ScrollView.java revision 0b8bb4282a7d1afb24f8c4d5beb2ca4ecc731116
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 com.android.internal.R; 20 21import android.content.Context; 22import android.content.res.TypedArray; 23import android.graphics.Rect; 24import android.util.AttributeSet; 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 java.util.List; 36 37/** 38 * Layout container for a view hierarchy that can be scrolled by the user, 39 * allowing it to be larger than the physical display. A ScrollView 40 * is a {@link FrameLayout}, meaning you should place one child in it 41 * containing the entire contents to scroll; this child may itself be a layout 42 * manager with a complex hierarchy of objects. A child that is often used 43 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 44 * array of top-level items that the user can scroll through. 45 * 46 * <p>The {@link TextView} class also 47 * takes care of its own scrolling, so does not require a ScrollView, but 48 * using the two together is possible to achieve the effect of a text view 49 * within a larger container. 50 * 51 * <p>ScrollView only supports vertical scrolling. 52 */ 53public class ScrollView extends FrameLayout { 54 static final int ANIMATED_SCROLL_GAP = 250; 55 56 static final float MAX_SCROLL_FACTOR = 0.5f; 57 58 59 private long mLastScroll; 60 61 private final Rect mTempRect = new Rect(); 62 private OverScroller mScroller; 63 64 /** 65 * Flag to indicate that we are moving focus ourselves. This is so the 66 * code that watches for focus changes initiated outside this ScrollView 67 * knows that it does not have to do anything. 68 */ 69 private boolean mScrollViewMovedFocus; 70 71 /** 72 * Position of the last motion event. 73 */ 74 private float mLastMotionY; 75 76 /** 77 * True when the layout has changed but the traversal has not come through yet. 78 * Ideally the view hierarchy would keep track of this for us. 79 */ 80 private boolean mIsLayoutDirty = true; 81 82 /** 83 * The child to give focus to in the event that a child has requested focus while the 84 * layout is dirty. This prevents the scroll from being wrong if the child has not been 85 * laid out before requesting focus. 86 */ 87 private View mChildToScrollTo = null; 88 89 /** 90 * True if the user is currently dragging this ScrollView around. This is 91 * not the same as 'is being flinged', which can be checked by 92 * mScroller.isFinished() (flinging begins when the user lifts his finger). 93 */ 94 private boolean mIsBeingDragged = false; 95 96 /** 97 * Determines speed during touch scrolling 98 */ 99 private VelocityTracker mVelocityTracker; 100 101 /** 102 * When set to true, the scroll view measure its child to make it fill the currently 103 * visible area. 104 */ 105 private boolean mFillViewport; 106 107 /** 108 * Whether arrow scrolling is animated. 109 */ 110 private boolean mSmoothScrollingEnabled = true; 111 112 private int mTouchSlop; 113 private int mMinimumVelocity; 114 private int mMaximumVelocity; 115 116 public ScrollView(Context context) { 117 this(context, null); 118 } 119 120 public ScrollView(Context context, AttributeSet attrs) { 121 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 122 } 123 124 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 125 super(context, attrs, defStyle); 126 initScrollView(); 127 128 TypedArray a = 129 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 130 131 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 132 133 a.recycle(); 134 } 135 136 @Override 137 protected float getTopFadingEdgeStrength() { 138 if (getChildCount() == 0) { 139 return 0.0f; 140 } 141 142 final int length = getVerticalFadingEdgeLength(); 143 if (mScrollY < length) { 144 return mScrollY / (float) length; 145 } 146 147 return 1.0f; 148 } 149 150 @Override 151 protected float getBottomFadingEdgeStrength() { 152 if (getChildCount() == 0) { 153 return 0.0f; 154 } 155 156 final int length = getVerticalFadingEdgeLength(); 157 final int bottomEdge = getHeight() - mPaddingBottom; 158 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 159 if (span < length) { 160 return span / (float) length; 161 } 162 163 return 1.0f; 164 } 165 166 /** 167 * @return The maximum amount this scroll view will scroll in response to 168 * an arrow event. 