ScrollView.java revision 9066cfe9886ac131c34d59ed0e2d287b0e3c0087
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>The {@link TextView} class also 49 * takes care of its own scrolling, so does not require a ScrollView, but 50 * using the two together is possible to achieve the effect of a text view 51 * within a larger container. 52 * 53 * <p>ScrollView only supports vertical scrolling. 54 */ 55public class ScrollView extends FrameLayout { 56 static final String TAG = "ScrollView"; 57 static final boolean localLOGV = false || Config.LOGV; 58 59 static final int ANIMATED_SCROLL_GAP = 250; 60 61 static final float MAX_SCROLL_FACTOR = 0.5f; 62 63 64 private long mLastScroll; 65 66 private final Rect mTempRect = new Rect(); 67 private Scroller mScroller; 68 69 /** 70 * Flag to indicate that we are moving focus ourselves. This is so the 71 * code that watches for focus changes initiated outside this ScrollView 72 * knows that it does not have to do anything. 73 */ 74 private boolean mScrollViewMovedFocus; 75 76 /** 77 * Position of the last motion event. 78 */ 79 private float mLastMotionY; 80 81 /** 82 * True when the layout has changed but the traversal has not come through yet. 83 * Ideally the view hierarchy would keep track of this for us. 84 */ 85 private boolean mIsLayoutDirty = true; 86 87 /** 88 * The child to give focus to in the event that a child has requested focus while the 89 * layout is dirty. This prevents the scroll from being wrong if the child has not been 90 * laid out before requesting focus. 91 */ 92 private View mChildToScrollTo = null; 93 94 /** 95 * True if the user is currently dragging this ScrollView around. This is 96 * not the same as 'is being flinged', which can be checked by 97 * mScroller.isFinished() (flinging begins when the user lifts his finger). 98 */ 99 private boolean mIsBeingDragged = false; 100 101 /** 102 * Determines speed during touch scrolling 103 */ 104 private VelocityTracker mVelocityTracker; 105 106 /** 107 * When set to true, the scroll view measure its child to make it fill the currently 108 * visible area. 109 */ 110 private boolean mFillViewport; 111 112 /** 113 * Whether arrow scrolling is animated. 114 */ 115 private boolean mSmoothScrollingEnabled = true; 116 117 private int mTouchSlop; 118 119 public ScrollView(Context context) { 120 this(context, null); 121 } 122 123 public ScrollView(Context context, AttributeSet attrs) { 124 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 125 } 126 127 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 128 super(context, attrs, defStyle); 129 initScrollView(); 130 131 TypedArray a = 132 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 133 134 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 135 136 a.recycle(); 137 } 138 139 @Override 140 protected float getTopFadingEdgeStrength() { 141 if (getChildCount() == 0) { 142 return 0.0f; 143 } 144 145 final int length = getVerticalFadingEdgeLength(); 146 if (mScrollY < length) { 147 return mScrollY / (float) length; 148 } 149 150 return 1.0f; 151 } 152 153 @Override 154 protected float getBottomFadingEdgeStrength() { 155 if (getChildCount() == 0) { 156 return 0.0f; 157 } 158 159 final int length = getVerticalFadingEdgeLength(); 160 final int bottomEdge = getHeight() - mPaddingBottom; 161 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 162 if (span < length) { 163 return span / (float) length; 164 } 165 166 return 1.0f; 167 } 168 169 /** 170 * @return The maximum amount this scroll view will scroll in response to 171 * an arrow event. 172 */ 173 public int getMaxScrollAmount() { 174 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 175 } 176 177 178 private void initScrollView() { 179 mScroller = new Scroller(getContext()); 180 setFocusable(true); 181 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 182 setWillNotDraw(false); 183 mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop(); 184 } 185 186 @Override 187 public void addView(View child) { 188 if (getChildCount() > 0) { 189 throw new IllegalStateException("ScrollView can host only one direct child"); 190 } 191 192 super.addView(child); 193 } 194 195 @Override 196 public void addView(View child, int index) { 197 if (getChildCount() > 0) { 198 throw new IllegalStateException("ScrollView can host only one direct child"); 199 } 200 201 super.addView(child, index); 202 } 203 204 @Override 205 