ScrollView.java revision 5916882c3f13429d29f95b89dd94bd2d5733da85
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 if (!(mIsBeingDragged = inChild((int) ev.getX(), (int) y))) { 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 = y; 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 pulledToY = oldY + deltaY; 537 if (pulledToY < 0) { 538 mEdgeGlowTop.onPull((float) deltaY / getHeight()); 539 } else if (pulledToY > range) { 540 mEdgeGlowBottom.onPull((float) deltaY / getHeight()); 541 } 542 } 543 break; 544 case MotionEvent.ACTION_UP: 545 if (mIsBeingDragged) { 546 final VelocityTracker velocityTracker = mVelocityTracker; 547 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 548 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 549 550 if (getChildCount() > 0) { 551 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 552 fling(-initialVelocity); 553 } else { 554 final int bottom = getScrollRange(); 555 if (mScroller.springback(mScrollX, mScrollY, 0, 0, 0, bottom)) { 556 invalidate(); 557 } 558 } 559 } 560 561 mActivePointerId = INVALID_POINTER; 562 mIsBeingDragged = false; 563 564 if (mVelocityTracker != null) { 565 mVelocityTracker.recycle(); 566 mVelocityTracker = null; 567 } 568 if (mEdgeGlowTop != null) { 569 mEdgeGlowTop.onRelease(); 570 mEdgeGlowBottom.onRelease(); 571 } 572 } 573 break; 574 case MotionEvent.ACTION_CANCEL: 575 if (mIsBeingDragged && getChildCount() > 0) { 576 if (mScroller.springback(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 577 invalidate(); 578 } 579 mActivePointerId = INVALID_POINTER; 580 mIsBeingDragged = false; 581 if (mVelocityTracker != null) { 582 mVelocityTracker.recycle(); 583 mVelocityTracker = null; 584 } 585 if (mEdgeGlowTop != null) { 586 mEdgeGlowTop.onRelease(); 587 mEdgeGlowBottom.onRelease(); 588 } 589 } 590 break; 591 case MotionEvent.ACTION_POINTER_UP: 592 onSecondaryPointerUp(ev); 593 break; 594 } 595 return true; 596 } 597 598 private void onSecondaryPointerUp(MotionEvent ev) { 599 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 600 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 601 final int pointerId = ev.getPointerId(pointerIndex); 602 if (pointerId == mActivePointerId) { 603 // This was our active pointer going up. Choose a new 604 // active pointer and adjust accordingly. 605 // TODO: Make this decision more intelligent. 606 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 607 mLastMotionY = ev.getY(newPointerIndex); 608 mActivePointerId = ev.getPointerId(newPointerIndex); 609 if (mVelocityTracker != null) { 610 mVelocityTracker.clear(); 611 } 612 } 613 } 614 615 @Override 616 protected void onOverscrolled(int scrollX, int scrollY, 617 boolean clampedX, boolean clampedY) { 618 // Treat animating scrolls differently; see #computeScroll() for why. 619 if (!mScroller.isFinished()) { 620 mScrollX = scrollX; 621 mScrollY = scrollY; 622 if (clampedY) { 623 mScroller.springback(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 624 } 625 } else { 626 super.scrollTo(scrollX, scrollY); 627 } 628 awakenScrollBars(); 629 } 630 631 private int getScrollRange() { 632 int scrollRange = 0; 633 if (getChildCount() > 0) { 634 View child = getChildAt(0); 635 scrollRange = Math.max(0, 636 child.getHeight() - getHeight() - mPaddingBottom - mPaddingTop); 637 } 638 return scrollRange; 639 } 640 641 /** 642 * <p> 643 * Finds the next focusable component that fits in this View's bounds 644 * (excluding fading edges) pretending that this View's top is located at 645 * the parameter top. 646 * </p> 647 * 648 * @param topFocus look for a candidate is the one at the top of the bounds 649 * if topFocus is true, or at the bottom of the bounds if topFocus is 650 * false 651 * @param top the top offset of the bounds in which a focusable must be 652 * found (the fading edge is assumed to start at this position) 653 * @param preferredFocusable the View that has highest priority and will be 654 * returned if it is within my bounds (null is valid) 655 * @return the next focusable component in the bounds or null if none can be 656 * found 657 */ 658 private View findFocusableViewInMyBounds(final boolean topFocus, 659 final int top, View preferredFocusable) { 660 /* 661 * The fading edge's transparent side should be considered for focus 662 * since it's mostly visible, so we divide the actual fading edge length 663 * by 2. 