169 */ 170 public int getMaxScrollAmount() { 171 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 172 } 173 174 175 private void initScrollView() { 176 mScroller = new OverScroller(getContext()); 177 setFocusable(true); 178 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 179 setWillNotDraw(false); 180 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 181 mTouchSlop = configuration.getScaledTouchSlop(); 182 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 183 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 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 if (getChildCount() > 0) { 286 final View child = getChildAt(0); 287 int height = getMeasuredHeight(); 288 if (child.getMeasuredHeight() < height) { 289 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 290 291 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 292 + mPaddingRight, lp.width); 293 height -= mPaddingTop; 294 height -= mPaddingBottom; 295 int childHeightMeasureSpec = 296 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 297 298 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 299 } 300 } 301 } 302 303 @Override 304 public boolean dispatchKeyEvent(KeyEvent event) { 305 // Let the focused view and/or our descendants get the key first 306 boolean handled = super.dispatchKeyEvent(event); 307 if (handled) { 308 return true; 309 } 310 return executeKeyEvent(event); 311 } 312 313 /** 314 * You can call this function yourself to have the scroll view perform 315 * scrolling from a key event, just as if the event had been dispatched to 316 * it by the view hierarchy. 317 * 318 * @param event The key event to execute. 319 * @return Return true if the event was handled, else false. 320 */ 321 public boolean executeKeyEvent(KeyEvent event) { 322 mTempRect.setEmpty(); 323 324 if (!canScroll()) { 325 if (isFocused()) { 326 View currentFocused = findFocus(); 327 if (currentFocused == this) currentFocused = null; 328 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 329 currentFocused, View.FOCUS_DOWN); 330 return nextFocused != null 331 && nextFocused != this 332 && nextFocused.requestFocus(View.FOCUS_DOWN); 333 } 334 return false; 335 } 336 337 boolean handled = false; 338 if (event.getAction() == KeyEvent.ACTION_DOWN) { 339 switch (event.getKeyCode()) { 340 case KeyEvent.KEYCODE_DPAD_UP: 341 if (!event.isAltPressed()) { 342 handled = arrowScroll(View.FOCUS_UP); 343 } else { 344 handled = fullScroll(View.FOCUS_UP); 345 } 346 break; 347 case KeyEvent.KEYCODE_DPAD_DOWN: 348 if (!event.isAltPressed()) { 349 handled = arrowScroll(View.FOCUS_DOWN); 350 } else { 351 handled = fullScroll(View.FOCUS_DOWN); 352 } 353 break; 354 case KeyEvent.KEYCODE_SPACE: 355 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 356 break; 357 } 358 } 359 360 return handled; 361 } 362 363 @Override 364 public boolean onInterceptTouchEvent(MotionEvent ev) { 365 /* 366 * This method JUST determines whether we want to intercept the motion. 367 * If we return true, onMotionEvent will be called and we do the actual 368 * scrolling there. 369 */ 370 371 /* 372 * Shortcut the most recurring case: the user is in the dragging 373 * state and he is moving his finger. We want to intercept this 374 * motion. 375 */ 376 final int action = ev.getAction(); 377 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 378 return true; 379 } 380 381 final float y = ev.getY(); 382 383 switch (action) { 384 case MotionEvent.ACTION_MOVE: 385 /* 386 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 387 * whether the user has moved far enough from his original down touch. 388 */ 389 390 /* 391 * Locally do absolute value. mLastMotionY is set to the y value 392 * of the down event. 393 */ 394 final int yDiff = (int) Math.abs(y - mLastMotionY); 395 if (yDiff > mTouchSlop) { 396 mIsBeingDragged = true; 397 mLastMotionY = y; 398 } 399 break; 400 401 case MotionEvent.ACTION_DOWN: 402 /* Remember location of down touch */ 403 mLastMotionY = y; 404 405 /* 406 * If being flinged and user touches the screen, initiate drag; 407 * otherwise don't. mScroller.isFinished should be false when 408 * being flinged. 409 */ 410 mIsBeingDragged = !mScroller.isFinished(); 411 break; 412 413 case MotionEvent.ACTION_CANCEL: 414 case MotionEvent.ACTION_UP: 415 /* Release the drag */ 416 mIsBeingDragged = false; 417 break; 418 } 419 420 /* 421 * The only time we want to intercept motion events is if we are in the 422 * drag mode. 423 */ 424 return mIsBeingDragged; 425 } 426 427 @Override 428 public boolean onTouchEvent(MotionEvent ev) { 429 430 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 431 // Don't handle edge touches immediately -- they may actually belong to one of our 432 // descendants. 