public void addView(View child, ViewGroup.LayoutParams params) { 206 if (getChildCount() > 0) { 207 throw new IllegalStateException("ScrollView can host only one direct child"); 208 } 209 210 super.addView(child, params); 211 } 212 213 @Override 214 public void addView(View child, int index, ViewGroup.LayoutParams params) { 215 if (getChildCount() > 0) { 216 throw new IllegalStateException("ScrollView can host only one direct child"); 217 } 218 219 super.addView(child, index, params); 220 } 221 222 /** 223 * @return Returns true this ScrollView can be scrolled 224 */ 225 private boolean canScroll() { 226 View child = getChildAt(0); 227 if (child != null) { 228 int childHeight = child.getHeight(); 229 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 230 } 231 return false; 232 } 233 234 /** 235 * Indicates whether this ScrollView's content is stretched to fill the viewport. 236 * 237 * @return True if the content fills the viewport, false otherwise. 238 */ 239 public boolean isFillViewport() { 240 return mFillViewport; 241 } 242 243 /** 244 * Indicates this ScrollView whether it should stretch its content height to fill 245 * the viewport or not. 246 * 247 * @param fillViewport True to stretch the content's height to the viewport's 248 * boundaries, false otherwise. 249 */ 250 public void setFillViewport(boolean fillViewport) { 251 if (fillViewport != mFillViewport) { 252 mFillViewport = fillViewport; 253 requestLayout(); 254 } 255 } 256 257 /** 258 * @return Whether arrow scrolling will animate its transition. 259 */ 260 public boolean isSmoothScrollingEnabled() { 261 return mSmoothScrollingEnabled; 262 } 263 264 /** 265 * Set whether arrow scrolling will animate its transition. 266 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 267 */ 268 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 269 mSmoothScrollingEnabled = smoothScrollingEnabled; 270 } 271 272 @Override 273 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 274 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 275 276 if (!mFillViewport) { 277 return; 278 } 279 280 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 281 if (heightMode == MeasureSpec.UNSPECIFIED) { 282 return; 283 } 284 285 final View child = getChildAt(0); 286 int height = getMeasuredHeight(); 287 if (child.getMeasuredHeight() < height) { 288 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 289 290 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 291 + mPaddingRight, lp.width); 292 height -= mPaddingTop; 293 height -= mPaddingBottom; 294 int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 295 296 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 297 } 298 } 299 300 @Override 301 public boolean dispatchKeyEvent(KeyEvent event) { 302 // Let the focused view and/or our descendants get the key first 303 boolean handled = super.dispatchKeyEvent(event); 304 if (handled) { 305 return true; 306 } 307 return executeKeyEvent(event); 308 } 309 310 /** 311 * You can call this function yourself to have the scroll view perform 312 * scrolling from a key event, just as if the event had been dispatched to 313 * it by the view hierarchy. 314 * 315 * @param event The key event to execute. 316 * @return Return true if the event was handled, else false. 317 */ 318 public boolean executeKeyEvent(KeyEvent event) { 319 mTempRect.setEmpty(); 320 321 if (!canScroll()) { 322 if (isFocused()) { 323 View currentFocused = findFocus(); 324 if (currentFocused == this) currentFocused = null; 325 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 326 currentFocused, View.FOCUS_DOWN); 327 return nextFocused != null 328 && nextFocused != this 329 && nextFocused.requestFocus(View.FOCUS_DOWN); 330 } 331 return false; 332 } 333 334 boolean handled = false; 335 if (event.getAction() == KeyEvent.ACTION_DOWN) { 336 switch (event.getKeyCode()) { 337 case KeyEvent.KEYCODE_DPAD_UP: 338 if (!event.isAltPressed()) { 339 handled = arrowScroll(View.FOCUS_UP); 340 } else { 341 handled = fullScroll(View.FOCUS_UP); 342 } 343 break; 344 case KeyEvent.KEYCODE_DPAD_DOWN: 345 if (!event.isAltPressed()) { 346 handled = arrowScroll(View.FOCUS_DOWN); 347 } else { 348 handled = fullScroll(View.FOCUS_DOWN); 349 } 350 break; 351 case KeyEvent.KEYCODE_SPACE: 352 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 353 break; 354 } 355 } 356 357 return handled; 358 } 359 360 @Override 361 public boolean onInterceptTouchEvent(MotionEvent ev) { 362 /* 363 * This method JUST determines whether we want to intercept the motion. 