664 */ 665 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 666 final int topWithoutFadingEdge = top + fadingEdgeLength; 667 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 668 669 if ((preferredFocusable != null) 670 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 671 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 672 return preferredFocusable; 673 } 674 675 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 676 bottomWithoutFadingEdge); 677 } 678 679 /** 680 * <p> 681 * Finds the next focusable component that fits in the specified bounds. 682 * </p> 683 * 684 * @param topFocus look for a candidate is the one at the top of the bounds 685 * if topFocus is true, or at the bottom of the bounds if topFocus is 686 * false 687 * @param top the top offset of the bounds in which a focusable must be 688 * found 689 * @param bottom the bottom offset of the bounds in which a focusable must 690 * be found 691 * @return the next focusable component in the bounds or null if none can 692 * be found 693 */ 694 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 695 696 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 697 View focusCandidate = null; 698 699 /* 700 * A fully contained focusable is one where its top is below the bound's 701 * top, and its bottom is above the bound's bottom. A partially 702 * contained focusable is one where some part of it is within the 703 * bounds, but it also has some part that is not within bounds. A fully contained 704 * focusable is preferred to a partially contained focusable. 705 */ 706 boolean foundFullyContainedFocusable = false; 707 708 int count = focusables.size(); 709 for (int i = 0; i < count; i++) { 710 View view = focusables.get(i); 711 int viewTop = view.getTop(); 712 int viewBottom = view.getBottom(); 713 714 if (top < viewBottom && viewTop < bottom) { 715 /* 716 * the focusable is in the target area, it is a candidate for 717 * focusing 718 */ 719 720 final boolean viewIsFullyContained = (top < viewTop) && 721 (viewBottom < bottom); 722 723 if (focusCandidate == null) { 724 /* No candidate, take this one */ 725 focusCandidate = view; 726 foundFullyContainedFocusable = viewIsFullyContained; 727 } else { 728 final boolean viewIsCloserToBoundary = 729 (topFocus && viewTop < focusCandidate.getTop()) || 730 (!topFocus && viewBottom > focusCandidate 731 .getBottom()); 732 733 if (foundFullyContainedFocusable) { 734 if (viewIsFullyContained && viewIsCloserToBoundary) { 735 /* 736 * We're dealing with only fully contained views, so 737 * it has to be closer to the boundary to beat our 738 * candidate 739 */ 740 focusCandidate = view; 741 } 742 } else { 743 if (viewIsFullyContained) { 744 /* Any fully contained view beats a partially contained view */ 745 focusCandidate = view; 746 foundFullyContainedFocusable = true; 747 } else if (viewIsCloserToBoundary) { 748 /* 749 * Partially contained view beats another partially 750 * contained view if it's closer 751 */ 752 focusCandidate = view; 753 } 754 } 755 } 756 } 757 } 758 759 return focusCandidate; 760 } 761 762 /** 763 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 764 * method will scroll the view by one page up or down and give the focus 765 * to the topmost/bottommost component in the new visible area. If no 766 * component is a good candidate for focus, this scrollview reclaims the 767 * focus.