ScrollView.java revision 39bc6197baa7482dd070878a63992e8212965a4d
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 mIsBeingDragged = getChildCount() != 0; 501 if (!mIsBeingDragged) { 502 return false; 503 } 504 505 /* 506 * If being flinged and user touches, stop the fling. isFinished 507 * will be false if being flinged. 508 */ 509 if (!mScroller.isFinished()) { 510 mScroller.abortAnimation(); 511 } 512 513 // Remember where the motion event started 514 mLastMotionY = ev.getY(); 515 mActivePointerId = ev.getPointerId(0); 516 break; 517 } 518 case MotionEvent.ACTION_MOVE: 519 if (mIsBeingDragged) { 520 // Scroll to follow the motion event 521 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 522 final float y = ev.getY(activePointerIndex); 523 final int deltaY = (int) (mLastMotionY - y); 524 mLastMotionY = y; 525 526 final int oldX = mScrollX; 527 final int oldY = mScrollY; 528 final int range = getScrollRange(); 529 if (overScrollBy(0, deltaY, 0, mScrollY, 0, range, 530 0, mOverscrollDistance, true)) { 531 // Break our velocity if we hit a scroll barrier. 532 mVelocityTracker.clear(); 533 } 534 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 535 536 final int overscrollMode = getOverScrollMode(); 537 if (overscrollMode == OVER_SCROLL_ALWAYS || 538 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { 539 final int pulledToY = oldY + deltaY; 540 if (pulledToY < 0) { 541 mEdgeGlowTop.onPull((float) deltaY / getHeight()); 542 if (!mEdgeGlowBottom.isFinished()) { 543 mEdgeGlowBottom.onRelease(); 544 } 545 } else if (pulledToY > range) { 546 mEdgeGlowBottom.onPull((float) deltaY / getHeight()); 547 if (!mEdgeGlowTop.isFinished()) { 548 mEdgeGlowTop.onRelease(); 549 } 550 } 551 if (mEdgeGlowTop != null 552 && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) { 553 invalidate(); 554 } 555 } 556 } 557 break; 558 case MotionEvent.ACTION_UP: 559 if (mIsBeingDragged) { 560 final VelocityTracker velocityTracker = mVelocityTracker; 561 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 562 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 563 564 if (getChildCount() > 0) { 565 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 566 fling(-initialVelocity); 567 } else { 568 final int bottom = getScrollRange(); 569 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, bottom)) { 570 invalidate(); 571 } 572 } 573 } 574 575 mActivePointerId = INVALID_POINTER; 576 mIsBeingDragged = false; 577 578 if (mVelocityTracker != null) { 579 mVelocityTracker.recycle(); 580 mVelocityTracker = null; 581 } 582 if (mEdgeGlowTop != null) { 583 mEdgeGlowTop.onRelease(); 584 mEdgeGlowBottom.onRelease(); 585 } 586 } 587 break; 588 case MotionEvent.ACTION_CANCEL: 589 if (mIsBeingDragged && getChildCount() > 0) { 590 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 591 invalidate(); 592 } 593 mActivePointerId = INVALID_POINTER; 594 mIsBeingDragged = false; 595 if (mVelocityTracker != null) { 596 mVelocityTracker.recycle(); 597 mVelocityTracker = null; 598 } 599 if (mEdgeGlowTop != null) { 600 mEdgeGlowTop.onRelease(); 601 mEdgeGlowBottom.onRelease(); 602 } 603 } 604 break; 605 case MotionEvent.ACTION_POINTER_UP: 606 onSecondaryPointerUp(ev); 607 break; 608 } 609 return true; 610 } 611 612 private void onSecondaryPointerUp(MotionEvent ev) { 613 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 614 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 615 final int pointerId = ev.getPointerId(pointerIndex); 616 if (pointerId == mActivePointerId) { 617 // This was our active pointer going up. Choose a new 618 // active pointer and adjust accordingly. 619 // TODO: Make this decision more intelligent. 620 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 621 mLastMotionY = ev.getY(newPointerIndex); 622 mActivePointerId = ev.getPointerId(newPointerIndex); 623 if (mVelocityTracker != null) { 624 mVelocityTracker.clear(); 625 } 626 } 627 } 628 629 @Override 630 protected void onOverScrolled(int scrollX, int scrollY, 631 boolean clampedX, boolean clampedY) { 632 // Treat animating scrolls differently; see #computeScroll() for why. 633 if (!mScroller.isFinished()) { 634 mScrollX = scrollX; 635 mScrollY = scrollY; 636 if (clampedY) { 637 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 638 } 639 } else { 640 super.scrollTo(scrollX, scrollY); 641 } 642 awakenScrollBars(); 643 } 644 645 private int getScrollRange() { 646 int scrollRange = 0; 647 if (getChildCount() > 0) { 648 View child = getChildAt(0); 649 scrollRange = Math.max(0, 650 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); 651 } 652 return scrollRange; 653 } 654 655 /** 656 * <p> 657 * Finds the next focusable component that fits in this View's bounds 658 * (excluding fading edges) pretending that this View's top is located at 659 * the parameter top. 660 * </p> 661 * 662 * @param topFocus look for a candidate is the one at the top of the bounds 663 * if topFocus is true, or at the bottom of the bounds if topFocus is 664 * false 665 * @param top the top offset of the bounds in which a focusable must be 666 * found (the fading edge is assumed to start at this position) 667 * @param preferredFocusable the View that has highest priority and will be 668 * returned if it is within my bounds (null is valid) 669 * @return the next focusable component in the bounds or null if none can be 670 * found 671 */ 672 private View findFocusableViewInMyBounds(final boolean topFocus, 673 final int top, View preferredFocusable) { 674 /* 675 * The fading edge's transparent side should be considered for focus 676 * since it's mostly visible, so we divide the actual fading edge length 677 * by 2. 678 */ 679 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 680 final int topWithoutFadingEdge = top + fadingEdgeLength; 681 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 682 683 if ((preferredFocusable != null) 684 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 685 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 686 return preferredFocusable; 687 } 688 689 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 690 bottomWithoutFadingEdge); 691 } 692 693 /** 694 * <p> 695 * Finds the next focusable component that fits in the specified bounds. 696 * </p> 697 * 698 * @param topFocus look for a candidate is the one at the top of the bounds 699 * if topFocus is true, or at the bottom of the bounds if topFocus is 700 * false 701 * @param top the top offset of the bounds in which a focusable must be 702 * found 703 * @param bottom the bottom offset of the bounds in which a focusable must 704 * be found 705 * @return the next focusable component in the bounds or null if none can 706 * be found 707 */ 708 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 709 710 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 711 View focusCandidate = null; 712 713 /* 714 * A fully contained focusable is one where its top is below the bound's 715 * top, and its bottom is above the bound's bottom. A partially 716 * contained focusable is one where some part of it is within the 717 * bounds, but it also has some part that is not within bounds. A fully contained 718 * focusable is preferred to a partially contained focusable. 719 */ 720 boolean foundFullyContainedFocusable = false; 721 722 int count = focusables.size(); 723 for (int i = 0; i < count; i++) { 724 View view = focusables.get(i); 725 int viewTop = view.getTop(); 726 int viewBottom = view.getBottom(); 727 728 if (top < viewBottom && viewTop < bottom) { 729 /* 730 * the focusable is in the target area, it is a candidate for 731 * focusing 732 */ 733 734 final boolean viewIsFullyContained = (top < viewTop) && 735 (viewBottom < bottom); 736 737 if (focusCandidate == null) { 738 /* No candidate, take this one */ 739 focusCandidate = view; 740 foundFullyContainedFocusable = viewIsFullyContained; 741 } else { 742 final boolean viewIsCloserToBoundary = 743 (topFocus && viewTop < focusCandidate.getTop()) || 744 (!topFocus && viewBottom > focusCandidate 745 .getBottom()); 746 747 if (foundFullyContainedFocusable) { 748 if (viewIsFullyContained && viewIsCloserToBoundary) { 749 /* 750 * We're dealing with only fully contained views, so 751 * it has to be closer to the boundary to beat our 752 * candidate 753 */ 754 focusCandidate = view; 755 } 756 } else { 757 if (viewIsFullyContained) { 758 /* Any fully contained view beats a partially contained view */ 759 focusCandidate = view; 760 foundFullyContainedFocusable = true; 761 } else if (viewIsCloserToBoundary) { 762 /* 763 * Partially contained view beats another partially 764 * contained view if it's closer 765 */ 766 focusCandidate = view; 767 } 768 } 769 } 770 } 771 } 772 773 return focusCandidate; 774 } 775 776 /** 777 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 778 * method will scroll the view by one page up or down and give the focus 779 * to the topmost/bottommost component in the new visible area. If no 780 * component is a good candidate for focus, this scrollview reclaims the 781 * focus.