 mVelocityTracker.addMovement(ev); 518 519 final int action = ev.getAction(); 520 521 switch (action & MotionEvent.ACTION_MASK) { 522 case MotionEvent.ACTION_DOWN: { 523 mIsBeingDragged = getChildCount() != 0; 524 if (!mIsBeingDragged) { 525 return false; 526 } 527 528 /* 529 * If being flinged and user touches, stop the fling. isFinished 530 * will be false if being flinged. 531 */ 532 if (!mScroller.isFinished()) { 533 mScroller.abortAnimation(); 534 if (mFlingStrictSpan != null) { 535 mFlingStrictSpan.finish(); 536 mFlingStrictSpan = null; 537 } 538 } 539 540 // Remember where the motion event started 541 mLastMotionY = ev.getY(); 542 mActivePointerId = ev.getPointerId(0); 543 break; 544 } 545 case MotionEvent.ACTION_MOVE: 546 if (mIsBeingDragged) { 547 // Scroll to follow the motion event 548 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 549 final float y = ev.getY(activePointerIndex); 550 final int deltaY = (int) (mLastMotionY - y); 551 mLastMotionY = y; 552 553 final int oldX = mScrollX; 554 final int oldY = mScrollY; 555 final int range = getScrollRange(); 556 if (overScrollBy(0, deltaY, 0, mScrollY, 0, range, 557 0, mOverscrollDistance, true)) { 558 // Break our velocity if we hit a scroll barrier. 559 mVelocityTracker.clear(); 560 } 561 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 562 563 final int overscrollMode = getOverScrollMode(); 564 if (overscrollMode == OVER_SCROLL_ALWAYS || 565 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { 566 final int pulledToY = oldY + deltaY; 567 if (pulledToY < 0) { 568 mEdgeGlowTop.onPull((float) deltaY / getHeight()); 569 if (!mEdgeGlowBottom.isFinished()) { 570 mEdgeGlowBottom.onRelease(); 571 } 572 } else if (pulledToY > range) { 573 mEdgeGlowBottom.onPull((float) deltaY / getHeight()); 574 if (!mEdgeGlowTop.isFinished()) { 575 mEdgeGlowTop.onRelease(); 576 } 577 } 578 if (mEdgeGlowTop != null 579 && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) { 580 invalidate(); 581 } 582 } 583 } 584 break; 585 case MotionEvent.ACTION_UP: 586 if (mIsBeingDragged) { 587 final VelocityTracker velocityTracker = mVelocityTracker; 588 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 589 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 590 591 if (getChildCount() > 0) { 592 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 593 fling(-initialVelocity); 594 } else { 595 final int bottom = getScrollRange(); 596 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, bottom)) { 597 invalidate(); 598 } 599 } 600 } 601 602 mActivePointerId = INVALID_POINTER; 603 endDrag(); 604 } 605 break; 606 case MotionEvent.ACTION_CANCEL: 607 if (mIsBeingDragged && getChildCount() > 0) { 608 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 609 invalidate(); 610 } 611 mActivePointerId = INVALID_POINTER; 612 endDrag(); 613 } 614 break; 615 case MotionEvent.ACTION_POINTER_DOWN: { 616 final int index = ev.getActionIndex(); 617 final float y = ev.getY(index); 618 mLastMotionY = y; 619 mActivePointerId = ev.getPointerId(index); 620 break; 621 } 622 case MotionEvent.ACTION_POINTER_UP: 623 onSecondaryPointerUp(ev); 624 mLastMotionY = ev.getY(ev.findPointerIndex(mActivePointerId)); 625 break; 626 } 627 return true; 628 } 629 630 private void onSecondaryPointerUp(MotionEvent ev) { 631 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 632 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 633 final int pointerId = ev.getPointerId(pointerIndex); 634 if (pointerId == mActivePointerId) { 635 // This was our active pointer going up. Choose a new 636 // active pointer and adjust accordingly. 637 // TODO: Make this decision more intelligent. 