ScrollView.java revision 54b6cfa9a9e5b861a9930af873580d6dc20f773c
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.view.FocusFinder; 24import android.view.KeyEvent; 25import android.view.MotionEvent; 26import android.view.VelocityTracker; 27import android.view.View; 28import android.view.ViewConfiguration; 29import android.view.ViewGroup; 30import android.view.ViewParent; 31import android.view.animation.AnimationUtils; 32 33import com.android.internal.R; 34 35import java.util.List; 36 37/** 38 * Layout container for a view hierarchy that can be scrolled by the user, 39 * allowing it to be larger than the physical display. A ScrollView 40 * is a {@link FrameLayout}, meaning you should place one child in it 41 * containing the entire contents to scroll; this child may itself be a layout 42 * manager with a complex hierarchy of objects. A child that is often used 43 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 44 * array of top-level items that the user can scroll through. 45 * 46 * <p>You should never use a ScrollView with a {@link ListView}, since 47 * ListView takes care of its own scrolling. Most importantly, doing this 48 * defeats all of the important optimizations in ListView for dealing with 49 * large lists, since it effectively forces the ListView to display its entire 50 * list of items to fill up the infinite container supplied by ScrollView. 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 */ 59public class ScrollView extends FrameLayout { 60 private static final int ANIMATED_SCROLL_GAP = 250; 61 62 /** 63 * When arrow scrolling, ListView will never scroll more than this factor 64 * times the height of the list. 65 */ 66 private static final float MAX_SCROLL_FACTOR = 0.5f; 67 68 69 private long mLastScroll; 70 71 private final Rect mTempRect = new Rect(); 72 private Scroller mScroller; 73 74 /** 75 * Flag to indicate that we are moving focus ourselves. This is so the 76 * code that watches for focus changes initiated outside this ScrollView 77 * knows that it does not have to do anything. 78 */ 79 private boolean mScrollViewMovedFocus; 80 81 /** 82 * Position of the last motion event. 83 */ 84 private float mLastMotionY; 85 86 /** 87 * True when the layout has changed but the traversal has not come through yet. 88 * Ideally the view hierarchy would keep track of this for us. 89 */ 90 private boolean mIsLayoutDirty = true; 91 92 /** 93 * The child to give focus to in the event that a child has requested focus while the 94 * layout is dirty. This prevents the scroll from being wrong if the child has not been 95 * laid out before requesting focus. 96 */ 97 private View mChildToScrollTo = null; 98 99 /** 100 * True if the user is currently dragging this ScrollView around. This is 101 * not the same as 'is being flinged', which can be checked by 102 * mScroller.isFinished() (flinging begins when the user lifts his finger). 103 */ 104 private boolean mIsBeingDragged = false; 105 106 /** 107 * Determines speed during touch scrolling 108 */ 109 private VelocityTracker mVelocityTracker; 110 111 /** 112 * When set to true, the scroll view measure its child to make it fill the currently 113 * visible area. 114 */ 115 private boolean mFillViewport; 116 117 /** 118 * Whether arrow scrolling is animated. 119 */ 120 private boolean mSmoothScrollingEnabled = true; 121 122 public ScrollView(Context context) { 123 super(context); 124 initScrollView(); 125 126 setVerticalScrollBarEnabled(true); 127 setVerticalFadingEdgeEnabled(true); 128 129 TypedArray a = context.obtainStyledAttributes(R.styleable.View); 130 131 initializeScrollbars(a); 132 initializeFadingEdge(a); 133 134 a.recycle(); 135 } 136 137 public ScrollView(Context context, AttributeSet attrs) { 138 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 139 } 140 141 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 142 super(context, attrs, defStyle); 143 initScrollView(); 144 145 TypedArray a = 146 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 147 148 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 149 150 a.recycle(); 151 } 152 153 @Override 154 protected float getTopFadingEdgeStrength() { 155 if (getChildCount() == 0) { 156 return 0.0f; 157 } 158 159 final int length = getVerticalFadingEdgeLength(); 160 if (mScrollY < length) { 161 return mScrollY / (float) length; 162 } 163 164 return 1.0f; 165 } 166 167 @Override 168 protected float getBottomFadingEdgeStrength() { 169 if (getChildCount() == 0) { 170 return 0.0f; 171 } 172 173 final int length = getVerticalFadingEdgeLength(); 174 final int bottom = getChildAt(0).getBottom(); 175 final int span = bottom - mScrollY - getHeight(); 176 if (span < length) { 177 return span / (float) length; 178 } 179 180 return 1.0f; 181 } 182 183 /** 184 * @return The maximum amount this scroll view will scroll in response to 185 * an arrow event. 