</p> 782 * 783 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 784 * to go one page up or 785 * {@link android.view.View#FOCUS_DOWN} to go one page down 786 * @return true if the key event is consumed by this method, false otherwise 787 */ 788 public boolean pageScroll(int direction) { 789 boolean down = direction == View.FOCUS_DOWN; 790 int height = getHeight(); 791 792 if (down) { 793 mTempRect.top = getScrollY() + height; 794 int count = getChildCount(); 795 if (count > 0) { 796 View view = getChildAt(count - 1); 797 if (mTempRect.top + height > view.getBottom()) { 798 mTempRect.top = view.getBottom() - height; 799 } 800 } 801 } else { 802 mTempRect.top = getScrollY() - height; 803 if (mTempRect.top < 0) { 804 mTempRect.top = 0; 805 } 806 } 807 mTempRect.bottom = mTempRect.top + height; 808 809 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 810 } 811 812 /** 813 * <p>Handles scrolling in response to a "home/end" shortcut press. This 814 * method will scroll the view to the top or bottom and give the focus 815 * to the topmost/bottommost component in the new visible area. If no 816 * component is a good candidate for focus, this scrollview reclaims the 817 * focus.</p> 818 * 819 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 820 * to go the top of the view or 821 * {@link android.view.View#FOCUS_DOWN} to go the bottom 822 * @return true if the key event is consumed by this method, false otherwise 823 */ 824 public boolean fullScroll(int direction) { 825 boolean down = direction == View.FOCUS_DOWN; 826 int height = getHeight(); 827 828 mTempRect.top = 0; 829 mTempRect.bottom = height; 830 831 if (down) { 832 int count = getChildCount(); 833 if (count > 0) { 834 View view = getChildAt(count - 1); 835 mTempRect.bottom = view.getBottom(); 836 mTempRect.top = mTempRect.bottom - height; 837 } 838 } 839 840 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 841 } 842 843 /** 844 * <p>Scrolls the view to make the area defined by <code>top</code> and 845 * <code>bottom</code> visible. This method attempts to give the focus 846 * to a component visible in this area. If no component can be focused in 847 * the new visible area, the focus is reclaimed by this scrollview.</p> 848 * 849 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 850 * to go upward 851 * {@link android.view.View#FOCUS_DOWN} to downward 852 * @param top the top offset of the new area to be made visible 853 * @param bottom the bottom offset of the new area to be made visible 854 * @return true if the key event is consumed by this method, false otherwise 855 */ 856 private boolean scrollAndFocus(int direction, int top, int bottom) { 857 boolean handled = true; 858 859 int height = getHeight(); 860 int containerTop = getScrollY(); 861 int containerBottom = containerTop + height; 862 boolean up = direction == View.FOCUS_UP; 863 864 View newFocused = findFocusableViewInBounds(up, top, bottom); 865 if (newFocused == null) { 866 newFocused = this; 867 } 868 869 if (top >= containerTop && bottom <= containerBottom) { 870 handled = false; 871 } else { 872 int delta = up ? (top - containerTop) : (bottom - containerBottom); 873 doScrollY(delta); 874 } 875 876 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 877 mScrollViewMovedFocus = true; 878 mScrollViewMovedFocus = false; 879 } 880 881 return handled; 882 } 883 884 /** 885 * Handle scrolling in response to an up or down arrow click. 