ScrollView.java revision 737e8fe2c7ce167bc68ad779160488007a5e0b1d
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.Resources; 23import android.content.res.TypedArray; 24import android.graphics.Canvas; 25import android.graphics.Rect; 26import android.graphics.drawable.Drawable; 27import android.util.AttributeSet; 28import android.view.FocusFinder; 29import android.view.KeyEvent; 30import android.view.MotionEvent; 31import android.view.VelocityTracker; 32import android.view.View; 33import android.view.ViewConfiguration; 34import android.view.ViewGroup; 35import android.view.ViewParent; 36import android.view.animation.AnimationUtils; 37 38import java.util.List; 39 40/** 41 * Layout container for a view hierarchy that can be scrolled by the user, 42 * allowing it to be larger than the physical display. A ScrollView 43 * is a {@link FrameLayout}, meaning you should place one child in it 44 * containing the entire contents to scroll; this child may itself be a layout 45 * manager with a complex hierarchy of objects. A child that is often used 46 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 47 * array of top-level items that the user can scroll through. 48 * 49 * <p>The {@link TextView} class also 50 * takes care of its own scrolling, so does not require a ScrollView, but 51 * using the two together is possible to achieve the effect of a text view 52 * within a larger container. 53 * 54 * <p>ScrollView only supports vertical scrolling. 55 */ 56public class ScrollView extends FrameLayout { 57 static final int ANIMATED_SCROLL_GAP = 250; 58 59 static final float MAX_SCROLL_FACTOR = 0.5f; 60 61 62 private long mLastScroll; 63 64 private final Rect mTempRect = new Rect(); 65 private OverScroller mScroller; 66 private EdgeGlow mEdgeGlowTop; 67 private EdgeGlow mEdgeGlowBottom; 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 private int mOverscrollDistance; 122 private int mOverflingDistance; 123 124 /** 125 * ID of the active pointer. This is used to retain consistency during 126 * drags/flings if multiple pointers are used. 127 */ 128 private int mActivePointerId = INVALID_POINTER; 129 130 /** 131 * Sentinel value for no current active pointer. 132 * Used by {@link #mActivePointerId}. 133 */ 134 private static final int INVALID_POINTER = -1; 135 136 public ScrollView(Context context) { 137 this(context, null); 138 } 139 140 public ScrollView(Context context, AttributeSet attrs) { 141 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 142 } 143 144 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 145 super(context, attrs, defStyle); 146 initScrollView(); 147 148 TypedArray a = 149 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 150 151 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 152 153 a.recycle(); 154 } 155 156 @Override 157 protected float getTopFadingEdgeStrength() { 158 if (getChildCount() == 0) { 159 return 0.0f; 160 } 161 162 final int length = getVerticalFadingEdgeLength(); 163 if (mScrollY < length) { 164 return mScrollY / (float) length; 165 } 166 167 return 1.0f; 168 } 169 170 @Override 171 protected float getBottomFadingEdgeStrength() { 172 if (getChildCount() == 0) { 173 return 0.0f; 174 } 175 176 final int length = getVerticalFadingEdgeLength(); 177 final int bottomEdge = getHeight() - mPaddingBottom; 178 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 179 if (span < length) { 180 return span / (float) length; 181 } 182 183 return 1.0f; 184 } 185 186 /** 187 * @return The maximum amount this scroll view will scroll in response to 188 * an arrow event. 189 */ 190 public int getMaxScrollAmount() { 191 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 192 } 193 194 195 private void initScrollView() { 196 mScroller = new OverScroller(getContext()); 197 setFocusable(true); 198 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 199 setWillNotDraw(false); 200 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 201 mTouchSlop = configuration.getScaledTouchSlop(); 202 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 203 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 204 mOverscrollDistance = configuration.getScaledOverscrollDistance(); 205 mOverflingDistance = configuration.getScaledOverflingDistance(); 206 } 207 208 @Override 209 public void addView(View child) { 210 if (getChildCount() > 0) { 211 throw new IllegalStateException("ScrollView can host only one direct child"); 212 } 213 214 super.addView(child); 215 } 216 217 @Override 218 public void addView(View child, int index) { 219 if (getChildCount() > 0) { 220 throw new IllegalStateException("ScrollView can host only one direct child"); 221 } 222 223 super.addView(child, index); 224 } 225 226 @Override 227 public void addView(View child, ViewGroup.LayoutParams params) { 228 if (getChildCount() > 0) { 229 throw new IllegalStateException("ScrollView can host only one direct child"); 230 } 231 232 super.addView(child, params); 233 } 234 235 @Override 236 public void addView(View child, int index, ViewGroup.LayoutParams params) { 237 if (getChildCount() > 0) { 238 throw new IllegalStateException("ScrollView can host only one direct child"); 239 } 240 241 super.addView(child, index, params); 242 } 243 244 /** 245 * @return Returns true this ScrollView can be scrolled 246 */ 247 private boolean canScroll() { 248 View child = getChildAt(0); 249 if (child != null) { 250 int childHeight = child.getHeight(); 251 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 252 } 253 return false; 254 } 255 256 /** 257 * Indicates whether this ScrollView's content is stretched to fill the viewport. 