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 17 package android.widget; 18 19 import com.android.internal.R; 20 21 import android.content.Context; 22 import android.content.res.TypedArray; 23 import android.graphics.Canvas; 24 import android.graphics.Rect; 25 import android.os.Bundle; 26 import android.os.StrictMode; 27 import android.util.AttributeSet; 28 import android.util.Log; 29 import android.view.FocusFinder; 30 import android.view.InputDevice; 31 import android.view.KeyEvent; 32 import android.view.MotionEvent; 33 import android.view.VelocityTracker; 34 import android.view.View; 35 import android.view.ViewConfiguration; 36 import android.view.ViewDebug; 37 import android.view.ViewGroup; 38 import android.view.ViewParent; 39 import android.view.accessibility.AccessibilityEvent; 40 import android.view.accessibility.AccessibilityNodeInfo; 41 import android.view.animation.AnimationUtils; 42 43 import java.util.List; 44 45 /** 46 * Layout container for a view hierarchy that can be scrolled by the user, 47 * allowing it to be larger than the physical display. A ScrollView 48 * is a {@link FrameLayout}, meaning you should place one child in it 49 * containing the entire contents to scroll; this child may itself be a layout 50 * manager with a complex hierarchy of objects. A child that is often used 51 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 52 * array of top-level items that the user can scroll through. 53 * <p>You should never use a ScrollView with a {@link ListView}, because 54 * ListView takes care of its own vertical scrolling. Most importantly, doing this 55 * defeats all of the important optimizations in ListView for dealing with 56 * large lists, since it effectively forces the ListView to display its entire 57 * list of items to fill up the infinite container supplied by ScrollView. 58 * <p>The {@link TextView} class also 59 * takes care of its own scrolling, so does not require a ScrollView, but 60 * using the two together is possible to achieve the effect of a text view 61 * within a larger container. 62 * 63 * <p>ScrollView only supports vertical scrolling. For horizontal scrolling, 64 * use {@link HorizontalScrollView}. 65 * 66 * @attr ref android.R.styleable#ScrollView_fillViewport 67 */ 68 public class ScrollView extends FrameLayout { 69 static final int ANIMATED_SCROLL_GAP = 250; 70 71 static final float MAX_SCROLL_FACTOR = 0.5f; 72 73 private static final String TAG = "ScrollView"; 74 75 private long mLastScroll; 76 77 private final Rect mTempRect = new Rect(); 78 private OverScroller mScroller; 79 private EdgeEffect mEdgeGlowTop; 80 private EdgeEffect mEdgeGlowBottom; 81 82 /** 83 * Position of the last motion event. 84 */ 85 private int mLastMotionY; 86 87 /** 88 * True when the layout has changed but the traversal has not come through yet. 89 * Ideally the view hierarchy would keep track of this for us. 90 */ 91 private boolean mIsLayoutDirty = true; 92 93 /** 94 * The child to give focus to in the event that a child has requested focus while the 95 * layout is dirty. This prevents the scroll from being wrong if the child has not been 96 * laid out before requesting focus. 97 */ 98 private View mChildToScrollTo = null; 99 100 /** 101 * True if the user is currently dragging this ScrollView around. This is 102 * not the same as 'is being flinged', which can be checked by 103 * mScroller.isFinished() (flinging begins when the user lifts his finger). 104 */ 105 private boolean mIsBeingDragged = false; 106 107 /** 108 * Determines speed during touch scrolling 109 */ 110 private VelocityTracker mVelocityTracker; 111 112 /** 113 * When set to true, the scroll view measure its child to make it fill the currently 114 * visible area. 115 */ 116 @ViewDebug.ExportedProperty(category = "layout") 117 private boolean mFillViewport; 118 119 /** 120 * Whether arrow scrolling is animated. 121 */ 122 private boolean mSmoothScrollingEnabled = true; 123 124 private int mTouchSlop; 125 private int mMinimumVelocity; 126 private int mMaximumVelocity; 127 128 private int mOverscrollDistance; 129 private int mOverflingDistance; 130 131 /** 132 * ID of the active pointer. This is used to retain consistency during 133 * drags/flings if multiple pointers are used. 134 */ 135 private int mActivePointerId = INVALID_POINTER; 136 137 /** 138 * The StrictMode "critical time span" objects to catch animation 139 * stutters. Non-null when a time-sensitive animation is 140 * in-flight. Must call finish() on them when done animating. 