186 */ 187 public int getMaxScrollAmount() { 188 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 189 } 190 191 192 private void initScrollView() { 193 mScroller = new Scroller(getContext()); 194 setFocusable(true); 195 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 196 setWillNotDraw(false); 197 } 198 199 @Override 200 public void addView(View child) { 201 if (getChildCount() > 0) { 202 throw new IllegalStateException("ScrollView can host only one direct child"); 203 } 204 205 super.addView(child); 206 } 207 208 @Override 209 public void addView(View child, int index) { 210 if (getChildCount() > 0) { 211 throw new IllegalStateException("ScrollView can host only one direct child"); 212 } 213 214 super.addView(child, index); 215 } 216 217 @Override 218 public void addView(View child, ViewGroup.LayoutParams params) { 219 if (getChildCount() > 0) { 220 throw new IllegalStateException("ScrollView can host only one direct child"); 221 } 222 223 super.addView(child, params); 224 } 225 226 @Override 227 public void addView(View child, int index, ViewGroup.LayoutParams params) { 228 if (getChildCount() > 0) { 229 throw new IllegalStateException("ScrollView can host only one direct child"); 230 } 231 232 super.addView(child, index, params); 233 } 234 235 /** 236 * @return Returns true this ScrollView can be scrolled 237 */ 238 private boolean canScroll() { 239 View child = getChildAt(0); 240 if (child != null) { 241 int childHeight = child.getHeight(); 242 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 243 } 244 return false; 245 } 246 247 /** 248 * Indicates whether this ScrollView's content is stretched to fill the viewport. 249 * 250 * @return True if the content fills the viewport, false otherwise. 251 */ 252 public boolean isFillViewport() { 253 return mFillViewport; 254 } 255 256 /** 257 * Indicates this ScrollView whether it should stretch its content height to fill 258 * the viewport or not. 259 * 260 * @param fillViewport True to stretch the content's height to the viewport's 261 * boundaries, false otherwise. 262 */ 263 public void setFillViewport(boolean fillViewport) { 264 if (fillViewport != mFillViewport) { 265 mFillViewport = fillViewport; 266 requestLayout(); 267 } 268 } 269 270 /** 271 * @return Whether arrow scrolling will animate its transition. 272 */ 273 public boolean isSmoothScrollingEnabled() { 274 return mSmoothScrollingEnabled; 275 } 276 277 /** 278 * Set whether arrow scrolling will animate its transition. 279 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 280 */ 281 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 282 mSmoothScrollingEnabled = smoothScrollingEnabled; 283 } 284 285 @Override 286 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 287 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 288 289 if (!mFillViewport) { 290 return; 291 } 292 293 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 294 if (heightMode == MeasureSpec.UNSPECIFIED) { 295 return; 296 } 297 298 final View child = getChildAt(0); 299 int height = getMeasuredHeight(); 300 if (child.getMeasuredHeight() < height) { 301 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 302 303 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 304 + mPaddingRight, lp.width); 305 height -= mPaddingTop; 306 height -= mPaddingBottom; 307 int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 308 309 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 310 } 311 } 312 313 @Override 314 public boolean dispatchKeyEvent(KeyEvent event) { 315 // Let the focused view and/or our descendants get the key first 316 boolean handled = super.dispatchKeyEvent(event); 317 if (handled) { 318 return true; 319 } 320 return executeKeyEvent(event); 321 } 322 323 /** 324 * You can call this function yourself to have the scroll view perform 325 * scrolling from a key event, just as if the event had been dispatched to 326 * it by the view hierarchy. 327 * 328 * @param event The key event to execute. 329 * @return Return true if the event was handled, else false. 