258 * 259 * @return True if the content fills the viewport, false otherwise. 260 */ 261 public boolean isFillViewport() { 262 return mFillViewport; 263 } 264 265 /** 266 * Indicates this ScrollView whether it should stretch its content height to fill 267 * the viewport or not. 268 * 269 * @param fillViewport True to stretch the content's height to the viewport's 270 * boundaries, false otherwise. 271 */ 272 public void setFillViewport(boolean fillViewport) { 273 if (fillViewport != mFillViewport) { 274 mFillViewport = fillViewport; 275 requestLayout(); 276 } 277 } 278 279 /** 280 * @return Whether arrow scrolling will animate its transition. 281 */ 282 public boolean isSmoothScrollingEnabled() { 283 return mSmoothScrollingEnabled; 284 } 285 286 /** 287 * Set whether arrow scrolling will animate its transition. 288 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 289 */ 290 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 291 mSmoothScrollingEnabled = smoothScrollingEnabled; 292 } 293 294 @Override 295 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 296 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 297 298 if (!mFillViewport) { 299 return; 300 } 301 302 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 303 if (heightMode == MeasureSpec.UNSPECIFIED) { 304 return; 305 } 306 307 if (getChildCount() > 0) { 308 final View child = getChildAt(0); 309 int height = getMeasuredHeight(); 310 if (child.getMeasuredHeight() < height) { 311 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 312 313 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 314 + mPaddingRight, lp.width); 315 height -= mPaddingTop; 316 height -= mPaddingBottom; 317 int childHeightMeasureSpec = 318 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 319 320 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 321 } 322 } 323 } 324 325 @Override 326 public boolean dispatchKeyEvent(KeyEvent event) { 327 // Let the focused view and/or our descendants get the key first 328 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 329 } 330 331 /** 332 * You can call this function yourself to have the scroll view perform 333 * scrolling from a key event, just as if the event had been dispatched to 334 * it by the view hierarchy. 335 * 336 * @param event The key event to execute. 337 * @return Return true if the event was handled, else false. 338 */ 339 public boolean executeKeyEvent(KeyEvent event) { 340 mTempRect.setEmpty(); 341 342 if (!canScroll()) { 343 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { 344 View currentFocused = findFocus(); 345 if (currentFocused == this) currentFocused = null; 346 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 347 currentFocused, View.FOCUS_DOWN); 348 return nextFocused != null 349 && nextFocused != this 350 && nextFocused.requestFocus(View.FOCUS_DOWN); 351 } 352 return false; 353 } 354 355 boolean handled = false; 356 if (event.getAction() == KeyEvent.ACTION_DOWN) { 357 switch (event.getKeyCode()) { 358 case KeyEvent.KEYCODE_DPAD_UP: 359 if (!event.isAltPressed()) { 360 handled = arrowScroll(View.FOCUS_UP); 361 } else { 362 handled = fullScroll(View.FOCUS_UP); 363 } 364 break; 365 case KeyEvent.KEYCODE_DPAD_DOWN: 366 if (!event.isAltPressed()) { 367 handled = arrowScroll(View.FOCUS_DOWN); 368 } else { 369 handled = fullScroll(View.FOCUS_DOWN); 370 } 371 break; 372 case KeyEvent.KEYCODE_SPACE: 373 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 374 break; 375 } 376 } 377 378 return handled; 379 } 380 381 private boolean inChild(int x, int y) { 382 if (getChildCount() > 0) { 383 final int scrollY = mScrollY; 384 final View child = getChildAt(0); 385 return !(y < child.getTop() - scrollY 386 || y >= child.getBottom() - scrollY 387 || x < child.getLeft() 388 || x >= child.getRight()); 389 } 390 return false; 391 } 392 393 @Override 394 public boolean onInterceptTouchEvent(MotionEvent ev) { 395 /* 396 * This method JUST determines whether we want to intercept the motion. 397 * If we return true, onMotionEvent will be called and we do the actual 398 * scrolling there. 399 */ 400 401 /* 402 * Shortcut the most recurring case: the user is in the dragging 403 * state and he is moving his finger. We want to intercept this 404 * motion. 405 */ 406 final int action = ev.getAction(); 407 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 408 return true; 409 } 410 411 switch (action & MotionEvent.ACTION_MASK) { 412 case MotionEvent.ACTION_MOVE: { 413 /* 414 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 415 * whether the user has moved far enough from his original down touch. 416 */ 417 418 /* 419 * Locally do absolute value. mLastMotionY is set to the y value 420 * of the down event. 421 */ 422 final int activePointerId = mActivePointerId; 423 if (activePointerId == INVALID_POINTER) { 424 // If we don't have a valid id, the touch down wasn't on content. 