141 * These are no-ops on user builds. 142 */ 143 private StrictMode.Span mScrollStrictSpan = null; // aka "drag" 144 private StrictMode.Span mFlingStrictSpan = null; 145 146 /** 147 * Sentinel value for no current active pointer. 148 * Used by {@link #mActivePointerId}. 149 */ 150 private static final int INVALID_POINTER = -1; 151 ScrollView(Context context)152 public ScrollView(Context context) { 153 this(context, null); 154 } 155 ScrollView(Context context, AttributeSet attrs)156 public ScrollView(Context context, AttributeSet attrs) { 157 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 158 } 159 ScrollView(Context context, AttributeSet attrs, int defStyle)160 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 161 super(context, attrs, defStyle); 162 initScrollView(); 163 164 TypedArray a = 165 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 166 167 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 168 169 a.recycle(); 170 } 171 172 @Override shouldDelayChildPressedState()173 public boolean shouldDelayChildPressedState() { 174 return true; 175 } 176 177 @Override getTopFadingEdgeStrength()178 protected float getTopFadingEdgeStrength() { 179 if (getChildCount() == 0) { 180 return 0.0f; 181 } 182 183 final int length = getVerticalFadingEdgeLength(); 184 if (mScrollY < length) { 185 return mScrollY / (float) length; 186 } 187 188 return 1.0f; 189 } 190 191 @Override getBottomFadingEdgeStrength()192 protected float getBottomFadingEdgeStrength() { 193 if (getChildCount() == 0) { 194 return 0.0f; 195 } 196 197 final int length = getVerticalFadingEdgeLength(); 198 final int bottomEdge = getHeight() - mPaddingBottom; 199 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 200 if (span < length) { 201 return span / (float) length; 202 } 203 204 return 1.0f; 205 } 206 207 /** 208 * @return The maximum amount this scroll view will scroll in response to 209 * an arrow event. 210 */ getMaxScrollAmount()211 public int getMaxScrollAmount() { 212 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 213 } 214 215 initScrollView()216 private void initScrollView() { 217 mScroller = new OverScroller(getContext()); 218 setFocusable(true); 219 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 220 setWillNotDraw(false); 221 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 222 mTouchSlop = configuration.getScaledTouchSlop(); 223 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 224 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 225 mOverscrollDistance = configuration.getScaledOverscrollDistance(); 226 mOverflingDistance = configuration.getScaledOverflingDistance(); 227 } 228 229 @Override addView(View child)230 public void addView(View child) { 231 if (getChildCount() > 0) { 232 throw new IllegalStateException("ScrollView can host only one direct child"); 233 } 234 235 super.addView(child); 236 } 237 238 @Override addView(View child, int index)239 public void addView(View child, int index) { 240 if (getChildCount() > 0) { 241 throw new IllegalStateException("ScrollView can host only one direct child"); 242 } 243 244 super.addView(child, index); 245 } 246 247 @Override addView(View child, ViewGroup.LayoutParams params)248 public void addView(View child, ViewGroup.LayoutParams params) { 249 if (getChildCount() > 0) { 250 throw new IllegalStateException("ScrollView can host only one direct child"); 251 } 252 253 super.addView(child, params); 254 } 255 256 @Override addView(View child, int index, ViewGroup.LayoutParams params)257 public void addView(View child, int index, ViewGroup.LayoutParams params) { 258 if (getChildCount() > 0) { 259 throw new IllegalStateException("ScrollView can host only one direct child"); 260 } 261 262 super.addView(child, index, params); 263 } 264 265 /** 266 * @return Returns true this ScrollView can be scrolled 267 */ canScroll()268 private boolean canScroll() { 269 View child = getChildAt(0); 270 if (child != null) { 271 int childHeight = child.getHeight(); 272 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 273 } 274 return false; 275 } 276 277 /** 278 * Indicates whether this ScrollView's content is stretched to fill the viewport. 279 * 280 * @return True if the content fills the viewport, false otherwise. 