638 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 639 mLastMotionY = ev.getY(newPointerIndex); 640 mActivePointerId = ev.getPointerId(newPointerIndex); 641 if (mVelocityTracker != null) { 642 mVelocityTracker.clear(); 643 } 644 } 645 } 646 647 @Override 648 public boolean onGenericMotionEvent(MotionEvent event) { 649 if ((event.getSource() & InputDevice.SOURCE_CLASS_POINTER) != 0) { 650 switch (event.getAction()) { 651 case MotionEvent.ACTION_SCROLL: { 652 if (!mIsBeingDragged) { 653 final float vscroll = event.getAxisValue(MotionEvent.AXIS_VSCROLL); 654 if (vscroll != 0) { 655 final int delta = (int) (vscroll * getVerticalScrollFactor()); 656 final int range = getScrollRange(); 657 int oldScrollY = mScrollY; 658 int newScrollY = oldScrollY - delta; 659 if (newScrollY < 0) { 660 newScrollY = 0; 661 } else if (newScrollY > range) { 662 newScrollY = range; 663 } 664 if (newScrollY != oldScrollY) { 665 super.scrollTo(mScrollX, newScrollY); 666 return true; 667 } 668 } 669 } 670 } 671 } 672 } 673 return super.onGenericMotionEvent(event); 674 } 675 676 @Override 677 protected void onOverScrolled(int scrollX, int scrollY, 678 boolean clampedX, boolean clampedY) { 679 // Treat animating scrolls differently; see #computeScroll() for why. 680 if (!mScroller.isFinished()) { 681 mScrollX = scrollX; 682 mScrollY = scrollY; 683 invalidateParentIfNeeded(); 684 if (clampedY) { 685 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 686 } 687 } else { 688 super.scrollTo(scrollX, scrollY); 689 } 690 awakenScrollBars(); 691 } 692 693 private int getScrollRange() { 694 int scrollRange = 0; 695 if (getChildCount() > 0) { 696 View child = getChildAt(0); 697 scrollRange = Math.max(0, 698 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); 699 } 700 return scrollRange; 701 } 702 703 /** 704 * <p> 705 * Finds the next focusable component that fits in this View's bounds 706 * (excluding fading edges) pretending that this View's top is located at 707 * the parameter top. 708 * </p> 709 * 710 * @param topFocus look for a candidate at the top of the bounds if topFocus is true, 711 * or at the bottom of the bounds if topFocus is false 712 * @param top the top offset of the bounds in which a focusable must be 713 * found (the fading edge is assumed to start at this position) 714 * @param preferredFocusable the View that has highest priority and will be 715 * returned if it is within my bounds (null is valid) 716 * @return the next focusable component in the bounds or null if none can be found 717 */ 718 private View findFocusableViewInMyBounds(final boolean topFocus, 719 final int top, View preferredFocusable) { 720 /* 721 * The fading edge's transparent side should be considered for focus 722 * since it's mostly visible, so we divide the actual fading edge length 723 * by 2. 724 */ 725 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 726 final int topWithoutFadingEdge = top + fadingEdgeLength; 727 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 728 729 if ((preferredFocusable != null) 730 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 731 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 732 return preferredFocusable; 733 } 734 735 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 736 bottomWithoutFadingEdge); 737 } 738 739 /** 740 * <p> 741 * Finds the next focusable component that fits in the specified bounds. 742 * </p> 743 * 744 * @param topFocus look for a candidate is the one at the top of the bounds 745 * if topFocus is true, or at the bottom of the bounds if topFocus is 746 * false 747 * @param top the top offset of the bounds in which a focusable must be 748 * found 749 * @param bottom the bottom offset of the bounds in which a focusable must 750 * be found 751 * @return the next focusable component in the bounds or null if none can 752 * be found 753 */ 754 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 755 756 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 757 View focusCandidate = null; 758 759 /* 760 * A fully contained focusable is one where its top is below the bound's 761 * top, and its bottom is above the bound's bottom. A partially 762 * contained focusable is one where some part of it is within the 763 * bounds, but it also has some part that is not within bounds. A fully contained 764 * focusable is preferred to a partially contained focusable. 