886 * 887 * @param direction The direction corresponding to the arrow key that was 888 * pressed 889 * @return True if we consumed the event, false otherwise 890 */ 891 public boolean arrowScroll(int direction) { 892 893 View currentFocused = findFocus(); 894 if (currentFocused == this) currentFocused = null; 895 896 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 897 898 final int maxJump = getMaxScrollAmount(); 899 900 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 901 nextFocused.getDrawingRect(mTempRect); 902 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 903 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 904 doScrollY(scrollDelta); 905 nextFocused.requestFocus(direction); 906 } else { 907 // no new focus 908 int scrollDelta = maxJump; 909 910 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 911 scrollDelta = getScrollY(); 912 } else if (direction == View.FOCUS_DOWN) { 913 if (getChildCount() > 0) { 914 int daBottom = getChildAt(0).getBottom(); 915 916 int screenBottom = getScrollY() + getHeight(); 917 918 if (daBottom - screenBottom < maxJump) { 919 scrollDelta = daBottom - screenBottom; 920 } 921 } 922 } 923 if (scrollDelta == 0) { 924 return false; 925 } 926 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 927 } 928 929 if (currentFocused != null && currentFocused.isFocused() 930 && isOffScreen(currentFocused)) { 931 // previously focused item still has focus and is off screen, give 932 // it up (take it back to ourselves) 933 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 934 // sure to 935 // get it) 936 final int descendantFocusability = getDescendantFocusability(); // save 937 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 938 requestFocus(); 939 setDescendantFocusability(descendantFocusability); // restore 940 } 941 return true; 942 } 943 944 /** 945 * @return whether the descendant of this scroll view is scrolled off 946 * screen. 947 */ 948 private boolean isOffScreen(View descendant) { 949 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 950 } 951 952 /** 953 * @return whether the descendant of this scroll view is within delta 954 * pixels of being on the screen. 955 */ 956 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 957 descendant.getDrawingRect(mTempRect); 958 offsetDescendantRectToMyCoords(descendant, mTempRect); 959 960 return (mTempRect.bottom + delta) >= getScrollY() 961 && (mTempRect.top - delta) <= (getScrollY() + height); 962 } 963 964 /** 965 * Smooth scroll by a Y delta 966 * 967 * @param delta the number of pixels to scroll by on the Y axis 968 */ 969 private void doScrollY(int delta) { 970 if (delta != 0) { 971 if (mSmoothScrollingEnabled) { 972 smoothScrollBy(0, delta); 973 } else { 974 scrollBy(0, delta); 975 } 976 } 977 } 978 979 /** 980 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 981 * 982 * @param dx the number of pixels to scroll by on the X axis 983 * @param dy the number of pixels to scroll by on the Y axis 984 */ 985 public final void smoothScrollBy(int dx, int dy) { 986 if (getChildCount() == 0) { 987 // Nothing to do. 988 return; 989 } 990 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 991 if (duration > ANIMATED_SCROLL_GAP) { 992 final int height = getHeight() - mPaddingBottom - mPaddingTop; 993 final int bottom = getChildAt(0).getHeight(); 994 final int maxY = Math.max(0, bottom - height); 995 final int scrollY = mScrollY; 996 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 997 998 mScroller.startScroll(mScrollX, scrollY, 0, dy); 999 invalidate(); 1000 } else { 1001 if (!mScroller.isFinished()) { 1002 mScroller.abortAnimation(); 1003 } 1004 scrollBy(dx, dy); 1005 } 1006 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1007 } 1008 1009 /** 1010 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1011 * 1012 * @param x the position where to scroll on the X axis 1013 * @param y the position where to scroll on the Y axis 1014 */ 1015 public final void smoothScrollTo(int x, int y) { 1016 smoothScrollBy(x - mScrollX, y - mScrollY); 1017 } 1018 1019 /** 1020 * <p>The scroll range of a scroll view is the overall height of all of its 1021 * children.</p> 1022 */ 1023 @Override 1024 protected int computeVerticalScrollRange() { 1025 final int count = getChildCount(); 1026 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1027 if (count == 0) { 1028 return contentHeight; 1029 } 1030 1031 int scrollRange = getChildAt(0).getBottom(); 1032 final int scrollY = mScrollY; 1033 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1034 if (scrollY < 0) { 1035 scrollRange -= scrollY; 1036 } else if (scrollY > overscrollBottom) { 1037 scrollRange += scrollY - overscrollBottom; 1038 } 1039 1040 return scrollRange; 1041 } 1042 1043 @Override 1044 protected int computeVerticalScrollOffset() { 1045 return Math.max(0, super.computeVerticalScrollOffset()); 1046 } 1047 1048 @Override 1049 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1050 