281 * 282 * @attr ref android.R.styleable#ScrollView_fillViewport 283 */ isFillViewport()284 public boolean isFillViewport() { 285 return mFillViewport; 286 } 287 288 /** 289 * Indicates this ScrollView whether it should stretch its content height to fill 290 * the viewport or not. 291 * 292 * @param fillViewport True to stretch the content's height to the viewport's 293 * boundaries, false otherwise. 294 * 295 * @attr ref android.R.styleable#ScrollView_fillViewport 296 */ setFillViewport(boolean fillViewport)297 public void setFillViewport(boolean fillViewport) { 298 if (fillViewport != mFillViewport) { 299 mFillViewport = fillViewport; 300 requestLayout(); 301 } 302 } 303 304 /** 305 * @return Whether arrow scrolling will animate its transition. 306 */ isSmoothScrollingEnabled()307 public boolean isSmoothScrollingEnabled() { 308 return mSmoothScrollingEnabled; 309 } 310 311 /** 312 * Set whether arrow scrolling will animate its transition. 313 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 314 */ setSmoothScrollingEnabled(boolean smoothScrollingEnabled)315 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 316 mSmoothScrollingEnabled = smoothScrollingEnabled; 317 } 318 319 @Override onMeasure(int widthMeasureSpec, int heightMeasureSpec)320 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 321 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 322 323 if (!mFillViewport) { 324 return; 325 } 326 327 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 328 if (heightMode == MeasureSpec.UNSPECIFIED) { 329 return; 330 } 331 332 if (getChildCount() > 0) { 333 final View child = getChildAt(0); 334 int height = getMeasuredHeight(); 335 if (child.getMeasuredHeight() < height) { 336 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 337 338 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, 339 mPaddingLeft + mPaddingRight, lp.width); 340 height -= mPaddingTop; 341 height -= mPaddingBottom; 342 int childHeightMeasureSpec = 343 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 344 345 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 346 } 347 } 348 } 349 350 @Override dispatchKeyEvent(KeyEvent event)351 public boolean dispatchKeyEvent(KeyEvent event) { 352 // Let the focused view and/or our descendants get the key first 353 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 354 } 355 356 /** 357 * You can call this function yourself to have the scroll view perform 358 * scrolling from a key event, just as if the event had been dispatched to 359 * it by the view hierarchy. 360 * 361 * @param event The key event to execute. 362 * @return Return true if the event was handled, else false. 363 */ executeKeyEvent(KeyEvent event)364 public boolean executeKeyEvent(KeyEvent event) { 365 mTempRect.setEmpty(); 366 367 if (!canScroll()) { 368 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { 369 View currentFocused = findFocus(); 370 if (currentFocused == this) currentFocused = null; 371 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 372 currentFocused, View.FOCUS_DOWN); 373 return nextFocused != null 374 && nextFocused != this 375 && nextFocused.requestFocus(View.FOCUS_DOWN); 376 } 377 return false; 378 } 379 380 boolean handled = false; 381 if (event.getAction() == KeyEvent.ACTION_DOWN) { 382 switch (event.getKeyCode()) { 383 case KeyEvent.KEYCODE_DPAD_UP: 384 if (!event.isAltPressed()) { 385 handled = arrowScroll(View.FOCUS_UP); 386 } else { 387 handled = fullScroll(View.FOCUS_UP); 388 } 389 break; 390 case KeyEvent.KEYCODE_DPAD_DOWN: 391 if (!event.isAltPressed()) { 392 handled = arrowScroll(View.FOCUS_DOWN); 393 } else { 394 handled = fullScroll(View.FOCUS_DOWN); 395 } 396 break; 397 case KeyEvent.KEYCODE_SPACE: 398 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 399 break; 400 } 401 } 402 403 return handled; 404 } 405 inChild(int x, int y)406 private boolean inChild(int x, int y) { 407 if (getChildCount() > 0) { 408 final int scrollY = mScrollY; 409 final View child = getChildAt(0); 410 return !