</p> 768 * 769 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 770 * to go one page up or 771 * {@link android.view.View#FOCUS_DOWN} to go one page down 772 * @return true if the key event is consumed by this method, false otherwise 773 */ 774 public boolean pageScroll(int direction) { 775 boolean down = direction == View.FOCUS_DOWN; 776 int height = getHeight(); 777 778 if (down) { 779 mTempRect.top = getScrollY() + height; 780 int count = getChildCount(); 781 if (count > 0) { 782 View view = getChildAt(count - 1); 783 if (mTempRect.top + height > view.getBottom()) { 784 mTempRect.top = view.getBottom() - height; 785 } 786 } 787 } else { 788 mTempRect.top = getScrollY() - height; 789 if (mTempRect.top < 0) { 790 mTempRect.top = 0; 791 } 792 } 793 mTempRect.bottom = mTempRect.top + height; 794 795 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 796 } 797 798 /** 799 * <p>Handles scrolling in response to a "home/end" shortcut press. This 800 * method will scroll the view to the top or bottom and give the focus 801 * to the topmost/bottommost component in the new visible area. If no 802 * component is a good candidate for focus, this scrollview reclaims the 803 * focus.</p> 804 * 805 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 806 * to go the top of the view or 807 * {@link android.view.View#FOCUS_DOWN} to go the bottom 808 * @return true if the key event is consumed by this method, false otherwise 809 */ 810 public boolean fullScroll(int direction) { 811 boolean down = direction == View.FOCUS_DOWN; 812 int height = getHeight(); 813 814 mTempRect.top = 0; 815 mTempRect.bottom = height; 816 817 if (down) { 818 int count = getChildCount(); 819 if (count > 0) { 820 View view = getChildAt(count - 1); 821 mTempRect.bottom = view.getBottom(); 822 mTempRect.top = mTempRect.bottom - height; 823 } 824 } 825 826 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 827 } 828 829 /** 830 * <p>Scrolls the view to make the area defined by <code>top</code> and 831 * <code>bottom</code> visible. This method attempts to give the focus 832 * to a component visible in this area. If no component can be focused in 833 * the new visible area, the focus is reclaimed by this scrollview.</p> 834 * 835 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 836 * to go upward 837 * {@link android.view.View#FOCUS_DOWN} to downward 838 * @param top the top offset of the new area to be made visible 839 * @param bottom the bottom offset of the new area to be made visible 840 * @return true if the key event is consumed by this method, false otherwise 841 */ 842 private boolean scrollAndFocus(int direction, int top, int bottom) { 843 boolean handled = true; 844 845 int height = getHeight(); 846 int containerTop = getScrollY(); 847 int containerBottom = containerTop + height; 848 boolean up = direction == View.FOCUS_UP; 849 850 View newFocused = findFocusableViewInBounds(up, top, bottom); 851 if (newFocused == null) { 852 newFocused = this; 853 } 854 855 if (top >= containerTop && bottom <= containerBottom) { 856 handled = false; 857 } else { 858 int delta = up ? (top - containerTop) : (bottom - containerBottom); 859 doScrollY(delta); 860 } 861 862 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 863 mScrollViewMovedFocus = true; 864 mScrollViewMovedFocus = false; 865 } 866 867 return handled; 868 } 869 870 /** 871 * Handle scrolling in response to an up or down arrow click. 872 * 873 * @param direction The direction corresponding to the arrow key that was 874 * pressed 875 * @return True if we consumed the event, false otherwise 876 */ 877 public boolean arrowScroll(int direction) { 878 879 View currentFocused = findFocus(); 880 if (currentFocused == this) currentFocused = null; 881 882 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 883 884 final int maxJump = getMaxScrollAmount(); 885 886 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 887 nextFocused.getDrawingRect(mTempRect); 888 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 889 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 890 doScrollY(scrollDelta); 891 nextFocused.requestFocus(direction); 892 } else { 893 // no new focus 894 int scrollDelta = maxJump; 895 896 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 897 scrollDelta = getScrollY(); 898 } else if (direction == View.FOCUS_DOWN) { 899 if (getChildCount() > 0) { 900 int daBottom = getChildAt(0).getBottom(); 901 902 int screenBottom = getScrollY() + getHeight(); 903 904 if (daBottom - screenBottom < maxJump) { 905 scrollDelta = daBottom - screenBottom; 906 } 907 } 908 } 909 if (scrollDelta == 0) { 910 return false; 911 } 912 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 