ScrollView.java revision 9266c558bf1d21ff647525ff99f7dadbca417309
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.content.Context; 20import android.content.res.TypedArray; 21import android.graphics.Rect; 22import android.util.AttributeSet; 23import android.util.Config; 24import android.util.Log; 25import android.view.FocusFinder; 26import android.view.KeyEvent; 27import android.view.MotionEvent; 28import android.view.VelocityTracker; 29import android.view.View; 30import android.view.ViewConfiguration; 31import android.view.ViewGroup; 32import android.view.ViewParent; 33import android.view.animation.AnimationUtils; 34 35import com.android.internal.R; 36 37import java.util.List; 38 39/** 40 * Layout container for a view hierarchy that can be scrolled by the user, 41 * allowing it to be larger than the physical display. A ScrollView 42 * is a {@link FrameLayout}, meaning you should place one child in it 43 * containing the entire contents to scroll; this child may itself be a layout 44 * manager with a complex hierarchy of objects. A child that is often used 45 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 46 * array of top-level items that the user can scroll through. 47 * 48 * <p>You should never use a ScrollView with a {@link ListView}, since 49 * ListView takes care of its own scrolling. Most importantly, doing this 50 * defeats all of the important optimizations in ListView for dealing with 51 * large lists, since it effectively forces the ListView to display its entire 52 * list of items to fill up the infinite container supplied by ScrollView. 53 * 54 * <p>The {@link TextView} class also 55 * takes care of its own scrolling, so does not require a ScrollView, but 56 * using the two together is possible to achieve the effect of a text view 57 * within a larger container. 58 * 59 * <p>ScrollView only supports vertical scrolling. 60 */ 61public class ScrollView extends FrameLayout { 62 static final String TAG = "ScrollView"; 63 static final boolean localLOGV = false || Config.LOGV; 64 65 private static final int ANIMATED_SCROLL_GAP = 250; 66 67 /** 68 * When arrow scrolling, ListView will never scroll more than this factor 69 * times the height of the list. 70 */ 71 private static final float MAX_SCROLL_FACTOR = 0.5f; 72 73 74 private long mLastScroll; 75 76 private final Rect mTempRect = new Rect(); 77 private Scroller mScroller; 78 79 /** 80 * Flag to indicate that we are moving focus ourselves. This is so the 81 * code that watches for focus changes initiated outside this ScrollView 82 * knows that it does not have to do anything. 83 */ 84 private boolean mScrollViewMovedFocus; 85 86 /** 87 * Position of the last motion event. 88 */ 89 private float mLastMotionY; 90 91 /** 92 * True when the layout has changed but the traversal has not come through yet. 93 * Ideally the view hierarchy would keep track of this for us. 94 */ 95 private boolean mIsLayoutDirty = true; 96 97 /** 98 * The child to give focus to in the event that a child has requested focus while the 99 * layout is dirty. This prevents the scroll from being wrong if the child has not been 100 * laid out before requesting focus. 101 */ 102 private View mChildToScrollTo = null; 103 104 /** 105 * True if the user is currently dragging this ScrollView around. This is 106 * not the same as 'is being flinged', which can be checked by 107 * mScroller.isFinished() (flinging begins when the user lifts his finger). 108 */ 109 private boolean mIsBeingDragged = false; 110 111 /** 112 * Determines speed during touch scrolling 113 */ 114 private VelocityTracker mVelocityTracker; 115 116 /** 117 * When set to true, the scroll view measure its child to make it fill the currently 118 * visible area. 119 */ 120 private boolean mFillViewport; 121 122 /** 123 * Whether arrow scrolling is animated. 124 */ 125 private boolean mSmoothScrollingEnabled = true; 126 127 public ScrollView(Context context) { 128 this(context, null); 129 } 130 131 public ScrollView(Context context, AttributeSet attrs) { 132 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 133 } 134 135 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 136 super(context, attrs, defStyle); 137 initScrollView(); 138 139 TypedArray a = 140 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 141 142 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 143 144 a.recycle(); 145 } 146 147 @Override 148 protected float getTopFadingEdgeStrength() { 149 if (getChildCount() == 0) { 150 return 0.0f; 151 } 152 153 final int length = getVerticalFadingEdgeLength(); 154 if (mScrollY < length) { 155 return mScrollY / (float) length; 156 } 157 158 return 1.0f; 159 } 160 161 @Override 162 protected float getBottomFadingEdgeStrength() { 163 if (getChildCount() == 0) { 164 return 0.0f; 165 } 166 167 final int length = getVerticalFadingEdgeLength(); 168 final int bottom = getChildAt(0).getBottom(); 169 final int span = bottom - mScrollY - getHeight(); 170 if (span < length) { 171 return span / (float) length; 172 } 173 174 return 1.0f; 175 } 176 177 /** 178 * @return The maximum amount this scroll view will scroll in response to 179 * an arrow event. 