ScrollView.java revision f013e1afd1e68af5e3b868c26a653bbfb39538f8
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 super(context); 129 initScrollView(); 130 131 setVerticalScrollBarEnabled(true); 132 setVerticalFadingEdgeEnabled(true); 133 134 TypedArray a = context.obtainStyledAttributes(R.styleable.View); 135 136 initializeScrollbars(a); 137 initializeFadingEdge(a); 138 139 a.recycle(); 140 } 141 142 public ScrollView(Context context, AttributeSet attrs) { 143 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 144 } 145 146 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 147 super(context, attrs, defStyle); 148 initScrollView(); 149 150 TypedArray a = 151 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 152 153 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 154 155 a.recycle(); 156 } 157 158 @Override 159 protected float getTopFadingEdgeStrength() { 160 if (getChildCount() == 0) { 161 return 0.0f; 162 } 163 164 final int length = getVerticalFadingEdgeLength(); 165 if (mScrollY < length) { 166 return mScrollY / (float) length; 167 } 168 169 return 1.0f; 170 } 171 172 @Override 173 protected float getBottomFadingEdgeStrength() { 174 if (getChildCount() == 0) { 175 return 0.0f; 176 } 177 178 final int length = getVerticalFadingEdgeLength(); 179 final int bottom = getChildAt(0).getBottom(); 180 final int span = bottom - mScrollY - getHeight(); 181 if (span < length) { 182 return span / (float) length; 183 } 184 185 return 1.0f; 186 } 187 188 /** 189 * @return The maximum amount this scroll view will scroll in response to 190 * an arrow event. 191 */ 192 public int getMaxScrollAmount() { 193 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 194 } 195 196 197 private void initScrollView() { 198 mScroller = new Scroller(getContext()); 199 setFocusable(true); 200 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 201 setWillNotDraw(false); 202 setScrollContainer(true); 203 } 204 205 @Override 206 public void addView(View child) { 207 if (getChildCount() > 0) { 208 throw new IllegalStateException("ScrollView can host only one direct child"); 209 } 210 211 super.addView(child); 212 } 213 214 @Override 215 public void addView(View child, int index) { 216 if (getChildCount() > 0) { 217 throw new IllegalStateException("ScrollView can host only one direct child"); 218 } 219 220 super.addView(child, index); 221 } 222 223 @Override 224 public void addView(View child, ViewGroup.LayoutParams params) { 225 if (getChildCount() > 0) { 226 throw new IllegalStateException("ScrollView can host only one direct child"); 227 } 228 229 super.addView(child, params); 230 } 231 232 @Override 233 public void addView(View child, int index, ViewGroup.LayoutParams params) { 234 if (getChildCount() > 0) { 235 throw new IllegalStateException("ScrollView can host only one direct child"); 236 } 237 238 super.addView(child, index, params); 239 } 240 241 /** 242 * @return Returns true this ScrollView can be scrolled 243 */ 244 private boolean canScroll() { 245 View child = getChildAt(0); 246 if (child != null) { 247 int childHeight = child.getHeight(); 248 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 249 } 250 return false; 251 } 252 253 /** 254 * Indicates whether this ScrollView's content is stretched to fill the viewport. 255 * 256 * @return True if the content fills the viewport, false otherwise. 257 */ 258 public boolean isFillViewport() { 259 return mFillViewport; 260 } 261 262 /** 263 * Indicates this ScrollView whether it should stretch its content height to fill 264 * the viewport or not. 265 * 266 * @param fillViewport True to stretch the content's height to the viewport's 267 * boundaries, false otherwise. 268 */ 269 public void setFillViewport(boolean fillViewport) { 270 if (fillViewport != mFillViewport) { 271 mFillViewport = fillViewport; 272 requestLayout(); 273 } 274 } 275 276 /** 277 * @return Whether arrow scrolling will animate its transition. 278 */ 279 public boolean isSmoothScrollingEnabled() { 280 return mSmoothScrollingEnabled; 281 } 282 283 /** 284 * Set whether arrow scrolling will animate its transition. 