913 } 914 915 if (currentFocused != null && currentFocused.isFocused() 916 && isOffScreen(currentFocused)) { 917 // previously focused item still has focus and is off screen, give 918 // it up (take it back to ourselves) 919 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 920 // sure to 921 // get it) 922 final int descendantFocusability = getDescendantFocusability(); // save 923 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 924 requestFocus(); 925 setDescendantFocusability(descendantFocusability); // restore 926 } 927 return true; 928 } 929 930 /** 931 * @return whether the descendant of this scroll view is scrolled off 932 * screen. 933 */ 934 private boolean isOffScreen(View descendant) { 935 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 936 } 937 938 /** 939 * @return whether the descendant of this scroll view is within delta 940 * pixels of being on the screen. 941 */ 942 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 943 descendant.getDrawingRect(mTempRect); 944 offsetDescendantRectToMyCoords(descendant, mTempRect); 945 946 return (mTempRect.bottom + delta) >= getScrollY() 947 && (mTempRect.top - delta) <= (getScrollY() + height); 948 } 949 950 /** 951 * Smooth scroll by a Y delta 952 * 953 * @param delta the number of pixels to scroll by on the Y axis 954 */ 955 private void doScrollY(int delta) { 956 if (delta != 0) { 957 if (mSmoothScrollingEnabled) { 958 smoothScrollBy(0, delta); 959 } else { 960 scrollBy(0, delta); 961 } 962 } 963 } 964 965 /** 966 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 967 * 968 * @param dx the number of pixels to scroll by on the X axis 969 * @param dy the number of pixels to scroll by on the Y axis 970 */ 971 public final void smoothScrollBy(int dx, int dy) { 972 if (getChildCount() == 0) { 973 // Nothing to do. 974 return; 975 } 976 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 977 if (duration > ANIMATED_SCROLL_GAP) { 978 final int height = getHeight() - mPaddingBottom - mPaddingTop; 979 final int bottom = getChildAt(0).getHeight(); 980 final int maxY = Math.max(0, bottom - height); 981 final int scrollY = mScrollY; 982 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 983 984 mScroller.startScroll(mScrollX, scrollY, 0, dy); 985 invalidate(); 986 } else { 987 if (!mScroller.isFinished()) { 988 mScroller.abortAnimation(); 989 } 990 scrollBy(dx, dy); 991 } 992 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 993 } 994 995 /** 996 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 997 * 998 * @param x the position where to scroll on the X axis 999 * @param y the position where to scroll on the Y axis 1000 */ 1001 public final void smoothScrollTo(int x, int y) { 1002 smoothScrollBy(x - mScrollX, y - mScrollY); 1003 } 1004 1005 /** 1006 * <p>The scroll range of a scroll view is the overall height of all of its 1007 * children.</p> 1008 */ 1009 @Override 1010 protected int computeVerticalScrollRange() { 1011 final int count = getChildCount(); 1012 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1013 if (count == 0) { 1014 return contentHeight; 1015 } 1016 1017 int scrollRange = getChildAt(0).getBottom(); 1018 final int scrollY = mScrollY; 1019 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1020 if (scrollY < 0) { 1021 scrollRange -= scrollY; 1022 } else if (scrollY > overscrollBottom) { 1023 scrollRange += scrollY - overscrollBottom; 1024 } 1025 1026 return scrollRange; 1027 } 1028 1029 @Override 1030 protected int computeVerticalScrollOffset() { 1031 return Math.max(0, super.computeVerticalScrollOffset()); 1032 } 1033 1034 @Override 1035 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1036 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1037 1038 int childWidthMeasureSpec; 1039 int childHeightMeasureSpec; 1040 1041 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1042 + mPaddingRight, lp.width); 1043 1044 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1045 1046 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1047 } 1048 1049 @Override 1050 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1051 int parentHeightMeasureSpec, int heightUsed) { 1052 