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1051 1052 int childWidthMeasureSpec; 1053 int childHeightMeasureSpec; 1054 1055 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1056 + mPaddingRight, lp.width); 1057 1058 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1059 1060 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1061 } 1062 1063 @Override 1064 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1065 int parentHeightMeasureSpec, int heightUsed) { 1066 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1067 1068 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1069 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1070 + widthUsed, lp.width); 1071 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1072 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1073 1074 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1075 } 1076 1077 @Override 1078 public void computeScroll() { 1079 if (mScroller.computeScrollOffset()) { 1080 // This is called at drawing time by ViewGroup. We don't want to 1081 // re-show the scrollbars at this point, which scrollTo will do, 1082 // so we replicate most of scrollTo here. 1083 // 1084 // It's a little odd to call onScrollChanged from inside the drawing. 1085 // 1086 // It is, except when you remember that computeScroll() is used to 1087 // animate scrolling. So unless we want to defer the onScrollChanged() 1088 // until the end of the animated scrolling, we don't really have a 1089 // choice here. 1090 // 1091 // I agree. The alternative, which I think would be worse, is to post 1092 // something and tell the subclasses later. This is bad because there 1093 // will be a window where mScrollX/Y is different from what the app 1094 // thinks it is. 1095 // 1096 int oldX = mScrollX; 1097 int oldY = mScrollY; 1098 int x = mScroller.getCurrX(); 1099 int y = mScroller.getCurrY(); 1100 1101 if (oldX != x || oldY != y) { 1102 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 1103 0, mOverflingDistance, false); 1104 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1105 1106 final int range = getScrollRange(); 1107 final int overscrollMode = getOverScrollMode(); 1108 if (overscrollMode == OVER_SCROLL_ALWAYS || 1109 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0)) { 1110 if (y < 0 && oldY >= 0) { 1111 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1112 } else if (y > range && oldY <= range) { 1113 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1114 } 1115 } 1116 } 1117 awakenScrollBars(); 1118 1119 // Keep on drawing until the animation has finished. 1120 postInvalidate(); 1121 } 1122 } 1123 1124 /** 1125 * Scrolls the view to the given child. 1126 * 1127 * @param child the View to scroll to 1128 */ 1129 private void scrollToChild(View child) { 1130 child.getDrawingRect(mTempRect); 1131 1132 /* Offset from child's local coordinates to ScrollView coordinates */ 1133 offsetDescendantRectToMyCoords(child, mTempRect); 1134 1135 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1136 1137 if (scrollDelta != 0) { 1138 scrollBy(0, scrollDelta); 1139 } 1140 } 1141 1142 /** 1143 * If rect is off screen, scroll just enough to get it (or at least the 1144 * first screen size chunk of it) on screen. 1145 * 1146 * @param rect The rectangle. 1147 * @param immediate True to scroll immediately without animation 1148 * @return true if scrolling was performed 1149 */ 1150 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1151 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1152 final boolean scroll = delta != 0; 1153 if (scroll) { 1154 if (immediate) { 1155 scrollBy(0, delta); 1156 } else { 1157 smoothScrollBy(0, delta); 1158 } 1159 } 1160 return scroll; 1161 } 1162 1163 /** 1164 * Compute the amount to scroll in the Y direction in order to get 1165 * a rectangle completely on the screen (or, if taller than the screen, 1166 * at least the first screen size chunk of it). 1167 * 1168 * @param rect The rect. 1169 * @return The scroll delta. 