180 */ 181 public int getMaxScrollAmount() { 182 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 183 } 184 185 186 private void initScrollView() { 187 mScroller = new Scroller(getContext()); 188 setFocusable(true); 189 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 190 setWillNotDraw(false); 191 } 192 193 @Override 194 public void addView(View child) { 195 if (getChildCount() > 0) { 196 throw new IllegalStateException("ScrollView can host only one direct child"); 197 } 198 199 super.addView(child); 200 } 201 202 @Override 203 public void addView(View child, int index) { 204 if (getChildCount() > 0) { 205 throw new IllegalStateException("ScrollView can host only one direct child"); 206 } 207 208 super.addView(child, index); 209 } 210 211 @Override 212 public void addView(View child, ViewGroup.LayoutParams params) { 213 if (getChildCount() > 0) { 214 throw new IllegalStateException("ScrollView can host only one direct child"); 215 } 216 217 super.addView(child, params); 218 } 219 220 @Override 221 public void addView(View child, int index, ViewGroup.LayoutParams params) { 222 if (getChildCount() > 0) { 223 throw new IllegalStateException("ScrollView can host only one direct child"); 224 } 225 226 super.addView(child, index, params); 227 } 228 229 /** 230 * @return Returns true this ScrollView can be scrolled 231 */ 232 private boolean canScroll() { 233 View child = getChildAt(0); 234 if (child != null) { 235 int childHeight = child.getHeight(); 236 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 237 } 238 return false; 239 } 240 241 /** 242 * Indicates whether this ScrollView's content is stretched to fill the viewport. 243 * 244 * @return True if the content fills the viewport, false otherwise. 245 */ 246 public boolean isFillViewport() { 247 return mFillViewport; 248 } 249 250 /** 251 * Indicates this ScrollView whether it should stretch its content height to fill 252 * the viewport or not. 253 * 254 * @param fillViewport True to stretch the content's height to the viewport's 255 * boundaries, false otherwise. 256 */ 257 public void setFillViewport(boolean fillViewport) { 258 if (fillViewport != mFillViewport) { 259 mFillViewport = fillViewport; 260 requestLayout(); 261 } 262 } 263 264 /** 265 * @return Whether arrow scrolling will animate its transition. 266 */ 267 public boolean isSmoothScrollingEnabled() { 268 return mSmoothScrollingEnabled; 269 } 270 271 /** 272 * Set whether arrow scrolling will animate its transition. 273 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 274 */ 275 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 276 mSmoothScrollingEnabled = smoothScrollingEnabled; 277 } 278 279 @Override 280 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 281 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 282 283 if (!mFillViewport) { 284 return; 285 } 286 287 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 288 if (heightMode == MeasureSpec.UNSPECIFIED) { 289 return; 290 } 291 292 final View child = getChildAt(0); 293 int height = getMeasuredHeight(); 294 if (child.getMeasuredHeight() < height) { 295 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 296 297 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 298 + mPaddingRight, lp.width); 299 height -= mPaddingTop; 300 height -= mPaddingBottom; 301 int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 302 303 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 304 } 305 } 306 307 @Override 308 public boolean dispatchKeyEvent(KeyEvent event) { 309 // Let the focused view and/or our descendants get the key first 310 boolean handled = super.dispatchKeyEvent(event); 311 if (handled) { 312 return true; 313 } 314 return executeKeyEvent(event); 315 } 316 317 /** 318 * You can call this function yourself to have the scroll view perform 319 * scrolling from a key event, just as if the event had been dispatched to 320 * it by the view hierarchy. 321 * 322 * @param event The key event to execute. 323 * @return Return true if the event was handled, else false. 