330 */ 331 public boolean executeKeyEvent(KeyEvent event) { 332 mTempRect.setEmpty(); 333 334 if (!canScroll()) { 335 if (isFocused()) { 336 View currentFocused = findFocus(); 337 if (currentFocused == this) currentFocused = null; 338 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 339 currentFocused, View.FOCUS_DOWN); 340 return nextFocused != null 341 && nextFocused != this 342 && nextFocused.requestFocus(View.FOCUS_DOWN); 343 } 344 return false; 345 } 346 347 boolean handled = false; 348 if (event.getAction() == KeyEvent.ACTION_DOWN) { 349 switch (event.getKeyCode()) { 350 case KeyEvent.KEYCODE_DPAD_UP: 351 if (!event.isAltPressed()) { 352 handled = arrowScroll(View.FOCUS_UP); 353 } else { 354 handled = fullScroll(View.FOCUS_UP); 355 } 356 break; 357 case KeyEvent.KEYCODE_DPAD_DOWN: 358 if (!event.isAltPressed()) { 359 handled = arrowScroll(View.FOCUS_DOWN); 360 } else { 361 handled = fullScroll(View.FOCUS_DOWN); 362 } 363 break; 364 case KeyEvent.KEYCODE_SPACE: 365 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 366 break; 367 } 368 } 369 370 return handled; 371 } 372 373 @Override 374 public boolean onInterceptTouchEvent(MotionEvent ev) { 375 /* 376 * This method JUST determines whether we want to intercept the motion. 377 * If we return true, onMotionEvent will be called and we do the actual 378 * scrolling there. 379 */ 380 381 /* 382 * Shortcut the most recurring case: the user is in the dragging 383 * state and he is moving his finger. We want to intercept this 384 * motion. 385 */ 386 final int action = ev.getAction(); 387 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 388 return true; 389 } 390 391 if (!canScroll()) { 392 mIsBeingDragged = false; 393 return false; 394 } 395 396 final float y = ev.getY(); 397 398 switch (action) { 399 case MotionEvent.ACTION_MOVE: 400 /* 401 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 402 * whether the user has moved far enough from his original down touch. 403 */ 404 405 /* 406 * Locally do absolute value. mLastMotionY is set to the y value 407 * of the down event. 408 */ 409 final int yDiff = (int) Math.abs(y - mLastMotionY); 410 if (yDiff > ViewConfiguration.getTouchSlop()) { 411 mIsBeingDragged = true; 412 } 413 break; 414 415 case MotionEvent.ACTION_DOWN: 416 /* Remember location of down touch */ 417 mLastMotionY = y; 418 419 /* 420 * If being flinged and user touches the screen, initiate drag; 421 * otherwise don't. mScroller.isFinished should be false when 422 * being flinged. 423 */ 424 mIsBeingDragged = !mScroller.isFinished(); 425 break; 426 427 case MotionEvent.ACTION_CANCEL: 428 case MotionEvent.ACTION_UP: 429 /* Release the drag */ 430 mIsBeingDragged = false; 431 break; 432 } 433 434 /* 435 * The only time we want to intercept motion events is if we are in the 436 * drag mode. 437 */ 438 return mIsBeingDragged; 439 } 440 441 @Override 442 public boolean onTouchEvent(MotionEvent ev) { 443 444 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 445 // Don't handle edge touches immediately -- they may actually belong to one of our 446 // descendants. 447 return false; 448 } 449 450 if (!canScroll()) { 451 return false; 452 } 453 454 if (mVelocityTracker == null) { 455 mVelocityTracker = VelocityTracker.obtain(); 456 } 457 mVelocityTracker.addMovement(ev); 458 459 final int action = ev.getAction(); 460 final float y = ev.getY(); 461 462 switch (action) { 463 case MotionEvent.ACTION_DOWN: 464 /* 465 * If being flinged and user touches, stop the fling. isFinished 466 * will be false if being flinged. 467 */ 468 if (!mScroller.isFinished()) { 469 mScroller.abortAnimation(); 470 } 471 472 // Remember where the motion event started 473 mLastMotionY = y; 474 break; 475 case MotionEvent.ACTION_MOVE: 476 // Scroll to follow the motion event 477 final int deltaY = (int) (mLastMotionY - y); 478 mLastMotionY = y; 479 480 if (deltaY < 0) { 481 if (mScrollY > 0) { 482 scrollBy(0, deltaY); 483 } 484 } else if (deltaY > 0) { 485 final int bottomEdge = getHeight() - mPaddingBottom; 486 final int availableToScroll = getChildAt(0).getBottom() - mScrollY - bottomEdge; 487 if (availableToScroll > 0) { 488 scrollBy(0, Math.min(availableToScroll, deltaY)); 489 } 490 } 491 break; 492 case MotionEvent.ACTION_UP: 493 final VelocityTracker velocityTracker = mVelocityTracker; 494 velocityTracker.computeCurrentVelocity(1000); 495 int initialVelocity = (int) velocityTracker.getYVelocity(); 496 497 if ((Math.abs(initialVelocity) > ViewConfiguration.getMinimumFlingVelocity()) && 498 (getChildCount() > 0)) { 499 fling(-initialVelocity); 