ScrollView.java revision 4de94de9c5ad18e1162fa30dd1149211485297c0
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 if (!mEdgeGlowBottom.isFinished()) { 541 mEdgeGlowBottom.onRelease(); 542 } 543 } else if (pulledToY > range) { 544 mEdgeGlowBottom.onPull((float) deltaY / getHeight()); 545 if (!mEdgeGlowTop.isFinished()) { 546 mEdgeGlowTop.onRelease(); 547 } 548 } 549 } 550 } 551 break; 552 case MotionEvent.ACTION_UP: 553 if (mIsBeingDragged) { 554 final VelocityTracker velocityTracker = mVelocityTracker; 555 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 556 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 557 558 if (getChildCount() > 0) { 559 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 560 fling(-initialVelocity); 561 } else { 562 final int bottom = getScrollRange(); 563 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, bottom)) { 564 invalidate(); 565 } 566 } 567 } 568 569 mActivePointerId = INVALID_POINTER; 570 mIsBeingDragged = false; 571 572 if (mVelocityTracker != null) { 573 mVelocityTracker.recycle(); 574 mVelocityTracker = null; 575 } 576 if (mEdgeGlowTop != null) { 577 mEdgeGlowTop.onRelease(); 578 mEdgeGlowBottom.onRelease(); 579 } 580 } 581 break; 582 case MotionEvent.ACTION_CANCEL: 583 if (mIsBeingDragged && getChildCount() > 0) { 584 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 585 invalidate(); 586 } 587 mActivePointerId = INVALID_POINTER; 588 mIsBeingDragged = false; 589 if (mVelocityTracker != null) { 590 mVelocityTracker.recycle(); 591 mVelocityTracker = null; 592 } 593 if (mEdgeGlowTop != null) { 594 mEdgeGlowTop.onRelease(); 595 mEdgeGlowBottom.onRelease(); 596 } 597 } 598 break; 599 case MotionEvent.ACTION_POINTER_UP: 600 onSecondaryPointerUp(ev); 601 break; 602 } 603 return true; 604 } 605 606 private void onSecondaryPointerUp(MotionEvent ev) { 607 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 608 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 609 final int pointerId = ev.getPointerId(pointerIndex); 610 if (pointerId == mActivePointerId) { 611 // This was our active pointer going up. Choose a new 612 // active pointer and adjust accordingly. 613 // TODO: Make this decision more intelligent. 614 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 615 mLastMotionY = ev.getY(newPointerIndex); 616 mActivePointerId = ev.getPointerId(newPointerIndex); 617 if (mVelocityTracker != null) { 618 mVelocityTracker.clear(); 619 } 620 } 621 } 622 623 @Override 624 protected void onOverScrolled(int scrollX, int scrollY, 625 boolean clampedX, boolean clampedY) { 626 // Treat animating scrolls differently; see #computeScroll() for why. 627 if (!mScroller.isFinished()) { 628 mScrollX = scrollX; 629 mScrollY = scrollY; 630 if (clampedY) { 631 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 632 } 633 } else { 634 super.scrollTo(scrollX, scrollY); 635 } 636 awakenScrollBars(); 637 } 638 639 private int getScrollRange() { 640 int scrollRange = 0; 641 if (getChildCount() > 0) { 642 View child = getChildAt(0); 643 scrollRange = Math.max(0, 644 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); 645 } 646 return scrollRange; 647 } 648 649 /** 650 * <p> 651 * Finds the next focusable component that fits in this View's bounds 652 * (excluding fading edges) pretending that this View's top is located at 653 * the parameter top. 654 * </p> 655 * 656 * @param topFocus look for a candidate is the one at the top of the bounds 657 * if topFocus is true, or at the bottom of the bounds if topFocus is 658 * false 659 * @param top the top offset of the bounds in which a focusable must be 660 * found (the fading edge is assumed to start at this position) 661 * @param preferredFocusable the View that has highest priority and will be 662 * returned if it is within my bounds (null is valid) 663 * @return the next focusable component in the bounds or null if none can be 664 * found 665 */ 666 private View findFocusableViewInMyBounds(final boolean topFocus, 667 final int top, View preferredFocusable) { 668 /* 669 * The fading edge's transparent side should be considered for focus 670 * since it's mostly visible, so we divide the actual fading edge length 671 * by 2. 