(y < child.getTop() - scrollY 411 || y >= child.getBottom() - scrollY 412 || x < child.getLeft() 413 || x >= child.getRight()); 414 } 415 return false; 416 } 417 initOrResetVelocityTracker()418 private void initOrResetVelocityTracker() { 419 if (mVelocityTracker == null) { 420 mVelocityTracker = VelocityTracker.obtain(); 421 } else { 422 mVelocityTracker.clear(); 423 } 424 } 425 initVelocityTrackerIfNotExists()426 private void initVelocityTrackerIfNotExists() { 427 if (mVelocityTracker == null) { 428 mVelocityTracker = VelocityTracker.obtain(); 429 } 430 } 431 recycleVelocityTracker()432 private void recycleVelocityTracker() { 433 if (mVelocityTracker != null) { 434 mVelocityTracker.recycle(); 435 mVelocityTracker = null; 436 } 437 } 438 439 @Override requestDisallowInterceptTouchEvent(boolean disallowIntercept)440 public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) { 441 if (disallowIntercept) { 442 recycleVelocityTracker(); 443 } 444 super.requestDisallowInterceptTouchEvent(disallowIntercept); 445 } 446 447 448 @Override onInterceptTouchEvent(MotionEvent ev)449 public boolean onInterceptTouchEvent(MotionEvent ev) { 450 /* 451 * This method JUST determines whether we want to intercept the motion. 452 * If we return true, onMotionEvent will be called and we do the actual 453 * scrolling there. 454 */ 455 456 /* 457 * Shortcut the most recurring case: the user is in the dragging 458 * state and he is moving his finger. We want to intercept this 459 * motion. 460 */ 461 final int action = ev.getAction(); 462 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 463 return true; 464 } 465 466 /* 467 * Don't try to intercept touch if we can't scroll anyway. 468 */ 469 if (getScrollY() == 0 && !canScrollVertically(1)) { 470 return false; 471 } 472 473 switch (action & MotionEvent.ACTION_MASK) { 474 case MotionEvent.ACTION_MOVE: { 475 /* 476 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 477 * whether the user has moved far enough from his original down touch. 478 */ 479 480 /* 481 * Locally do absolute value. mLastMotionY is set to the y value 482 * of the down event. 483 */ 484 final int activePointerId = mActivePointerId; 485 if (activePointerId == INVALID_POINTER) { 486 // If we don't have a valid id, the touch down wasn't on content. 487 break; 488 } 489 490 final int pointerIndex = ev.findPointerIndex(activePointerId); 491 if (pointerIndex == -1) { 492 Log.e(TAG, "Invalid pointerId=" + activePointerId 493 + " in onInterceptTouchEvent"); 494 break; 495 } 496 497 final int y = (int) ev.getY(pointerIndex); 498 final int yDiff = Math.abs(y - mLastMotionY); 499 if (yDiff > mTouchSlop) { 500 mIsBeingDragged = true; 501 mLastMotionY = y; 502 initVelocityTrackerIfNotExists(); 503 mVelocityTracker.addMovement(ev); 504 if (mScrollStrictSpan == null) { 505 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 506 } 507 final ViewParent parent = getParent(); 508 if (parent != null) { 509 parent.requestDisallowInterceptTouchEvent(true); 510 } 511 } 512 break; 513 } 514 515 case MotionEvent.ACTION_DOWN: { 516 final int y = (int) ev.getY(); 517 if (!inChild((int) ev.getX(), (int) y)) { 518 mIsBeingDragged = false; 519 recycleVelocityTracker(); 520 break; 521 } 522 523 /* 524 * Remember location of down touch. 525 * ACTION_DOWN always refers to pointer index 0. 526 */ 527 mLastMotionY = y; 528 mActivePointerId = ev.getPointerId(0); 529 530 initOrResetVelocityTracker(); 531 mVelocityTracker.addMovement(ev); 532 /* 533 * If being flinged and user touches the screen, initiate drag; 534 * otherwise don't. mScroller.isFinished should be false when 535 * being flinged. 536 */ 537 mIsBeingDragged = !mScroller.isFinished(); 538 if (mIsBeingDragged && mScrollStrictSpan == null) { 539 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 540 } 541 break; 542 } 543 544 case MotionEvent.ACTION_CANCEL: 545 case MotionEvent.ACTION_UP: 546 /* Release the drag */ 547 mIsBeingDragged = false; 548 mActivePointerId = INVALID_POINTER; 549 recycleVelocityTracker(); 550 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 551 postInvalidateOnAnimation(); 552 } 553 break; 554 case MotionEvent.ACTION_POINTER_UP: 555 onSecondaryPointerUp(ev); 556 break; 557 } 558 559 /* 560 * The only time we want to intercept motion events is if we are in the 561 * drag mode. 562 */ 563 return mIsBeingDragged; 564 } 565 566 @Override onTouchEvent(MotionEvent ev)567 public boolean onTouchEvent(MotionEvent ev) { 568 initVelocityTrackerIfNotExists(); 569 mVelocityTracker.addMovement(ev); 570 571 final int action = ev.getAction(); 572 573 switch (action & MotionEvent.ACTION_MASK) { 574 case MotionEvent.ACTION_DOWN: { 575 if (getChildCount() == 0) { 576 return false; 577 } 578 if ((mIsBeingDragged = !mScroller.isFinished())) { 579 final ViewParent parent = getParent(); 580 if (parent != null) { 581 parent.requestDisallowInterceptTouchEvent(true); 582 } 583 } 584 585 /* 586 * If being flinged and user touches, stop the fling. isFinished 587 * will be false if being flinged. 