500 } 501 502 if (mVelocityTracker != null) { 503 mVelocityTracker.recycle(); 504 mVelocityTracker = null; 505 } 506 } 507 return true; 508 } 509 510 /** 511 * <p> 512 * Finds the next focusable component that fits in this View's bounds 513 * (excluding fading edges) pretending that this View's top is located at 514 * the parameter top. 515 * </p> 516 * 517 * @param topFocus look for a candidate is the one at the top of the bounds 518 * if topFocus is true, or at the bottom of the bounds if topFocus is 519 * false 520 * @param top the top offset of the bounds in which a focusable must be 521 * found (the fading edge is assumed to start at this position) 522 * @param preferredFocusable the View that has highest priority and will be 523 * returned if it is within my bounds (null is valid) 524 * @return the next focusable component in the bounds or null if none can be 525 * found 526 */ 527 private View findFocusableViewInMyBounds(final boolean topFocus, 528 final int top, View preferredFocusable) { 529 /* 530 * The fading edge's transparent side should be considered for focus 531 * since it's mostly visible, so we divide the actual fading edge length 532 * by 2. 533 */ 534 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 535 final int topWithoutFadingEdge = top + fadingEdgeLength; 536 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 537 538 if ((preferredFocusable != null) 539 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 540 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 541 return preferredFocusable; 542 } 543 544 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 545 bottomWithoutFadingEdge); 546 } 547 548 /** 549 * <p> 550 * Finds the next focusable component that fits in the specified bounds. 551 * </p> 552 * 553 * @param topFocus look for a candidate is the one at the top of the bounds 554 * if topFocus is true, or at the bottom of the bounds if topFocus is 555 * false 556 * @param top the top offset of the bounds in which a focusable must be 557 * found 558 * @param bottom the bottom offset of the bounds in which a focusable must 559 * be found 560 * @return the next focusable component in the bounds or null if none can 561 * be found 562 */ 563 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 564 565 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 566 View focusCandidate = null; 567 568 /* 569 * A fully contained focusable is one where its top is below the bound's 570 * top, and its bottom is above the bound's bottom. A partially 571 * contained focusable is one where some part of it is within the 572 * bounds, but it also has some part that is not within bounds. A fully contained 573 * focusable is preferred to a partially contained focusable. 574 */ 575 boolean foundFullyContainedFocusable = false; 576 577 int count = focusables.size(); 578 for (int i = 0; i < count; i++) { 579 View view = focusables.get(i); 580 int viewTop = view.getTop(); 581 int viewBottom = view.getBottom(); 582 583 if (top < viewBottom && viewTop < bottom) { 584 /* 585 * the focusable is in the target area, it is a candidate for 586 * focusing 587 */ 588 589 final boolean viewIsFullyContained = (top < viewTop) && 590 (viewBottom < bottom); 591 592 if (focusCandidate == null) { 593 /* No candidate, take this one */ 594 focusCandidate = view; 595 foundFullyContainedFocusable = viewIsFullyContained; 596 } else { 597 final boolean viewIsCloserToBoundary = 598 (topFocus && viewTop < focusCandidate.getTop()) || 599 (!topFocus && viewBottom > focusCandidate 600 .getBottom()); 601 602 if (foundFullyContainedFocusable) { 603 if (viewIsFullyContained && viewIsCloserToBoundary) { 604 /* 605 * We're dealing with only fully contained views, so 606 * it has to be closer to the boundary to beat our 607 * candidate 608 */ 609 focusCandidate = view; 610 } 611 } else { 612 if (viewIsFullyContained) { 613 /* Any fully contained view beats a partially contained view */ 614 focusCandidate = view; 615 foundFullyContainedFocusable = true; 616 } else if (viewIsCloserToBoundary) { 617 /* 618 * Partially contained view beats another partially 619 * contained view if it's closer 620 */ 621 focusCandidate = view; 622 } 623 } 624 } 625 } 626 } 627 628 return focusCandidate; 629 } 630 631 /** 632 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 633 * method will scroll the view by one page up or down and give the focus 634 * to the topmost/bottommost component in the new visible area. If no 635 * component is a good candidate for focus, this scrollview reclaims the 636 * focus.