672 */ 673 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 674 final int topWithoutFadingEdge = top + fadingEdgeLength; 675 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 676 677 if ((preferredFocusable != null) 678 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 679 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 680 return preferredFocusable; 681 } 682 683 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 684 bottomWithoutFadingEdge); 685 } 686 687 /** 688 * <p> 689 * Finds the next focusable component that fits in the specified bounds. 690 * </p> 691 * 692 * @param topFocus look for a candidate is the one at the top of the bounds 693 * if topFocus is true, or at the bottom of the bounds if topFocus is 694 * false 695 * @param top the top offset of the bounds in which a focusable must be 696 * found 697 * @param bottom the bottom offset of the bounds in which a focusable must 698 * be found 699 * @return the next focusable component in the bounds or null if none can 700 * be found 701 */ 702 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 703 704 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 705 View focusCandidate = null; 706 707 /* 708 * A fully contained focusable is one where its top is below the bound's 709 * top, and its bottom is above the bound's bottom. A partially 710 * contained focusable is one where some part of it is within the 711 * bounds, but it also has some part that is not within bounds. A fully contained 712 * focusable is preferred to a partially contained focusable. 713 */ 714 boolean foundFullyContainedFocusable = false; 715 716 int count = focusables.size(); 717 for (int i = 0; i < count; i++) { 718 View view = focusables.get(i); 719 int viewTop = view.getTop(); 720 int viewBottom = view.getBottom(); 721 722 if (top < viewBottom && viewTop < bottom) { 723 /* 724 * the focusable is in the target area, it is a candidate for 725 * focusing 726 */ 727 728 final boolean viewIsFullyContained = (top < viewTop) && 729 (viewBottom < bottom); 730 731 if (focusCandidate == null) { 732 /* No candidate, take this one */ 733 focusCandidate = view; 734 foundFullyContainedFocusable = viewIsFullyContained; 735 } else { 736 final boolean viewIsCloserToBoundary = 737 (topFocus && viewTop < focusCandidate.getTop()) || 738 (!topFocus && viewBottom > focusCandidate 739 .getBottom()); 740 741 if (foundFullyContainedFocusable) { 742 if (viewIsFullyContained && viewIsCloserToBoundary) { 743 /* 744 * We're dealing with only fully contained views, so 745 * it has to be closer to the boundary to beat our 746 * candidate 747 */ 748 focusCandidate = view; 749 } 750 } else { 751 if (viewIsFullyContained) { 752 /* Any fully contained view beats a partially contained view */ 753 focusCandidate = view; 754 foundFullyContainedFocusable = true; 755 } else if (viewIsCloserToBoundary) { 756 /* 757 * Partially contained view beats another partially 758 * contained view if it's closer 759 */ 760 focusCandidate = view; 761 } 762 } 763 } 764 } 765 } 766 767 return focusCandidate; 768 } 769 770 /** 771 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 772 * method will scroll the view by one page up or down and give the focus 773 * to the topmost/bottommost component in the new visible area. If no 774 * component is a good candidate for focus, this scrollview reclaims the 775 * focus.</p> 776 * 777 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 778 * to go one page up or 779 * {@link android.view.View#FOCUS_DOWN} to go one page down 780 * @return true if the key event is consumed by this method, false otherwise 781 */ 782 public boolean pageScroll(int direction) { 783 boolean down = direction == View.FOCUS_DOWN; 784 int height = getHeight(); 785 786 if (down) { 787 mTempRect.top = getScrollY() + height; 788 int count = getChildCount(); 789 if (count > 0) { 790 View view = getChildAt(count - 1); 791 if (mTempRect.top + height > view.getBottom()) { 792 mTempRect.top = view.getBottom() - height; 793 } 794 } 795 } else { 796 mTempRect.top = getScrollY() - height; 797 if (mTempRect.top < 0) { 798 mTempRect.top = 0; 799 } 800 } 801 mTempRect.bottom = mTempRect.top + height; 802 803 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 804 } 805 806 /** 807 * <p>Handles scrolling in response to a "home/end" shortcut press. This 808 * method will scroll the view to the top or bottom and give the focus 809 * to the topmost/bottommost component in the new visible area. If no 810 * component is a good candidate for focus, this scrollview reclaims the 811 * focus.