765 */ 766 boolean foundFullyContainedFocusable = false; 767 768 int count = focusables.size(); 769 for (int i = 0; i < count; i++) { 770 View view = focusables.get(i); 771 int viewTop = view.getTop(); 772 int viewBottom = view.getBottom(); 773 774 if (top < viewBottom && viewTop < bottom) { 775 /* 776 * the focusable is in the target area, it is a candidate for 777 * focusing 778 */ 779 780 final boolean viewIsFullyContained = (top < viewTop) && 781 (viewBottom < bottom); 782 783 if (focusCandidate == null) { 784 /* No candidate, take this one */ 785 focusCandidate = view; 786 foundFullyContainedFocusable = viewIsFullyContained; 787 } else { 788 final boolean viewIsCloserToBoundary = 789 (topFocus && viewTop < focusCandidate.getTop()) || 790 (!topFocus && viewBottom > focusCandidate 791 .getBottom()); 792 793 if (foundFullyContainedFocusable) { 794 if (viewIsFullyContained && viewIsCloserToBoundary) { 795 /* 796 * We're dealing with only fully contained views, so 797 * it has to be closer to the boundary to beat our 798 * candidate 799 */ 800 focusCandidate = view; 801 } 802 } else { 803 if (viewIsFullyContained) { 804 /* Any fully contained view beats a partially contained view */ 805 focusCandidate = view; 806 foundFullyContainedFocusable = true; 807 } else if (viewIsCloserToBoundary) { 808 /* 809 * Partially contained view beats another partially 810 * contained view if it's closer 811 */ 812 focusCandidate = view; 813 } 814 } 815 } 816 } 817 } 818 819 return focusCandidate; 820 } 821 822 /** 823 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 824 * method will scroll the view by one page up or down and give the focus 825 * to the topmost/bottommost component in the new visible area. If no 826 * component is a good candidate for focus, this scrollview reclaims the 827 * focus.</p> 828 * 829 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 830 * to go one page up or 831 * {@link android.view.View#FOCUS_DOWN} to go one page down 832 * @return true if the key event is consumed by this method, false otherwise 833 */ 834 public boolean pageScroll(int direction) { 835 boolean down = direction == View.FOCUS_DOWN; 836 int height = getHeight(); 837 838 if (down) { 839 mTempRect.top = getScrollY() + height; 840 int count = getChildCount(); 841 if (count > 0) { 842 View view = getChildAt(count - 1); 843 if (mTempRect.top + height > view.getBottom()) { 844 mTempRect.top = view.getBottom() - height; 845 } 846 } 847 } else { 848 mTempRect.top = getScrollY() - height; 849 if (mTempRect.top < 0) { 850 mTempRect.top = 0; 851 } 852 } 853 mTempRect.bottom = mTempRect.top + height; 854 855 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 856 } 857 858 /** 859 * <p>Handles scrolling in response to a "home/end" shortcut press. This 860 * method will scroll the view to the top or bottom and give the focus 861 * to the topmost/bottommost component in the new visible area. If no 862 * component is a good candidate for focus, this scrollview reclaims the 863 * focus.</p> 864 * 865 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 866 * to go the top of the view or 867 * {@link android.view.View#FOCUS_DOWN} to go the bottom 868 * @return true if the key event is consumed by this method, false otherwise 869 */ 870 public boolean fullScroll(int direction) { 871 boolean down = direction == View.FOCUS_DOWN; 872 int height = getHeight(); 873 874 mTempRect.top = 0; 875 mTempRect.bottom = height; 876 877 if (down) { 878 int count = getChildCount(); 879 if (count > 0) { 880 View view = getChildAt(count - 1); 881 mTempRect.bottom = view.getBottom() + mPaddingBottom; 882 mTempRect.top = mTempRect.bottom - height; 883 } 884 } 885 886 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 887 } 888 889 /** 890 * <p>Scrolls the view to make the area defined by <code>top</code> and 891 * <code>bottom</code> visible. This method attempts to give the focus 892 * to a component visible in this area. If no component can be focused in 893 * the new visible area, the focus is reclaimed by this ScrollView.