</p> 637 * 638 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 639 * to go one page up or 640 * {@link android.view.View#FOCUS_DOWN} to go one page down 641 * @return true if the key event is consumed by this method, false otherwise 642 */ 643 public boolean pageScroll(int direction) { 644 boolean down = direction == View.FOCUS_DOWN; 645 int height = getHeight(); 646 647 if (down) { 648 mTempRect.top = getScrollY() + height; 649 int count = getChildCount(); 650 if (count > 0) { 651 View view = getChildAt(count - 1); 652 if (mTempRect.top + height > view.getBottom()) { 653 mTempRect.top = view.getBottom() - height; 654 } 655 } 656 } else { 657 mTempRect.top = getScrollY() - height; 658 if (mTempRect.top < 0) { 659 mTempRect.top = 0; 660 } 661 } 662 mTempRect.bottom = mTempRect.top + height; 663 664 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 665 } 666 667 /** 668 * <p>Handles scrolling in response to a "home/end" shortcut press. This 669 * method will scroll the view to the top or bottom and give the focus 670 * to the topmost/bottommost component in the new visible area. If no 671 * component is a good candidate for focus, this scrollview reclaims the 672 * focus.</p> 673 * 674 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 675 * to go the top of the view or 676 * {@link android.view.View#FOCUS_DOWN} to go the bottom 677 * @return true if the key event is consumed by this method, false otherwise 678 */ 679 public boolean fullScroll(int direction) { 680 boolean down = direction == View.FOCUS_DOWN; 681 int height = getHeight(); 682 683 mTempRect.top = 0; 684 mTempRect.bottom = height; 685 686 if (down) { 687 int count = getChildCount(); 688 if (count > 0) { 689 View view = getChildAt(count - 1); 690 mTempRect.bottom = view.getBottom(); 691 mTempRect.top = mTempRect.bottom - height; 692 } 693 } 694 695 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 696 } 697 698 /** 699 * <p>Scrolls the view to make the area defined by <code>top</code> and 700 * <code>bottom</code> visible. This method attempts to give the focus 701 * to a component visible in this area. If no component can be focused in 702 * the new visible area, the focus is reclaimed by this scrollview.</p> 703 * 704 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 705 * to go upward 706 * {@link android.view.View#FOCUS_DOWN} to downward 707 * @param top the top offset of the new area to be made visible 708 * @param bottom the bottom offset of the new area to be made visible 709 * @return true if the key event is consumed by this method, false otherwise 710 */ 711 private boolean scrollAndFocus(int direction, int top, int bottom) { 712 boolean handled = true; 713 714 int height = getHeight(); 715 int containerTop = getScrollY(); 716 int containerBottom = containerTop + height; 717 boolean up = direction == View.FOCUS_UP; 718 719 View newFocused = findFocusableViewInBounds(up, top, bottom); 720 if (newFocused == null) { 721 newFocused = this; 722 } 723 724 if (top >= containerTop && bottom <= containerBottom) { 725 handled = false; 726 } else { 727 int delta = up ? (top - containerTop) : (bottom - containerBottom); 728 doScrollY(delta); 729 } 730 731 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 732 mScrollViewMovedFocus = true; 733 mScrollViewMovedFocus = false; 734 } 735 736 return handled; 737 } 738 739 /** 740 * Handle scrolling in response to an up or down arrow click. 741 * 742 * @param direction The direction corresponding to the arrow key that was 743 * pressed 744 * @return True if we consumed the event, false otherwise 745 */ 746 public boolean arrowScroll(int direction) { 747 748 View currentFocused = findFocus(); 749 if (currentFocused == this) currentFocused = null; 750 751 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 752 753 final int maxJump = getMaxScrollAmount(); 754 755 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 756 nextFocused.getDrawingRect(mTempRect); 757 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 758 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 759 doScrollY(scrollDelta); 760 nextFocused.requestFocus(direction); 761 } else { 762 // no new focus 763 int scrollDelta = maxJump; 764 765 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 766 scrollDelta = getScrollY(); 767 } else if (direction == View.FOCUS_DOWN) { 768 769 int daBottom = getChildAt(getChildCount() - 1).getBottom(); 770 771 