</p> 812 * 813 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 814 * to go the top of the view or 815 * {@link android.view.View#FOCUS_DOWN} to go the bottom 816 * @return true if the key event is consumed by this method, false otherwise 817 */ 818 public boolean fullScroll(int direction) { 819 boolean down = direction == View.FOCUS_DOWN; 820 int height = getHeight(); 821 822 mTempRect.top = 0; 823 mTempRect.bottom = height; 824 825 if (down) { 826 int count = getChildCount(); 827 if (count > 0) { 828 View view = getChildAt(count - 1); 829 mTempRect.bottom = view.getBottom(); 830 mTempRect.top = mTempRect.bottom - height; 831 } 832 } 833 834 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 835 } 836 837 /** 838 * <p>Scrolls the view to make the area defined by <code>top</code> and 839 * <code>bottom</code> visible. This method attempts to give the focus 840 * to a component visible in this area. If no component can be focused in 841 * the new visible area, the focus is reclaimed by this scrollview.</p> 842 * 843 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 844 * to go upward 845 * {@link android.view.View#FOCUS_DOWN} to downward 846 * @param top the top offset of the new area to be made visible 847 * @param bottom the bottom offset of the new area to be made visible 848 * @return true if the key event is consumed by this method, false otherwise 849 */ 850 private boolean scrollAndFocus(int direction, int top, int bottom) { 851 boolean handled = true; 852 853 int height = getHeight(); 854 int containerTop = getScrollY(); 855 int containerBottom = containerTop + height; 856 boolean up = direction == View.FOCUS_UP; 857 858 View newFocused = findFocusableViewInBounds(up, top, bottom); 859 if (newFocused == null) { 860 newFocused = this; 861 } 862 863 if (top >= containerTop && bottom <= containerBottom) { 864 handled = false; 865 } else { 866 int delta = up ? (top - containerTop) : (bottom - containerBottom); 867 doScrollY(delta); 868 } 869 870 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 871 mScrollViewMovedFocus = true; 872 mScrollViewMovedFocus = false; 873 } 874 875 return handled; 876 } 877 878 /** 879 * Handle scrolling in response to an up or down arrow click. 880 * 881 * @param direction The direction corresponding to the arrow key that was 882 * pressed 883 * @return True if we consumed the event, false otherwise 884 */ 885 public boolean arrowScroll(int direction) { 886 887 View currentFocused = findFocus(); 888 if (currentFocused == this) currentFocused = null; 889 890 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 891 892 final int maxJump = getMaxScrollAmount(); 893 894 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 895 nextFocused.getDrawingRect(mTempRect); 896 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 897 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 898 doScrollY(scrollDelta); 899 nextFocused.requestFocus(direction); 900 } else { 901 // no new focus 902 int scrollDelta = maxJump; 903 904 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 905 scrollDelta = getScrollY(); 906 } else if (direction == View.FOCUS_DOWN) { 907 if (getChildCount() > 0) { 908 int daBottom = getChildAt(0).getBottom(); 909 910 int screenBottom = getScrollY() + getHeight(); 911 912 if (daBottom - screenBottom < maxJump) { 913 scrollDelta = daBottom - screenBottom; 914 } 915 } 916 } 917 if (scrollDelta == 0) { 918 return false; 919 } 920 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 921 } 922 923 if (currentFocused != null && currentFocused.isFocused() 924 && isOffScreen(currentFocused)) { 925 // previously focused item still has focus and is off screen, give 926 // it up (take it back to ourselves) 927 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 928 // sure to 929 // get it) 930 final int descendantFocusability = getDescendantFocusability(); // save 931 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 932 requestFocus(); 933 setDescendantFocusability(descendantFocusability); // restore 934 } 935 return true; 936 } 937 938 /** 939 * @return whether the descendant of this scroll view is scrolled off 940 * screen. 