364 * If we return true, onMotionEvent will be called and we do the actual 365 * scrolling there. 366 */ 367 368 /* 369 * Shortcut the most recurring case: the user is in the dragging 370 * state and he is moving his finger. We want to intercept this 371 * motion. 372 */ 373 final int action = ev.getAction(); 374 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 375 return true; 376 } 377 378 if (!canScroll()) { 379 mIsBeingDragged = false; 380 return false; 381 } 382 383 final float y = ev.getY(); 384 385 switch (action) { 386 case MotionEvent.ACTION_MOVE: 387 /* 388 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 389 * whether the user has moved far enough from his original down touch. 390 */ 391 392 /* 393 * Locally do absolute value. mLastMotionY is set to the y value 394 * of the down event. 395 */ 396 final int yDiff = (int) Math.abs(y - mLastMotionY); 397 if (yDiff > mTouchSlop) { 398 mIsBeingDragged = true; 399 } 400 break; 401 402 case MotionEvent.ACTION_DOWN: 403 /* Remember location of down touch */ 404 mLastMotionY = y; 405 406 /* 407 * If being flinged and user touches the screen, initiate drag; 408 * otherwise don't. mScroller.isFinished should be false when 409 * being flinged. 410 */ 411 mIsBeingDragged = !mScroller.isFinished(); 412 break; 413 414 case MotionEvent.ACTION_CANCEL: 415 case MotionEvent.ACTION_UP: 416 /* Release the drag */ 417 mIsBeingDragged = false; 418 break; 419 } 420 421 /* 422 * The only time we want to intercept motion events is if we are in the 423 * drag mode. 424 */ 425 return mIsBeingDragged; 426 } 427 428 @Override 429 public boolean onTouchEvent(MotionEvent ev) { 430 431 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 432 // Don't handle edge touches immediately -- they may actually belong to one of our 433 // descendants. 434 return false; 435 } 436 437 if (!canScroll()) { 438 return false; 439 } 440 441 if (mVelocityTracker == null) { 442 mVelocityTracker = VelocityTracker.obtain(); 443 } 444 mVelocityTracker.addMovement(ev); 445 446 final int action = ev.getAction(); 447 final float y = ev.getY(); 448 449 switch (action) { 450 case MotionEvent.ACTION_DOWN: 451 /* 452 * If being flinged and user touches, stop the fling. isFinished 453 * will be false if being flinged. 454 */ 455 if (!mScroller.isFinished()) { 456 mScroller.abortAnimation(); 457 } 458 459 // Remember where the motion event started 460 mLastMotionY = y; 461 break; 462 case MotionEvent.ACTION_MOVE: 463 // Scroll to follow the motion event 464 final int deltaY = (int) (mLastMotionY - y); 465 mLastMotionY = y; 466 467 if (deltaY < 0) { 468 if (mScrollY > 0) { 469 scrollBy(0, deltaY); 470 } 471 } else if (deltaY > 0) { 472 final int bottomEdge = getHeight() - mPaddingBottom; 473 final int availableToScroll = getChildAt(0).getBottom() - mScrollY - bottomEdge; 474 if (availableToScroll > 0) { 475 scrollBy(0, Math.min(availableToScroll, deltaY)); 476 } 477 } 478 break; 479 case MotionEvent.ACTION_UP: 480 final VelocityTracker velocityTracker = mVelocityTracker; 481 velocityTracker.computeCurrentVelocity(1000); 482 int initialVelocity = (int) velocityTracker.getYVelocity(); 483 484 if ((Math.abs(initialVelocity) > 485 ViewConfiguration.get(mContext).getScaledMinimumFlingVelocity()) && 486 getChildCount() > 0) { 487 fling(-initialVelocity); 488 } 489 490 if (mVelocityTracker != null) { 491 mVelocityTracker.recycle(); 492 mVelocityTracker = null; 493 } 494 } 495 return true; 496 } 497 498 /** 499 * <p> 500 * Finds the next focusable component that fits in this View's bounds 501 * (excluding fading edges) pretending that this View's top is located at 502 * the parameter top. 503 * </p> 504 * 505 * @param topFocus look for a candidate is the one at the top of the bounds 506 * if topFocus is true, or at the bottom of the bounds if topFocus is 507 * false 508 * @param top the top offset of the bounds in which a focusable must be 509 * found (the fading edge is assumed to start at this position) 510 * @param preferredFocusable the View that has highest priority and will be 511 * returned if it is within my bounds (null is valid) 512 * @return the next focusable component in the bounds or null if none can be 513 * found 514 */ 515 private View findFocusableViewInMyBounds(final boolean topFocus, 516 final int top, View preferredFocusable) { 517 /* 518 * The fading edge's transparent side should be considered for focus 519 * since it's mostly visible, so we divide the actual fading edge length 520 * by 2. 