int screenBottom = getScrollY() + getHeight(); 772 773 if (daBottom - screenBottom < maxJump) { 774 scrollDelta = daBottom - screenBottom; 775 } 776 } 777 if (scrollDelta == 0) { 778 return false; 779 } 780 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 781 } 782 783 if (currentFocused != null && currentFocused.isFocused() 784 && isOffScreen(currentFocused)) { 785 // previously focused item still has focus and is off screen, give 786 // it up (take it back to ourselves) 787 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 788 // sure to 789 // get it) 790 final int descendantFocusability = getDescendantFocusability(); // save 791 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 792 requestFocus(); 793 setDescendantFocusability(descendantFocusability); // restore 794 } 795 return true; 796 } 797 798 /** 799 * @return whether the descendant of this scroll view is scrolled off 800 * screen. 801 */ 802 private boolean isOffScreen(View descendant) { 803 return !isWithinDeltaOfScreen(descendant, 0); 804 } 805 806 /** 807 * @return whether the descendant of this scroll view is within delta 808 * pixels of being on the screen. 809 */ 810 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 811 descendant.getDrawingRect(mTempRect); 812 offsetDescendantRectToMyCoords(descendant, mTempRect); 813 814 return (mTempRect.bottom + delta) >= getScrollY() 815 && (mTempRect.top - delta) <= (getScrollY() + getHeight()); 816 } 817 818 /** 819 * Smooth scroll by a Y delta 820 * 821 * @param delta the number of pixels to scroll by on the X axis 822 */ 823 private void doScrollY(int delta) { 824 if (delta != 0) { 825 if (mSmoothScrollingEnabled) { 826 smoothScrollBy(0, delta); 827 } else { 828 scrollBy(0, delta); 829 } 830 } 831 } 832 833 /** 834 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 835 * 836 * @param dx the number of pixels to scroll by on the X axis 837 * @param dy the number of pixels to scroll by on the Y axis 838 */ 839 public final void smoothScrollBy(int dx, int dy) { 840 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 841 if (duration > ANIMATED_SCROLL_GAP) { 842 mScroller.startScroll(mScrollX, mScrollY, dx, dy); 843 invalidate(); 844 } else { 845 if (!mScroller.isFinished()) { 846 mScroller.abortAnimation(); 847 } 848 scrollBy(dx, dy); 849 } 850 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 851 } 852 853 /** 854 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 855 * 856 * @param x the position where to scroll on the X axis 857 * @param y the position where to scroll on the Y axis 858 */ 859 public final void smoothScrollTo(int x, int y) { 860 smoothScrollBy(x - mScrollX, y - mScrollY); 861 } 862 863 /** 864 * <p>The scroll range of a scroll view is the overall height of all of its 865 * children.</p> 866 */ 867 @Override 868 protected int computeVerticalScrollRange() { 869 int count = getChildCount(); 870 return count == 0 ? getHeight() : (getChildAt(0)).getBottom(); 871 } 872 873 874 @Override 875 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 876 ViewGroup.LayoutParams lp = child.getLayoutParams(); 877 878 int childWidthMeasureSpec; 879 int childHeightMeasureSpec; 880 881 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 882 + mPaddingRight, lp.width); 883 884 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 885 886 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 887 } 888 889 @Override 890 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 891 int parentHeightMeasureSpec, int heightUsed) { 892 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 893 894 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 895 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 896 + widthUsed, lp.width); 897 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 898 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 899 900 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 901 } 902 903 @Override 904 public void computeScroll() { 905 if (mScroller.computeScrollOffset()) { 906 // This is called at drawing time by ViewGroup. We don't want to 907 // re-show the scrollbars at this point, which scrollTo will do, 908 // so we replicate most of scrollTo here. 909 // 910 // It's a little odd to call onScrollChanged from inside the drawing. 