941 */ 942 private boolean isOffScreen(View descendant) { 943 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 944 } 945 946 /** 947 * @return whether the descendant of this scroll view is within delta 948 * pixels of being on the screen. 949 */ 950 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 951 descendant.getDrawingRect(mTempRect); 952 offsetDescendantRectToMyCoords(descendant, mTempRect); 953 954 return (mTempRect.bottom + delta) >= getScrollY() 955 && (mTempRect.top - delta) <= (getScrollY() + height); 956 } 957 958 /** 959 * Smooth scroll by a Y delta 960 * 961 * @param delta the number of pixels to scroll by on the Y axis 962 */ 963 private void doScrollY(int delta) { 964 if (delta != 0) { 965 if (mSmoothScrollingEnabled) { 966 smoothScrollBy(0, delta); 967 } else { 968 scrollBy(0, delta); 969 } 970 } 971 } 972 973 /** 974 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 975 * 976 * @param dx the number of pixels to scroll by on the X axis 977 * @param dy the number of pixels to scroll by on the Y axis 978 */ 979 public final void smoothScrollBy(int dx, int dy) { 980 if (getChildCount() == 0) { 981 // Nothing to do. 982 return; 983 } 984 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 985 if (duration > ANIMATED_SCROLL_GAP) { 986 final int height = getHeight() - mPaddingBottom - mPaddingTop; 987 final int bottom = getChildAt(0).getHeight(); 988 final int maxY = Math.max(0, bottom - height); 989 final int scrollY = mScrollY; 990 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 991 992 mScroller.startScroll(mScrollX, scrollY, 0, dy); 993 invalidate(); 994 } else { 995 if (!mScroller.isFinished()) { 996 mScroller.abortAnimation(); 997 } 998 scrollBy(dx, dy); 999 } 1000 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1001 } 1002 1003 /** 1004 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1005 * 1006 * @param x the position where to scroll on the X axis 1007 * @param y the position where to scroll on the Y axis 1008 */ 1009 public final void smoothScrollTo(int x, int y) { 1010 smoothScrollBy(x - mScrollX, y - mScrollY); 1011 } 1012 1013 /** 1014 * <p>The scroll range of a scroll view is the overall height of all of its 1015 * children.</p> 1016 */ 1017 @Override 1018 protected int computeVerticalScrollRange() { 1019 final int count = getChildCount(); 1020 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1021 if (count == 0) { 1022 return contentHeight; 1023 } 1024 1025 int scrollRange = getChildAt(0).getBottom(); 1026 final int scrollY = mScrollY; 1027 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1028 if (scrollY < 0) { 1029 scrollRange -= scrollY; 1030 } else if (scrollY > overscrollBottom) { 1031 scrollRange += scrollY - overscrollBottom; 1032 } 1033 1034 return scrollRange; 1035 } 1036 1037 @Override 1038 protected int computeVerticalScrollOffset() { 1039 return Math.max(0, super.computeVerticalScrollOffset()); 1040 } 1041 1042 @Override 1043 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1044 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1045 1046 int childWidthMeasureSpec; 1047 int childHeightMeasureSpec; 1048 1049 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1050 + mPaddingRight, lp.width); 1051 1052 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1053 1054 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1055 } 1056 1057 @Override 1058 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1059 int parentHeightMeasureSpec, int heightUsed) { 1060 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1061 1062 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1063 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1064 + widthUsed, lp.width); 1065 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1066 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1067 1068 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1069 } 1070 1071 @Override 1072 public void computeScroll() { 1073 if (mScroller.computeScrollOffset()) { 1074 // This is called at drawing time by ViewGroup. We don't want to 1075 // re-show the scrollbars at this point, which scrollTo will do, 1076 // so we replicate most of scrollTo here. 1077 // 1078 // It's a little odd to call onScrollChanged from inside the drawing. 