521 */ 522 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 523 final int topWithoutFadingEdge = top + fadingEdgeLength; 524 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 525 526 if ((preferredFocusable != null) 527 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 528 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 529 return preferredFocusable; 530 } 531 532 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 533 bottomWithoutFadingEdge); 534 } 535 536 /** 537 * <p> 538 * Finds the next focusable component that fits in the specified bounds. 539 * </p> 540 * 541 * @param topFocus look for a candidate is the one at the top of the bounds 542 * if topFocus is true, or at the bottom of the bounds if topFocus is 543 * false 544 * @param top the top offset of the bounds in which a focusable must be 545 * found 546 * @param bottom the bottom offset of the bounds in which a focusable must 547 * be found 548 * @return the next focusable component in the bounds or null if none can 549 * be found 550 */ 551 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 552 553 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 554 View focusCandidate = null; 555 556 /* 557 * A fully contained focusable is one where its top is below the bound's 558 * top, and its bottom is above the bound's bottom. A partially 559 * contained focusable is one where some part of it is within the 560 * bounds, but it also has some part that is not within bounds. A fully contained 561 * focusable is preferred to a partially contained focusable. 562 */ 563 boolean foundFullyContainedFocusable = false; 564 565 int count = focusables.size(); 566 for (int i = 0; i < count; i++) { 567 View view = focusables.get(i); 568 int viewTop = view.getTop(); 569 int viewBottom = view.getBottom(); 570 571 if (top < viewBottom && viewTop < bottom) { 572 /* 573 * the focusable is in the target area, it is a candidate for 574 * focusing 575 */ 576 577 final boolean viewIsFullyContained = (top < viewTop) && 578 (viewBottom < bottom); 579 580 if (focusCandidate == null) { 581 /* No candidate, take this one */ 582 focusCandidate = view; 583 foundFullyContainedFocusable = viewIsFullyContained; 584 } else { 585 final boolean viewIsCloserToBoundary = 586 (topFocus && viewTop < focusCandidate.getTop()) || 587 (!topFocus && viewBottom > focusCandidate 588 .getBottom()); 589 590 if (foundFullyContainedFocusable) { 591 if (viewIsFullyContained && viewIsCloserToBoundary) { 592 /* 593 * We're dealing with only fully contained views, so 594 * it has to be closer to the boundary to beat our 595 * candidate 596 */ 597 focusCandidate = view; 598 } 599 } else { 600 if (viewIsFullyContained) { 601 /* Any fully contained view beats a partially contained view */ 602 focusCandidate = view; 603 foundFullyContainedFocusable = true; 604 } else if (viewIsCloserToBoundary) { 605 /* 606 * Partially contained view beats another partially 607 * contained view if it's closer 608 */ 609 focusCandidate = view; 610 } 611 } 612 } 613 } 614 } 615 616 return focusCandidate; 617 } 618 619 /** 620 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 621 * method will scroll the view by one page up or down and give the focus 622 * to the topmost/bottommost component in the new visible area. If no 623 * component is a good candidate for focus, this scrollview reclaims the 624 * focus.</p> 625 * 626 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 627 * to go one page up or 628 * {@link android.view.View#FOCUS_DOWN} to go one page down 629 * @return true if the key event is consumed by this method, false otherwise 630 */ 631 public boolean pageScroll(int direction) { 632 boolean down = direction == View.FOCUS_DOWN; 633 int height = getHeight(); 634 635 if (down) { 636 mTempRect.top = getScrollY() + height; 637 int count = getChildCount(); 638 if (count > 0) { 639 View view = getChildAt(count - 1); 640 if (mTempRect.top + height > view.getBottom()) { 641 mTempRect.top = view.getBottom() - height; 642 } 643 } 644 } else { 645 mTempRect.top = getScrollY() - height; 646 if (mTempRect.top < 0) { 647 mTempRect.top = 0; 648 } 649 } 650 mTempRect.bottom = mTempRect.top + height; 651 652 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 653 } 654 655 /** 656 * <p>Handles scrolling in response to a "home/end" shortcut press. This 657 * method will scroll the view to the top or bottom and give the focus 658 * to the topmost/bottommost component in the new visible area. If no 659 * component is a good candidate for focus, this scrollview reclaims the 660 * focus.