425 break; 426 } 427 428 final int pointerIndex = ev.findPointerIndex(activePointerId); 429 final float y = ev.getY(pointerIndex); 430 final int yDiff = (int) Math.abs(y - mLastMotionY); 431 if (yDiff > mTouchSlop) { 432 mIsBeingDragged = true; 433 mLastMotionY = y; 434 } 435 break; 436 } 437 438 case MotionEvent.ACTION_DOWN: { 439 final float y = ev.getY(); 440 if (!inChild((int) ev.getX(), (int) y)) { 441 mIsBeingDragged = false; 442 break; 443 } 444 445 /* 446 * Remember location of down touch. 447 * ACTION_DOWN always refers to pointer index 0. 448 */ 449 mLastMotionY = y; 450 mActivePointerId = ev.getPointerId(0); 451 452 /* 453 * If being flinged and user touches the screen, initiate drag; 454 * otherwise don't. mScroller.isFinished should be false when 455 * being flinged. 456 */ 457 mIsBeingDragged = !mScroller.isFinished(); 458 break; 459 } 460 461 case MotionEvent.ACTION_CANCEL: 462 case MotionEvent.ACTION_UP: 463 /* Release the drag */ 464 mIsBeingDragged = false; 465 mActivePointerId = INVALID_POINTER; 466 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 467 invalidate(); 468 } 469 break; 470 case MotionEvent.ACTION_POINTER_UP: 471 onSecondaryPointerUp(ev); 472 break; 473 } 474 475 /* 476 * The only time we want to intercept motion events is if we are in the 477 * drag mode. 478 */ 479 return mIsBeingDragged; 480 } 481 482 @Override 483 public boolean onTouchEvent(MotionEvent ev) { 484 485 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 486 // Don't handle edge touches immediately -- they may actually belong to one of our 487 // descendants. 488 return false; 489 } 490 491 if (mVelocityTracker == null) { 492 mVelocityTracker = VelocityTracker.obtain(); 493 } 494 mVelocityTracker.addMovement(ev); 495 496 final int action = ev.getAction(); 497 498 switch (action & MotionEvent.ACTION_MASK) { 499 case MotionEvent.ACTION_DOWN: { 500 final float y = ev.getY(); 501 mIsBeingDragged = true; 502 503 /* 504 * If being flinged and user touches, stop the fling. isFinished 505 * will be false if being flinged. 506 */ 507 if (!mScroller.isFinished()) { 508 mScroller.abortAnimation(); 509 } 510 511 // Remember where the motion event started 512 mLastMotionY = y; 513 mActivePointerId = ev.getPointerId(0); 514 break; 515 } 516 case MotionEvent.ACTION_MOVE: 517 if (mIsBeingDragged) { 518 // Scroll to follow the motion event 519 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 520 final float y = ev.getY(activePointerIndex); 521 final int deltaY = (int) (mLastMotionY - y); 522 mLastMotionY = y; 523 524 final int oldX = mScrollX; 525 final int oldY = mScrollY; 526 final int range = getScrollRange(); 527 if (overScrollBy(0, deltaY, 0, mScrollY, 0, range, 528 0, mOverscrollDistance, true)) { 529 // Break our velocity if we hit a scroll barrier. 530 mVelocityTracker.clear(); 531 } 532 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 533 534 final int overscrollMode = getOverScrollMode(); 535 if (overscrollMode == OVER_SCROLL_ALWAYS || 536 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { 537 final int pulledToY = oldY + deltaY; 538 if (pulledToY < 0) { 539 mEdgeGlowTop.onPull((float) deltaY / getHeight()); 540 } else if (pulledToY > range) { 541 mEdgeGlowBottom.onPull((float) deltaY / getHeight()); 542 } 543 } 544 } 545 break; 546 case MotionEvent.ACTION_UP: 547 if (mIsBeingDragged) { 548 final VelocityTracker velocityTracker = mVelocityTracker; 549 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 550 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 551 552 if (getChildCount() > 0) { 553 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 554 fling(-initialVelocity); 555 } else { 556 final int bottom = getScrollRange(); 557 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, bottom)) { 558 invalidate(); 559 } 560 } 561 } 562 563 mActivePointerId = INVALID_POINTER; 564 mIsBeingDragged = false; 565 566 if (mVelocityTracker != null) { 567 mVelocityTracker.recycle(); 568 mVelocityTracker = null; 569 } 570 if (mEdgeGlowTop != null) { 571 mEdgeGlowTop.onRelease(); 572 mEdgeGlowBottom.onRelease(); 573 } 574 } 575 break; 576 case MotionEvent.ACTION_CANCEL: 577 if (mIsBeingDragged && getChildCount() > 0) { 578 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 579 invalidate(); 580 } 581 mActivePointerId = INVALID_POINTER; 582 mIsBeingDragged = false; 583 if (mVelocityTracker != null) { 584 mVelocityTracker.recycle(); 585 mVelocityTracker = null; 586 } 587 if (mEdgeGlowTop != null) { 588 mEdgeGlowTop.onRelease(); 589 mEdgeGlowBottom.onRelease(); 590 } 591 } 592 break; 593 case MotionEvent.ACTION_POINTER_UP: 594 onSecondaryPointerUp(ev); 595 break; 596 } 597 return true; 598 } 599 600 private void onSecondaryPointerUp(MotionEvent ev) { 601 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 602 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 603 final int pointerId = ev.getPointerId(pointerIndex); 604 if (pointerId == mActivePointerId) { 605 // This was our active pointer going up. Choose a new 606 // active pointer and adjust accordingly. 607 // TODO: Make this decision more intelligent. 