1079 // 1080 // It is, except when you remember that computeScroll() is used to 1081 // animate scrolling. So unless we want to defer the onScrollChanged() 1082 // until the end of the animated scrolling, we don't really have a 1083 // choice here. 1084 // 1085 // I agree. The alternative, which I think would be worse, is to post 1086 // something and tell the subclasses later. This is bad because there 1087 // will be a window where mScrollX/Y is different from what the app 1088 // thinks it is. 1089 // 1090 int oldX = mScrollX; 1091 int oldY = mScrollY; 1092 int x = mScroller.getCurrX(); 1093 int y = mScroller.getCurrY(); 1094 1095 if (oldX != x || oldY != y) { 1096 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 1097 0, mOverflingDistance, false); 1098 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1099 1100 final int range = getScrollRange(); 1101 final int overscrollMode = getOverScrollMode(); 1102 if (overscrollMode == OVER_SCROLL_ALWAYS || 1103 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { 1104 if (y < 0 && oldY >= 0) { 1105 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1106 } else if (y > range && oldY <= range) { 1107 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1108 } 1109 } 1110 } 1111 awakenScrollBars(); 1112 1113 // Keep on drawing until the animation has finished. 1114 postInvalidate(); 1115 } 1116 } 1117 1118 /** 1119 * Scrolls the view to the given child. 1120 * 1121 * @param child the View to scroll to 1122 */ 1123 private void scrollToChild(View child) { 1124 child.getDrawingRect(mTempRect); 1125 1126 /* Offset from child's local coordinates to ScrollView coordinates */ 1127 offsetDescendantRectToMyCoords(child, mTempRect); 1128 1129 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1130 1131 if (scrollDelta != 0) { 1132 scrollBy(0, scrollDelta); 1133 } 1134 } 1135 1136 /** 1137 * If rect is off screen, scroll just enough to get it (or at least the 1138 * first screen size chunk of it) on screen. 1139 * 1140 * @param rect The rectangle. 1141 * @param immediate True to scroll immediately without animation 1142 * @return true if scrolling was performed 1143 */ 1144 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1145 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1146 final boolean scroll = delta != 0; 1147 if (scroll) { 1148 if (immediate) { 1149 scrollBy(0, delta); 1150 } else { 1151 smoothScrollBy(0, delta); 1152 } 1153 } 1154 return scroll; 1155 } 1156 1157 /** 1158 * Compute the amount to scroll in the Y direction in order to get 1159 * a rectangle completely on the screen (or, if taller than the screen, 1160 * at least the first screen size chunk of it). 1161 * 1162 * @param rect The rect. 1163 * @return The scroll delta. 1164 */ 1165 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1166 if (getChildCount() == 0) return 0; 1167 1168 int height = getHeight(); 1169 int screenTop = getScrollY(); 1170 int screenBottom = screenTop + height; 1171 1172 int fadingEdge = getVerticalFadingEdgeLength(); 1173 1174 // leave room for top fading edge as long as rect isn't at very top 1175 if (rect.top > 0) { 1176 screenTop += fadingEdge; 1177 } 1178 1179 // leave room for bottom fading edge as long as rect isn't at very bottom 1180 if (rect.bottom < getChildAt(0).getHeight()) { 1181 screenBottom -= fadingEdge; 1182 } 1183 1184 int scrollYDelta = 0; 1185 1186 if (rect.bottom > screenBottom && rect.top > screenTop) { 1187 // need to move down to get it in view: move down just enough so 1188 // that the entire rectangle is in view (or at least the first 1189 // screen size chunk). 