ScrollView.java revision 4296fc4d326447875c26a925f12b3935632f13bb
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 private int mMinimumVelocity; 119 private int mMaximumVelocity; 120 121 public ScrollView(Context context) { 122 this(context, null); 123 } 124 125 public ScrollView(Context context, AttributeSet attrs) { 126 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 127 } 128 129 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 130 super(context, attrs, defStyle); 131 initScrollView(); 132 133 TypedArray a = 134 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 135 136 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 137 138 a.recycle(); 139 } 140 141 @Override 142 protected float getTopFadingEdgeStrength() { 143 if (getChildCount() == 0) { 144 return 0.0f; 145 } 146 147 final int length = getVerticalFadingEdgeLength(); 148 if (mScrollY < length) { 149 return mScrollY / (float) length; 150 } 151 152 return 1.0f; 153 } 154 155 @Override 156 protected float getBottomFadingEdgeStrength() { 157 if (getChildCount() == 0) { 158 return 0.0f; 159 } 160 161 final int length = getVerticalFadingEdgeLength(); 162 final int bottomEdge = getHeight() - mPaddingBottom; 163 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 164 if (span < length) { 165 return span / (float) length; 166 } 167 168 return 1.0f; 169 } 170 171 /** 172 * @return The maximum amount this scroll view will scroll in response to 173 * an arrow event. 174 */ 175 public int getMaxScrollAmount() { 176 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 177 } 178 179 180 private void initScrollView() { 181 mScroller = new Scroller(getContext()); 182 setFocusable(true); 183 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 184 setWillNotDraw(false); 185 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 186 mTouchSlop = configuration.getScaledTouchSlop(); 187 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 188 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 189 } 190 191 @Override 192 public void addView(View child) { 193 if (getChildCount() > 0) { 194 throw new IllegalStateException("ScrollView can host only one direct child"); 195 } 196 197 super.addView(child); 198 } 199 200 @Override 201 public void addView(View child, int index) { 202 if (getChildCount() > 0) { 203 throw new IllegalStateException("ScrollView can host only one direct child"); 204 } 205 206 super.addView(child, index); 207 } 208 209 @Override 210 public void addView(View child, ViewGroup.LayoutParams params) { 211 if (getChildCount() > 0) { 212 throw new IllegalStateException("ScrollView can host only one direct child"); 213 } 214 215 super.addView(child, params); 216 } 217 218 @Override 219 public void addView(View child, int index, ViewGroup.LayoutParams params) { 220 if (getChildCount() > 0) { 221 throw new IllegalStateException("ScrollView can host only one direct child"); 222 } 223 224 super.addView(child, index, params); 225 } 226 227 /** 228 * @return Returns true this ScrollView can be scrolled 229 */ 230 private boolean canScroll() { 231 View child = getChildAt(0); 232 if (child != null) { 233 int childHeight = child.getHeight(); 234 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 235 } 236 return false; 237 } 238 239 /** 240 * Indicates whether this ScrollView's content is stretched to fill the viewport. 241 * 242 * @return True if the content fills the viewport, false otherwise. 243 */ 244 public boolean isFillViewport() { 245 return mFillViewport; 246 } 247 248 /** 249 * Indicates this ScrollView whether it should stretch its content height to fill 250 * the viewport or not. 251 * 252 * @param fillViewport True to stretch the content's height to the viewport's 253 * boundaries, false otherwise. 254 */ 255 public void setFillViewport(boolean fillViewport) { 256 if (fillViewport != mFillViewport) { 257 mFillViewport = fillViewport; 258 requestLayout(); 259 } 260 } 261 262 /** 263 * @return Whether arrow scrolling will animate its transition. 264 */ 265 public boolean isSmoothScrollingEnabled() { 266 return mSmoothScrollingEnabled; 267 } 268 269 /** 270 * Set whether arrow scrolling will animate its transition. 