1170 */ 1171 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1172 if (getChildCount() == 0) return 0; 1173 1174 int height = getHeight(); 1175 int screenTop = getScrollY(); 1176 int screenBottom = screenTop + height; 1177 1178 int fadingEdge = getVerticalFadingEdgeLength(); 1179 1180 // leave room for top fading edge as long as rect isn't at very top 1181 if (rect.top > 0) { 1182 screenTop += fadingEdge; 1183 } 1184 1185 // leave room for bottom fading edge as long as rect isn't at very bottom 1186 if (rect.bottom < getChildAt(0).getHeight()) { 1187 screenBottom -= fadingEdge; 1188 } 1189 1190 int scrollYDelta = 0; 1191 1192 if (rect.bottom > screenBottom && rect.top > screenTop) { 1193 // need to move down to get it in view: move down just enough so 1194 // that the entire rectangle is in view (or at least the first 1195 // screen size chunk). 1196 1197 if (rect.height() > height) { 1198 // just enough to get screen size chunk on 1199 scrollYDelta += (rect.top - screenTop); 1200 } else { 1201 // get entire rect at bottom of screen 1202 scrollYDelta += (rect.bottom - screenBottom); 1203 } 1204 1205 // make sure we aren't scrolling beyond the end of our content 1206 int bottom = getChildAt(0).getBottom(); 1207 int distanceToBottom = bottom - screenBottom; 1208 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1209 1210 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1211 // need to move up to get it in view: move up just enough so that 1212 // entire rectangle is in view (or at least the first screen 1213 // size chunk of it). 1214 1215 if (rect.height() > height) { 1216 // screen size chunk 1217 scrollYDelta -= (screenBottom - rect.bottom); 1218 } else { 1219 // entire rect at top 1220 scrollYDelta -= (screenTop - rect.top); 1221 } 1222 1223 // make sure we aren't scrolling any further than the top our content 1224 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1225 } 1226 return scrollYDelta; 1227 } 1228 1229 @Override 1230 public void requestChildFocus(View child, View focused) { 1231 if (!mScrollViewMovedFocus) { 1232 if (!mIsLayoutDirty) { 1233 scrollToChild(focused); 1234 } else { 1235 // The child may not be laid out yet, we can't compute the scroll yet 1236 mChildToScrollTo = focused; 1237 } 1238 } 1239 super.requestChildFocus(child, focused); 1240 } 1241 1242 1243 /** 1244 * When looking for focus in children of a scroll view, need to be a little 1245 * more careful not to give focus to something that is scrolled off screen. 1246 * 1247 * This is more expensive than the default {@link android.view.ViewGroup} 1248 * implementation, otherwise this behavior might have been made the default. 1249 */ 1250 @Override 1251 protected boolean onRequestFocusInDescendants(int direction, 1252 Rect previouslyFocusedRect) { 1253 1254 // convert from forward / backward notation to up / down / left / right 1255 // (ugh). 1256 if (direction == View.FOCUS_FORWARD) { 1257 direction = View.FOCUS_DOWN; 1258 } else if (direction == View.FOCUS_BACKWARD) { 1259 direction = View.FOCUS_UP; 1260 } 1261 1262 final View nextFocus = previouslyFocusedRect == null ? 1263 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1264 FocusFinder.getInstance().findNextFocusFromRect(this, 1265 previouslyFocusedRect, direction); 1266 1267 if (nextFocus == null) { 1268 return false; 1269 } 1270 1271 if (isOffScreen(nextFocus)) { 1272 return false; 1273 } 1274 1275 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1276 } 1277 1278 @Override 1279 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1280 boolean immediate) { 1281 // offset into coordinate space of this scroll view 1282 rectangle.offset(child.getLeft() - child.getScrollX(), 1283 child.getTop() - child.getScrollY()); 1284 1285 return scrollToChildRect(rectangle, immediate); 1286 } 1287 1288 @Override 1289 public void requestLayout() { 1290 mIsLayoutDirty = true; 1291 super.requestLayout(); 1292 } 1293 1294 @Override 1295 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1296 super.onLayout(changed, l, t, r, b); 1297 mIsLayoutDirty = false; 1298 // Give a child focus if it needs it 1299 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1300 scrollToChild(mChildToScrollTo); 1301 } 1302 mChildToScrollTo = null; 1303 1304 // Calling this with the present values causes it to re-clam them 1305 scrollTo(mScrollX, mScrollY); 1306 } 1307 1308 @Override 1309 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1310 super.onSizeChanged(w, h, oldw, oldh); 1311 1312 View currentFocused = findFocus(); 1313 if (null == currentFocused || this == currentFocused) 1314 return; 1315 1316 // If the currently-focused view was visible on the screen when the 1317 // screen was at the old height, then scroll the screen to make that 1318 // view visible with the new screen height. 