1190 1191 if (rect.height() > height) { 1192 // just enough to get screen size chunk on 1193 scrollYDelta += (rect.top - screenTop); 1194 } else { 1195 // get entire rect at bottom of screen 1196 scrollYDelta += (rect.bottom - screenBottom); 1197 } 1198 1199 // make sure we aren't scrolling beyond the end of our content 1200 int bottom = getChildAt(0).getBottom(); 1201 int distanceToBottom = bottom - screenBottom; 1202 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1203 1204 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1205 // need to move up to get it in view: move up just enough so that 1206 // entire rectangle is in view (or at least the first screen 1207 // size chunk of it). 1208 1209 if (rect.height() > height) { 1210 // screen size chunk 1211 scrollYDelta -= (screenBottom - rect.bottom); 1212 } else { 1213 // entire rect at top 1214 scrollYDelta -= (screenTop - rect.top); 1215 } 1216 1217 // make sure we aren't scrolling any further than the top our content 1218 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1219 } 1220 return scrollYDelta; 1221 } 1222 1223 @Override 1224 public void requestChildFocus(View child, View focused) { 1225 if (!mScrollViewMovedFocus) { 1226 if (!mIsLayoutDirty) { 1227 scrollToChild(focused); 1228 } else { 1229 // The child may not be laid out yet, we can't compute the scroll yet 1230 mChildToScrollTo = focused; 1231 } 1232 } 1233 super.requestChildFocus(child, focused); 1234 } 1235 1236 1237 /** 1238 * When looking for focus in children of a scroll view, need to be a little 1239 * more careful not to give focus to something that is scrolled off screen. 1240 * 1241 * This is more expensive than the default {@link android.view.ViewGroup} 1242 * implementation, otherwise this behavior might have been made the default. 1243 */ 1244 @Override 1245 protected boolean onRequestFocusInDescendants(int direction, 1246 Rect previouslyFocusedRect) { 1247 1248 // convert from forward / backward notation to up / down / left / right 1249 // (ugh). 1250 if (direction == View.FOCUS_FORWARD) { 1251 direction = View.FOCUS_DOWN; 1252 } else if (direction == View.FOCUS_BACKWARD) { 1253 direction = View.FOCUS_UP; 1254 } 1255 1256 final View nextFocus = previouslyFocusedRect == null ? 1257 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1258 FocusFinder.getInstance().findNextFocusFromRect(this, 1259 previouslyFocusedRect, direction); 1260 1261 if (nextFocus == null) { 1262 return false; 1263 } 1264 1265 if (isOffScreen(nextFocus)) { 1266 return false; 1267 } 1268 1269 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1270 } 1271 1272 @Override 1273 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1274 boolean immediate) { 1275 // offset into coordinate space of this scroll view 1276 rectangle.offset(child.getLeft() - child.getScrollX(), 1277 child.getTop() - child.getScrollY()); 1278 1279 return scrollToChildRect(rectangle, immediate); 1280 } 1281 1282 @Override 1283 public void requestLayout() { 1284 mIsLayoutDirty = true; 1285 super.requestLayout(); 1286 } 1287 1288 @Override 1289 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1290 super.onLayout(changed, l, t, r, b); 1291 mIsLayoutDirty = false; 1292 // Give a child focus if it needs it 1293 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1294 scrollToChild(mChildToScrollTo); 1295 } 1296 mChildToScrollTo = null; 1297 1298 // Calling this with the present values causes it to re-clam them 1299 scrollTo(mScrollX, mScrollY); 1300 } 1301 1302 @Override 1303 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1304 super.onSizeChanged(w, h, oldw, oldh); 1305 1306 View currentFocused = findFocus(); 1307 if (null == currentFocused || this == currentFocused) 1308 return; 1309 1310 // If the currently-focused view was visible on the screen when the 1311 // screen was at the old height, then scroll the screen to make that 1312 // view visible with the new screen height. 