433 return false; 434 } 435 436 if (mVelocityTracker == null) { 437 mVelocityTracker = VelocityTracker.obtain(); 438 } 439 mVelocityTracker.addMovement(ev); 440 441 final int action = ev.getAction(); 442 final float y = ev.getY(); 443 444 switch (action) { 445 case MotionEvent.ACTION_DOWN: 446 /* 447 * If being flinged and user touches, stop the fling. isFinished 448 * will be false if being flinged. 449 */ 450 if (!mScroller.isFinished()) { 451 mScroller.abortAnimation(); 452 } 453 454 // Remember where the motion event started 455 mLastMotionY = y; 456 break; 457 case MotionEvent.ACTION_MOVE: 458 // Scroll to follow the motion event 459 final int deltaY = (int) (mLastMotionY - y); 460 mLastMotionY = y; 461 462 overscrollBy(0, deltaY, 0, mScrollY, 0, getScrollRange(), 463 0, getOverscrollMax()); 464 break; 465 case MotionEvent.ACTION_UP: 466 final VelocityTracker velocityTracker = mVelocityTracker; 467 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 468 int initialVelocity = (int) velocityTracker.getYVelocity(); 469 470 if (getChildCount() > 0) { 471 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 472 fling(-initialVelocity); 473 } else { 474 final int bottom = getScrollRange(); 475 if (mScroller.springback(mScrollX, mScrollY, 0, 0, 0, bottom)) { 476 invalidate(); 477 } 478 } 479 } 480 481 if (mVelocityTracker != null) { 482 mVelocityTracker.recycle(); 483 mVelocityTracker = null; 484 } 485 } 486 return true; 487 } 488 489 @Override 490 protected void onOverscrolled(int scrollX, int scrollY, 491 boolean clampedX, boolean clampedY) { 492 // Treat animating scrolls differently; see #computeScroll() for why. 493 if (!mScroller.isFinished()) { 494 mScrollX = scrollX; 495 mScrollY = scrollY; 496 if (clampedY) { 497 mScroller.springback(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 498 } 499 } else { 500 super.scrollTo(scrollX, scrollY); 501 } 502 } 503 504 private int getOverscrollMax() { 505 int childCount = getChildCount(); 506 int containerOverscroll = (getHeight() - mPaddingBottom - mPaddingTop) / 3; 507 if (childCount > 0) { 508 return Math.min(containerOverscroll, getChildAt(0).getHeight() / 3); 509 } else { 510 return containerOverscroll; 511 } 512 } 513 514 private int getScrollRange() { 515 int scrollRange = 0; 516 if (getChildCount() > 0) { 517 View child = getChildAt(0); 518 scrollRange = Math.max(0, 519 child.getHeight() - getHeight() - mPaddingBottom - mPaddingTop); 520 } 521 return scrollRange; 522 } 523 524 /** 525 * <p> 526 * Finds the next focusable component that fits in this View's bounds 527 * (excluding fading edges) pretending that this View's top is located at 528 * the parameter top. 529 * </p> 530 * 531 * @param topFocus look for a candidate is the one at the top of the bounds 532 * if topFocus is true, or at the bottom of the bounds if topFocus is 533 * false 534 * @param top the top offset of the bounds in which a focusable must be 535 * found (the fading edge is assumed to start at this position) 536 * @param preferredFocusable the View that has highest priority and will be 537 * returned if it is within my bounds (null is valid) 538 * @return the next focusable component in the bounds or null if none can be 539 * found 540 */ 541 private View findFocusableViewInMyBounds(final boolean topFocus, 542 final int top, View preferredFocusable) { 543 /* 544 * The fading edge's transparent side should be considered for focus 545 * since it's mostly visible, so we divide the actual fading edge length 546 * by 2. 547 */ 548 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 549 final int topWithoutFadingEdge = top + fadingEdgeLength; 550 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 551 552 if ((preferredFocusable != null) 553 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 554 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 555 return preferredFocusable; 556 } 557 558 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 559 bottomWithoutFadingEdge); 560 } 561 562 /** 563 * <p> 564 * Finds the next focusable component that fits in the specified bounds. 