</p> 894 * 895 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 896 * to go upward, {@link android.view.View#FOCUS_DOWN} to downward 897 * @param top the top offset of the new area to be made visible 898 * @param bottom the bottom offset of the new area to be made visible 899 * @return true if the key event is consumed by this method, false otherwise 900 */ 901 private boolean scrollAndFocus(int direction, int top, int bottom) { 902 boolean handled = true; 903 904 int height = getHeight(); 905 int containerTop = getScrollY(); 906 int containerBottom = containerTop + height; 907 boolean up = direction == View.FOCUS_UP; 908 909 View newFocused = findFocusableViewInBounds(up, top, bottom); 910 if (newFocused == null) { 911 newFocused = this; 912 } 913 914 if (top >= containerTop && bottom <= containerBottom) { 915 handled = false; 916 } else { 917 int delta = up ? (top - containerTop) : (bottom - containerBottom); 918 doScrollY(delta); 919 } 920 921 if (newFocused != findFocus()) newFocused.requestFocus(direction); 922 923 return handled; 924 } 925 926 /** 927 * Handle scrolling in response to an up or down arrow click. 928 * 929 * @param direction The direction corresponding to the arrow key that was 930 * pressed 931 * @return True if we consumed the event, false otherwise 932 */ 933 public boolean arrowScroll(int direction) { 934 935 View currentFocused = findFocus(); 936 if (currentFocused == this) currentFocused = null; 937 938 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 939 940 final int maxJump = getMaxScrollAmount(); 941 942 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 943 nextFocused.getDrawingRect(mTempRect); 944 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 945 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 946 doScrollY(scrollDelta); 947 nextFocused.requestFocus(direction); 948 } else { 949 // no new focus 950 int scrollDelta = maxJump; 951 952 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 953 scrollDelta = getScrollY(); 954 } else if (direction == View.FOCUS_DOWN) { 955 if (getChildCount() > 0) { 956 int daBottom = getChildAt(0).getBottom(); 957 int screenBottom = getScrollY() + getHeight() - mPaddingBottom; 958 if (daBottom - screenBottom < maxJump) { 959 scrollDelta = daBottom - screenBottom; 960 } 961 } 962 } 963 if (scrollDelta == 0) { 964 return false; 965 } 966 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 967 } 968 969 if (currentFocused != null && currentFocused.isFocused() 970 && isOffScreen(currentFocused)) { 971 // previously focused item still has focus and is off screen, give 972 // it up (take it back to ourselves) 973 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 974 // sure to 975 // get it) 976 final int descendantFocusability = getDescendantFocusability(); // save 977 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 978 requestFocus(); 979 setDescendantFocusability(descendantFocusability); // restore 980 } 981 return true; 982 } 983 984 /** 985 * @return whether the descendant of this scroll view is scrolled off 986 * screen. 987 */ 988 private boolean isOffScreen(View descendant) { 989 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 990 } 991 992 /** 993 * @return whether the descendant of this scroll view is within delta 994 * pixels of being on the screen. 995 */ 996 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 997 descendant.getDrawingRect(mTempRect); 998 offsetDescendantRectToMyCoords(descendant, mTempRect); 999 1000 return (mTempRect.bottom + delta) >= getScrollY() 1001 && (mTempRect.top - delta) <= (getScrollY() + height); 1002 } 1003 1004 /** 1005 * Smooth scroll by a Y delta 1006 * 1007 * @param delta the number of pixels to scroll by on the Y axis 1008 */ 1009 private void doScrollY(int delta) { 1010 if (delta != 0) { 1011 if (mSmoothScrollingEnabled) { 1012 smoothScrollBy(0, delta); 1013 } else { 1014 scrollBy(0, delta); 1015 } 1016 } 1017 } 1018 1019 /** 1020 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 1021 * 1022 * @param dx the number of pixels to scroll by on the X axis 1023 * @param dy the number of pixels to scroll by on the Y axis 1024 */ 1025 