324 */ 325 public boolean executeKeyEvent(KeyEvent event) { 326 mTempRect.setEmpty(); 327 328 if (!canScroll()) { 329 if (isFocused()) { 330 View currentFocused = findFocus(); 331 if (currentFocused == this) currentFocused = null; 332 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 333 currentFocused, View.FOCUS_DOWN); 334 return nextFocused != null 335 && nextFocused != this 336 && nextFocused.requestFocus(View.FOCUS_DOWN); 337 } 338 return false; 339 } 340 341 boolean handled = false; 342 if (event.getAction() == KeyEvent.ACTION_DOWN) { 343 switch (event.getKeyCode()) { 344 case KeyEvent.KEYCODE_DPAD_UP: 345 if (!event.isAltPressed()) { 346 handled = arrowScroll(View.FOCUS_UP); 347 } else { 348 handled = fullScroll(View.FOCUS_UP); 349 } 350 break; 351 case KeyEvent.KEYCODE_DPAD_DOWN: 352 if (!event.isAltPressed()) { 353 handled = arrowScroll(View.FOCUS_DOWN); 354 } else { 355 handled = fullScroll(View.FOCUS_DOWN); 356 } 357 break; 358 case KeyEvent.KEYCODE_SPACE: 359 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 360 break; 361 } 362 } 363 364 return handled; 365 } 366 367 @Override 368 public boolean onInterceptTouchEvent(MotionEvent ev) { 369 /* 370 * This method JUST determines whether we want to intercept the motion. 371 * If we return true, onMotionEvent will be called and we do the actual 372 * scrolling there. 373 */ 374 375 /* 376 * Shortcut the most recurring case: the user is in the dragging 377 * state and he is moving his finger. We want to intercept this 378 * motion. 379 */ 380 final int action = ev.getAction(); 381 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 382 return true; 383 } 384 385 if (!canScroll()) { 386 mIsBeingDragged = false; 387 return false; 388 } 389 390 final float y = ev.getY(); 391 392 switch (action) { 393 case MotionEvent.ACTION_MOVE: 394 /* 395 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 396 * whether the user has moved far enough from his original down touch. 397 */ 398 399 /* 400 * Locally do absolute value. mLastMotionY is set to the y value 401 * of the down event. 402 */ 403 final int yDiff = (int) Math.abs(y - mLastMotionY); 404 if (yDiff > ViewConfiguration.getTouchSlop()) { 405 mIsBeingDragged = true; 406 } 407 break; 408 409 case MotionEvent.ACTION_DOWN: 410 /* Remember location of down touch */ 411 mLastMotionY = y; 412 413 /* 414 * If being flinged and user touches the screen, initiate drag; 415 * otherwise don't. mScroller.isFinished should be false when 416 * being flinged. 417 */ 418 mIsBeingDragged = !mScroller.isFinished(); 419 break; 420 421 case MotionEvent.ACTION_CANCEL: 422 case MotionEvent.ACTION_UP: 423 /* Release the drag */ 424 mIsBeingDragged = false; 425 break; 426 } 427 428 /* 429 * The only time we want to intercept motion events is if we are in the 430 * drag mode. 431 */ 432 return mIsBeingDragged; 433 } 434 435 @Override 436 public boolean onTouchEvent(MotionEvent ev) { 437 438 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 439 // Don't handle edge touches immediately -- they may actually belong to one of our 440 // descendants. 441 return false; 442 } 443 444 if (!canScroll()) { 445 return false; 446 } 447 448 if (mVelocityTracker == null) { 449 mVelocityTracker = VelocityTracker.obtain(); 450 } 451 mVelocityTracker.addMovement(ev); 452 453 final int action = ev.getAction(); 454 final float y = ev.getY(); 455 456 switch (action) { 457 case MotionEvent.ACTION_DOWN: 458 /* 459 * If being flinged and user touches, stop the fling. isFinished 460 * will be false if being flinged. 461 */ 462 if (!mScroller.isFinished()) { 463 mScroller.abortAnimation(); 464 } 465 466 // Remember where the motion event started 467 mLastMotionY = y; 468 break; 469 case MotionEvent.ACTION_MOVE: 470 // Scroll to follow the motion event 471 final int deltaY = (int) (mLastMotionY - y); 472 mLastMotionY = y; 473 474 if (deltaY < 0) { 475 if (mScrollY > 0) { 476 scrollBy(0, deltaY); 477 } 478 } else if (deltaY > 0) { 479 final int bottomEdge = getHeight() - mPaddingBottom; 480 final int availableToScroll = getChildAt(0).getBottom() - mScrollY - bottomEdge; 481 if (availableToScroll > 0) { 482 scrollBy(0, Math.min(availableToScroll, deltaY)); 483 } 484 } 485 break; 486 case MotionEvent.ACTION_UP: 487 final VelocityTracker velocityTracker = mVelocityTracker; 488 velocityTracker.computeCurrentVelocity(1000); 489 int initialVelocity = (int) velocityTracker.getYVelocity(); 490 491 if ((Math.abs(initialVelocity) > ViewConfiguration.getMinimumFlingVelocity()) && 492 (getChildCount() > 0)) { 493 fling(-initialVelocity); 494 } 495 496 if (mVelocityTracker != null) { 497 mVelocityTracker.recycle(); 498 mVelocityTracker = null; 499 } 500 } 501 return true; 502 } 503 504 /** 505 * <p> 506 * Finds the next focusable component that fits in this View's