</p> 661 * 662 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 663 * to go the top of the view or 664 * {@link android.view.View#FOCUS_DOWN} to go the bottom 665 * @return true if the key event is consumed by this method, false otherwise 666 */ 667 public boolean fullScroll(int direction) { 668 boolean down = direction == View.FOCUS_DOWN; 669 int height = getHeight(); 670 671 mTempRect.top = 0; 672 mTempRect.bottom = height; 673 674 if (down) { 675 int count = getChildCount(); 676 if (count > 0) { 677 View view = getChildAt(count - 1); 678 mTempRect.bottom = view.getBottom(); 679 mTempRect.top = mTempRect.bottom - height; 680 } 681 } 682 683 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 684 } 685 686 /** 687 * <p>Scrolls the view to make the area defined by <code>top</code> and 688 * <code>bottom</code> visible. This method attempts to give the focus 689 * to a component visible in this area. If no component can be focused in 690 * the new visible area, the focus is reclaimed by this scrollview.</p> 691 * 692 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 693 * to go upward 694 * {@link android.view.View#FOCUS_DOWN} to downward 695 * @param top the top offset of the new area to be made visible 696 * @param bottom the bottom offset of the new area to be made visible 697 * @return true if the key event is consumed by this method, false otherwise 698 */ 699 private boolean scrollAndFocus(int direction, int top, int bottom) { 700 boolean handled = true; 701 702 int height = getHeight(); 703 int containerTop = getScrollY(); 704 int containerBottom = containerTop + height; 705 boolean up = direction == View.FOCUS_UP; 706 707 View newFocused = findFocusableViewInBounds(up, top, bottom); 708 if (newFocused == null) { 709 newFocused = this; 710 } 711 712 if (top >= containerTop && bottom <= containerBottom) { 713 handled = false; 714 } else { 715 int delta = up ? (top - containerTop) : (bottom - containerBottom); 716 doScrollY(delta); 717 } 718 719 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 720 mScrollViewMovedFocus = true; 721 mScrollViewMovedFocus = false; 722 } 723 724 return handled; 725 } 726 727 /** 728 * Handle scrolling in response to an up or down arrow click. 729 * 730 * @param direction The direction corresponding to the arrow key that was 731 * pressed 732 * @return True if we consumed the event, false otherwise 733 */ 734 public boolean arrowScroll(int direction) { 735 736 View currentFocused = findFocus(); 737 if (currentFocused == this) currentFocused = null; 738 739 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 740 741 final int maxJump = getMaxScrollAmount(); 742 743 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 744 nextFocused.getDrawingRect(mTempRect); 745 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 746 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 747 doScrollY(scrollDelta); 748 nextFocused.requestFocus(direction); 749 } else { 750 // no new focus 751 int scrollDelta = maxJump; 752 753 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 754 scrollDelta = getScrollY(); 755 } else if (direction == View.FOCUS_DOWN) { 756 757 int daBottom = getChildAt(getChildCount() - 1).getBottom(); 758 759 int screenBottom = getScrollY() + getHeight(); 760 761 if (daBottom - screenBottom < maxJump) { 762 scrollDelta = daBottom - screenBottom; 763 } 764 } 765 if (scrollDelta == 0) { 766 return false; 767 } 768 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 769 } 770 771 if (currentFocused != null && currentFocused.isFocused() 772 && isOffScreen(currentFocused)) { 773 // previously focused item still has focus and is off screen, give 774 // it up (take it back to ourselves) 775 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 776 // sure to 777 // get it) 778 final int descendantFocusability = getDescendantFocusability(); // save 779 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 780 requestFocus(); 781 setDescendantFocusability(descendantFocusability); // restore 782 } 783 return true; 784 } 785 786 /** 787 * @return whether the descendant of this scroll view is scrolled off 788 * screen. 