1319 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1320 currentFocused.getDrawingRect(mTempRect); 1321 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1322 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1323 doScrollY(scrollDelta); 1324 } 1325 } 1326 1327 /** 1328 * Return true if child is an descendant of parent, (or equal to the parent). 1329 */ 1330 private boolean isViewDescendantOf(View child, View parent) { 1331 if (child == parent) { 1332 return true; 1333 } 1334 1335 final ViewParent theParent = child.getParent(); 1336 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1337 } 1338 1339 /** 1340 * Fling the scroll view 1341 * 1342 * @param velocityY The initial velocity in the Y direction. Positive 1343 * numbers mean that the finger/cursor is moving down the screen, 1344 * which means we want to scroll towards the top. 1345 */ 1346 public void fling(int velocityY) { 1347 if (getChildCount() > 0) { 1348 int height = getHeight() - mPaddingBottom - mPaddingTop; 1349 int bottom = getChildAt(0).getHeight(); 1350 1351 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1352 Math.max(0, bottom - height), 0, height/2); 1353 1354 final boolean movingDown = velocityY > 0; 1355 1356 View newFocused = 1357 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1358 if (newFocused == null) { 1359 newFocused = this; 1360 } 1361 1362 if (newFocused != findFocus() 1363 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1364 mScrollViewMovedFocus = true; 1365 mScrollViewMovedFocus = false; 1366 } 1367 1368 invalidate(); 1369 } 1370 } 1371 1372 /** 1373 * {@inheritDoc} 1374 * 1375 * <p>This version also clamps the scrolling to the bounds of our child. 1376 */ 1377 @Override 1378 public void scrollTo(int x, int y) { 1379 // we rely on the fact the View.scrollBy calls scrollTo. 1380 if (getChildCount() > 0) { 1381 View child = getChildAt(0); 1382 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1383 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1384 if (x != mScrollX || y != mScrollY) { 1385 super.scrollTo(x, y); 1386 } 1387 } 1388 } 1389 1390 @Override 1391 public void setOverScrollMode(int mode) { 1392 if (mode != OVER_SCROLL_NEVER) { 1393 if (mEdgeGlowTop == null) { 1394 final Resources res = getContext().getResources(); 1395 final Drawable edge = res.getDrawable(R.drawable.overscroll_edge); 1396 final Drawable glow = res.getDrawable(R.drawable.overscroll_glow); 1397 mEdgeGlowTop = new EdgeGlow(edge, glow); 1398 mEdgeGlowBottom = new EdgeGlow(edge, glow); 1399 } 1400 } else { 1401 mEdgeGlowTop = null; 1402 mEdgeGlowBottom = null; 1403 } 1404 super.setOverScrollMode(mode); 1405 } 1406 1407 @Override 1408 public void draw(Canvas canvas) { 1409 super.draw(canvas); 1410 if (mEdgeGlowTop != null) { 1411 final int scrollY = mScrollY; 1412 if (!mEdgeGlowTop.isFinished()) { 1413 final int restoreCount = canvas.save(); 1414 final int width = getWidth(); 1415 1416 canvas.translate(-width / 2, Math.min(0, scrollY)); 1417 mEdgeGlowTop.setSize(width * 2, getHeight()); 1418 if (mEdgeGlowTop.draw(canvas)) { 1419 invalidate(); 1420 } 1421 canvas.restoreToCount(restoreCount); 1422 } 1423 if (!mEdgeGlowBottom.isFinished()) { 1424 final int restoreCount = canvas.save(); 1425 final int width = getWidth(); 1426 final int height = getHeight(); 1427 1428 canvas.translate(-width / 2, Math.max(getScrollRange(), scrollY) + height); 1429 canvas.rotate(180, width, 0); 1430 mEdgeGlowBottom.setSize(width * 2, height); 1431 if (mEdgeGlowBottom.draw(canvas)) { 1432 invalidate(); 1433 } 1434 canvas.restoreToCount(restoreCount); 1435 } 1436 } 1437 } 1438 1439 private int clamp(int n, int my, int child) { 1440 if (my >= child || n < 0) { 1441 /* my >= child is this case: 1442 * |--------------- me ---------------| 1443 * |------ child ------| 1444 * or 1445 * |--------------- me ---------------| 1446 * |------ child ------| 1447 * or 1448 * |--------------- me ---------------| 1449 * |------ child ------| 1450 * 1451 * n < 0 is this case: 1452 * |------ me ------| 1453 * |-------- child --------| 1454 * |-- mScrollX --| 1455 */ 1456 return 0; 1457 } 1458 if ((my+n) > child) { 1459 /* this case: 1460 * |------ me ------| 1461 * |------ child ------| 1462 * |-- mScrollX --| 1463 */ 1464 return child-my; 1465 } 1466 return n; 1467 } 1468} 1469