bounds 507 * (excluding fading edges) pretending that this View's top is located at 508 * the parameter top. 509 * </p> 510 * 511 * @param topFocus look for a candidate is the one at the top of the bounds 512 * if topFocus is true, or at the bottom of the bounds if topFocus is 513 * false 514 * @param top the top offset of the bounds in which a focusable must be 515 * found (the fading edge is assumed to start at this position) 516 * @param preferredFocusable the View that has highest priority and will be 517 * returned if it is within my bounds (null is valid) 518 * @return the next focusable component in the bounds or null if none can be 519 * found 520 */ 521 private View findFocusableViewInMyBounds(final boolean topFocus, 522 final int top, View preferredFocusable) { 523 /* 524 * The fading edge's transparent side should be considered for focus 525 * since it's mostly visible, so we divide the actual fading edge length 526 * by 2. 527 */ 528 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 529 final int topWithoutFadingEdge = top + fadingEdgeLength; 530 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 531 532 if ((preferredFocusable != null) 533 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 534 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 535 return preferredFocusable; 536 } 537 538 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 539 bottomWithoutFadingEdge); 540 } 541 542 /** 543 * <p> 544 * Finds the next focusable component that fits in the specified bounds. 545 * </p> 546 * 547 * @param topFocus look for a candidate is the one at the top of the bounds 548 * if topFocus is true, or at the bottom of the bounds if topFocus is 549 * false 550 * @param top the top offset of the bounds in which a focusable must be 551 * found 552 * @param bottom the bottom offset of the bounds in which a focusable must 553 * be found 554 * @return the next focusable component in the bounds or null if none can 555 * be found 556 */ 557 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 558 559 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 560 View focusCandidate = null; 561 562 /* 563 * A fully contained focusable is one where its top is below the bound's 564 * top, and its bottom is above the bound's bottom. A partially 565 * contained focusable is one where some part of it is within the 566 * bounds, but it also has some part that is not within bounds. A fully contained 567 * focusable is preferred to a partially contained focusable. 568 */ 569 boolean foundFullyContainedFocusable = false; 570 571 int count = focusables.size(); 572 for (int i = 0; i < count; i++) { 573 View view = focusables.get(i); 574 int viewTop = view.getTop(); 575 int viewBottom = view.getBottom(); 576 577 if (top < viewBottom && viewTop < bottom) { 578 /* 579 * the focusable is in the target area, it is a candidate for 580 * focusing 581 */ 582 583 final boolean viewIsFullyContained = (top < viewTop) && 584 (viewBottom < bottom); 585 586 if (focusCandidate == null) { 587 /* No candidate, take this one */ 588 focusCandidate = view; 589 foundFullyContainedFocusable = viewIsFullyContained; 590 } else { 591 final boolean viewIsCloserToBoundary = 592 (topFocus && viewTop < focusCandidate.getTop()) || 593 (!topFocus && viewBottom > focusCandidate 594 .getBottom()); 595 596 if (foundFullyContainedFocusable) { 597 if (viewIsFullyContained && viewIsCloserToBoundary) { 598 /* 599 * We're dealing with only fully contained views, so 600 * it has to be closer to the boundary to beat our 601 * candidate 602 */ 603 focusCandidate = view; 604 } 605 } else { 606 if (viewIsFullyContained) { 607 /* Any fully contained view beats a partially contained view */ 608 focusCandidate = view; 609 foundFullyContainedFocusable = true; 610 } else if (viewIsCloserToBoundary) { 611 /* 612 * Partially contained view beats another partially 613 * contained view if it's closer 614 */ 615 focusCandidate = view; 616 } 617 } 618 } 619 } 620 } 621 622 return focusCandidate; 623 } 624 625 /** 626 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 627 * method will scroll the view by one page up or down and give the focus 628 * to the topmost/bottommost component in the new visible area. If no 629 * component is a good candidate for focus, this scrollview reclaims the 630 * focus.