285 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 286 */ 287 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 288 mSmoothScrollingEnabled = smoothScrollingEnabled; 289 } 290 291 @Override 292 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 293 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 294 295 if (!mFillViewport) { 296 return; 297 } 298 299 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 300 if (heightMode == MeasureSpec.UNSPECIFIED) { 301 return; 302 } 303 304 final View child = getChildAt(0); 305 int height = getMeasuredHeight(); 306 if (child.getMeasuredHeight() < height) { 307 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 308 309 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 310 + mPaddingRight, lp.width); 311 height -= mPaddingTop; 312 height -= mPaddingBottom; 313 int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 314 315 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 316 } 317 } 318 319 @Override 320 public boolean dispatchKeyEvent(KeyEvent event) { 321 // Let the focused view and/or our descendants get the key first 322 boolean handled = super.dispatchKeyEvent(event); 323 if (handled) { 324 return true; 325 } 326 return executeKeyEvent(event); 327 } 328 329 /** 330 * You can call this function yourself to have the scroll view perform 331 * scrolling from a key event, just as if the event had been dispatched to 332 * it by the view hierarchy. 333 * 334 * @param event The key event to execute. 335 * @return Return true if the event was handled, else false. 336 */ 337 public boolean executeKeyEvent(KeyEvent event) { 338 mTempRect.setEmpty(); 339 340 if (!canScroll()) { 341 if (isFocused()) { 342 View currentFocused = findFocus(); 343 if (currentFocused == this) currentFocused = null; 344 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 345 currentFocused, View.FOCUS_DOWN); 346 return nextFocused != null 347 && nextFocused != this 348 && nextFocused.requestFocus(View.FOCUS_DOWN); 349 } 350 return false; 351 } 352 353 boolean handled = false; 354 if (event.getAction() == KeyEvent.ACTION_DOWN) { 355 switch (event.getKeyCode()) { 356 case KeyEvent.KEYCODE_DPAD_UP: 357 if (!event.isAltPressed()) { 358 handled = arrowScroll(View.FOCUS_UP); 359 } else { 360 handled = fullScroll(View.FOCUS_UP); 361 } 362 break; 363 case KeyEvent.KEYCODE_DPAD_DOWN: 364 if (!event.isAltPressed()) { 365 handled = arrowScroll(View.FOCUS_DOWN); 366 } else { 367 handled = fullScroll(View.FOCUS_DOWN); 368 } 369 break; 370 case KeyEvent.KEYCODE_SPACE: 371 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 372 break; 373 } 374 } 375 376 return handled; 377 } 378 379 @Override 380 public boolean onInterceptTouchEvent(MotionEvent ev) { 381 /* 382 * This method JUST determines whether we want to intercept the motion. 383 * If we return true, onMotionEvent will be called and we do the actual 384 * scrolling there. 385 */ 386 387 /* 388 * Shortcut the most recurring case: the user is in the dragging 389 * state and he is moving his finger. We want to intercept this 390 * motion. 391 */ 392 final int action = ev.getAction(); 393 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 394 return true; 395 } 396 397 if (!canScroll()) { 398 mIsBeingDragged = false; 399 return false; 400 } 401 402 final float y = ev.getY(); 403 404 switch (action) { 405 case MotionEvent.ACTION_MOVE: 406 /* 407 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 408 * whether the user has moved far enough from his original down touch. 409 */ 410 411 /* 412 * Locally do absolute value. mLastMotionY is set to the y value 413 * of the down event. 414 */ 415 final int yDiff = (int) Math.abs(y - mLastMotionY); 416 if (yDiff > ViewConfiguration.getTouchSlop()) { 417 mIsBeingDragged = true; 418 } 419 break; 420 421 case MotionEvent.ACTION_DOWN: 422 /* Remember location of down touch */ 423 mLastMotionY = y; 424 425 /* 426 * If being flinged and user touches the screen, initiate drag; 427 * otherwise don't. mScroller.isFinished should be false when 428 * being flinged. 