565 * </p> 566 * 567 * @param topFocus look for a candidate is the one at the top of the bounds 568 * if topFocus is true, or at the bottom of the bounds if topFocus is 569 * false 570 * @param top the top offset of the bounds in which a focusable must be 571 * found 572 * @param bottom the bottom offset of the bounds in which a focusable must 573 * be found 574 * @return the next focusable component in the bounds or null if none can 575 * be found 576 */ 577 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 578 579 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 580 View focusCandidate = null; 581 582 /* 583 * A fully contained focusable is one where its top is below the bound's 584 * top, and its bottom is above the bound's bottom. A partially 585 * contained focusable is one where some part of it is within the 586 * bounds, but it also has some part that is not within bounds. A fully contained 587 * focusable is preferred to a partially contained focusable. 588 */ 589 boolean foundFullyContainedFocusable = false; 590 591 int count = focusables.size(); 592 for (int i = 0; i < count; i++) { 593 View view = focusables.get(i); 594 int viewTop = view.getTop(); 595 int viewBottom = view.getBottom(); 596 597 if (top < viewBottom && viewTop < bottom) { 598 /* 599 * the focusable is in the target area, it is a candidate for 600 * focusing 601 */ 602 603 final boolean viewIsFullyContained = (top < viewTop) && 604 (viewBottom < bottom); 605 606 if (focusCandidate == null) { 607 /* No candidate, take this one */ 608 focusCandidate = view; 609 foundFullyContainedFocusable = viewIsFullyContained; 610 } else { 611 final boolean viewIsCloserToBoundary = 612 (topFocus && viewTop < focusCandidate.getTop()) || 613 (!topFocus && viewBottom > focusCandidate 614 .getBottom()); 615 616 if (foundFullyContainedFocusable) { 617 if (viewIsFullyContained && viewIsCloserToBoundary) { 618 /* 619 * We're dealing with only fully contained views, so 620 * it has to be closer to the boundary to beat our 621 * candidate 622 */ 623 focusCandidate = view; 624 } 625 } else { 626 if (viewIsFullyContained) { 627 /* Any fully contained view beats a partially contained view */ 628 focusCandidate = view; 629 foundFullyContainedFocusable = true; 630 } else if (viewIsCloserToBoundary) { 631 /* 632 * Partially contained view beats another partially 633 * contained view if it's closer 634 */ 635 focusCandidate = view; 636 } 637 } 638 } 639 } 640 } 641 642 return focusCandidate; 643 } 644 645 /** 646 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 647 * method will scroll the view by one page up or down and give the focus 648 * to the topmost/bottommost component in the new visible area. If no 649 * component is a good candidate for focus, this scrollview reclaims the 650 * focus.</p> 651 * 652 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 653 * to go one page up or 654 * {@link android.view.View#FOCUS_DOWN} to go one page down 655 * @return true if the key event is consumed by this method, false otherwise 656 */ 657 public boolean pageScroll(int direction) { 658 boolean down = direction == View.FOCUS_DOWN; 659 int height = getHeight(); 660 661 if (down) { 662 mTempRect.top = getScrollY() + height; 663 int count = getChildCount(); 664 if (count > 0) { 665 View view = getChildAt(count - 1); 666 if (mTempRect.top + height > view.getBottom()) { 667 mTempRect.top = view.getBottom() - height; 668 } 669 } 670 } else { 671 mTempRect.top = getScrollY() - height; 672 if (mTempRect.top < 0) { 673 mTempRect.top = 0; 674 } 675 } 676 mTempRect.bottom = mTempRect.top + height; 677 678 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 679 } 680 681 /** 682 * <p>Handles scrolling in response to a "home/end" shortcut press. This 683 * method will scroll the view to the top or bottom and give the focus 684 * to the topmost/bottommost component in the new visible area. If no 685 * component is a good candidate for focus, this scrollview reclaims the 686 * focus.</p> 687 * 688 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 689 * to go the top of the view or 690 * {@link android.view.View#FOCUS_DOWN} to go the bottom 691 * @return true if the key event is consumed by this method, false otherwise 692 */ 693 public boolean fullScroll(int direction) { 694 boolean down = direction == View.FOCUS_DOWN; 695 int height = getHeight(); 696 697 mTempRect.top = 0; 698 mTempRect.bottom = height; 699 700 if (down) { 701 int count = getChildCount(); 702 if (count > 0) { 703 View view = getChildAt(count - 1); 704 mTempRect.bottom = view.getBottom(); 705 mTempRect.top = mTempRect.bottom - height; 706 } 707 } 708 709 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 710 } 711 712 /** 713 * <p>Scrolls the view to make the area defined by <code>top</code> and 714 * <code>bottom</code> visible. This method attempts to give the focus 715 * to a component visible in this area. If no component can be focused in 716 * the new visible area, the focus is reclaimed by this scrollview.