</p> 631 * 632 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 633 * to go one page up or 634 * {@link android.view.View#FOCUS_DOWN} to go one page down 635 * @return true if the key event is consumed by this method, false otherwise 636 */ 637 public boolean pageScroll(int direction) { 638 boolean down = direction == View.FOCUS_DOWN; 639 int height = getHeight(); 640 641 if (down) { 642 mTempRect.top = getScrollY() + height; 643 int count = getChildCount(); 644 if (count > 0) { 645 View view = getChildAt(count - 1); 646 if (mTempRect.top + height > view.getBottom()) { 647 mTempRect.top = view.getBottom() - height; 648 } 649 } 650 } else { 651 mTempRect.top = getScrollY() - height; 652 if (mTempRect.top < 0) { 653 mTempRect.top = 0; 654 } 655 } 656 mTempRect.bottom = mTempRect.top + height; 657 658 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 659 } 660 661 /** 662 * <p>Handles scrolling in response to a "home/end" shortcut press. This 663 * method will scroll the view to the top or bottom and give the focus 664 * to the topmost/bottommost component in the new visible area. If no 665 * component is a good candidate for focus, this scrollview reclaims the 666 * focus.</p> 667 * 668 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 669 * to go the top of the view or 670 * {@link android.view.View#FOCUS_DOWN} to go the bottom 671 * @return true if the key event is consumed by this method, false otherwise 672 */ 673 public boolean fullScroll(int direction) { 674 boolean down = direction == View.FOCUS_DOWN; 675 int height = getHeight(); 676 677 mTempRect.top = 0; 678 mTempRect.bottom = height; 679 680 if (down) { 681 int count = getChildCount(); 682 if (count > 0) { 683 View view = getChildAt(count - 1); 684 mTempRect.bottom = view.getBottom(); 685 mTempRect.top = mTempRect.bottom - height; 686 } 687 } 688 689 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 690 } 691 692 /** 693 * <p>Scrolls the view to make the area defined by <code>top</code> and 694 * <code>bottom</code> visible. This method attempts to give the focus 695 * to a component visible in this area. If no component can be focused in 696 * the new visible area, the focus is reclaimed by this scrollview.</p> 697 * 698 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 699 * to go upward 700 * {@link android.view.View#FOCUS_DOWN} to downward 701 * @param top the top offset of the new area to be made visible 702 * @param bottom the bottom offset of the new area to be made visible 703 * @return true if the key event is consumed by this method, false otherwise 704 */ 705 private boolean scrollAndFocus(int direction, int top, int bottom) { 706 boolean handled = true; 707 708 int height = getHeight(); 709 int containerTop = getScrollY(); 710 int containerBottom = containerTop + height; 711 boolean up = direction == View.FOCUS_UP; 712 713 View newFocused = findFocusableViewInBounds(up, top, bottom); 714 if (newFocused == null) { 715 newFocused = this; 716 } 717 718 if (top >= containerTop && bottom <= containerBottom) { 719 handled = false; 720 } else { 721 int delta = up ? (top - containerTop) : (bottom - containerBottom); 722 doScrollY(delta); 723 } 724 725 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 726 mScrollViewMovedFocus = true; 727 mScrollViewMovedFocus = false; 728 } 729 730 return handled; 731 } 732 733 /** 734 * Handle scrolling in response to an up or down arrow click. 735 * 736 * @param direction The direction corresponding to the arrow key that was 737 * pressed 738 * @return True if we consumed the event, false otherwise 739 */ 740 public boolean arrowScroll(int direction) { 741 742 View currentFocused = findFocus(); 743 if (currentFocused == this) currentFocused = null; 744 745 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 746 747 final int maxJump = getMaxScrollAmount(); 748 749 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 750 nextFocused.getDrawingRect(mTempRect); 751 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 752 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 753 doScrollY(scrollDelta); 754 nextFocused.requestFocus(direction); 755 } else { 756 // no new focus 757 int scrollDelta = maxJump; 758 759 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 760 scrollDelta = getScrollY(); 761 } else if (direction == View.FOCUS_DOWN) { 762 763 int daBottom = getChildAt(getChildCount() - 1).getBottom(); 764 765 int screenBottom = getScrollY() + getHeight(); 766 767 if (daBottom - screenBottom < maxJump) { 768 scrollDelta = daBottom - screenBottom; 769 } 770 } 771 if (scrollDelta == 0) { 772 return false; 773 } 774 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 775 } 776 777 if (currentFocused != null && currentFocused.isFocused() 778 && isOffScreen(currentFocused)) { 779 // previously focused item still has focus and is off screen, give 780 // it up (take it back to ourselves) 781 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 782 // sure to 783 // get it) 784 final int descendantFocusability = getDescendantFocusability(); // save 785 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 786 requestFocus(); 787 setDescendantFocusability(descendantFocusability); // restore 788 } 789 return true; 790 } 791 792 /** 793 * @return whether the descendant of this scroll view is scrolled off 794 * screen. 