public final void smoothScrollBy(int dx, int dy) { 1026 if (getChildCount() == 0) { 1027 // Nothing to do. 1028 return; 1029 } 1030 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 1031 if (duration > ANIMATED_SCROLL_GAP) { 1032 final int height = getHeight() - mPaddingBottom - mPaddingTop; 1033 final int bottom = getChildAt(0).getHeight(); 1034 final int maxY = Math.max(0, bottom - height); 1035 final int scrollY = mScrollY; 1036 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 1037 1038 mScroller.startScroll(mScrollX, scrollY, 0, dy); 1039 invalidate(); 1040 } else { 1041 if (!mScroller.isFinished()) { 1042 mScroller.abortAnimation(); 1043 if (mFlingStrictSpan != null) { 1044 mFlingStrictSpan.finish(); 1045 mFlingStrictSpan = null; 1046 } 1047 } 1048 scrollBy(dx, dy); 1049 } 1050 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1051 } 1052 1053 /** 1054 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1055 * 1056 * @param x the position where to scroll on the X axis 1057 * @param y the position where to scroll on the Y axis 1058 */ 1059 public final void smoothScrollTo(int x, int y) { 1060 smoothScrollBy(x - mScrollX, y - mScrollY); 1061 } 1062 1063 /** 1064 * <p>The scroll range of a scroll view is the overall height of all of its 1065 * children.</p> 1066 */ 1067 @Override 1068 protected int computeVerticalScrollRange() { 1069 final int count = getChildCount(); 1070 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1071 if (count == 0) { 1072 return contentHeight; 1073 } 1074 1075 int scrollRange = getChildAt(0).getBottom(); 1076 final int scrollY = mScrollY; 1077 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1078 if (scrollY < 0) { 1079 scrollRange -= scrollY; 1080 } else if (scrollY > overscrollBottom) { 1081 scrollRange += scrollY - overscrollBottom; 1082 } 1083 1084 return scrollRange; 1085 } 1086 1087 @Override 1088 protected int computeVerticalScrollOffset() { 1089 return Math.max(0, super.computeVerticalScrollOffset()); 1090 } 1091 1092 @Override 1093 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1094 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1095 1096 int childWidthMeasureSpec; 1097 int childHeightMeasureSpec; 1098 1099 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1100 + mPaddingRight, lp.width); 1101 1102 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1103 1104 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1105 } 1106 1107 @Override 1108 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1109 int parentHeightMeasureSpec, int heightUsed) { 1110 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1111 1112 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1113 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1114 + widthUsed, lp.width); 1115 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1116 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1117 1118 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1119 } 1120 1121 @Override 1122 public void computeScroll() { 1123 if (mScroller.computeScrollOffset()) { 1124 // This is called at drawing time by ViewGroup. We don't want to 1125 // re-show the scrollbars at this point, which scrollTo will do, 1126 // so we replicate most of scrollTo here. 1127 // 1128 // It's a little odd to call onScrollChanged from inside the drawing. 1129 // 1130 // It is, except when you remember that computeScroll() is used to 1131 // animate scrolling. So unless we want to defer the onScrollChanged() 1132 // until the end of the animated scrolling, we don't really have a 1133 // choice here. 1134 // 1135 // I agree. The alternative, which I think would be worse, is to post 1136 // something and tell the subclasses later. This is bad because there 1137 // will be a window where mScrollX/Y is different from what the app 1138 // thinks it is. 1139 // 1140 int oldX = mScrollX; 1141 int oldY = mScrollY; 1142 int x = mScroller.getCurrX(); 1143 int y = mScroller.getCurrY(); 1144 1145 if (oldX != x || oldY != y) { 1146 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 1147 0, mOverflingDistance, false); 1148 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1149 1150 final int range = getScrollRange(); 1151 final int overscrollMode = getOverScrollMode(); 1152 if (overscrollMode == OVER_SCROLL_ALWAYS || 1153 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { 1154 if (y < 0 && oldY >= 0) { 1155 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1156 } else if (y > range && oldY <= range) { 1157 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1158 } 1159 } 1160 } 1161 awakenScrollBars(); 1162 1163 // Keep on drawing until the animation has finished. 