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1053 1054 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1055 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1056 + widthUsed, lp.width); 1057 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1058 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1059 1060 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1061 } 1062 1063 @Override 1064 public void computeScroll() { 1065 if (mScroller.computeScrollOffset()) { 1066 // This is called at drawing time by ViewGroup. We don't want to 1067 // re-show the scrollbars at this point, which scrollTo will do, 1068 // so we replicate most of scrollTo here. 1069 // 1070 // It's a little odd to call onScrollChanged from inside the drawing. 1071 // 1072 // It is, except when you remember that computeScroll() is used to 1073 // animate scrolling. So unless we want to defer the onScrollChanged() 1074 // until the end of the animated scrolling, we don't really have a 1075 // choice here. 1076 // 1077 // I agree. The alternative, which I think would be worse, is to post 1078 // something and tell the subclasses later. This is bad because there 1079 // will be a window where mScrollX/Y is different from what the app 1080 // thinks it is. 1081 // 1082 int oldX = mScrollX; 1083 int oldY = mScrollY; 1084 int x = mScroller.getCurrX(); 1085 int y = mScroller.getCurrY(); 1086 1087 if (oldX != x || oldY != y) { 1088 overscrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 1089 0, mOverflingDistance, false); 1090 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1091 1092 final int range = getScrollRange(); 1093 if (y < 0 && oldY >= 0) { 1094 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1095 } else if (y > range && oldY <= range) { 1096 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1097 } 1098 } 1099 awakenScrollBars(); 1100 1101 // Keep on drawing until the animation has finished. 1102 postInvalidate(); 1103 } 1104 } 1105 1106 /** 1107 * Scrolls the view to the given child. 1108 * 1109 * @param child the View to scroll to 1110 */ 1111 private void scrollToChild(View child) { 1112 child.getDrawingRect(mTempRect); 1113 1114 /* Offset from child's local coordinates to ScrollView coordinates */ 1115 offsetDescendantRectToMyCoords(child, mTempRect); 1116 1117 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1118 1119 if (scrollDelta != 0) { 1120 scrollBy(0, scrollDelta); 1121 } 1122 } 1123 1124 /** 1125 * If rect is off screen, scroll just enough to get it (or at least the 1126 * first screen size chunk of it) on screen. 1127 * 1128 * @param rect The rectangle. 1129 * @param immediate True to scroll immediately without animation 1130 * @return true if scrolling was performed 1131 */ 1132 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1133 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1134 final boolean scroll = delta != 0; 1135 if (scroll) { 1136 if (immediate) { 1137 scrollBy(0, delta); 1138 } else { 1139 smoothScrollBy(0, delta); 1140 } 1141 } 1142 return scroll; 1143 } 1144 1145 /** 1146 * Compute the amount to scroll in the Y direction in order to get 1147 * a rectangle completely on the screen (or, if taller than the screen, 1148 * at least the first screen size chunk of it). 1149 * 1150 * @param rect The rect. 1151 * @return The scroll delta. 1152 */ 1153 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1154 if (getChildCount() == 0) return 0; 1155 1156 int height = getHeight(); 1157 int screenTop = getScrollY(); 1158 int screenBottom = screenTop + height; 1159 1160 int fadingEdge = getVerticalFadingEdgeLength(); 1161 1162 // leave room for top fading edge as long as rect isn't at very top 1163 if (rect.top > 0) { 1164 screenTop += fadingEdge; 1165 } 1166 1167 // leave room for bottom fading edge as long as rect isn't at very bottom 1168 if (rect.bottom < getChildAt(0).getHeight()) { 1169 screenBottom -= fadingEdge; 1170 } 1171 1172 int scrollYDelta = 0; 1173 1174 if (rect.bottom > screenBottom && rect.top > screenTop) { 1175 // need to move down to get it in view: move down just enough so 1176 // that the entire rectangle is in view (or at least the first 1177 // screen size chunk). 