608 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 609 mLastMotionY = ev.getY(newPointerIndex); 610 mActivePointerId = ev.getPointerId(newPointerIndex); 611 if (mVelocityTracker != null) { 612 mVelocityTracker.clear(); 613 } 614 } 615 } 616 617 @Override 618 protected void onOverScrolled(int scrollX, int scrollY, 619 boolean clampedX, boolean clampedY) { 620 // Treat animating scrolls differently; see #computeScroll() for why. 621 if (!mScroller.isFinished()) { 622 mScrollX = scrollX; 623 mScrollY = scrollY; 624 if (clampedY) { 625 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 626 } 627 } else { 628 super.scrollTo(scrollX, scrollY); 629 } 630 awakenScrollBars(); 631 } 632 633 private int getScrollRange() { 634 int scrollRange = 0; 635 if (getChildCount() > 0) { 636 View child = getChildAt(0); 637 scrollRange = Math.max(0, 638 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); 639 } 640 return scrollRange; 641 } 642 643 /** 644 * <p> 645 * Finds the next focusable component that fits in this View's bounds 646 * (excluding fading edges) pretending that this View's top is located at 647 * the parameter top. 648 * </p> 649 * 650 * @param topFocus look for a candidate is the one at the top of the bounds 651 * if topFocus is true, or at the bottom of the bounds if topFocus is 652 * false 653 * @param top the top offset of the bounds in which a focusable must be 654 * found (the fading edge is assumed to start at this position) 655 * @param preferredFocusable the View that has highest priority and will be 656 * returned if it is within my bounds (null is valid) 657 * @return the next focusable component in the bounds or null if none can be 658 * found 659 */ 660 private View findFocusableViewInMyBounds(final boolean topFocus, 661 final int top, View preferredFocusable) { 662 /* 663 * The fading edge's transparent side should be considered for focus 664 * since it's mostly visible, so we divide the actual fading edge length 665 * by 2. 666 */ 667 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 668 final int topWithoutFadingEdge = top + fadingEdgeLength; 669 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 670 671 if ((preferredFocusable != null) 672 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 673 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 674 return preferredFocusable; 675 } 676 677 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 678 bottomWithoutFadingEdge); 679 } 680 681 /** 682 * <p> 683 * Finds the next focusable component that fits in the specified bounds. 684 * </p> 685 * 686 * @param topFocus look for a candidate is the one at the top of the bounds 687 * if topFocus is true, or at the bottom of the bounds if topFocus is 688 * false 689 * @param top the top offset of the bounds in which a focusable must be 690 * found 691 * @param bottom the bottom offset of the bounds in which a focusable must 692 * be found 693 * @return the next focusable component in the bounds or null if none can 694 * be found 695 */ 696 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 697 698 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 699 View focusCandidate = null; 700 701 /* 702 * A fully contained focusable is one where its top is below the bound's 703 * top, and its bottom is above the bound's bottom. A partially 704 * contained focusable is one where some part of it is within the 705 * bounds, but it also has some part that is not within bounds. A fully contained 706 * focusable is preferred to a partially contained focusable. 707 */ 708 boolean foundFullyContainedFocusable = false; 709 710 int count = focusables.size(); 711 for (int i = 0; i < count; i++) { 712 View view = focusables.get(i); 713 int viewTop = view.getTop(); 714 int viewBottom = view.getBottom(); 715 716 if (top < viewBottom && viewTop < bottom) { 717 /* 718 * the focusable is in the target area, it is a candidate for 719 * focusing 720 */ 721 722 final boolean viewIsFullyContained = (top < viewTop) && 723 (viewBottom < bottom); 724 725 if (focusCandidate == null) { 726 /* No candidate, take this one */ 727 focusCandidate = view; 728 foundFullyContainedFocusable = viewIsFullyContained; 729 } else { 730 final boolean viewIsCloserToBoundary = 731 (topFocus && viewTop < focusCandidate.getTop()) || 732 (!topFocus && viewBottom > focusCandidate 733 .getBottom()); 734 735 if (foundFullyContainedFocusable) { 736 if (viewIsFullyContained && viewIsCloserToBoundary) { 737 /* 738 * We're dealing with only fully contained views, so 739 * it has to be closer to the boundary to beat our 740 * candidate 741 */ 742 focusCandidate = view; 743 } 744 } else { 745 if (viewIsFullyContained) { 746 /* Any fully contained view beats a partially contained view */ 747 focusCandidate = view; 748 foundFullyContainedFocusable = true; 749 } else if (viewIsCloserToBoundary) { 750 /* 751 * Partially contained view beats another partially 752 * contained view if it's closer 753 */ 754 focusCandidate = view; 755 } 756 } 757 } 758 } 759 } 760 761 return focusCandidate; 762 } 763 764 /** 765 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 766 * method will scroll the view by one page up or down and give the focus 767 * to the topmost/bottommost component in the new visible area. If no 768 * component is a good candidate for focus, this scrollview reclaims the 769 * focus.