271 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 272 */ 273 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 274 mSmoothScrollingEnabled = smoothScrollingEnabled; 275 } 276 277 @Override 278 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 279 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 280 281 if (!mFillViewport) { 282 return; 283 } 284 285 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 286 if (heightMode == MeasureSpec.UNSPECIFIED) { 287 return; 288 } 289 290 final View child = getChildAt(0); 291 int height = getMeasuredHeight(); 292 if (child.getMeasuredHeight() < height) { 293 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 294 295 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 296 + mPaddingRight, lp.width); 297 height -= mPaddingTop; 298 height -= mPaddingBottom; 299 int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 300 301 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 302 } 303 } 304 305 @Override 306 public boolean dispatchKeyEvent(KeyEvent event) { 307 // Let the focused view and/or our descendants get the key first 308 boolean handled = super.dispatchKeyEvent(event); 309 if (handled) { 310 return true; 311 } 312 return executeKeyEvent(event); 313 } 314 315 /** 316 * You can call this function yourself to have the scroll view perform 317 * scrolling from a key event, just as if the event had been dispatched to 318 * it by the view hierarchy. 319 * 320 * @param event The key event to execute. 321 * @return Return true if the event was handled, else false. 322 */ 323 public boolean executeKeyEvent(KeyEvent event) { 324 mTempRect.setEmpty(); 325 326 if (!canScroll()) { 327 if (isFocused()) { 328 View currentFocused = findFocus(); 329 if (currentFocused == this) currentFocused = null; 330 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 331 currentFocused, View.FOCUS_DOWN); 332 return nextFocused != null 333 && nextFocused != this 334 && nextFocused.requestFocus(View.FOCUS_DOWN); 335 } 336 return false; 337 } 338 339 boolean handled = false; 340 if (event.getAction() == KeyEvent.ACTION_DOWN) { 341 switch (event.getKeyCode()) { 342 case KeyEvent.KEYCODE_DPAD_UP: 343 if (!event.isAltPressed()) { 344 handled = arrowScroll(View.FOCUS_UP); 345 } else { 346 handled = fullScroll(View.FOCUS_UP); 347 } 348 break; 349 case KeyEvent.KEYCODE_DPAD_DOWN: 350 if (!event.isAltPressed()) { 351 handled = arrowScroll(View.FOCUS_DOWN); 352 } else { 353 handled = fullScroll(View.FOCUS_DOWN); 354 } 355 break; 356 case KeyEvent.KEYCODE_SPACE: 357 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 358 break; 359 } 360 } 361 362 return handled; 363 } 364 365 @Override 366 public boolean onInterceptTouchEvent(MotionEvent ev) { 367 /* 368 * This method JUST determines whether we want to intercept the motion. 369 * If we return true, onMotionEvent will be called and we do the actual 370 * scrolling there. 371 */ 372 373 /* 374 * Shortcut the most recurring case: the user is in the dragging 375 * state and he is moving his finger. We want to intercept this 376 * motion. 377 */ 378 final int action = ev.getAction(); 379 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 380 return true; 381 } 382 383 if (!canScroll()) { 384 mIsBeingDragged = false; 385 return false; 386 } 387 388 final float y = ev.getY(); 389 390 switch (action) { 391 case MotionEvent.ACTION_MOVE: 392 /* 393 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 394 * whether the user has moved far enough from his original down touch. 395 */ 396 397 /* 398 * Locally do absolute value. mLastMotionY is set to the y value 399 * of the down event. 400 */ 401 final int yDiff = (int) Math.abs(y - mLastMotionY); 402 if (yDiff > mTouchSlop) { 403 mIsBeingDragged = true; 404 } 405 break; 406 407 case MotionEvent.ACTION_DOWN: 408 /* Remember location of down touch */ 409 mLastMotionY = y; 410 411 /* 412 * If being flinged and user touches the screen, initiate drag; 413 * otherwise don't. mScroller.isFinished should be false when 414 * being flinged. 415 */ 416 mIsBeingDragged = !mScroller.isFinished(); 417 break; 418 419 case MotionEvent.ACTION_CANCEL: 420 case MotionEvent.ACTION_UP: 421 /* Release the drag */ 422 mIsBeingDragged = false; 423 break; 424 } 425 426 /* 427 * The only time we want to intercept motion events is if we are in the 428 * drag mode. 429 */ 430 return mIsBeingDragged; 431 } 432 433 @Override 434 public boolean onTouchEvent(MotionEvent ev) { 435 436 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 437 // Don't handle edge touches immediately -- they may actually belong to one of our 438 // descendants. 439 return false; 440 } 441 442 if (!canScroll()) { 443 return false; 444 } 445 446 if (mVelocityTracker == null) { 447 mVelocityTracker = VelocityTracker.obtain(); 448 } 449 mVelocityTracker.addMovement(ev); 450 451 final int action = ev.getAction(); 452 final float y = ev.getY(); 453 454 switch (action) { 455 case MotionEvent.ACTION_DOWN: 456 /* 457 * If being flinged and user touches, stop the fling. isFinished 458 * will be false if being flinged. 