429 */ 430 mIsBeingDragged = !mScroller.isFinished(); 431 break; 432 433 case MotionEvent.ACTION_CANCEL: 434 case MotionEvent.ACTION_UP: 435 /* Release the drag */ 436 mIsBeingDragged = false; 437 break; 438 } 439 440 /* 441 * The only time we want to intercept motion events is if we are in the 442 * drag mode. 443 */ 444 return mIsBeingDragged; 445 } 446 447 @Override 448 public boolean onTouchEvent(MotionEvent ev) { 449 450 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 451 // Don't handle edge touches immediately -- they may actually belong to one of our 452 // descendants. 453 return false; 454 } 455 456 if (!canScroll()) { 457 return false; 458 } 459 460 if (mVelocityTracker == null) { 461 mVelocityTracker = VelocityTracker.obtain(); 462 } 463 mVelocityTracker.addMovement(ev); 464 465 final int action = ev.getAction(); 466 final float y = ev.getY(); 467 468 switch (action) { 469 case MotionEvent.ACTION_DOWN: 470 /* 471 * If being flinged and user touches, stop the fling. isFinished 472 * will be false if being flinged. 473 */ 474 if (!mScroller.isFinished()) { 475 mScroller.abortAnimation(); 476 } 477 478 // Remember where the motion event started 479 mLastMotionY = y; 480 break; 481 case MotionEvent.ACTION_MOVE: 482 // Scroll to follow the motion event 483 final int deltaY = (int) (mLastMotionY - y); 484 mLastMotionY = y; 485 486 if (deltaY < 0) { 487 if (mScrollY > 0) { 488 scrollBy(0, deltaY); 489 } 490 } else if (deltaY > 0) { 491 final int bottomEdge = getHeight() - mPaddingBottom; 492 final int availableToScroll = getChildAt(0).getBottom() - mScrollY - bottomEdge; 493 if (availableToScroll > 0) { 494 scrollBy(0, Math.min(availableToScroll, deltaY)); 495 } 496 } 497 break; 498 case MotionEvent.ACTION_UP: 499 final VelocityTracker velocityTracker = mVelocityTracker; 500 velocityTracker.computeCurrentVelocity(1000); 501 int initialVelocity = (int) velocityTracker.getYVelocity(); 502 503 if ((Math.abs(initialVelocity) > ViewConfiguration.getMinimumFlingVelocity()) && 504 (getChildCount() > 0)) { 505 fling(-initialVelocity); 506 } 507 508 if (mVelocityTracker != null) { 509 mVelocityTracker.recycle(); 510 mVelocityTracker = null; 511 } 512 } 513 return true; 514 } 515 516 /** 517 * <p> 518 * Finds the next focusable component that fits in this View's bounds 519 * (excluding fading edges) pretending that this View's top is located at 520 * the parameter top. 521 * </p> 522 * 523 * @param topFocus look for a candidate is the one at the top of the bounds 524 * if topFocus is true, or at the bottom of the bounds if topFocus is 525 * false 526 * @param top the top offset of the bounds in which a focusable must be 527 * found (the fading edge is assumed to start at this position) 528 * @param preferredFocusable the View that has highest priority and will be 529 * returned if it is within my bounds (null is valid) 530 * @return the next focusable component in the bounds or null if none can be 531 * found 532 */ 533 private View findFocusableViewInMyBounds(final boolean topFocus, 534 final int top, View preferredFocusable) { 535 /* 536 * The fading edge's transparent side should be considered for focus 537 * since it's mostly visible, so we divide the actual fading edge length 538 * by 2. 539 */ 540 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 541 final int topWithoutFadingEdge = top + fadingEdgeLength; 542 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 543 544 if ((preferredFocusable != null) 545 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 546 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 547 return preferredFocusable; 548 } 549 550 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 551 bottomWithoutFadingEdge); 552 } 553 554 /** 555 * <p> 556 * Finds the next focusable component that fits in the specified bounds. 557 * </p> 558 * 559 * @param topFocus look for a candidate is the one at the top of the bounds 560 * if topFocus is true, or at the bottom of the bounds if topFocus is 561 * false 562 * @param top the top offset of the bounds in which a focusable must be 563 * found 564 * @param bottom the bottom offset of the bounds in which a focusable must 565 * be found 566 * @return the next focusable component in the bounds or null if none can 567 * be found 568 */ 569 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 570 571 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 572 View focusCandidate = null; 573 574 /* 575 * A fully contained focusable is one where its top is below the bound's 576 * top, and its bottom is above the bound's bottom. A partially 577 * contained focusable is one where some part of it is within the 578 * bounds, but it also has some part that is not within bounds. A fully contained 579 * focusable is preferred to a partially contained focusable. 