</p> 770 * 771 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 772 * to go one page up or 773 * {@link android.view.View#FOCUS_DOWN} to go one page down 774 * @return true if the key event is consumed by this method, false otherwise 775 */ 776 public boolean pageScroll(int direction) { 777 boolean down = direction == View.FOCUS_DOWN; 778 int height = getHeight(); 779 780 if (down) { 781 mTempRect.top = getScrollY() + height; 782 int count = getChildCount(); 783 if (count > 0) { 784 View view = getChildAt(count - 1); 785 if (mTempRect.top + height > view.getBottom()) { 786 mTempRect.top = view.getBottom() - height; 787 } 788 } 789 } else { 790 mTempRect.top = getScrollY() - height; 791 if (mTempRect.top < 0) { 792 mTempRect.top = 0; 793 } 794 } 795 mTempRect.bottom = mTempRect.top + height; 796 797 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 798 } 799 800 /** 801 * <p>Handles scrolling in response to a "home/end" shortcut press. This 802 * method will scroll the view to the top or bottom and give the focus 803 * to the topmost/bottommost component in the new visible area. If no 804 * component is a good candidate for focus, this scrollview reclaims the 805 * focus.</p> 806 * 807 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 808 * to go the top of the view or 809 * {@link android.view.View#FOCUS_DOWN} to go the bottom 810 * @return true if the key event is consumed by this method, false otherwise 811 */ 812 public boolean fullScroll(int direction) { 813 boolean down = direction == View.FOCUS_DOWN; 814 int height = getHeight(); 815 816 mTempRect.top = 0; 817 mTempRect.bottom = height; 818 819 if (down) { 820 int count = getChildCount(); 821 if (count > 0) { 822 View view = getChildAt(count - 1); 823 mTempRect.bottom = view.getBottom(); 824 mTempRect.top = mTempRect.bottom - height; 825 } 826 } 827 828 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 829 } 830 831 /** 832 * <p>Scrolls the view to make the area defined by <code>top</code> and 833 * <code>bottom</code> visible. This method attempts to give the focus 834 * to a component visible in this area. If no component can be focused in 835 * the new visible area, the focus is reclaimed by this scrollview.</p> 836 * 837 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 838 * to go upward 839 * {@link android.view.View#FOCUS_DOWN} to downward 840 * @param top the top offset of the new area to be made visible 841 * @param bottom the bottom offset of the new area to be made visible 842 * @return true if the key event is consumed by this method, false otherwise 843 */ 844 private boolean scrollAndFocus(int direction, int top, int bottom) { 845 boolean handled = true; 846 847 int height = getHeight(); 848 int containerTop = getScrollY(); 849 int containerBottom = containerTop + height; 850 boolean up = direction == View.FOCUS_UP; 851 852 View newFocused = findFocusableViewInBounds(up, top, bottom); 853 if (newFocused == null) { 854 newFocused = this; 855 } 856 857 if (top >= containerTop && bottom <= containerBottom) { 858 handled = false; 859 } else { 860 int delta = up ? (top - containerTop) : (bottom - containerBottom); 861 doScrollY(delta); 862 } 863 864 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 865 mScrollViewMovedFocus = true; 866 mScrollViewMovedFocus = false; 867 } 868 869 return handled; 870 } 871 872 /** 873 * Handle scrolling in response to an up or down arrow click. 874 * 875 * @param direction The direction corresponding to the arrow key that was 876 * pressed 877 * @return True if we consumed the event, false otherwise 878 */ 879 public boolean arrowScroll(int direction) { 880 881 View currentFocused = findFocus(); 882 if (currentFocused == this) currentFocused = null; 883 884 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 885 886 final int maxJump = getMaxScrollAmount(); 887 888 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 889 nextFocused.getDrawingRect(mTempRect); 890 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 891 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 892 doScrollY(scrollDelta); 893 nextFocused.requestFocus(direction); 894 } else { 895 // no new focus 896 int scrollDelta = maxJump; 897 898 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 899 scrollDelta = getScrollY(); 900 } else if (direction == View.FOCUS_DOWN) { 901 if (getChildCount() > 0) { 902 int daBottom = getChildAt(0).getBottom(); 903 904 int screenBottom = getScrollY() + getHeight(); 905 906 if (daBottom - screenBottom < maxJump) { 907 scrollDelta = daBottom - screenBottom; 908 } 909 } 910 } 911 if (scrollDelta == 0) { 912 return false; 913 } 914 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 915 } 916 917 if (currentFocused != null && currentFocused.isFocused() 918 && isOffScreen(currentFocused)) { 919 // previously focused item still has focus and is off screen, give 920 // it up (take it back to ourselves) 921 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 922 // sure to 923 // get it) 924 final int descendantFocusability = getDescendantFocusability(); // save 925 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 926 requestFocus(); 927 setDescendantFocusability(descendantFocusability); // restore 928 } 929 return true; 930 } 931 932 /** 933 * @return whether the descendant of this scroll view is scrolled off 934 * screen. 935 */ 936 private boolean isOffScreen(View descendant) { 937 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 938 } 939 940 /** 941 * @return whether the descendant of this scroll view is within delta 942 * pixels of being on the screen. 