459 */ 460 if (!mScroller.isFinished()) { 461 mScroller.abortAnimation(); 462 } 463 464 // Remember where the motion event started 465 mLastMotionY = y; 466 break; 467 case MotionEvent.ACTION_MOVE: 468 // Scroll to follow the motion event 469 final int deltaY = (int) (mLastMotionY - y); 470 mLastMotionY = y; 471 472 if (deltaY < 0) { 473 if (mScrollY > 0) { 474 scrollBy(0, deltaY); 475 } 476 } else if (deltaY > 0) { 477 final int bottomEdge = getHeight() - mPaddingBottom; 478 final int availableToScroll = getChildAt(0).getBottom() - mScrollY - bottomEdge; 479 if (availableToScroll > 0) { 480 scrollBy(0, Math.min(availableToScroll, deltaY)); 481 } 482 } 483 break; 484 case MotionEvent.ACTION_UP: 485 final VelocityTracker velocityTracker = mVelocityTracker; 486 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 487 int initialVelocity = (int) velocityTracker.getYVelocity(); 488 489 if ((Math.abs(initialVelocity) > mMinimumVelocity) && getChildCount() > 0) { 490 fling(-initialVelocity); 491 } 492 493 if (mVelocityTracker != null) { 494 mVelocityTracker.recycle(); 495 mVelocityTracker = null; 496 } 497 } 498 return true; 499 } 500 501 /** 502 * <p> 503 * Finds the next focusable component that fits in this View's bounds 504 * (excluding fading edges) pretending that this View's top is located at 505 * the parameter top. 506 * </p> 507 * 508 * @param topFocus look for a candidate is the one at the top of the bounds 509 * if topFocus is true, or at the bottom of the bounds if topFocus is 510 * false 511 * @param top the top offset of the bounds in which a focusable must be 512 * found (the fading edge is assumed to start at this position) 513 * @param preferredFocusable the View that has highest priority and will be 514 * returned if it is within my bounds (null is valid) 515 * @return the next focusable component in the bounds or null if none can be 516 * found 517 */ 518 private View findFocusableViewInMyBounds(final boolean topFocus, 519 final int top, View preferredFocusable) { 520 /* 521 * The fading edge's transparent side should be considered for focus 522 * since it's mostly visible, so we divide the actual fading edge length 523 * by 2. 524 */ 525 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 526 final int topWithoutFadingEdge = top + fadingEdgeLength; 527 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 528 529 if ((preferredFocusable != null) 530 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 531 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 532 return preferredFocusable; 533 } 534 535 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 536 bottomWithoutFadingEdge); 537 } 538 539 /** 540 * <p> 541 * Finds the next focusable component that fits in the specified bounds. 542 * </p> 543 * 544 * @param topFocus look for a candidate is the one at the top of the bounds 545 * if topFocus is true, or at the bottom of the bounds if topFocus is 546 * false 547 * @param top the top offset of the bounds in which a focusable must be 548 * found 549 * @param bottom the bottom offset of the bounds in which a focusable must 550 * be found 551 * @return the next focusable component in the bounds or null if none can 552 * be found 553 */ 554 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 555 556 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 557 View focusCandidate = null; 558 559 /* 560 * A fully contained focusable is one where its top is below the bound's 561 * top, and its bottom is above the bound's bottom. A partially 562 * contained focusable is one where some part of it is within the 563 * bounds, but it also has some part that is not within bounds. A fully contained 564 * focusable is preferred to a partially contained focusable. 565 */ 566 boolean foundFullyContainedFocusable = false; 567 568 int count = focusables.size(); 569 for (int i = 0; i < count; i++) { 570 View view = focusables.get(i); 571 int viewTop = view.getTop(); 572 int viewBottom = view.getBottom(); 573 574 if (top < viewBottom && viewTop < bottom) { 575 /* 576 * the focusable is in the target area, it is a candidate for 577 * focusing 578 */ 579 580 final boolean viewIsFullyContained = (top < viewTop) && 581 (viewBottom < bottom); 582 583 if (focusCandidate == null) { 584 /* No candidate, take this one */ 585 focusCandidate = view; 586 foundFullyContainedFocusable = viewIsFullyContained; 587 } else { 588 final boolean viewIsCloserToBoundary = 589 (topFocus && viewTop < focusCandidate.getTop()) || 590 (!topFocus && viewBottom > focusCandidate 591 .getBottom()); 592 593 if (foundFullyContainedFocusable) { 594 if (viewIsFullyContained && viewIsCloserToBoundary) { 595 /* 596 * We're dealing with only fully contained views, so 597 * it has to be closer to the boundary to beat our 598 * candidate 599 */ 600 focusCandidate = view; 601 } 602 } else { 603 if (viewIsFullyContained) { 604 /* Any fully contained view beats a partially contained view */ 605 focusCandidate = view; 606 foundFullyContainedFocusable = true; 607 } else if (viewIsCloserToBoundary) { 608 /* 609 * Partially contained view beats another partially 610 * contained view if it's closer 611 */ 612 focusCandidate = view; 613 } 614 } 615 } 616 } 617 } 618 619 return focusCandidate; 620 } 621 622 /** 623 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 624 * method will scroll the view by one page up or down and give the focus 625 * to the topmost/bottommost component in the new visible area. If no 626 * component is a good candidate for focus, this scrollview reclaims the 627 * focus.</p> 628 * 629 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 630 * to go one page up or 631 * {@link android.view.View#FOCUS_DOWN} to go one page down 632 * @return true if the key event is consumed by this method, false otherwise 633 */ 634 public boolean pageScroll(int direction) { 635 boolean down = direction == View.FOCUS_DOWN; 636 int height = getHeight(); 637 638 if (down) { 639 mTempRect.top = getScrollY() + height; 640 int count = getChildCount(); 641 if (count > 0) { 642 View view = getChildAt(count - 1); 643 if (mTempRect.top + height > view.getBottom()) { 644 mTempRect.top = view.getBottom() - height; 645 } 646 } 647 } else { 648 mTempRect.top = getScrollY() - height; 649 if (mTempRect.top < 0) { 650 mTempRect.top = 0; 651 } 652 } 653 mTempRect.bottom = mTempRect.top + height; 654 655 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 656 } 657 658 /** 659 * <p>Handles scrolling in response to a "home/end" shortcut press. This 660 * method will scroll the view to the top or bottom and give the focus 661 * to the topmost/bottommost component in the new visible area. If no 662 * component is a good candidate for focus, this scrollview reclaims the 663 * focus.</p> 664 * 665 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 666 * to go the top of the view or 667 * {@link android.view.View#FOCUS_DOWN} to go the bottom 668 * @return true if the key event is consumed by this method, false otherwise 669 */ 670 public boolean fullScroll(int direction) { 671 boolean down = direction == View.FOCUS_DOWN; 672 int height = getHeight(); 673 674 mTempRect.top = 0; 675 mTempRect.bottom = height; 676 677 if (down) { 678 int count = getChildCount(); 679 if (count > 0) { 680 View view = getChildAt(count - 1); 681 mTempRect.bottom = view.getBottom(); 682 mTempRect.top = mTempRect.bottom - height; 683 } 684 } 685 686 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 687 } 688 689 /** 690 * <p>Scrolls the view to make the area defined by <code>top</code> and 691 * <code>bottom</code> visible. This method attempts to give the focus 692 * to a component visible in this area. If no component can be focused in 693 * the new visible area, the focus is reclaimed by this scrollview.</p> 694 * 695 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 696 * to go upward 697 * {@link android.view.View#FOCUS_DOWN} to downward 698 * @param top the top offset of the new area to be made visible 699 * @param bottom the bottom offset of the new area to be made visible 700 * @return true if the key event is consumed by this method, false otherwise 701 */ 702 private boolean scrollAndFocus(int direction, int top, int bottom) { 703 boolean handled = true; 704 705 int height = getHeight(); 706 int containerTop = getScrollY(); 707 int containerBottom = containerTop + height; 708 boolean up = direction == View.FOCUS_UP; 709 710 View newFocused = findFocusableViewInBounds(up, top, bottom); 711 if (newFocused == null) { 712 newFocused = this; 713 } 714 715 if (top >= containerTop && bottom <= containerBottom) { 716 handled = false; 717 } else { 718 int delta = up ? (top - containerTop) : (bottom - containerBottom); 719 doScrollY(delta); 720 } 721 722 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 723 mScrollViewMovedFocus = true; 724 mScrollViewMovedFocus = false; 725 } 726 727 return handled; 728 } 729 730 /** 731 * Handle scrolling in response to an up or down arrow click. 