1164 postInvalidate(); 1165 } else { 1166 if (mFlingStrictSpan != null) { 1167 mFlingStrictSpan.finish(); 1168 mFlingStrictSpan = null; 1169 } 1170 } 1171 } 1172 1173 /** 1174 * Scrolls the view to the given child. 1175 * 1176 * @param child the View to scroll to 1177 */ 1178 private void scrollToChild(View child) { 1179 child.getDrawingRect(mTempRect); 1180 1181 /* Offset from child's local coordinates to ScrollView coordinates */ 1182 offsetDescendantRectToMyCoords(child, mTempRect); 1183 1184 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1185 1186 if (scrollDelta != 0) { 1187 scrollBy(0, scrollDelta); 1188 } 1189 } 1190 1191 /** 1192 * If rect is off screen, scroll just enough to get it (or at least the 1193 * first screen size chunk of it) on screen. 1194 * 1195 * @param rect The rectangle. 1196 * @param immediate True to scroll immediately without animation 1197 * @return true if scrolling was performed 1198 */ 1199 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1200 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1201 final boolean scroll = delta != 0; 1202 if (scroll) { 1203 if (immediate) { 1204 scrollBy(0, delta); 1205 } else { 1206 smoothScrollBy(0, delta); 1207 } 1208 } 1209 return scroll; 1210 } 1211 1212 /** 1213 * Compute the amount to scroll in the Y direction in order to get 1214 * a rectangle completely on the screen (or, if taller than the screen, 1215 * at least the first screen size chunk of it). 1216 * 1217 * @param rect The rect. 1218 * @return The scroll delta. 1219 */ 1220 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1221 if (getChildCount() == 0) return 0; 1222 1223 int height = getHeight(); 1224 int screenTop = getScrollY(); 1225 int screenBottom = screenTop + height; 1226 1227 int fadingEdge = getVerticalFadingEdgeLength(); 1228 1229 // leave room for top fading edge as long as rect isn't at very top 1230 if (rect.top > 0) { 1231 screenTop += fadingEdge; 1232 } 1233 1234 // leave room for bottom fading edge as long as rect isn't at very bottom 1235 if (rect.bottom < getChildAt(0).getHeight()) { 1236 screenBottom -= fadingEdge; 1237 } 1238 1239 int scrollYDelta = 0; 1240 1241 if (rect.bottom > screenBottom && rect.top > screenTop) { 1242 // need to move down to get it in view: move down just enough so 1243 // that the entire rectangle is in view (or at least the first 1244 // screen size chunk). 1245 1246 if (rect.height() > height) { 1247 // just enough to get screen size chunk on 1248 scrollYDelta += (rect.top - screenTop); 1249 } else { 1250 // get entire rect at bottom of screen 1251 scrollYDelta += (rect.bottom - screenBottom); 1252 } 1253 1254 // make sure we aren't scrolling beyond the end of our content 1255 int bottom = getChildAt(0).getBottom(); 1256 int distanceToBottom = bottom - screenBottom; 1257 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1258 1259 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1260 // need to move up to get it in view: move up just enough so that 1261 // entire rectangle is in view (or at least the first screen 1262 // size chunk of it). 