943 */ 944 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 945 descendant.getDrawingRect(mTempRect); 946 offsetDescendantRectToMyCoords(descendant, mTempRect); 947 948 return (mTempRect.bottom + delta) >= getScrollY() 949 && (mTempRect.top - delta) <= (getScrollY() + height); 950 } 951 952 /** 953 * Smooth scroll by a Y delta 954 * 955 * @param delta the number of pixels to scroll by on the Y axis 956 */ 957 private void doScrollY(int delta) { 958 if (delta != 0) { 959 if (mSmoothScrollingEnabled) { 960 smoothScrollBy(0, delta); 961 } else { 962 scrollBy(0, delta); 963 } 964 } 965 } 966 967 /** 968 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 969 * 970 * @param dx the number of pixels to scroll by on the X axis 971 * @param dy the number of pixels to scroll by on the Y axis 972 */ 973 public final void smoothScrollBy(int dx, int dy) { 974 if (getChildCount() == 0) { 975 // Nothing to do. 976 return; 977 } 978 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 979 if (duration > ANIMATED_SCROLL_GAP) { 980 final int height = getHeight() - mPaddingBottom - mPaddingTop; 981 final int bottom = getChildAt(0).getHeight(); 982 final int maxY = Math.max(0, bottom - height); 983 final int scrollY = mScrollY; 984 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 985 986 mScroller.startScroll(mScrollX, scrollY, 0, dy); 987 invalidate(); 988 } else { 989 if (!mScroller.isFinished()) { 990 mScroller.abortAnimation(); 991 } 992 scrollBy(dx, dy); 993 } 994 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 995 } 996 997 /** 998 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 999 * 1000 * @param x the position where to scroll on the X axis 1001 * @param y the position where to scroll on the Y axis 1002 */ 1003 public final void smoothScrollTo(int x, int y) { 1004 smoothScrollBy(x - mScrollX, y - mScrollY); 1005 } 1006 1007 /** 1008 * <p>The scroll range of a scroll view is the overall height of all of its 1009 * children.</p> 1010 */ 1011 @Override 1012 protected int computeVerticalScrollRange() { 1013 final int count = getChildCount(); 1014 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1015 if (count == 0) { 1016 return contentHeight; 1017 } 1018 1019 int scrollRange = getChildAt(0).getBottom(); 1020 final int scrollY = mScrollY; 1021 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1022 if (scrollY < 0) { 1023 scrollRange -= scrollY; 1024 } else if (scrollY > overscrollBottom) { 1025 scrollRange += scrollY - overscrollBottom; 1026 } 1027 1028 return scrollRange; 1029 } 1030 1031 @Override 1032 protected int computeVerticalScrollOffset() { 1033 return Math.max(0, super.computeVerticalScrollOffset()); 1034 } 1035 1036 @Override 1037 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1038 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1039 1040 int childWidthMeasureSpec; 1041 int childHeightMeasureSpec; 1042 1043 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1044 + mPaddingRight, lp.width); 1045 1046 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1047 1048 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1049 } 1050 1051 @Override 1052 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1053 int parentHeightMeasureSpec, int heightUsed) { 1054 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1055 1056 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1057 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1058 + widthUsed, lp.width); 1059 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1060 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1061 1062 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1063 } 1064 1065 @Override 1066 public void computeScroll() { 1067 if (mScroller.computeScrollOffset()) { 1068 // This is called at drawing time by ViewGroup. We don't want to 1069 // re-show the scrollbars at this point, which scrollTo will do, 1070 // so we replicate most of scrollTo here. 1071 // 1072 // It's a little odd to call onScrollChanged from inside the drawing. 1073 // 1074 // It is, except when you remember that computeScroll() is used to 1075 // animate scrolling. So unless we want to defer the onScrollChanged() 1076 // until the end of the animated scrolling, we don't really have a 1077 // choice here. 1078 // 1079 // I agree. The alternative, which I think would be worse, is to post 1080 // something and tell the subclasses later. This is bad because there 1081 // will be a window where mScrollX/Y is different from what the app 1082 // thinks it is. 1083 // 1084 int oldX = mScrollX; 1085 int oldY = mScrollY; 1086 int x = mScroller.getCurrX(); 1087 int y = mScroller.getCurrY(); 1088 1089 if (oldX != x || oldY != y) { 1090 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 1091 0, mOverflingDistance, false); 1092 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1093 1094 final int range = getScrollRange(); 1095 final int overscrollMode = getOverScrollMode(); 1096 if (overscrollMode == OVER_SCROLL_ALWAYS || 1097 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { 1098 if (y < 0 && oldY >= 0) { 1099 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1100 } else if (y > range && oldY <= range) { 1101 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1102 } 1103 } 1104 } 1105 awakenScrollBars(); 1106 1107 // Keep on drawing until the animation has finished. 