732 * 733 * @param direction The direction corresponding to the arrow key that was 734 * pressed 735 * @return True if we consumed the event, false otherwise 736 */ 737 public boolean arrowScroll(int direction) { 738 739 View currentFocused = findFocus(); 740 if (currentFocused == this) currentFocused = null; 741 742 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 743 744 final int maxJump = getMaxScrollAmount(); 745 746 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 747 nextFocused.getDrawingRect(mTempRect); 748 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 749 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 750 doScrollY(scrollDelta); 751 nextFocused.requestFocus(direction); 752 } else { 753 // no new focus 754 int scrollDelta = maxJump; 755 756 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 757 scrollDelta = getScrollY(); 758 } else if (direction == View.FOCUS_DOWN) { 759 760 int daBottom = getChildAt(getChildCount() - 1).getBottom(); 761 762 int screenBottom = getScrollY() + getHeight(); 763 764 if (daBottom - screenBottom < maxJump) { 765 scrollDelta = daBottom - screenBottom; 766 } 767 } 768 if (scrollDelta == 0) { 769 return false; 770 } 771 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 772 } 773 774 if (currentFocused != null && currentFocused.isFocused() 775 && isOffScreen(currentFocused)) { 776 // previously focused item still has focus and is off screen, give 777 // it up (take it back to ourselves) 778 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 779 // sure to 780 // get it) 781 final int descendantFocusability = getDescendantFocusability(); // save 782 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 783 requestFocus(); 784 setDescendantFocusability(descendantFocusability); // restore 785 } 786 return true; 787 } 788 789 /** 790 * @return whether the descendant of this scroll view is scrolled off 791 * screen. 792 */ 793 private boolean isOffScreen(View descendant) { 794 return !isWithinDeltaOfScreen(descendant, 0); 795 } 796 797 /** 798 * @return whether the descendant of this scroll view is within delta 799 * pixels of being on the screen. 800 */ 801 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 802 descendant.getDrawingRect(mTempRect); 803 offsetDescendantRectToMyCoords(descendant, mTempRect); 804 805 return (mTempRect.bottom + delta) >= getScrollY() 806 && (mTempRect.top - delta) <= (getScrollY() + getHeight()); 807 } 808 809 /** 810 * Smooth scroll by a Y delta 811 * 812 * @param delta the number of pixels to scroll by on the Y axis 813 */ 814 private void doScrollY(int delta) { 815 if (delta != 0) { 816 if (mSmoothScrollingEnabled) { 817 smoothScrollBy(0, delta); 818 } else { 819 scrollBy(0, delta); 820 } 821 } 822 } 823 824 /** 825 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 826 * 827 * @param dx the number of pixels to scroll by on the X axis 828 * @param dy the number of pixels to scroll by on the Y axis 829 */ 830 public final void smoothScrollBy(int dx, int dy) { 831 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 832 if (duration > ANIMATED_SCROLL_GAP) { 833 if (localLOGV) Log.v(TAG, "Smooth scroll: mScrollY=" + mScrollY 834 + " dy=" + dy); 835 mScroller.startScroll(mScrollX, mScrollY, dx, dy); 836 invalidate(); 837 } else { 838 if (!mScroller.isFinished()) { 839 mScroller.abortAnimation(); 840 } 841 if (localLOGV) Log.v(TAG, "Immediate scroll: mScrollY=" + mScrollY 842 + " dy=" + dy); 843 scrollBy(dx, dy); 844 } 845 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 846 } 847 848 /** 849 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 850 * 851 * @param x the position where to scroll on the X axis 852 * @param y the position where to scroll on the Y axis 853 */ 854 public final void smoothScrollTo(int x, int y) { 855 smoothScrollBy(x - mScrollX, y - mScrollY); 856 } 857 858 /** 859 * <p>The scroll range of a scroll view is the overall height of all of its 860 * children.