795 */ 796 private boolean isOffScreen(View descendant) { 797 return !isWithinDeltaOfScreen(descendant, 0); 798 } 799 800 /** 801 * @return whether the descendant of this scroll view is within delta 802 * pixels of being on the screen. 803 */ 804 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 805 descendant.getDrawingRect(mTempRect); 806 offsetDescendantRectToMyCoords(descendant, mTempRect); 807 808 return (mTempRect.bottom + delta) >= getScrollY() 809 && (mTempRect.top - delta) <= (getScrollY() + getHeight()); 810 } 811 812 /** 813 * Smooth scroll by a Y delta 814 * 815 * @param delta the number of pixels to scroll by on the X axis 816 */ 817 private void doScrollY(int delta) { 818 if (delta != 0) { 819 if (mSmoothScrollingEnabled) { 820 smoothScrollBy(0, delta); 821 } else { 822 scrollBy(0, delta); 823 } 824 } 825 } 826 827 /** 828 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 829 * 830 * @param dx the number of pixels to scroll by on the X axis 831 * @param dy the number of pixels to scroll by on the Y axis 832 */ 833 public final void smoothScrollBy(int dx, int dy) { 834 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 835 if (duration > ANIMATED_SCROLL_GAP) { 836 if (localLOGV) Log.v(TAG, "Smooth scroll: mScrollY=" + mScrollY 837 + " dy=" + dy); 838 mScroller.startScroll(mScrollX, mScrollY, dx, dy); 839 invalidate(); 840 } else { 841 if (!mScroller.isFinished()) { 842 mScroller.abortAnimation(); 843 } 844 if (localLOGV) Log.v(TAG, "Immediate scroll: mScrollY=" + mScrollY 845 + " dy=" + dy); 846 scrollBy(dx, dy); 847 } 848 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 849 } 850 851 /** 852 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 853 * 854 * @param x the position where to scroll on the X axis 855 * @param y the position where to scroll on the Y axis 856 */ 857 public final void smoothScrollTo(int x, int y) { 858 smoothScrollBy(x - mScrollX, y - mScrollY); 859 } 860 861 /** 862 * <p>The scroll range of a scroll view is the overall height of all of its 863 * children.</p> 864 */ 865 @Override 866 protected int computeVerticalScrollRange() { 867 int count = getChildCount(); 868 return count == 0 ? getHeight() : (getChildAt(0)).getBottom(); 869 } 870 871 872 @Override 873 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 874 ViewGroup.LayoutParams lp = child.getLayoutParams(); 875 876 int childWidthMeasureSpec; 877 int childHeightMeasureSpec; 878 879 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 880 + mPaddingRight, lp.width); 881 882 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 883 884 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 885 } 886 887 @Override 888 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 889 int parentHeightMeasureSpec, int heightUsed) { 890 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 891 892 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 893 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 894 + widthUsed, lp.width); 895 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 896 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 897 898 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 899 } 900 901 @Override 902 public void computeScroll() { 903 if (mScroller.computeScrollOffset()) { 904 // This is called at drawing time by ViewGroup. We don't want to 905 // re-show the scrollbars at this point, which scrollTo will do, 906 // so we replicate most of scrollTo here. 907 // 908 // It's a little odd to call onScrollChanged from inside the drawing. 909 // 910 // It is, except when you remember that computeScroll() is used to 911 // animate scrolling. So unless we want to defer the onScrollChanged() 912 // until the end of the animated scrolling, we don't really have a 913 // choice here. 914 // 915 // I agree. The alternative, which I think would be worse, is to post 916 // something and tell the subclasses later. This is bad because there 917 // will be a window where mScrollX/Y is different from what the app 918 // thinks it is. 919 // 920 int oldX = mScrollX; 921 int oldY = mScrollY; 922 int x = mScroller.getCurrX(); 923 int y = mScroller.getCurrY(); 924 if (getChildCount() > 0) { 925 View child = getChildAt(0); 926 mScrollX = clamp(x, this.getWidth(), child.getWidth()); 927 mScrollY = clamp(y, this.getHeight(), child.getHeight()); 928 if (localLOGV) Log.v(TAG, "mScrollY=" + mScrollY + " y=" + y 929 + " height=" + this.getHeight() 930 + " child height=" + child.getHeight()); 931 } else { 932 mScrollX = x; 933 mScrollY = y; 934 } 935 if (oldX != mScrollX || oldY != mScrollY) { 936 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 937 } 938 939 // Keep on drawing until the animation has finished. 