580 */ 581 boolean foundFullyContainedFocusable = false; 582 583 int count = focusables.size(); 584 for (int i = 0; i < count; i++) { 585 View view = focusables.get(i); 586 int viewTop = view.getTop(); 587 int viewBottom = view.getBottom(); 588 589 if (top < viewBottom && viewTop < bottom) { 590 /* 591 * the focusable is in the target area, it is a candidate for 592 * focusing 593 */ 594 595 final boolean viewIsFullyContained = (top < viewTop) && 596 (viewBottom < bottom); 597 598 if (focusCandidate == null) { 599 /* No candidate, take this one */ 600 focusCandidate = view; 601 foundFullyContainedFocusable = viewIsFullyContained; 602 } else { 603 final boolean viewIsCloserToBoundary = 604 (topFocus && viewTop < focusCandidate.getTop()) || 605 (!topFocus && viewBottom > focusCandidate 606 .getBottom()); 607 608 if (foundFullyContainedFocusable) { 609 if (viewIsFullyContained && viewIsCloserToBoundary) { 610 /* 611 * We're dealing with only fully contained views, so 612 * it has to be closer to the boundary to beat our 613 * candidate 614 */ 615 focusCandidate = view; 616 } 617 } else { 618 if (viewIsFullyContained) { 619 /* Any fully contained view beats a partially contained view */ 620 focusCandidate = view; 621 foundFullyContainedFocusable = true; 622 } else if (viewIsCloserToBoundary) { 623 /* 624 * Partially contained view beats another partially 625 * contained view if it's closer 626 */ 627 focusCandidate = view; 628 } 629 } 630 } 631 } 632 } 633 634 return focusCandidate; 635 } 636 637 /** 638 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 639 * method will scroll the view by one page up or down and give the focus 640 * to the topmost/bottommost component in the new visible area. If no 641 * component is a good candidate for focus, this scrollview reclaims the 642 * focus.</p> 643 * 644 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 645 * to go one page up or 646 * {@link android.view.View#FOCUS_DOWN} to go one page down 647 * @return true if the key event is consumed by this method, false otherwise 648 */ 649 public boolean pageScroll(int direction) { 650 boolean down = direction == View.FOCUS_DOWN; 651 int height = getHeight(); 652 653 if (down) { 654 mTempRect.top = getScrollY() + height; 655 int count = getChildCount(); 656 if (count > 0) { 657 View view = getChildAt(count - 1); 658 if (mTempRect.top + height > view.getBottom()) { 659 mTempRect.top = view.getBottom() - height; 660 } 661 } 662 } else { 663 mTempRect.top = getScrollY() - height; 664 if (mTempRect.top < 0) { 665 mTempRect.top = 0; 666 } 667 } 668 mTempRect.bottom = mTempRect.top + height; 669 670 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 671 } 672 673 /** 674 * <p>Handles scrolling in response to a "home/end" shortcut press. This 675 * method will scroll the view to the top or bottom and give the focus 676 * to the topmost/bottommost component in the new visible area. If no 677 * component is a good candidate for focus, this scrollview reclaims the 678 * focus.</p> 679 * 680 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 681 * to go the top of the view or 682 * {@link android.view.View#FOCUS_DOWN} to go the bottom 683 * @return true if the key event is consumed by this method, false otherwise 684 */ 685 public boolean fullScroll(int direction) { 686 boolean down = direction == View.FOCUS_DOWN; 687 int height = getHeight(); 688 689 mTempRect.top = 0; 690 mTempRect.bottom = height; 691 692 if (down) { 693 int count = getChildCount(); 694 if (count > 0) { 695 View view = getChildAt(count - 1); 696 mTempRect.bottom = view.getBottom(); 697 mTempRect.top = mTempRect.bottom - height; 698 } 699 } 700 701 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 702 } 703 704 /** 705 * <p>Scrolls the view to make the area defined by <code>top</code> and 706 * <code>bottom</code> visible. This method attempts to give the focus 707 * to a component visible in this area. If no component can be focused in 708 * the new visible area, the focus is reclaimed by this scrollview.