</p> 861 */ 862 @Override 863 protected int computeVerticalScrollRange() { 864 int count = getChildCount(); 865 return count == 0 ? getHeight() : (getChildAt(0)).getBottom(); 866 } 867 868 869 @Override 870 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 871 ViewGroup.LayoutParams lp = child.getLayoutParams(); 872 873 int childWidthMeasureSpec; 874 int childHeightMeasureSpec; 875 876 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 877 + mPaddingRight, lp.width); 878 879 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 880 881 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 882 } 883 884 @Override 885 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 886 int parentHeightMeasureSpec, int heightUsed) { 887 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 888 889 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 890 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 891 + widthUsed, lp.width); 892 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 893 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 894 895 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 896 } 897 898 @Override 899 public void computeScroll() { 900 if (mScroller.computeScrollOffset()) { 901 // This is called at drawing time by ViewGroup. We don't want to 902 // re-show the scrollbars at this point, which scrollTo will do, 903 // so we replicate most of scrollTo here. 904 // 905 // It's a little odd to call onScrollChanged from inside the drawing. 906 // 907 // It is, except when you remember that computeScroll() is used to 908 // animate scrolling. So unless we want to defer the onScrollChanged() 909 // until the end of the animated scrolling, we don't really have a 910 // choice here. 911 // 912 // I agree. The alternative, which I think would be worse, is to post 913 // something and tell the subclasses later. This is bad because there 914 // will be a window where mScrollX/Y is different from what the app 915 // thinks it is. 916 // 917 int oldX = mScrollX; 918 int oldY = mScrollY; 919 int x = mScroller.getCurrX(); 920 int y = mScroller.getCurrY(); 921 if (getChildCount() > 0) { 922 View child = getChildAt(0); 923 mScrollX = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 924 mScrollY = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 925 if (localLOGV) Log.v(TAG, "mScrollY=" + mScrollY + " y=" + y 926 + " height=" + this.getHeight() 927 + " child height=" + child.getHeight()); 928 } else { 929 mScrollX = x; 930 mScrollY = y; 931 } 932 if (oldX != mScrollX || oldY != mScrollY) { 933 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 934 } 935 936 // Keep on drawing until the animation has finished. 937 postInvalidate(); 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 (localLOGV) Log.v(TAG, "child=" + rect.toShortString() 1009 + " screenTop=" + screenTop + " screenBottom=" + screenBottom 1010 + " height=" + height); 1011 if (rect.bottom > screenBottom && rect.top > screenTop) { 1012 // need to move down to get it in view: move down just enough so 1013 // that the entire rectangle is in view (or at least the first 1014 // screen size chunk). 1015 1016 if (rect.height() > height) { 1017 // just enough to get screen size chunk on 1018 scrollYDelta += (rect.top - screenTop); 1019 } else { 1020 // get entire rect at bottom of screen 1021 scrollYDelta += (rect.bottom - screenBottom); 1022 } 1023 1024 // make sure we aren't scrolling beyond the end of our content 1025 int bottom = getChildAt(getChildCount() - 1).getBottom(); 1026 int distanceToBottom = bottom - screenBottom; 1027 if (localLOGV) Log.v(TAG, "scrollYDelta=" + scrollYDelta 1028 + " distanceToBottom=" + distanceToBottom); 1029 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1030 1031 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1032 // need to move up to get it in view: move up just enough so that 1033 // entire rectangle is in view (or at least the first screen 1034 // size chunk of it). 1035 1036 if (rect.height() > height) { 1037 // screen size chunk 1038 scrollYDelta -= (screenBottom - rect.bottom); 1039 } else { 1040 // entire rect at top 1041 scrollYDelta -= (screenTop - rect.top); 1042 } 1043 1044 // make sure we aren't scrolling any further than the top our content 1045 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1046 } 1047 return scrollYDelta; 1048 } 1049 1050 @Override 1051 public void requestChildFocus(View child, View focused) { 1052 if (!mScrollViewMovedFocus) { 1053 if (!mIsLayoutDirty) { 1054 scrollToChild(focused); 1055 } else { 1056 // The child may not be laid out yet, we can't compute the scroll yet 1057 mChildToScrollTo = focused; 1058 } 1059 } 1060 super.requestChildFocus(child, focused); 1061 } 1062 1063 1064 /** 1065 * When looking for focus in children of a scroll view, need to be a little 1066 * more careful not to give focus to something that is scrolled off screen. 1067 * 1068 * This is more expensive than the default {@link android.view.ViewGroup} 1069 * implementation, otherwise this behavior might have been made the default. 1070 */ 1071 @Override 1072 protected boolean onRequestFocusInDescendants(int direction, 1073 Rect previouslyFocusedRect) { 1074 1075 // convert from forward / backward notation to up / down / left / right 1076 // (ugh). 