789 */ 790 private boolean isOffScreen(View descendant) { 791 return !isWithinDeltaOfScreen(descendant, 0); 792 } 793 794 /** 795 * @return whether the descendant of this scroll view is within delta 796 * pixels of being on the screen. 797 */ 798 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 799 descendant.getDrawingRect(mTempRect); 800 offsetDescendantRectToMyCoords(descendant, mTempRect); 801 802 return (mTempRect.bottom + delta) >= getScrollY() 803 && (mTempRect.top - delta) <= (getScrollY() + getHeight()); 804 } 805 806 /** 807 * Smooth scroll by a Y delta 808 * 809 * @param delta the number of pixels to scroll by on the Y axis 810 */ 811 private void doScrollY(int delta) { 812 if (delta != 0) { 813 if (mSmoothScrollingEnabled) { 814 smoothScrollBy(0, delta); 815 } else { 816 scrollBy(0, delta); 817 } 818 } 819 } 820 821 /** 822 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 823 * 824 * @param dx the number of pixels to scroll by on the X axis 825 * @param dy the number of pixels to scroll by on the Y axis 826 */ 827 public final void smoothScrollBy(int dx, int dy) { 828 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 829 if (duration > ANIMATED_SCROLL_GAP) { 830 if (localLOGV) Log.v(TAG, "Smooth scroll: mScrollY=" + mScrollY 831 + " dy=" + dy); 832 mScroller.startScroll(mScrollX, mScrollY, dx, dy); 833 invalidate(); 834 } else { 835 if (!mScroller.isFinished()) { 836 mScroller.abortAnimation(); 837 } 838 if (localLOGV) Log.v(TAG, "Immediate scroll: mScrollY=" + mScrollY 839 + " dy=" + dy); 840 scrollBy(dx, dy); 841 } 842 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 843 } 844 845 /** 846 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 847 * 848 * @param x the position where to scroll on the X axis 849 * @param y the position where to scroll on the Y axis 850 */ 851 public final void smoothScrollTo(int x, int y) { 852 smoothScrollBy(x - mScrollX, y - mScrollY); 853 } 854 855 /** 856 * <p>The scroll range of a scroll view is the overall height of all of its 857 * children.</p> 858 */ 859 @Override 860 protected int computeVerticalScrollRange() { 861 int count = getChildCount(); 862 return count == 0 ? getHeight() : (getChildAt(0)).getBottom(); 863 } 864 865 866 @Override 867 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 868 ViewGroup.LayoutParams lp = child.getLayoutParams(); 869 870 int childWidthMeasureSpec; 871 int childHeightMeasureSpec; 872 873 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 874 + mPaddingRight, lp.width); 875 876 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 877 878 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 879 } 880 881 @Override 882 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 883 int parentHeightMeasureSpec, int heightUsed) { 884 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 885 886 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 887 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 888 + widthUsed, lp.width); 889 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 890 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 891 892 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 893 } 894 895 @Override 896 public void computeScroll() { 897 if (mScroller.computeScrollOffset()) { 898 // This is called at drawing time by ViewGroup. We don't want to 899 // re-show the scrollbars at this point, which scrollTo will do, 900 // so we replicate most of scrollTo here. 901 // 902 // It's a little odd to call onScrollChanged from inside the drawing. 903 // 904 // It is, except when you remember that computeScroll() is used to 905 // animate scrolling. So unless we want to defer the onScrollChanged() 906 // until the end of the animated scrolling, we don't really have a 907 // choice here. 908 // 909 // I agree. The alternative, which I think would be worse, is to post 910 // something and tell the subclasses later. This is bad because there 911 // will be a window where mScrollX/Y is different from what the app 912 // thinks it is. 913 // 914 int oldX = mScrollX; 915 int oldY = mScrollY; 916 int x = mScroller.getCurrX(); 917 int y = mScroller.getCurrY(); 918 if (getChildCount() > 0) { 919 View child = getChildAt(0); 920 mScrollX = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 921 mScrollY = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 922 if (localLOGV) Log.v(TAG, "mScrollY=" + mScrollY + " y=" + y 923 + " height=" + this.getHeight() 924 + " child height=" + child.getHeight()); 925 } else { 926 mScrollX = x; 927 mScrollY = y; 928 } 929 if (oldX != mScrollX || oldY != mScrollY) { 930 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 931 } 932 933 // Keep on drawing until the animation has finished. 