911 // 912 // It is, except when you remember that computeScroll() is used to 913 // animate scrolling. So unless we want to defer the onScrollChanged() 914 // until the end of the animated scrolling, we don't really have a 915 // choice here. 916 // 917 // I agree. The alternative, which I think would be worse, is to post 918 // something and tell the subclasses later. This is bad because there 919 // will be a window where mScrollX/Y is different from what the app 920 // thinks it is. 921 // 922 int oldX = mScrollX; 923 int oldY = mScrollY; 924 int x = mScroller.getCurrX(); 925 int y = mScroller.getCurrY(); 926 if (getChildCount() > 0) { 927 View child = getChildAt(0); 928 mScrollX = clamp(x, this.getWidth(), child.getWidth()); 929 mScrollY = clamp(y, this.getHeight(), child.getHeight()); 930 } else { 931 mScrollX = x; 932 mScrollY = y; 933 } 934 if (oldX != mScrollX || oldY != mScrollY) { 935 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 936 postInvalidate(); // So we draw again 937 } 938 } 939 } 940 941 /** 942 * Scrolls the view to the given child. 943 * 944 * @param child the View to scroll to 945 */ 946 private void scrollToChild(View child) { 947 child.getDrawingRect(mTempRect); 948 949 /* Offset from child's local coordinates to ScrollView coordinates */ 950 offsetDescendantRectToMyCoords(child, mTempRect); 951 952 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 953 954 if (scrollDelta != 0) { 955 scrollBy(0, scrollDelta); 956 } 957 } 958 959 /** 960 * If rect is off screen, scroll just enough to get it (or at least the 961 * first screen size chunk of it) on screen. 962 * 963 * @param rect The rectangle. 964 * @param immediate True to scroll immediately without animation 965 * @return true if scrolling was performed 966 */ 967 private boolean scrollToChildRect(Rect rect, boolean immediate) { 968 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 969 final boolean scroll = delta != 0; 970 if (scroll) { 971 if (immediate) { 972 scrollBy(0, delta); 973 } else { 974 smoothScrollBy(0, delta); 975 } 976 } 977 return scroll; 978 } 979 980 /** 981 * Compute the amount to scroll in the Y direction in order to get 982 * a rectangle completely on the screen (or, if taller than the screen, 983 * at least the first screen size chunk of it). 984 * 985 * @param rect The rect. 986 * @return The scroll delta. 987 */ 988 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 989 990 int height = getHeight(); 991 int screenTop = getScrollY(); 992 int screenBottom = screenTop + height; 993 994 int fadingEdge = getVerticalFadingEdgeLength(); 995 996 // leave room for top fading edge as long as rect isn't at very top 997 if (rect.top > 0) { 998 screenTop += fadingEdge; 999 } 1000 1001 // leave room for bottom fading edge as long as rect isn't at very bottom 1002 if (rect.bottom < getChildAt(0).getHeight()) { 1003 screenBottom -= fadingEdge; 1004 } 1005 1006 int scrollYDelta = 0; 1007 1008 if (rect.bottom > screenBottom && rect.top > screenTop) { 1009 // need to move down to get it in view: move down just enough so 1010 // that the entire rectangle is in view (or at least the first 1011 // screen size chunk). 1012 1013 if (rect.height() > height) { 1014 // just enough to get screen size chunk on 1015 scrollYDelta += (rect.top - screenTop); 1016 } else { 1017 // get entire rect at bottom of screen 1018 scrollYDelta += (rect.bottom - screenBottom); 1019 } 1020 1021 // make sure we aren't scrolling beyond the end of our content 1022 int bottom = getChildAt(getChildCount() - 1).getBottom(); 1023 int distanceToBottom = bottom - screenBottom; 1024 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1025 1026 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1027 // need to move up to get it in view: move up just enough so that 1028 // entire rectangle is in view (or at least the first screen 1029 // size chunk of it). 1030 1031 if (rect.height() > height) { 1032 // screen size chunk 1033 scrollYDelta -= (screenBottom - rect.bottom); 1034 } else { 1035 // entire rect at top 1036 scrollYDelta -= (screenTop - rect.top); 1037 } 1038 1039 // make sure we aren't scrolling any further than the top our content 1040 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1041 } 1042 return scrollYDelta; 1043 } 1044 1045 @Override 1046 public void requestChildFocus(View child, View focused) { 1047 if (!mScrollViewMovedFocus) { 1048 if (!mIsLayoutDirty) { 1049 scrollToChild(focused); 1050 } else { 1051 // The child may not be laid out yet, we can't compute the scroll yet 1052 mChildToScrollTo = focused; 1053 } 1054 } 1055 super.requestChildFocus(child, focused); 1056 } 1057 1058 1059 /** 1060 * When looking for focus in children of a scroll view, need to be a little 1061 * more careful not to give focus to something that is scrolled off screen. 