1263 1264 if (rect.height() > height) { 1265 // screen size chunk 1266 scrollYDelta -= (screenBottom - rect.bottom); 1267 } else { 1268 // entire rect at top 1269 scrollYDelta -= (screenTop - rect.top); 1270 } 1271 1272 // make sure we aren't scrolling any further than the top our content 1273 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1274 } 1275 return scrollYDelta; 1276 } 1277 1278 @Override 1279 public void requestChildFocus(View child, View focused) { 1280 if (!mIsLayoutDirty) { 1281 scrollToChild(focused); 1282 } else { 1283 // The child may not be laid out yet, we can't compute the scroll yet 1284 mChildToScrollTo = focused; 1285 } 1286 super.requestChildFocus(child, focused); 1287 } 1288 1289 1290 /** 1291 * When looking for focus in children of a scroll view, need to be a little 1292 * more careful not to give focus to something that is scrolled off screen. 1293 * 1294 * This is more expensive than the default {@link android.view.ViewGroup} 1295 * implementation, otherwise this behavior might have been made the default. 1296 */ 1297 @Override 1298 protected boolean onRequestFocusInDescendants(int direction, 1299 Rect previouslyFocusedRect) { 1300 1301 // convert from forward / backward notation to up / down / left / right 1302 // (ugh). 1303 if (direction == View.FOCUS_FORWARD) { 1304 direction = View.FOCUS_DOWN; 1305 } else if (direction == View.FOCUS_BACKWARD) { 1306 direction = View.FOCUS_UP; 1307 } 1308 1309 final View nextFocus = previouslyFocusedRect == null ? 1310 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1311 FocusFinder.getInstance().findNextFocusFromRect(this, 1312 previouslyFocusedRect, direction); 1313 1314 if (nextFocus == null) { 1315 return false; 1316 } 1317 1318 if (isOffScreen(nextFocus)) { 1319 return false; 1320 } 1321 1322 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1323 } 1324 1325 @Override 1326 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1327 boolean immediate) { 1328 // offset into coordinate space of this scroll view 1329 rectangle.offset(child.getLeft() - child.getScrollX(), 1330 child.getTop() - child.getScrollY()); 1331 1332 return scrollToChildRect(rectangle, immediate); 1333 } 1334 1335 @Override 1336 public void requestLayout() { 1337 mIsLayoutDirty = true; 1338 super.requestLayout(); 1339 } 1340 1341 @Override 1342 protected void onDetachedFromWindow() { 1343 super.onDetachedFromWindow(); 1344 1345 if (mScrollStrictSpan != null) { 1346 mScrollStrictSpan.finish(); 1347 mScrollStrictSpan = null; 1348 } 1349 if (mFlingStrictSpan != null) { 1350 mFlingStrictSpan.finish(); 1351 mFlingStrictSpan = null; 1352 } 1353 } 1354 1355 @Override 1356 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1357 super.onLayout(changed, l, t, r, b); 1358 mIsLayoutDirty = false; 1359 // Give a child focus if it needs it 1360 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1361 scrollToChild(mChildToScrollTo); 1362 } 1363 mChildToScrollTo = null; 1364 1365 // Calling this with the present values causes it to re-clam them 1366 scrollTo(mScrollX, mScrollY); 1367 } 1368 1369 @Override 1370 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1371 super.onSizeChanged(w, h, oldw, oldh); 1372 1373 View currentFocused = findFocus(); 1374 if (null == currentFocused || this == currentFocused) 1375 return; 1376 1377 // If the currently-focused view was visible on the screen when the 1378 // screen was at the old height, then scroll the screen to make that 1379 // view visible with the new screen height. 1380 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1381 currentFocused.getDrawingRect(mTempRect); 1382 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1383 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1384 doScrollY(scrollDelta); 1385 } 1386 } 1387 1388 /** 1389 * Return true if child is an descendant of parent, (or equal to the parent). 