</p> 709 * 710 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 711 * to go upward 712 * {@link android.view.View#FOCUS_DOWN} to downward 713 * @param top the top offset of the new area to be made visible 714 * @param bottom the bottom offset of the new area to be made visible 715 * @return true if the key event is consumed by this method, false otherwise 716 */ 717 private boolean scrollAndFocus(int direction, int top, int bottom) { 718 boolean handled = true; 719 720 int height = getHeight(); 721 int containerTop = getScrollY(); 722 int containerBottom = containerTop + height; 723 boolean up = direction == View.FOCUS_UP; 724 725 View newFocused = findFocusableViewInBounds(up, top, bottom); 726 if (newFocused == null) { 727 newFocused = this; 728 } 729 730 if (top >= containerTop && bottom <= containerBottom) { 731 handled = false; 732 } else { 733 int delta = up ? (top - containerTop) : (bottom - containerBottom); 734 doScrollY(delta); 735 } 736 737 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 738 mScrollViewMovedFocus = true; 739 mScrollViewMovedFocus = false; 740 } 741 742 return handled; 743 } 744 745 /** 746 * Handle scrolling in response to an up or down arrow click. 747 * 748 * @param direction The direction corresponding to the arrow key that was 749 * pressed 750 * @return True if we consumed the event, false otherwise 751 */ 752 public boolean arrowScroll(int direction) { 753 754 View currentFocused = findFocus(); 755 if (currentFocused == this) currentFocused = null; 756 757 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 758 759 final int maxJump = getMaxScrollAmount(); 760 761 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 762 nextFocused.getDrawingRect(mTempRect); 763 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 764 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 765 doScrollY(scrollDelta); 766 nextFocused.requestFocus(direction); 767 } else { 768 // no new focus 769 int scrollDelta = maxJump; 770 771 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 772 scrollDelta = getScrollY(); 773 } else if (direction == View.FOCUS_DOWN) { 774 775 int daBottom = getChildAt(getChildCount() - 1).getBottom(); 776 777 int screenBottom = getScrollY() + getHeight(); 778 779 if (daBottom - screenBottom < maxJump) { 780 scrollDelta = daBottom - screenBottom; 781 } 782 } 783 if (scrollDelta == 0) { 784 return false; 785 } 786 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 787 } 788 789 if (currentFocused != null && currentFocused.isFocused() 790 && isOffScreen(currentFocused)) { 791 // previously focused item still has focus and is off screen, give 792 // it up (take it back to ourselves) 793 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 794 // sure to 795 // get it) 796 final int descendantFocusability = getDescendantFocusability(); // save 797 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 798 requestFocus(); 799 setDescendantFocusability(descendantFocusability); // restore 800 } 801 return true; 802 } 803 804 /** 805 * @return whether the descendant of this scroll view is scrolled off 806 * screen. 807 */ 808 private boolean isOffScreen(View descendant) { 809 return !isWithinDeltaOfScreen(descendant, 0); 810 } 811 812 /** 813 * @return whether the descendant of this scroll view is within delta 814 * pixels of being on the screen. 815 */ 816 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 817 descendant.getDrawingRect(mTempRect); 818 offsetDescendantRectToMyCoords(descendant, mTempRect); 819 820 return (mTempRect.bottom + delta) >= getScrollY() 821 && (mTempRect.top - delta) <= (getScrollY() + getHeight()); 822 } 823 824 /** 825 * Smooth scroll by a Y delta 826 * 827 * @param delta the number of pixels to scroll by on the X axis 828 */ 829 private void doScrollY(int delta) { 830 if (delta != 0) { 831 if (mSmoothScrollingEnabled) { 832 smoothScrollBy(0, delta); 833 } else { 834 scrollBy(0, delta); 835 } 836 } 837 } 838 839 /** 840 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 841 * 842 * @param dx the number of pixels to scroll by on the X axis 843 * @param dy