</p> 717 * 718 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 719 * to go upward 720 * {@link android.view.View#FOCUS_DOWN} to downward 721 * @param top the top offset of the new area to be made visible 722 * @param bottom the bottom offset of the new area to be made visible 723 * @return true if the key event is consumed by this method, false otherwise 724 */ 725 private boolean scrollAndFocus(int direction, int top, int bottom) { 726 boolean handled = true; 727 728 int height = getHeight(); 729 int containerTop = getScrollY(); 730 int containerBottom = containerTop + height; 731 boolean up = direction == View.FOCUS_UP; 732 733 View newFocused = findFocusableViewInBounds(up, top, bottom); 734 if (newFocused == null) { 735 newFocused = this; 736 } 737 738 if (top >= containerTop && bottom <= containerBottom) { 739 handled = false; 740 } else { 741 int delta = up ? (top - containerTop) : (bottom - containerBottom); 742 doScrollY(delta); 743 } 744 745 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 746 mScrollViewMovedFocus = true; 747 mScrollViewMovedFocus = false; 748 } 749 750 return handled; 751 } 752 753 /** 754 * Handle scrolling in response to an up or down arrow click. 755 * 756 * @param direction The direction corresponding to the arrow key that was 757 * pressed 758 * @return True if we consumed the event, false otherwise 759 */ 760 public boolean arrowScroll(int direction) { 761 762 View currentFocused = findFocus(); 763 if (currentFocused == this) currentFocused = null; 764 765 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 766 767 final int maxJump = getMaxScrollAmount(); 768 769 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 770 nextFocused.getDrawingRect(mTempRect); 771 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 772 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 773 doScrollY(scrollDelta); 774 nextFocused.requestFocus(direction); 775 } else { 776 // no new focus 777 int scrollDelta = maxJump; 778 779 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 780 scrollDelta = getScrollY(); 781 } else if (direction == View.FOCUS_DOWN) { 782 if (getChildCount() > 0) { 783 int daBottom = getChildAt(0).getBottom(); 784 785 int screenBottom = getScrollY() + getHeight(); 786 787 if (daBottom - screenBottom < maxJump) { 788 scrollDelta = daBottom - screenBottom; 789 } 790 } 791 } 792 if (scrollDelta == 0) { 793 return false; 794 } 795 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 796 } 797 798 if (currentFocused != null && currentFocused.isFocused() 799 && isOffScreen(currentFocused)) { 800 // previously focused item still has focus and is off screen, give 801 // it up (take it back to ourselves) 802 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 803 // sure to 804 // get it) 805 final int descendantFocusability = getDescendantFocusability(); // save 806 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 807 requestFocus(); 808 setDescendantFocusability(descendantFocusability); // restore 809 } 810 return true; 811 } 812 813 /** 814 * @return whether the descendant of this scroll view is scrolled off 815 * screen. 816 */ 817 private boolean isOffScreen(View descendant) { 818 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 819 } 820 821 /** 822 * @return whether the descendant of this scroll view is within delta 823 * pixels of being on the screen. 