1108 postInvalidate(); 1109 } 1110 } 1111 1112 /** 1113 * Scrolls the view to the given child. 1114 * 1115 * @param child the View to scroll to 1116 */ 1117 private void scrollToChild(View child) { 1118 child.getDrawingRect(mTempRect); 1119 1120 /* Offset from child's local coordinates to ScrollView coordinates */ 1121 offsetDescendantRectToMyCoords(child, mTempRect); 1122 1123 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1124 1125 if (scrollDelta != 0) { 1126 scrollBy(0, scrollDelta); 1127 } 1128 } 1129 1130 /** 1131 * If rect is off screen, scroll just enough to get it (or at least the 1132 * first screen size chunk of it) on screen. 1133 * 1134 * @param rect The rectangle. 1135 * @param immediate True to scroll immediately without animation 1136 * @return true if scrolling was performed 1137 */ 1138 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1139 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1140 final boolean scroll = delta != 0; 1141 if (scroll) { 1142 if (immediate) { 1143 scrollBy(0, delta); 1144 } else { 1145 smoothScrollBy(0, delta); 1146 } 1147 } 1148 return scroll; 1149 } 1150 1151 /** 1152 * Compute the amount to scroll in the Y direction in order to get 1153 * a rectangle completely on the screen (or, if taller than the screen, 1154 * at least the first screen size chunk of it). 1155 * 1156 * @param rect The rect. 1157 * @return The scroll delta. 1158 */ 1159 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1160 if (getChildCount() == 0) return 0; 1161 1162 int height = getHeight(); 1163 int screenTop = getScrollY(); 1164 int screenBottom = screenTop + height; 1165 1166 int fadingEdge = getVerticalFadingEdgeLength(); 1167 1168 // leave room for top fading edge as long as rect isn't at very top 1169 if (rect.top > 0) { 1170 screenTop += fadingEdge; 1171 } 1172 1173 // leave room for bottom fading edge as long as rect isn't at very bottom 1174 if (rect.bottom < getChildAt(0).getHeight()) { 1175 screenBottom -= fadingEdge; 1176 } 1177 1178 int scrollYDelta = 0; 1179 1180 if (rect.bottom > screenBottom && rect.top > screenTop) { 1181 // need to move down to get it in view: move down just enough so 1182 // that the entire rectangle is in view (or at least the first 1183 // screen size chunk). 1184 1185 if (rect.height() > height) { 1186 // just enough to get screen size chunk on 1187 scrollYDelta += (rect.top - screenTop); 1188 } else { 1189 // get entire rect at bottom of screen 1190 scrollYDelta += (rect.bottom - screenBottom); 1191 } 1192 1193 // make sure we aren't scrolling beyond the end of our content 1194 int bottom = getChildAt(0).getBottom(); 1195 int distanceToBottom = bottom - screenBottom; 1196 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1197 1198 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1199 // need to move up to get it in view: move up just enough so that 1200 // entire rectangle is in view (or at least the first screen 1201 // size chunk of it). 1202 1203 if (rect.height() > height) { 1204 // screen size chunk 1205 scrollYDelta -= (screenBottom - rect.bottom); 1206 } else { 1207 // entire rect at top 1208 scrollYDelta -= (screenTop - rect.top); 1209 } 1210 1211 // make sure we aren't scrolling any further than the top our content 1212 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1213 } 1214 return scrollYDelta; 1215 } 1216 1217 @Override 1218 public void requestChildFocus(View child, View focused) { 1219 if (!mScrollViewMovedFocus) { 1220 if (!mIsLayoutDirty) { 1221 scrollToChild(focused); 1222 } else { 1223 // The child may not be laid out yet, we can't compute the scroll yet 1224 mChildToScrollTo = focused; 1225 } 1226 } 1227 super.requestChildFocus(child, focused); 1228 } 1229 1230 1231 /** 1232 * When looking for focus in children of a scroll view, need to be a little 1233 * more careful not to give focus to something that is scrolled off screen. 1234 * 1235 * This is more expensive than the default {@link android.view.ViewGroup} 1236 * implementation, otherwise this behavior might have been made the default. 1237 */ 1238 @Override 1239 protected boolean onRequestFocusInDescendants(int direction, 1240 Rect previouslyFocusedRect) { 1241 1242 // convert from forward / backward notation to up / down / left / right 1243 // (ugh). 1244 if (direction == View.FOCUS_FORWARD) { 1245 direction = View.FOCUS_DOWN; 1246 } else if (direction == View.FOCUS_BACKWARD) { 1247 direction = View.FOCUS_UP; 1248 } 1249 1250 final View nextFocus = previouslyFocusedRect == null ? 