1178 1179 if (rect.height() > height) { 1180 // just enough to get screen size chunk on 1181 scrollYDelta += (rect.top - screenTop); 1182 } else { 1183 // get entire rect at bottom of screen 1184 scrollYDelta += (rect.bottom - screenBottom); 1185 } 1186 1187 // make sure we aren't scrolling beyond the end of our content 1188 int bottom = getChildAt(0).getBottom(); 1189 int distanceToBottom = bottom - screenBottom; 1190 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1191 1192 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1193 // need to move up to get it in view: move up just enough so that 1194 // entire rectangle is in view (or at least the first screen 1195 // size chunk of it). 1196 1197 if (rect.height() > height) { 1198 // screen size chunk 1199 scrollYDelta -= (screenBottom - rect.bottom); 1200 } else { 1201 // entire rect at top 1202 scrollYDelta -= (screenTop - rect.top); 1203 } 1204 1205 // make sure we aren't scrolling any further than the top our content 1206 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1207 } 1208 return scrollYDelta; 1209 } 1210 1211 @Override 1212 public void requestChildFocus(View child, View focused) { 1213 if (!mScrollViewMovedFocus) { 1214 if (!mIsLayoutDirty) { 1215 scrollToChild(focused); 1216 } else { 1217 // The child may not be laid out yet, we can't compute the scroll yet 1218 mChildToScrollTo = focused; 1219 } 1220 } 1221 super.requestChildFocus(child, focused); 1222 } 1223 1224 1225 /** 1226 * When looking for focus in children of a scroll view, need to be a little 1227 * more careful not to give focus to something that is scrolled off screen. 1228 * 1229 * This is more expensive than the default {@link android.view.ViewGroup} 1230 * implementation, otherwise this behavior might have been made the default. 1231 */ 1232 @Override 1233 protected boolean onRequestFocusInDescendants(int direction, 1234 Rect previouslyFocusedRect) { 1235 1236 // convert from forward / backward notation to up / down / left / right 1237 // (ugh). 1238 if (direction == View.FOCUS_FORWARD) { 1239 direction = View.FOCUS_DOWN; 1240 } else if (direction == View.FOCUS_BACKWARD) { 1241 direction = View.FOCUS_UP; 1242 } 1243 1244 final View nextFocus = previouslyFocusedRect == null ? 1245 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1246 FocusFinder.getInstance().findNextFocusFromRect(this, 1247 previouslyFocusedRect, direction); 1248 1249 if (nextFocus == null) { 1250 return false; 1251 } 1252 1253 if (isOffScreen(nextFocus)) { 1254 return false; 1255 } 1256 1257 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1258 } 1259 1260 @Override 1261 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1262 boolean immediate) { 1263 // offset into coordinate space of this scroll view 1264 rectangle.offset(child.getLeft() - child.getScrollX(), 1265 child.getTop() - child.getScrollY()); 1266 1267 return scrollToChildRect(rectangle, immediate); 1268 } 1269 1270 @Override 1271 public void requestLayout() { 1272 mIsLayoutDirty = true; 1273 super.requestLayout(); 1274 } 1275 1276 @Override 1277 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1278 super.onLayout(changed, l, t, r, b); 1279 mIsLayoutDirty = false; 1280 // Give a child focus if it needs it 1281 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1282 scrollToChild(mChildToScrollTo); 1283 } 1284 mChildToScrollTo = null; 1285 1286 // Calling this with the present values causes it to re-clam them 1287 scrollTo(mScrollX, mScrollY); 1288 } 1289 1290 @Override 1291 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1292 super.onSizeChanged(w, h, oldw, oldh); 1293 1294 View currentFocused = findFocus(); 1295 if (null == currentFocused || this == currentFocused) 1296 return; 1297 1298 // If the currently-focused view was visible on the screen when the 1299 // screen was at the old height, then scroll the screen to make that 1300 // view visible with the new screen height. 