1077 if (direction == View.FOCUS_FORWARD) { 1078 direction = View.FOCUS_DOWN; 1079 } else if (direction == View.FOCUS_BACKWARD) { 1080 direction = View.FOCUS_UP; 1081 } 1082 1083 final View nextFocus = previouslyFocusedRect == null ? 1084 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1085 FocusFinder.getInstance().findNextFocusFromRect(this, 1086 previouslyFocusedRect, direction); 1087 1088 if (nextFocus == null) { 1089 return false; 1090 } 1091 1092 if (isOffScreen(nextFocus)) { 1093 return false; 1094 } 1095 1096 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1097 } 1098 1099 @Override 1100 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1101 boolean immediate) { 1102 // offset into coordinate space of this scroll view 1103 rectangle.offset(child.getLeft() - child.getScrollX(), 1104 child.getTop() - child.getScrollY()); 1105 1106 return scrollToChildRect(rectangle, immediate); 1107 } 1108 1109 @Override 1110 public void requestLayout() { 1111 mIsLayoutDirty = true; 1112 super.requestLayout(); 1113 } 1114 1115 @Override 1116 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1117 super.onLayout(changed, l, t, r, b); 1118 mIsLayoutDirty = false; 1119 // Give a child focus if it needs it 1120 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1121 scrollToChild(mChildToScrollTo); 1122 } 1123 mChildToScrollTo = null; 1124 1125 // Calling this with the present values causes it to re-clam them 1126 scrollTo(mScrollX, mScrollY); 1127 } 1128 1129 @Override 1130 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1131 super.onSizeChanged(w, h, oldw, oldh); 1132 1133 View currentFocused = findFocus(); 1134 if (null == currentFocused || this == currentFocused) 1135 return; 1136 1137 final int maxJump = mBottom - mTop; 1138 1139 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1140 currentFocused.getDrawingRect(mTempRect); 1141 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1142 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1143 doScrollY(scrollDelta); 1144 } 1145 } 1146 1147 /** 1148 * Return true if child is an descendant of parent, (or equal to the parent). 1149 */ 1150 private boolean isViewDescendantOf(View child, View parent) { 1151 if (child == parent) { 1152 return true; 1153 } 1154 1155 final ViewParent theParent = child.getParent(); 1156 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1157 } 1158 1159 /** 1160 * Fling the scroll view 1161 * 1162 * @param velocityY The initial velocity in the Y direction. Positive 1163 * numbers mean that the finger/curor is moving down the screen, 1164 * which means we want to scroll towards the top. 1165 */ 1166 public void fling(int velocityY) { 1167 int height = getHeight() - mPaddingBottom - mPaddingTop; 1168 int bottom = getChildAt(0).getHeight(); 1169 1170 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, bottom - height); 1171 1172 final boolean movingDown = velocityY > 0; 1173 1174 View newFocused = 1175 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1176 if (newFocused == null) { 1177 newFocused = this; 1178 } 1179 1180 if (newFocused != findFocus() 1181 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1182 mScrollViewMovedFocus = true; 1183 mScrollViewMovedFocus = false; 1184 } 1185 1186 invalidate(); 1187 } 1188 1189 /** 1190 * {@inheritDoc} 1191 * 1192 * <p>This version also clamps the scrolling to the bounds of our child. 1193 */ 1194 public void scrollTo(int x, int y) { 1195 // we rely on the fact the View.scrollBy calls scrollTo. 1196 if (getChildCount() > 0) { 1197 View child = getChildAt(0); 1198 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1199 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1200 if (x != mScrollX || y != mScrollY) { 1201 super.scrollTo(x, y); 1202 } 1203 } 1204 } 1205 1206 private int clamp(int n, int my, int child) { 1207 if (my >= child || n < 0) { 1208 /* my >= child is this case: 1209 * |--------------- me ---------------| 1210 * |------ child ------| 1211 * or 1212 * |--------------- me ---------------| 1213 * |------ child ------| 1214 * or 1215 * |--------------- me ---------------| 1216 * |------ child ------| 1217 * 1218 * n < 0 is this case: 1219 * |------ me ------| 1220 * |-------- child --------| 1221 * |-- mScrollX --| 1222 */ 1223 return 0; 1224 } 1225 if ((my+n) > child) { 1226 /* this case: 1227 * |------ me ------| 1228 * |------ child ------| 1229 * |-- mScrollX --| 1230 */ 1231 return child-my; 1232 } 1233 return n; 1234 } 1235} 1236