1062 * 1063 * This is more expensive than the default {@link android.view.ViewGroup} 1064 * implementation, otherwise this behavior might have been made the default. 1065 */ 1066 @Override 1067 protected boolean onRequestFocusInDescendants(int direction, 1068 Rect previouslyFocusedRect) { 1069 1070 // convert from forward / backward notation to up / down / left / right 1071 // (ugh). 1072 if (direction == View.FOCUS_FORWARD) { 1073 direction = View.FOCUS_DOWN; 1074 } else if (direction == View.FOCUS_BACKWARD) { 1075 direction = View.FOCUS_UP; 1076 } 1077 1078 final View nextFocus = previouslyFocusedRect == null ? 1079 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1080 FocusFinder.getInstance().findNextFocusFromRect(this, 1081 previouslyFocusedRect, direction); 1082 1083 if (nextFocus == null) { 1084 return false; 1085 } 1086 1087 if (isOffScreen(nextFocus)) { 1088 return false; 1089 } 1090 1091 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1092 } 1093 1094 @Override 1095 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1096 boolean immediate) { 1097 // offset into coordinate space of this scroll view 1098 rectangle.offset(child.getLeft() - child.getScrollX(), 1099 child.getTop() - child.getScrollY()); 1100 1101 // note: until bug 1137695 is fixed, disable smooth scrolling for this api 1102 return scrollToChildRect(rectangle, true);//immediate); 1103 } 1104 1105 @Override 1106 public void requestLayout() { 1107 mIsLayoutDirty = true; 1108 super.requestLayout(); 1109 } 1110 1111 @Override 1112 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1113 super.onLayout(changed, l, t, r, b); 1114 mIsLayoutDirty = false; 1115 // Give a child focus if it needs it 1116 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1117 scrollToChild(mChildToScrollTo); 1118 } 1119 mChildToScrollTo = null; 1120 1121 // Calling this with the present values causes it to re-clam them 1122 scrollTo(mScrollX, mScrollY); 1123 } 1124 1125 /** 1126 * Return true if child is an descendant of parent, (or equal to the parent). 1127 */ 1128 private boolean isViewDescendantOf(View child, View parent) { 1129 if (child == parent) { 1130 return true; 1131 } 1132 1133 final ViewParent theParent = child.getParent(); 1134 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1135 } 1136 1137 /** 1138 * Fling the scroll view 1139 * 1140 * @param velocityY The initial velocity in the Y direction. Positive 1141 * numbers mean that the finger/curor is moving down the screen, 1142 * which means we want to scroll towards the top. 1143 */ 1144 public void fling(int velocityY) { 1145 int height = getHeight(); 1146 int bottom = getChildAt(getChildCount() - 1).getBottom(); 1147 1148 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, bottom - height); 1149 1150 final boolean movingDown = velocityY > 0; 1151 1152 View newFocused = 1153 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1154 if (newFocused == null) { 1155 newFocused = this; 1156 } 1157 1158 if (newFocused != findFocus() 1159 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1160 mScrollViewMovedFocus = true; 1161 mScrollViewMovedFocus = false; 1162 } 1163 1164 invalidate(); 1165 } 1166 1167 /** 1168 * {@inheritDoc} 1169 * 1170 * <p>This version also clamps the scrolling to the bounds of our child. 1171 */ 1172 public void scrollTo(int x, int y) { 1173 // we rely on the fact the View.scrollBy calls scrollTo. 1174 if (getChildCount() > 0) { 1175 View child = getChildAt(0); 1176 x = clamp(x, this.getWidth(), child.getWidth()); 1177 y = clamp(y, this.getHeight(), child.getHeight()); 1178 if (x != mScrollX || y != mScrollY) { 1179 super.scrollTo(x, y); 1180 } 1181 } 1182 } 1183 1184 private int clamp(int n, int my, int child) { 1185 if (my >= child || n < 0) { 1186 /* my >= child is this case: 1187 * |--------------- me ---------------| 1188 * |------ child ------| 1189 * or 1190 * |--------------- me ---------------| 1191 * |------ child ------| 1192 * or 1193 * |--------------- me ---------------| 1194 * |------ child ------| 1195 * 1196 * n < 0 is this case: 1197 * |------ me ------| 1198 * |-------- child --------| 1199 * |-- mScrollX --| 1200 */ 1201 return 0; 1202 } 1203 if ((my+n) > child) { 1204 /* this case: 1205 * |------ me ------| 1206 * |------ child ------| 1207 * |-- mScrollX --| 1208 */ 1209 return child-my; 1210 } 1211 return n; 1212 } 1213} 1214