1301 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1302 currentFocused.getDrawingRect(mTempRect); 1303 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1304 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1305 doScrollY(scrollDelta); 1306 } 1307 } 1308 1309 /** 1310 * Return true if child is an descendant of parent, (or equal to the parent). 1311 */ 1312 private boolean isViewDescendantOf(View child, View parent) { 1313 if (child == parent) { 1314 return true; 1315 } 1316 1317 final ViewParent theParent = child.getParent(); 1318 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1319 } 1320 1321 /** 1322 * Fling the scroll view 1323 * 1324 * @param velocityY The initial velocity in the Y direction. Positive 1325 * numbers mean that the finger/cursor is moving down the screen, 1326 * which means we want to scroll towards the top. 1327 */ 1328 public void fling(int velocityY) { 1329 if (getChildCount() > 0) { 1330 int height = getHeight() - mPaddingBottom - mPaddingTop; 1331 int bottom = getChildAt(0).getHeight(); 1332 1333 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1334 Math.max(0, bottom - height), 0, height/2); 1335 1336 final boolean movingDown = velocityY > 0; 1337 1338 View newFocused = 1339 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1340 if (newFocused == null) { 1341 newFocused = this; 1342 } 1343 1344 if (newFocused != findFocus() 1345 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1346 mScrollViewMovedFocus = true; 1347 mScrollViewMovedFocus = false; 1348 } 1349 1350 invalidate(); 1351 } 1352 } 1353 1354 /** 1355 * {@inheritDoc} 1356 * 1357 * <p>This version also clamps the scrolling to the bounds of our child. 1358 */ 1359 @Override 1360 public void scrollTo(int x, int y) { 1361 // we rely on the fact the View.scrollBy calls scrollTo. 1362 if (getChildCount() > 0) { 1363 View child = getChildAt(0); 1364 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1365 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1366 if (x != mScrollX || y != mScrollY) { 1367 super.scrollTo(x, y); 1368 } 1369 } 1370 } 1371 1372 @Override 1373 public void setOverscrollMode(int mode) { 1374 if (mode != OVERSCROLL_NEVER) { 1375 if (mEdgeGlowTop == null) { 1376 final Resources res = getContext().getResources(); 1377 final Drawable edge = res.getDrawable(R.drawable.overscroll_edge); 1378 final Drawable glow = res.getDrawable(R.drawable.overscroll_glow); 1379 mEdgeGlowTop = new EdgeGlow(edge, glow); 1380 mEdgeGlowBottom = new EdgeGlow(edge, glow); 1381 } 1382 } else { 1383 mEdgeGlowTop = null; 1384 mEdgeGlowBottom = null; 1385 } 1386 super.setOverscrollMode(mode); 1387 } 1388 1389 @Override 1390 public void draw(Canvas canvas) { 1391 super.draw(canvas); 1392 if (mEdgeGlowTop != null) { 1393 final int scrollY = mScrollY; 1394 if (!mEdgeGlowTop.isFinished()) { 1395 final int restoreCount = canvas.save(); 1396 final int width = getWidth(); 1397 1398 canvas.translate(-width / 2, Math.min(0, scrollY)); 1399 mEdgeGlowTop.setSize(width * 2, getHeight()); 1400 if (mEdgeGlowTop.draw(canvas)) { 1401 invalidate(); 1402 } 1403 canvas.restoreToCount(restoreCount); 1404 } 1405 if (!mEdgeGlowBottom.isFinished()) { 1406 final int restoreCount = canvas.save(); 1407 final int width = getWidth(); 1408 final int height = getHeight(); 1409 1410 canvas.translate(-width / 2, Math.max(getScrollRange(), scrollY) + height); 1411 canvas.rotate(180, width, 0); 1412 mEdgeGlowBottom.setSize(width * 2, height); 1413 if (mEdgeGlowBottom.draw(canvas)) { 1414 invalidate(); 1415 } 1416 canvas.restoreToCount(restoreCount); 1417 } 1418 } 1419 } 1420 1421 private int clamp(int n, int my, int child) { 1422 if (my >= child || n < 0) { 1423 /* my >= child is this case: 1424 * |--------------- me ---------------| 1425 * |------ child ------| 1426 * or 1427 * |--------------- me ---------------| 1428 * |------ child ------| 1429 * or 1430 * |--------------- me ---------------| 1431 * |------ child ------| 1432 * 1433 * n < 0 is this case: 1434 * |------ me ------| 1435 * |-------- child --------| 1436 * |-- mScrollX --| 1437 */ 1438 return 0; 1439 } 1440 if ((my+n) > child) { 1441 /* this case: 1442 * |------ me ------| 1443 * |------ child ------| 1444 * |-- mScrollX --| 1445 */ 1446 return child-my; 1447 } 1448 return n; 1449 } 1450} 1451