934 postInvalidate(); 935 } 936 } 937 938 /** 939 * Scrolls the view to the given child. 940 * 941 * @param child the View to scroll to 942 */ 943 private void scrollToChild(View child) { 944 child.getDrawingRect(mTempRect); 945 946 /* Offset from child's local coordinates to ScrollView coordinates */ 947 offsetDescendantRectToMyCoords(child, mTempRect); 948 949 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 950 951 if (scrollDelta != 0) { 952 scrollBy(0, scrollDelta); 953 } 954 } 955 956 /** 957 * If rect is off screen, scroll just enough to get it (or at least the 958 * first screen size chunk of it) on screen. 959 * 960 * @param rect The rectangle. 961 * @param immediate True to scroll immediately without animation 962 * @return true if scrolling was performed 963 */ 964 private boolean scrollToChildRect(Rect rect, boolean immediate) { 965 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 966 final boolean scroll = delta != 0; 967 if (scroll) { 968 if (immediate) { 969 scrollBy(0, delta); 970 } else { 971 smoothScrollBy(0, delta); 972 } 973 } 974 return scroll; 975 } 976 977 /** 978 * Compute the amount to scroll in the Y direction in order to get 979 * a rectangle completely on the screen (or, if taller than the screen, 980 * at least the first screen size chunk of it). 981 * 982 * @param rect The rect. 983 * @return The scroll delta. 984 */ 985 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 986 987 int height = getHeight(); 988 int screenTop = getScrollY(); 989 int screenBottom = screenTop + height; 990 991 int fadingEdge = getVerticalFadingEdgeLength(); 992 993 // leave room for top fading edge as long as rect isn't at very top 994 if (rect.top > 0) { 995 screenTop += fadingEdge; 996 } 997 998 // leave room for bottom fading edge as long as rect isn't at very bottom 999 if (rect.bottom < getChildAt(0).getHeight()) { 1000 screenBottom -= fadingEdge; 1001 } 1002 1003 int scrollYDelta = 0; 1004 1005 if (localLOGV) Log.v(TAG, "child=" + rect.toShortString() 1006 + " screenTop=" + screenTop + " screenBottom=" + screenBottom 1007 + " height=" + height); 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 if (localLOGV) Log.v(TAG, "scrollYDelta=" + scrollYDelta 1025 + " distanceToBottom=" + distanceToBottom); 1026 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1027 1028 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1029 // need to move up to get it in view: move up just enough so that 1030 // entire rectangle is in view (or at least the first screen 1031 // size chunk of it). 1032 1033 if (rect.height() > height) { 1034 // screen size chunk 1035 scrollYDelta -= (screenBottom - rect.bottom); 1036 } else { 1037 // entire rect at top 1038 scrollYDelta -= (screenTop - rect.top); 1039 } 1040 1041 // make sure we aren't scrolling any further than the top our content 1042 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1043 } 1044 return scrollYDelta; 1045 } 1046 1047 @Override 1048 public void requestChildFocus(View child, View focused) { 1049 if (!mScrollViewMovedFocus) { 1050 if (!mIsLayoutDirty) { 1051 scrollToChild(focused); 1052 } else { 1053 // The child may not be laid out yet, we can't compute the scroll yet 1054 mChildToScrollTo = focused; 1055 } 1056 } 1057 super.requestChildFocus(child, focused); 1058 } 1059 1060 1061 /** 1062 * When looking for focus in children of a scroll view, need to be a little 1063 * more careful not to give focus to something that is scrolled off screen. 1064 * 1065 * This is more expensive than the default {@link android.view.ViewGroup} 1066 * implementation, otherwise this behavior might have been made the default. 1067 */ 1068 @Override 1069 protected boolean onRequestFocusInDescendants(int direction, 1070 Rect previouslyFocusedRect) { 1071 1072 // convert from forward / backward notation to up / down / left / right 1073 // (ugh). 