the number of pixels to scroll by on the Y axis 844 */ 845 public final void smoothScrollBy(int dx, int dy) { 846 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 847 if (duration > ANIMATED_SCROLL_GAP) { 848 if (localLOGV) Log.v(TAG, "Smooth scroll: mScrollY=" + mScrollY 849 + " dy=" + dy); 850 mScroller.startScroll(mScrollX, mScrollY, dx, dy); 851 invalidate(); 852 } else { 853 if (!mScroller.isFinished()) { 854 mScroller.abortAnimation(); 855 } 856 if (localLOGV) Log.v(TAG, "Immediate scroll: mScrollY=" + mScrollY 857 + " dy=" + dy); 858 scrollBy(dx, dy); 859 } 860 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 861 } 862 863 /** 864 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 865 * 866 * @param x the position where to scroll on the X axis 867 * @param y the position where to scroll on the Y axis 868 */ 869 public final void smoothScrollTo(int x, int y) { 870 smoothScrollBy(x - mScrollX, y - mScrollY); 871 } 872 873 /** 874 * <p>The scroll range of a scroll view is the overall height of all of its 875 * children.</p> 876 */ 877 @Override 878 protected int computeVerticalScrollRange() { 879 int count = getChildCount(); 880 return count == 0 ? getHeight() : (getChildAt(0)).getBottom(); 881 } 882 883 884 @Override 885 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 886 ViewGroup.LayoutParams lp = child.getLayoutParams(); 887 888 int childWidthMeasureSpec; 889 int childHeightMeasureSpec; 890 891 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 892 + mPaddingRight, lp.width); 893 894 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 895 896 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 897 } 898 899 @Override 900 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 901 int parentHeightMeasureSpec, int heightUsed) { 902 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 903 904 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 905 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 906 + widthUsed, lp.width); 907 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 908 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 909 910 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 911 } 912 913 @Override 914 public void computeScroll() { 915 if (mScroller.computeScrollOffset()) { 916 // This is called at drawing time by ViewGroup. We don't want to 917 // re-show the scrollbars at this point, which scrollTo will do, 918 // so we replicate most of scrollTo here. 919 // 920 // It's a little odd to call onScrollChanged from inside the drawing. 921 // 922 // It is, except when you remember that computeScroll() is used to 923 // animate scrolling. So unless we want to defer the onScrollChanged() 924 // until the end of the animated scrolling, we don't really have a 925 // choice here. 926 // 927 // I agree. The alternative, which I think would be worse, is to post 928 // something and tell the subclasses later. This is bad because there 929 // will be a window where mScrollX/Y is different from what the app 930 // thinks it is. 931 // 932 int oldX = mScrollX; 933 int oldY = mScrollY; 934 int x = mScroller.getCurrX(); 935 int y = mScroller.getCurrY(); 936 if (getChildCount() > 0) { 937 View child = getChildAt(0); 938 mScrollX = clamp(x, this.getWidth(), child.getWidth()); 939 mScrollY = clamp(y, this.getHeight(), child.getHeight()); 940 if (localLOGV) Log.v(TAG, "mScrollY=" + mScrollY + " y=" + y 941 + " height=" + this.getHeight() 942 + " child height=" + child.getHeight()); 943 } else { 944 mScrollX = x; 945 mScrollY = y; 946 } 947 if (oldX != mScrollX || oldY != mScrollY) { 948 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 949 } 950 951 // Keep on drawing until the animation has finished. 952 postInvalidate(); 953 } 954 } 955 956 /** 957 * Scrolls the view to the given child. 958 * 959 * @param child the View to scroll to 960 */ 961 private void scrollToChild(View child) { 962 child.getDrawingRect(mTempRect); 963 964 /* Offset from child's local coordinates to ScrollView coordinates */ 965 offsetDescendantRectToMyCoords(child, mTempRect); 966 967 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 968 969 if (scrollDelta != 0) { 970 scrollBy(0, scrollDelta); 971 } 972 } 973 974 /** 975 * If rect is off screen, scroll just enough to get it (or at least the 976 * first screen size chunk of it) on screen. 