824 */ 825 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 826 descendant.getDrawingRect(mTempRect); 827 offsetDescendantRectToMyCoords(descendant, mTempRect); 828 829 return (mTempRect.bottom + delta) >= getScrollY() 830 && (mTempRect.top - delta) <= (getScrollY() + height); 831 } 832 833 /** 834 * Smooth scroll by a Y delta 835 * 836 * @param delta the number of pixels to scroll by on the Y axis 837 */ 838 private void doScrollY(int delta) { 839 if (delta != 0) { 840 if (mSmoothScrollingEnabled) { 841 smoothScrollBy(0, delta); 842 } else { 843 scrollBy(0, delta); 844 } 845 } 846 } 847 848 /** 849 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 850 * 851 * @param dx the number of pixels to scroll by on the X axis 852 * @param dy the number of pixels to scroll by on the Y axis 853 */ 854 public final void smoothScrollBy(int dx, int dy) { 855 if (getChildCount() == 0) { 856 // Nothing to do. 857 return; 858 } 859 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 860 if (duration > ANIMATED_SCROLL_GAP) { 861 final int height = getHeight() - mPaddingBottom - mPaddingTop; 862 final int bottom = getChildAt(0).getHeight(); 863 final int maxY = Math.max(0, bottom - height); 864 final int scrollY = mScrollY; 865 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 866 867 mScroller.startScroll(mScrollX, scrollY, 0, dy); 868 awakenScrollBars(mScroller.getDuration()); 869 invalidate(); 870 } else { 871 if (!mScroller.isFinished()) { 872 mScroller.abortAnimation(); 873 } 874 scrollBy(dx, dy); 875 } 876 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 877 } 878 879 /** 880 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 881 * 882 * @param x the position where to scroll on the X axis 883 * @param y the position where to scroll on the Y axis 884 */ 885 public final void smoothScrollTo(int x, int y) { 886 smoothScrollBy(x - mScrollX, y - mScrollY); 887 } 888 889 /** 890 * <p>The scroll range of a scroll view is the overall height of all of its 891 * children.</p> 892 */ 893 @Override 894 protected int computeVerticalScrollRange() { 895 int count = getChildCount(); 896 if (count == 0) { 897 return getHeight(); 898 } 899 900 int scrollRange = getChildAt(0).getBottom(); 901 int scrollY = mScrollY; 902 int overscrollBottom = scrollRange - getHeight() - mPaddingBottom - mPaddingTop; 903 if (scrollY < 0) { 904 scrollRange -= scrollY; 905 } else if (scrollY > overscrollBottom) { 906 scrollRange += scrollY - overscrollBottom; 907 } 908 909 return scrollRange; 910 } 911 912 @Override 913 protected int computeVerticalScrollOffset() { 914 return Math.max(0, super.computeVerticalScrollOffset()); 915 } 916 917 @Override 918 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 919 ViewGroup.LayoutParams lp = child.getLayoutParams(); 920 921 int childWidthMeasureSpec; 922 int childHeightMeasureSpec; 923 924 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 925 + mPaddingRight, lp.width); 926 927 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 928 929 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 930 } 931 932 @Override 933 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 934 int parentHeightMeasureSpec, int heightUsed) { 935 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 936 937 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 938 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 939 + widthUsed, lp.width); 940 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 941 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 942 943 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 944 } 945 946 @Override 947 public void computeScroll() { 948 if (mScroller.computeScrollOffset()) { 949 // This is called at drawing time by ViewGroup. We don't want to 950 // re-show the scrollbars at this point, which scrollTo will do, 951 // so we replicate most of scrollTo here. 952 // 953 // It's a little odd to call onScrollChanged from inside the drawing. 954 // 955 // It is, except when you remember that computeScroll() is used to 956 // animate scrolling. So unless we want to defer the onScrollChanged() 957 // until the end of the animated scrolling, we don't really have a 958 // choice here. 959 // 960 // I agree. The alternative, which I think would be worse, is to post 961 // something and tell the subclasses later. This is bad because there 962 // will be a window where mScrollX/Y is different from what the app 963 // thinks it is. 964 // 965 int oldX = mScrollX; 966 int oldY = mScrollY; 967 int x = mScroller.getCurrX(); 968 int y = mScroller.getCurrY(); 969 970 if (oldX != x || oldY != y) { 971 overscrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 972 0, getOverscrollMax()); 973 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 974 } 975 976 // Keep on drawing until the animation has finished. 977 postInvalidate(); 978 } 979 } 980 981 /** 982 * Scrolls the view to the given child. 