940 postInvalidate(); 941 } 942 } 943 944 /** 945 * Scrolls the view to the given child. 946 * 947 * @param child the View to scroll to 948 */ 949 private void scrollToChild(View child) { 950 child.getDrawingRect(mTempRect); 951 952 /* Offset from child's local coordinates to ScrollView coordinates */ 953 offsetDescendantRectToMyCoords(child, mTempRect); 954 955 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 956 957 if (scrollDelta != 0) { 958 scrollBy(0, scrollDelta); 959 } 960 } 961 962 /** 963 * If rect is off screen, scroll just enough to get it (or at least the 964 * first screen size chunk of it) on screen. 965 * 966 * @param rect The rectangle. 967 * @param immediate True to scroll immediately without animation 968 * @return true if scrolling was performed 969 */ 970 private boolean scrollToChildRect(Rect rect, boolean immediate) { 971 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 972 final boolean scroll = delta != 0; 973 if (scroll) { 974 if (immediate) { 975 scrollBy(0, delta); 976 } else { 977 smoothScrollBy(0, delta); 978 } 979 } 980 return scroll; 981 } 982 983 /** 984 * Compute the amount to scroll in the Y direction in order to get 985 * a rectangle completely on the screen (or, if taller than the screen, 986 * at least the first screen size chunk of it). 987 * 988 * @param rect The rect. 989 * @return The scroll delta. 990 */ 991 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 992 993 int height = getHeight(); 994 int screenTop = getScrollY(); 995 int screenBottom = screenTop + height; 996 997 int fadingEdge = getVerticalFadingEdgeLength(); 998 999 // leave room for top fading edge as long as rect isn't at very top 1000 if (rect.top > 0) { 1001 screenTop += fadingEdge; 1002 } 1003 1004 // leave room for bottom fading edge as long as rect isn't at very bottom 1005 if (rect.bottom < getChildAt(0).getHeight()) { 1006 screenBottom -= fadingEdge; 1007 } 1008 1009 int scrollYDelta = 0; 1010 1011 if (localLOGV) Log.v(TAG, "child=" + rect.toShortString() 1012 + " screenTop=" + screenTop + " screenBottom=" + screenBottom 1013 + " height=" + height); 1014 if (rect.bottom > screenBottom && rect.top > screenTop) { 1015 // need to move down to get it in view: move down just enough so 1016 // that the entire rectangle is in view (or at least the first 1017 // screen size chunk). 1018 1019 if (rect.height() > height) { 1020 // just enough to get screen size chunk on 1021 scrollYDelta += (rect.top - screenTop); 1022 } else { 1023 // get entire rect at bottom of screen 1024 scrollYDelta += (rect.bottom - screenBottom); 1025 } 1026 1027 // make sure we aren't scrolling beyond the end of our content 1028 int bottom = getChildAt(getChildCount() - 1).getBottom(); 1029 int distanceToBottom = bottom - screenBottom; 1030 if (localLOGV) Log.v(TAG, "scrollYDelta=" + scrollYDelta 1031 + " distanceToBottom=" + distanceToBottom); 1032 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1033 1034 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1035 // need to move up to get it in view: move up just enough so that 1036 // entire rectangle is in view (or at least the first screen 1037 // size chunk of it). 1038 1039 if (rect.height() > height) { 1040 // screen size chunk 1041 scrollYDelta -= (screenBottom - rect.bottom); 1042 } else { 1043 // entire rect at top 1044 scrollYDelta -= (screenTop - rect.top); 1045 } 1046 1047 // make sure we aren't scrolling any further than the top our content 1048 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1049 } 1050 return scrollYDelta; 1051 } 1052 1053 @Override 1054 public void requestChildFocus(View child, View focused) { 1055 if (!mScrollViewMovedFocus) { 1056 if (!mIsLayoutDirty) { 1057 scrollToChild(focused); 1058 } else { 1059 // The child may not be laid out yet, we can't compute the scroll yet 1060 mChildToScrollTo = focused; 1061 } 1062 } 1063 super.requestChildFocus(child, focused); 1064 } 1065 1066 1067 /** 1068 * When looking for focus in children of a scroll view, need to be a little 1069 * more careful not to give focus to something that is scrolled off screen. 1070 * 1071 * This is more expensive than the default {@link android.view.ViewGroup} 1072 * implementation, otherwise this behavior might have been made the default. 