977 * 978 * @param rect The rectangle. 979 * @param immediate True to scroll immediately without animation 980 * @return true if scrolling was performed 981 */ 982 private boolean scrollToChildRect(Rect rect, boolean immediate) { 983 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 984 final boolean scroll = delta != 0; 985 if (scroll) { 986 if (immediate) { 987 scrollBy(0, delta); 988 } else { 989 smoothScrollBy(0, delta); 990 } 991 } 992 return scroll; 993 } 994 995 /** 996 * Compute the amount to scroll in the Y direction in order to get 997 * a rectangle completely on the screen (or, if taller than the screen, 998 * at least the first screen size chunk of it). 999 * 1000 * @param rect The rect. 1001 * @return The scroll delta. 1002 */ 1003 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1004 1005 int height = getHeight(); 1006 int screenTop = getScrollY(); 1007 int screenBottom = screenTop + height; 1008 1009 int fadingEdge = getVerticalFadingEdgeLength(); 1010 1011 // leave room for top fading edge as long as rect isn't at very top 1012 if (rect.top > 0) { 1013 screenTop += fadingEdge; 1014 } 1015 1016 // leave room for bottom fading edge as long as rect isn't at very bottom 1017 if (rect.bottom < getChildAt(0).getHeight()) { 1018 screenBottom -= fadingEdge; 1019 } 1020 1021 int scrollYDelta = 0; 1022 1023 if (localLOGV) Log.v(TAG, "child=" + rect.toShortString() 1024 + " screenTop=" + screenTop + " screenBottom=" + screenBottom 1025 + " height=" + height); 1026 if (rect.bottom > screenBottom && rect.top > screenTop) { 1027 // need to move down to get it in view: move down just enough so 1028 // that the entire rectangle is in view (or at least the first 1029 // screen size chunk). 1030 1031 if (rect.height() > height) { 1032 // just enough to get screen size chunk on 1033 scrollYDelta += (rect.top - screenTop); 1034 } else { 1035 // get entire rect at bottom of screen 1036 scrollYDelta += (rect.bottom - screenBottom); 1037 } 1038 1039 // make sure we aren't scrolling beyond the end of our content 1040 int bottom = getChildAt(getChildCount() - 1).getBottom(); 1041 int distanceToBottom = bottom - screenBottom; 1042 if (localLOGV) Log.v(TAG, "scrollYDelta=" + scrollYDelta 1043 + " distanceToBottom=" + distanceToBottom); 1044 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1045 1046 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1047 // need to move up to get it in view: move up just enough so that 1048 // entire rectangle is in view (or at least the first screen 1049 // size chunk of it). 1050 1051 if (rect.height() > height) { 1052 // screen size chunk 1053 scrollYDelta -= (screenBottom - rect.bottom); 1054 } else { 1055 // entire rect at top 1056 scrollYDelta -= (screenTop - rect.top); 1057 } 1058 1059 // make sure we aren't scrolling any further than the top our content 1060 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1061 } 1062 return scrollYDelta; 1063 } 1064 1065 @Override 1066 public void requestChildFocus(View child, View focused) { 1067 if (!mScrollViewMovedFocus) { 1068 if (!mIsLayoutDirty) { 1069 scrollToChild(focused); 1070 } else { 1071 // The child may not be laid out yet, we can't compute the scroll yet 1072 mChildToScrollTo = focused; 1073 } 1074 } 1075 super.requestChildFocus(child, focused); 1076 } 1077 1078 1079 /** 1080 * When looking for focus in children of a scroll view, need to be a little 1081 * more careful not to give focus to something that is scrolled off screen. 1082 * 1083 * This is more expensive than the default {@link android.view.ViewGroup} 1084 * implementation, otherwise this behavior might have been made the default. 1085 */ 1086 @Override 1087 protected boolean onRequestFocusInDescendants(int direction, 1088 Rect previouslyFocusedRect) { 1089 1090 // convert from forward / backward notation to up / down / left / right 1091 // (ugh). 1092 if (direction == View.FOCUS_FORWARD) { 1093 direction = View.FOCUS_DOWN; 1094 } else if (direction == View.FOCUS_BACKWARD) { 1095 direction = View.FOCUS_UP; 1096 } 1097 1098 final View nextFocus = previouslyFocusedRect == null ? 