1251 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1252 FocusFinder.getInstance().findNextFocusFromRect(this, 1253 previouslyFocusedRect, direction); 1254 1255 if (nextFocus == null) { 1256 return false; 1257 } 1258 1259 if (isOffScreen(nextFocus)) { 1260 return false; 1261 } 1262 1263 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1264 } 1265 1266 @Override 1267 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1268 boolean immediate) { 1269 // offset into coordinate space of this scroll view 1270 rectangle.offset(child.getLeft() - child.getScrollX(), 1271 child.getTop() - child.getScrollY()); 1272 1273 return scrollToChildRect(rectangle, immediate); 1274 } 1275 1276 @Override 1277 public void requestLayout() { 1278 mIsLayoutDirty = true; 1279 super.requestLayout(); 1280 } 1281 1282 @Override 1283 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1284 super.onLayout(changed, l, t, r, b); 1285 mIsLayoutDirty = false; 1286 // Give a child focus if it needs it 1287 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1288 scrollToChild(mChildToScrollTo); 1289 } 1290 mChildToScrollTo = null; 1291 1292 // Calling this with the present values causes it to re-clam them 1293 scrollTo(mScrollX, mScrollY); 1294 } 1295 1296 @Override 1297 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1298 super.onSizeChanged(w, h, oldw, oldh); 1299 1300 View currentFocused = findFocus(); 1301 if (null == currentFocused || this == currentFocused) 1302 return; 1303 1304 // If the currently-focused view was visible on the screen when the 1305 // screen was at the old height, then scroll the screen to make that 1306 // view visible with the new screen height. 1307 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1308 currentFocused.getDrawingRect(mTempRect); 1309 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1310 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1311 doScrollY(scrollDelta); 1312 } 1313 } 1314 1315 /** 1316 * Return true if child is an descendant of parent, (or equal to the parent). 1317 */ 1318 private boolean isViewDescendantOf(View child, View parent) { 1319 if (child == parent) { 1320 return true; 1321 } 1322 1323 final ViewParent theParent = child.getParent(); 1324 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1325 } 1326 1327 /** 1328 * Fling the scroll view 1329 * 1330 * @param velocityY The initial velocity in the Y direction. Positive 1331 * numbers mean that the finger/cursor is moving down the screen, 1332 * which means we want to scroll towards the top. 1333 */ 1334 public void fling(int velocityY) { 1335 if (getChildCount() > 0) { 1336 int height = getHeight() - mPaddingBottom - mPaddingTop; 1337 int bottom = getChildAt(0).getHeight(); 1338 1339 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1340 Math.max(0, bottom - height), 0, height/2); 1341 1342 final boolean movingDown = velocityY > 0; 1343 1344 View newFocused = 1345 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1346 if (newFocused == null) { 1347 newFocused = this; 1348 } 1349 1350 if (newFocused != findFocus() 1351 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1352 mScrollViewMovedFocus = true; 1353 mScrollViewMovedFocus = false; 1354 } 1355 1356 invalidate(); 1357 } 1358 } 1359 1360 /** 1361 * {@inheritDoc} 1362 * 1363 * <p>This version also clamps the scrolling to the bounds of our child. 1364 */ 1365 @Override 1366 public void scrollTo(int x, int y) { 1367 // we rely on the fact the View.scrollBy calls scrollTo. 1368 if (getChildCount() > 0) { 1369 View child = getChildAt(0); 1370 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1371 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1372 if (x != mScrollX || y != mScrollY) { 1373 super.scrollTo(x, y); 1374 } 1375 } 1376 } 1377 1378 @Override 1379 public void setOverScrollMode(int mode) { 1380 if (mode != OVER_SCROLL_NEVER) { 1381 if (mEdgeGlowTop == null) { 1382 final Resources res = getContext().getResources(); 1383 final Drawable edge = res.getDrawable(R.drawable.overscroll_edge); 1384 final Drawable glow = res.getDrawable(R.drawable.overscroll_glow); 1385 mEdgeGlowTop = new EdgeGlow(edge, glow); 1386 mEdgeGlowBottom = new EdgeGlow(edge, glow); 1387 } 1388 } else { 1389 mEdgeGlowTop = null; 1390 mEdgeGlowBottom = null; 1391 } 1392 super.setOverScrollMode(mode); 1393 } 1394 1395 @Override 1396 public void draw(Canvas canvas) { 1397 super.draw(canvas); 1398 if (mEdgeGlowTop != null) { 1399 final int scrollY = mScrollY; 1400 if (!mEdgeGlowTop.isFinished()) { 1401 final int restoreCount = canvas.save(); 1402 final int width = getWidth(); 1403 1404 canvas.translate(-width / 2, Math.min(0, scrollY)); 1405 mEdgeGlowTop.setSize(width * 2, getHeight()); 1406 if (mEdgeGlowTop.draw(canvas)) { 1407 invalidate(); 1408 } 1409 canvas.restoreToCount(restoreCount); 1410 } 1411 if (!mEdgeGlowBottom.isFinished()) { 1412 final int restoreCount = canvas.save(); 1413 final int width = getWidth(); 1414 final int height = getHeight(); 1415 1416 canvas.translate(-width / 2, Math.max(getScrollRange(), scrollY) + height); 1417 canvas.rotate(180, width, 0); 1418 mEdgeGlowBottom.setSize(width * 2, height); 1419 if (mEdgeGlowBottom.draw(canvas)) { 1420 invalidate(); 1421 } 1422 canvas.restoreToCount(restoreCount); 1423 } 1424 } 1425 } 1426 1427 private int clamp(int n, int my, int child) { 1428 if (my >= child || n < 0) { 1429 /* my >= child is this case: 1430 * |--------------- me ---------------| 1431 * |------ child ------| 1432 * or 1433 * |--------------- me ---------------| 1434 * |------ child ------| 1435 * or 1436 * |--------------- me ---------------| 1437 * |------ child ------| 1438 * 1439 * n < 0 is this case: 1440 * |------ me ------| 1441 * |-------- child --------| 1442 * |-- mScrollX --| 1443 */ 1444 return 0; 1445 } 1446 if ((my+n) > child) { 1447 /* this case: 1448 * |------ me ------| 1449 * |------ child ------| 1450 * |-- mScrollX --| 1451 */ 1452 return child-my; 1453 } 1454 return n; 1455 } 1456} 1457