983 * 984 * @param child the View to scroll to 985 */ 986 private void scrollToChild(View child) { 987 child.getDrawingRect(mTempRect); 988 989 /* Offset from child's local coordinates to ScrollView coordinates */ 990 offsetDescendantRectToMyCoords(child, mTempRect); 991 992 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 993 994 if (scrollDelta != 0) { 995 scrollBy(0, scrollDelta); 996 } 997 } 998 999 /** 1000 * If rect is off screen, scroll just enough to get it (or at least the 1001 * first screen size chunk of it) on screen. 1002 * 1003 * @param rect The rectangle. 1004 * @param immediate True to scroll immediately without animation 1005 * @return true if scrolling was performed 1006 */ 1007 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1008 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1009 final boolean scroll = delta != 0; 1010 if (scroll) { 1011 if (immediate) { 1012 scrollBy(0, delta); 1013 } else { 1014 smoothScrollBy(0, delta); 1015 } 1016 } 1017 return scroll; 1018 } 1019 1020 /** 1021 * Compute the amount to scroll in the Y direction in order to get 1022 * a rectangle completely on the screen (or, if taller than the screen, 1023 * at least the first screen size chunk of it). 1024 * 1025 * @param rect The rect. 1026 * @return The scroll delta. 1027 */ 1028 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1029 if (getChildCount() == 0) return 0; 1030 1031 int height = getHeight(); 1032 int screenTop = getScrollY(); 1033 int screenBottom = screenTop + height; 1034 1035 int fadingEdge = getVerticalFadingEdgeLength(); 1036 1037 // leave room for top fading edge as long as rect isn't at very top 1038 if (rect.top > 0) { 1039 screenTop += fadingEdge; 1040 } 1041 1042 // leave room for bottom fading edge as long as rect isn't at very bottom 1043 if (rect.bottom < getChildAt(0).getHeight()) { 1044 screenBottom -= fadingEdge; 1045 } 1046 1047 int scrollYDelta = 0; 1048 1049 if (rect.bottom > screenBottom && rect.top > screenTop) { 1050 // need to move down to get it in view: move down just enough so 1051 // that the entire rectangle is in view (or at least the first 1052 // screen size chunk). 1053 1054 if (rect.height() > height) { 1055 // just enough to get screen size chunk on 1056 scrollYDelta += (rect.top - screenTop); 1057 } else { 1058 // get entire rect at bottom of screen 1059 scrollYDelta += (rect.bottom - screenBottom); 1060 } 1061 1062 // make sure we aren't scrolling beyond the end of our content 1063 int bottom = getChildAt(0).getBottom(); 1064 int distanceToBottom = bottom - screenBottom; 1065 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1066 1067 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1068 // need to move up to get it in view: move up just enough so that 1069 // entire rectangle is in view (or at least the first screen 1070 // size chunk of it). 1071 1072 if (rect.height() > height) { 1073 // screen size chunk 1074 scrollYDelta -= (screenBottom - rect.bottom); 1075 } else { 1076 // entire rect at top 1077 scrollYDelta -= (screenTop - rect.top); 1078 } 1079 1080 // make sure we aren't scrolling any further than the top our content 1081 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1082 } 1083 return scrollYDelta; 1084 } 1085 1086 @Override 1087 public void requestChildFocus(View child, View focused) { 1088 if (!mScrollViewMovedFocus) { 1089 if (!mIsLayoutDirty) { 1090 scrollToChild(focused); 1091 } else { 1092 // The child may not be laid out yet, we can't compute the scroll yet 1093 mChildToScrollTo = focused; 1094 } 1095 } 1096 super.requestChildFocus(child, focused); 1097 } 1098 1099 1100 /** 1101 * When looking for focus in children of a scroll view, need to be a little 1102 * more careful not to give focus to something that is scrolled off screen. 1103 * 1104 * This is more expensive than the default {@link android.view.ViewGroup} 1105 * implementation, otherwise this behavior might have been made the default. 1106 */ 1107 @Override 1108 protected boolean onRequestFocusInDescendants(int direction, 1109 Rect previouslyFocusedRect) { 1110 1111 // convert from forward / backward notation to up / down / left / right 1112 // (ugh). 1113 if (direction == View.FOCUS_FORWARD) { 1114 direction = View.FOCUS_DOWN; 1115 } else if (direction == View.FOCUS_BACKWARD) { 1116 direction = View.FOCUS_UP; 1117 } 1118 1119 final View nextFocus = previouslyFocusedRect == null ? 