1099 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1100 FocusFinder.getInstance().findNextFocusFromRect(this, 1101 previouslyFocusedRect, direction); 1102 1103 if (nextFocus == null) { 1104 return false; 1105 } 1106 1107 if (isOffScreen(nextFocus)) { 1108 return false; 1109 } 1110 1111 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1112 } 1113 1114 @Override 1115 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1116 boolean immediate) { 1117 // offset into coordinate space of this scroll view 1118 rectangle.offset(child.getLeft() - child.getScrollX(), 1119 child.getTop() - child.getScrollY()); 1120 1121 return scrollToChildRect(rectangle, immediate); 1122 } 1123 1124 @Override 1125 public void requestLayout() { 1126 mIsLayoutDirty = true; 1127 super.requestLayout(); 1128 } 1129 1130 @Override 1131 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1132 super.onLayout(changed, l, t, r, b); 1133 mIsLayoutDirty = false; 1134 // Give a child focus if it needs it 1135 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1136 scrollToChild(mChildToScrollTo); 1137 } 1138 mChildToScrollTo = null; 1139 1140 // Calling this with the present values causes it to re-clam them 1141 scrollTo(mScrollX, mScrollY); 1142 } 1143 1144 @Override 1145 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1146 super.onSizeChanged(w, h, oldw, oldh); 1147 1148 View currentFocused = findFocus(); 1149 if (null == currentFocused || this == currentFocused) 1150 return; 1151 1152 final int maxJump = mBottom - mTop; 1153 1154 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1155 currentFocused.getDrawingRect(mTempRect); 1156 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1157 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1158 doScrollY(scrollDelta); 1159 } 1160 } 1161 1162 /** 1163 * Return true if child is an descendant of parent, (or equal to the parent). 1164 */ 1165 private boolean isViewDescendantOf(View child, View parent) { 1166 if (child == parent) { 1167 return true; 1168 } 1169 1170 final ViewParent theParent = child.getParent(); 1171 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1172 } 1173 1174 /** 1175 * Fling the scroll view 1176 * 1177 * @param velocityY The initial velocity in the Y direction. Positive 1178 * numbers mean that the finger/curor is moving down the screen, 1179 * which means we want to scroll towards the top. 1180 */ 1181 public void fling(int velocityY) { 1182 int height = getHeight(); 1183 int bottom = getChildAt(getChildCount() - 1).getBottom(); 1184 1185 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, bottom - height); 1186 1187 final boolean movingDown = velocityY > 0; 1188 1189 View newFocused = 1190 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1191 if (newFocused == null) { 1192 newFocused = this; 1193 } 1194 1195 if (newFocused != findFocus() 1196 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1197 mScrollViewMovedFocus = true; 1198 mScrollViewMovedFocus = false; 1199 } 1200 1201 invalidate(); 1202 } 1203 1204 /** 1205 * {@inheritDoc} 1206 * 1207 * <p>This version also clamps the scrolling to the bounds of our child. 1208 */ 1209 public void scrollTo(int x, int y) { 1210 // we rely on the fact the View.scrollBy calls scrollTo. 1211 if (getChildCount() > 0) { 1212 View child = getChildAt(0); 1213 x = clamp(x, this.getWidth(), child.getWidth()); 1214 y = clamp(y, this.getHeight(), child.getHeight()); 1215 if (x != mScrollX || y != mScrollY) { 1216 super.scrollTo(x, y); 1217 } 1218 } 1219 } 1220 1221 private int clamp(int n, int my, int child) { 1222 if (my >= child || n < 0) { 1223 /* my >= child is this case: 1224 * |--------------- me ---------------| 1225 * |------ child ------| 1226 * or 1227 * |--------------- me ---------------| 1228 * |------ child ------| 1229 * or 1230 * |--------------- me ---------------| 1231 * |------ child ------| 1232 * 1233 * n < 0 is this case: 1234 * |------ me ------| 1235 * |-------- child --------| 1236 * |-- mScrollX --| 1237 */ 1238 return 0; 1239 } 1240 if ((my+n) > child) { 1241 /* this case: 1242 * |------ me ------| 1243 * |------ child ------| 1244 * |-- mScrollX --| 1245 */ 1246 return child-my; 1247 } 1248 return n; 1249 } 1250} 1251