1073 */ 1074 @Override 1075 protected boolean onRequestFocusInDescendants(int direction, 1076 Rect previouslyFocusedRect) { 1077 1078 // convert from forward / backward notation to up / down / left / right 1079 // (ugh). 1080 if (direction == View.FOCUS_FORWARD) { 1081 direction = View.FOCUS_DOWN; 1082 } else if (direction == View.FOCUS_BACKWARD) { 1083 direction = View.FOCUS_UP; 1084 } 1085 1086 final View nextFocus = previouslyFocusedRect == null ? 1087 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1088 FocusFinder.getInstance().findNextFocusFromRect(this, 1089 previouslyFocusedRect, direction); 1090 1091 if (nextFocus == null) { 1092 return false; 1093 } 1094 1095 if (isOffScreen(nextFocus)) { 1096 return false; 1097 } 1098 1099 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1100 } 1101 1102 @Override 1103 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1104 boolean immediate) { 1105 // offset into coordinate space of this scroll view 1106 rectangle.offset(child.getLeft() - child.getScrollX(), 1107 child.getTop() - child.getScrollY()); 1108 1109 return scrollToChildRect(rectangle, immediate); 1110 } 1111 1112 @Override 1113 public void requestLayout() { 1114 mIsLayoutDirty = true; 1115 super.requestLayout(); 1116 } 1117 1118 @Override 1119 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1120 super.onLayout(changed, l, t, r, b); 1121 mIsLayoutDirty = false; 1122 // Give a child focus if it needs it 1123 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1124 scrollToChild(mChildToScrollTo); 1125 } 1126 mChildToScrollTo = null; 1127 1128 // Calling this with the present values causes it to re-clam them 1129 scrollTo(mScrollX, mScrollY); 1130 } 1131 1132 @Override 1133 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1134 super.onSizeChanged(w, h, oldw, oldh); 1135 1136 View currentFocused = findFocus(); 1137 if (null == currentFocused || this == currentFocused) 1138 return; 1139 1140 final int maxJump = mBottom - mTop; 1141 1142 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1143 currentFocused.getDrawingRect(mTempRect); 1144 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1145 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1146 doScrollY(scrollDelta); 1147 } 1148 } 1149 1150 /** 1151 * Return true if child is an descendant of parent, (or equal to the parent). 1152 */ 1153 private boolean isViewDescendantOf(View child, View parent) { 1154 if (child == parent) { 1155 return true; 1156 } 1157 1158 final ViewParent theParent = child.getParent(); 1159 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1160 } 1161 1162 /** 1163 * Fling the scroll view 1164 * 1165 * @param velocityY The initial velocity in the Y direction. Positive 1166 * numbers mean that the finger/curor is moving down the screen, 1167 * which means we want to scroll towards the top. 1168 */ 1169 public void fling(int velocityY) { 1170 int height = getHeight(); 1171 int bottom = getChildAt(getChildCount() - 1).getBottom(); 1172 1173 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, bottom - height); 1174 1175 final boolean movingDown = velocityY > 0; 1176 1177 View newFocused = 1178 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1179 if (newFocused == null) { 1180 newFocused = this; 1181 } 1182 1183 if (newFocused != findFocus() 1184 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1185 mScrollViewMovedFocus = true; 1186 mScrollViewMovedFocus = false; 1187 } 1188 1189 invalidate(); 1190 } 1191 1192 /** 1193 * {@inheritDoc} 1194 * 1195 * <p>This version also clamps the scrolling to the bounds of our child. 1196 */ 1197 public void scrollTo(int x, int y) { 1198 // we rely on the fact the View.scrollBy calls scrollTo. 1199 if (getChildCount() > 0) { 1200 View child = getChildAt(0); 1201 x = clamp(x, this.getWidth(), child.getWidth()); 1202 y = clamp(y, this.getHeight(), child.getHeight()); 1203 if (x != mScrollX || y != mScrollY) { 1204 super.scrollTo(x, y); 1205 } 1206 } 1207 } 1208 1209 private int clamp(int n, int my, int child) { 1210 if (my >= child || n < 0) { 1211 /* my >= child is this case: 1212 * |--------------- me ---------------| 1213 * |------ child ------| 1214 * or 1215 * |--------------- me ---------------| 1216 * |------ child ------| 1217 * or 1218 * |--------------- me ---------------| 1219 * |------ child ------| 1220 * 1221 * n < 0 is this case: 1222 * |------ me ------| 1223 * |-------- child --------| 1224 * |-- mScrollX --| 1225 */ 1226 return 0; 1227 } 1228 if ((my+n) > child) { 1229 /* this case: 1230 * |------ me ------| 1231 * |------ child ------| 1232 * |-- mScrollX --| 1233 */ 1234 return child-my; 1235 } 1236 return n; 1237 } 1238} 1239