1074 if (direction == View.FOCUS_FORWARD) { 1075 direction = View.FOCUS_DOWN; 1076 } else if (direction == View.FOCUS_BACKWARD) { 1077 direction = View.FOCUS_UP; 1078 } 1079 1080 final View nextFocus = previouslyFocusedRect == null ? 1081 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1082 FocusFinder.getInstance().findNextFocusFromRect(this, 1083 previouslyFocusedRect, direction); 1084 1085 if (nextFocus == null) { 1086 return false; 1087 } 1088 1089 if (isOffScreen(nextFocus)) { 1090 return false; 1091 } 1092 1093 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1094 } 1095 1096 @Override 1097 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1098 boolean immediate) { 1099 // offset into coordinate space of this scroll view 1100 rectangle.offset(child.getLeft() - child.getScrollX(), 1101 child.getTop() - child.getScrollY()); 1102 1103 return scrollToChildRect(rectangle, immediate); 1104 } 1105 1106 @Override 1107 public void requestLayout() { 1108 mIsLayoutDirty = true; 1109 super.requestLayout(); 1110 } 1111 1112 @Override 1113 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1114 super.onLayout(changed, l, t, r, b); 1115 mIsLayoutDirty = false; 1116 // Give a child focus if it needs it 1117 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1118 scrollToChild(mChildToScrollTo); 1119 } 1120 mChildToScrollTo = null; 1121 1122 // Calling this with the present values causes it to re-clam them 1123 scrollTo(mScrollX, mScrollY); 1124 } 1125 1126 @Override 1127 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1128 super.onSizeChanged(w, h, oldw, oldh); 1129 1130 View currentFocused = findFocus(); 1131 if (null == currentFocused || this == currentFocused) 1132 return; 1133 1134 final int maxJump = mBottom - mTop; 1135 1136 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1137 currentFocused.getDrawingRect(mTempRect); 1138 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1139 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1140 doScrollY(scrollDelta); 1141 } 1142 } 1143 1144 /** 1145 * Return true if child is an descendant of parent, (or equal to the parent). 1146 */ 1147 private boolean isViewDescendantOf(View child, View parent) { 1148 if (child == parent) { 1149 return true; 1150 } 1151 1152 final ViewParent theParent = child.getParent(); 1153 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1154 } 1155 1156 /** 1157 * Fling the scroll view 1158 * 1159 * @param velocityY The initial velocity in the Y direction. Positive 1160 * numbers mean that the finger/curor is moving down the screen, 1161 * which means we want to scroll towards the top. 1162 */ 1163 public void fling(int velocityY) { 1164 int height = getHeight() - mPaddingBottom - mPaddingTop; 1165 int bottom = getChildAt(0).getHeight(); 1166 1167 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, bottom - height); 1168 1169 final boolean movingDown = velocityY > 0; 1170 1171 View newFocused = 1172 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1173 if (newFocused == null) { 1174 newFocused = this; 1175 } 1176 1177 if (newFocused != findFocus() 1178 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1179 mScrollViewMovedFocus = true; 1180 mScrollViewMovedFocus = false; 1181 } 1182 1183 invalidate(); 1184 } 1185 1186 /** 1187 * {@inheritDoc} 1188 * 1189 * <p>This version also clamps the scrolling to the bounds of our child. 1190 */ 1191 public void scrollTo(int x, int y) { 1192 // we rely on the fact the View.scrollBy calls scrollTo. 1193 if (getChildCount() > 0) { 1194 View child = getChildAt(0); 1195 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1196 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1197 if (x != mScrollX || y != mScrollY) { 1198 super.scrollTo(x, y); 1199 } 1200 } 1201 } 1202 1203 private int clamp(int n, int my, int child) { 1204 if (my >= child || n < 0) { 1205 /* my >= child is this case: 1206 * |--------------- me ---------------| 1207 * |------ child ------| 1208 * or 1209 * |--------------- me ---------------| 1210 * |------ child ------| 1211 * or 1212 * |--------------- me ---------------| 1213 * |------ child ------| 1214 * 1215 * n < 0 is this case: 1216 * |------ me ------| 1217 * |-------- child --------| 1218 * |-- mScrollX --| 1219 */ 1220 return 0; 1221 } 1222 if ((my+n) > child) { 1223 /* this case: 1224 * |------ me ------| 1225 * |------ child ------| 1226 * |-- mScrollX --| 1227 */ 1228 return child-my; 1229 } 1230 return n; 1231 } 1232} 1233