1120 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1121 FocusFinder.getInstance().findNextFocusFromRect(this, 1122 previouslyFocusedRect, direction); 1123 1124 if (nextFocus == null) { 1125 return false; 1126 } 1127 1128 if (isOffScreen(nextFocus)) { 1129 return false; 1130 } 1131 1132 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1133 } 1134 1135 @Override 1136 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1137 boolean immediate) { 1138 // offset into coordinate space of this scroll view 1139 rectangle.offset(child.getLeft() - child.getScrollX(), 1140 child.getTop() - child.getScrollY()); 1141 1142 return scrollToChildRect(rectangle, immediate); 1143 } 1144 1145 @Override 1146 public void requestLayout() { 1147 mIsLayoutDirty = true; 1148 super.requestLayout(); 1149 } 1150 1151 @Override 1152 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1153 super.onLayout(changed, l, t, r, b); 1154 mIsLayoutDirty = false; 1155 // Give a child focus if it needs it 1156 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1157 scrollToChild(mChildToScrollTo); 1158 } 1159 mChildToScrollTo = null; 1160 1161 // Calling this with the present values causes it to re-clam them 1162 scrollTo(mScrollX, mScrollY); 1163 } 1164 1165 @Override 1166 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1167 super.onSizeChanged(w, h, oldw, oldh); 1168 1169 View currentFocused = findFocus(); 1170 if (null == currentFocused || this == currentFocused) 1171 return; 1172 1173 // If the currently-focused view was visible on the screen when the 1174 // screen was at the old height, then scroll the screen to make that 1175 // view visible with the new screen height. 1176 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1177 currentFocused.getDrawingRect(mTempRect); 1178 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1179 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1180 doScrollY(scrollDelta); 1181 } 1182 } 1183 1184 /** 1185 * Return true if child is an descendant of parent, (or equal to the parent). 1186 */ 1187 private boolean isViewDescendantOf(View child, View parent) { 1188 if (child == parent) { 1189 return true; 1190 } 1191 1192 final ViewParent theParent = child.getParent(); 1193 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1194 } 1195 1196 /** 1197 * Fling the scroll view 1198 * 1199 * @param velocityY The initial velocity in the Y direction. Positive 1200 * numbers mean that the finger/curor is moving down the screen, 1201 * which means we want to scroll towards the top. 1202 */ 1203 public void fling(int velocityY) { 1204 if (getChildCount() > 0) { 1205 int height = getHeight() - mPaddingBottom - mPaddingTop; 1206 int bottom = getChildAt(0).getHeight(); 1207 1208 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1209 Math.max(0, bottom - height), 0, height/2); 1210 1211 final boolean movingDown = velocityY > 0; 1212 1213 View newFocused = 1214 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1215 if (newFocused == null) { 1216 newFocused = this; 1217 } 1218 1219 if (newFocused != findFocus() 1220 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1221 mScrollViewMovedFocus = true; 1222 mScrollViewMovedFocus = false; 1223 } 1224 1225 awakenScrollBars(mScroller.getDuration()); 1226 invalidate(); 1227 } 1228 } 1229 1230 /** 1231 * {@inheritDoc} 1232 * 1233 * <p>This version also clamps the scrolling to the bounds of our child. 1234 */ 1235 public void scrollTo(int x, int y) { 1236 // we rely on the fact the View.scrollBy calls scrollTo. 1237 if (getChildCount() > 0) { 1238 View child = getChildAt(0); 1239 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1240 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1241 if (x != mScrollX || y != mScrollY) { 1242 super.scrollTo(x, y); 1243 } 1244 } 1245 } 1246 1247 private int clamp(int n, int my, int child) { 1248 if (my >= child || n < 0) { 1249 /* my >= child is this case: 1250 * |--------------- me ---------------| 1251 * |------ child ------| 1252 * or 1253 * |--------------- me ---------------| 1254 * |------ child ------| 1255 * or 1256 * |--------------- me ---------------| 1257 * |------ child ------| 1258 * 1259 * n < 0 is this case: 1260 * |------ me ------| 1261 * |-------- child --------| 1262 * |-- mScrollX --| 1263 */ 1264 return 0; 1265 } 1266 if ((my+n) > child) { 1267 /* this case: 1268 * |------ me ------| 1269 * |------ child ------| 1270 * |-- mScrollX --| 1271 */ 1272 return child-my; 1273 } 1274 return n; 1275 } 1276} 1277