1313 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1314 currentFocused.getDrawingRect(mTempRect); 1315 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1316 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1317 doScrollY(scrollDelta); 1318 } 1319 } 1320 1321 /** 1322 * Return true if child is an descendant of parent, (or equal to the parent). 1323 */ 1324 private boolean isViewDescendantOf(View child, View parent) { 1325 if (child == parent) { 1326 return true; 1327 } 1328 1329 final ViewParent theParent = child.getParent(); 1330 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1331 } 1332 1333 /** 1334 * Fling the scroll view 1335 * 1336 * @param velocityY The initial velocity in the Y direction. Positive 1337 * numbers mean that the finger/cursor is moving down the screen, 1338 * which means we want to scroll towards the top. 1339 */ 1340 public void fling(int velocityY) { 1341 if (getChildCount() > 0) { 1342 int height = getHeight() - mPaddingBottom - mPaddingTop; 1343 int bottom = getChildAt(0).getHeight(); 1344 1345 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1346 Math.max(0, bottom - height), 0, height/2); 1347 1348 final boolean movingDown = velocityY > 0; 1349 1350 View newFocused = 1351 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1352 if (newFocused == null) { 1353 newFocused = this; 1354 } 1355 1356 if (newFocused != findFocus() 1357 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1358 mScrollViewMovedFocus = true; 1359 mScrollViewMovedFocus = false; 1360 } 1361 1362 invalidate(); 1363 } 1364 } 1365 1366 /** 1367 * {@inheritDoc} 1368 * 1369 * <p>This version also clamps the scrolling to the bounds of our child. 1370 */ 1371 @Override 1372 public void scrollTo(int x, int y) { 1373 // we rely on the fact the View.scrollBy calls scrollTo. 1374 if (getChildCount() > 0) { 1375 View child = getChildAt(0); 1376 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1377 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1378 if (x != mScrollX || y != mScrollY) { 1379 super.scrollTo(x, y); 1380 } 1381 } 1382 } 1383 1384 @Override 1385 public void setOverScrollMode(int mode) { 1386 if (mode != OVER_SCROLL_NEVER) { 1387 if (mEdgeGlowTop == null) { 1388 final Resources res = getContext().getResources(); 1389 final Drawable edge = res.getDrawable(R.drawable.overscroll_edge); 1390 final Drawable glow = res.getDrawable(R.drawable.overscroll_glow); 1391 mEdgeGlowTop = new EdgeGlow(edge, glow); 1392 mEdgeGlowBottom = new EdgeGlow(edge, glow); 1393 } 1394 } else { 1395 mEdgeGlowTop = null; 1396 mEdgeGlowBottom = null; 1397 } 1398 super.setOverScrollMode(mode); 1399 } 1400 1401 @Override 1402 public void draw(Canvas canvas) { 1403 super.draw(canvas); 1404 if (mEdgeGlowTop != null) { 1405 final int scrollY = mScrollY; 1406 if (!mEdgeGlowTop.isFinished()) { 1407 final int restoreCount = canvas.save(); 1408 final int width = getWidth(); 1409 1410 canvas.translate(-width / 2, Math.min(0, scrollY)); 1411 mEdgeGlowTop.setSize(width * 2, getHeight()); 1412 if (mEdgeGlowTop.draw(canvas)) { 1413 invalidate(); 1414 } 1415 canvas.restoreToCount(restoreCount); 1416 } 1417 if (!mEdgeGlowBottom.isFinished()) { 1418 final int restoreCount = canvas.save(); 1419 final int width = getWidth(); 1420 final int height = getHeight(); 1421 1422 canvas.translate(-width / 2, Math.max(getScrollRange(), scrollY) + height); 1423 canvas.rotate(180, width, 0); 1424 mEdgeGlowBottom.setSize(width * 2, height); 1425 if (mEdgeGlowBottom.draw(canvas)) { 1426 invalidate(); 1427 } 1428 canvas.restoreToCount(restoreCount); 1429 } 1430 } 1431 } 1432 1433 private int clamp(int n, int my, int child) { 1434 if (my >= child || n < 0) { 1435 /* my >= child is this case: 1436 * |--------------- me ---------------| 1437 * |------ child ------| 1438 * or 1439 * |--------------- me ---------------| 1440 * |------ child ------| 1441 * or 1442 * |--------------- me ---------------| 1443 * |------ child ------| 1444 * 1445 * n < 0 is this case: 1446 * |------ me ------| 1447 * |-------- child --------| 1448 * |-- mScrollX --| 1449 */ 1450 return 0; 1451 } 1452 if ((my+n) > child) { 1453 /* this case: 1454 * |------ me ------| 1455 * |------ child ------| 1456 * |-- mScrollX --| 1457 */ 1458 return child-my; 1459 } 1460 return n; 1461 } 1462} 1463