1390 */ 1391 private boolean isViewDescendantOf(View child, View parent) { 1392 if (child == parent) { 1393 return true; 1394 } 1395 1396 final ViewParent theParent = child.getParent(); 1397 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1398 } 1399 1400 /** 1401 * Fling the scroll view 1402 * 1403 * @param velocityY The initial velocity in the Y direction. Positive 1404 * numbers mean that the finger/cursor is moving down the screen, 1405 * which means we want to scroll towards the top. 1406 */ 1407 public void fling(int velocityY) { 1408 if (getChildCount() > 0) { 1409 int height = getHeight() - mPaddingBottom - mPaddingTop; 1410 int bottom = getChildAt(0).getHeight(); 1411 1412 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1413 Math.max(0, bottom - height), 0, height/2); 1414 1415 final boolean movingDown = velocityY > 0; 1416 1417 View currentFocused = findFocus(); 1418 View newFocused = 1419 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), currentFocused); 1420 if (newFocused == null) { 1421 newFocused = this; 1422 } 1423 1424 if (newFocused != currentFocused) { 1425 newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP); 1426 } 1427 1428 if (mFlingStrictSpan == null) { 1429 mFlingStrictSpan = StrictMode.enterCriticalSpan("ScrollView-fling"); 1430 } 1431 1432 invalidate(); 1433 } 1434 } 1435 1436 private void endDrag() { 1437 mIsBeingDragged = false; 1438 1439 if (mVelocityTracker != null) { 1440 mVelocityTracker.recycle(); 1441 mVelocityTracker = null; 1442 } 1443 1444 if (mEdgeGlowTop != null) { 1445 mEdgeGlowTop.onRelease(); 1446 mEdgeGlowBottom.onRelease(); 1447 } 1448 1449 if (mScrollStrictSpan != null) { 1450 mScrollStrictSpan.finish(); 1451 mScrollStrictSpan = null; 1452 } 1453 } 1454 1455 /** 1456 * {@inheritDoc} 1457 * 1458 * <p>This version also clamps the scrolling to the bounds of our child. 1459 */ 1460 @Override 1461 public void scrollTo(int x, int y) { 1462 // we rely on the fact the View.scrollBy calls scrollTo. 1463 if (getChildCount() > 0) { 1464 View child = getChildAt(0); 1465 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1466 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1467 if (x != mScrollX || y != mScrollY) { 1468 super.scrollTo(x, y); 1469 } 1470 } 1471 } 1472 1473 @Override 1474 public void setOverScrollMode(int mode) { 1475 if (mode != OVER_SCROLL_NEVER) { 1476 if (mEdgeGlowTop == null) { 1477 Context context = getContext(); 1478 final Resources res = context.getResources(); 1479 final Drawable edge = res.getDrawable(R.drawable.overscroll_edge); 1480 final Drawable glow = res.getDrawable(R.drawable.overscroll_glow); 1481 mEdgeGlowTop = new EdgeGlow(context, edge, glow); 1482 mEdgeGlowBottom = new EdgeGlow(context, edge, glow); 1483 } 1484 } else { 1485 mEdgeGlowTop = null; 1486 mEdgeGlowBottom = null; 1487 } 1488 super.setOverScrollMode(mode); 1489 } 1490 1491 @Override 1492 public void draw(Canvas canvas) { 1493 super.draw(canvas); 1494 if (mEdgeGlowTop != null) { 1495 final int scrollY = mScrollY; 1496 if (!mEdgeGlowTop.isFinished()) { 1497 final int restoreCount = canvas.save(); 1498 final int width = getWidth() - mPaddingLeft - mPaddingRight; 1499 1500 canvas.translate(mPaddingLeft, Math.min(0, scrollY)); 1501 mEdgeGlowTop.setSize(width, getHeight()); 1502 if (mEdgeGlowTop.draw(canvas)) { 1503 invalidate(); 1504 } 1505 canvas.restoreToCount(restoreCount); 1506 } 1507 if (!mEdgeGlowBottom.isFinished()) { 1508 final int restoreCount = canvas.save(); 1509 final int width = getWidth() - mPaddingLeft - mPaddingRight; 1510 final int height = getHeight(); 1511 1512 canvas.translate(-width + mPaddingLeft, 1513 Math.max(getScrollRange(), scrollY) + height); 1514 canvas.rotate(180, width, 0); 1515 mEdgeGlowBottom.setSize(width, height); 1516 if (mEdgeGlowBottom.draw(canvas)) { 1517 invalidate(); 1518 } 1519 canvas.restoreToCount(restoreCount); 1520 } 1521 } 1522 } 1523 1524 private int clamp(int n, int my, int child) { 1525 if (my >= child || n < 0) { 1526 /* my >= child is this case: 1527 * |--------------- me ---------------| 1528 * |------ child ------| 1529 * or 1530 * |--------------- me ---------------| 1531 * |------ child ------| 1532 * or 1533 * |--------------- me ---------------| 1534 * |------ child ------| 1535 * 1536 * n < 0 is this case: 1537 * |------ me ------| 1538 * |-------- child --------| 1539 * |-- mScrollX --| 1540 */ 1541 return 0; 1542 } 1543 if ((my+n) > child) { 1544 /* this case: 1545 * |------ me ------| 1546 * |------ child ------| 1547 * |-- mScrollX --| 1548 */ 1549 return child-my; 1550 } 1551 return n; 1552 } 1553} 1554