588 */ 589 if (!mScroller.isFinished()) { 590 mScroller.abortAnimation(); 591 if (mFlingStrictSpan != null) { 592 mFlingStrictSpan.finish(); 593 mFlingStrictSpan = null; 594 } 595 } 596 597 // Remember where the motion event started 598 mLastMotionY = (int) ev.getY(); 599 mActivePointerId = ev.getPointerId(0); 600 break; 601 } 602 case MotionEvent.ACTION_MOVE: 603 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 604 if (activePointerIndex == -1) { 605 Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent"); 606 break; 607 } 608 609 final int y = (int) ev.getY(activePointerIndex); 610 int deltaY = mLastMotionY - y; 611 if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) { 612 final ViewParent parent = getParent(); 613 if (parent != null) { 614 parent.requestDisallowInterceptTouchEvent(true); 615 } 616 mIsBeingDragged = true; 617 if (deltaY > 0) { 618 deltaY -= mTouchSlop; 619 } else { 620 deltaY += mTouchSlop; 621 } 622 } 623 if (mIsBeingDragged) { 624 // Scroll to follow the motion event 625 mLastMotionY = y; 626 627 final int oldX = mScrollX; 628 final int oldY = mScrollY; 629 final int range = getScrollRange(); 630 final int overscrollMode = getOverScrollMode(); 631 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || 632 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 633 634 if (overScrollBy(0, deltaY, 0, mScrollY, 635 0, range, 0, mOverscrollDistance, true)) { 636 // Break our velocity if we hit a scroll barrier. 637 mVelocityTracker.clear(); 638 } 639 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 640 641 if (canOverscroll) { 642 final int pulledToY = oldY + deltaY; 643 if (pulledToY < 0) { 644 mEdgeGlowTop.onPull((float) deltaY / getHeight()); 645 if (!mEdgeGlowBottom.isFinished()) { 646 mEdgeGlowBottom.onRelease(); 647 } 648 } else if (pulledToY > range) { 649 mEdgeGlowBottom.onPull((float) deltaY / getHeight()); 650 if (!mEdgeGlowTop.isFinished()) { 651 mEdgeGlowTop.onRelease(); 652 } 653 } 654 if (mEdgeGlowTop != null 655 && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) { 656 postInvalidateOnAnimation(); 657 } 658 } 659 } 660 break; 661 case MotionEvent.ACTION_UP: 662 if (mIsBeingDragged) { 663 final VelocityTracker velocityTracker = mVelocityTracker; 664 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 665 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 666 667 if (getChildCount() > 0) { 668 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 669 fling(-initialVelocity); 670 } else { 671 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, 672 getScrollRange())) { 673 postInvalidateOnAnimation(); 674 } 675 } 676 } 677 678 mActivePointerId = INVALID_POINTER; 679 endDrag(); 680 } 681 break; 682 case MotionEvent.ACTION_CANCEL: 683 if (mIsBeingDragged && getChildCount() > 0) { 684 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 685 postInvalidateOnAnimation(); 686 } 687 mActivePointerId = INVALID_POINTER; 688 endDrag(); 689 } 690 break; 691 case MotionEvent.ACTION_POINTER_DOWN: { 692 final int index = ev.getActionIndex(); 693 mLastMotionY = (int) ev.getY(index); 694 mActivePointerId = ev.getPointerId(index); 695 break; 696 } 697 case MotionEvent.ACTION_POINTER_UP: 698 onSecondaryPointerUp(ev); 699 mLastMotionY = (int) ev.getY(ev.findPointerIndex(mActivePointerId)); 700 break; 701 } 702 return true; 703 } 704 onSecondaryPointerUp(MotionEvent ev)705 private void onSecondaryPointerUp(MotionEvent ev) { 706 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 707 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 708 final int pointerId = ev.getPointerId(pointerIndex); 709 if (pointerId == mActivePointerId) { 710 // This was our active pointer going up. Choose a new 711 // active pointer and adjust accordingly. 712 // TODO: Make this decision more intelligent. 713 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 714 mLastMotionY = (int) ev.getY(newPointerIndex); 715 mActivePointerId = ev.getPointerId(newPointerIndex); 716 if (mVelocityTracker != null) { 717 mVelocityTracker.clear(); 718 } 719 } 720 } 721 722 @Override onGenericMotionEvent(MotionEvent event)723 public boolean onGenericMotionEvent(MotionEvent event) { 724 if ((event.getSource() & InputDevice.SOURCE_CLASS_POINTER) != 0) { 725 switch (event.getAction()) { 726 case MotionEvent.ACTION_SCROLL: { 727 if (!mIsBeingDragged) { 728 final float vscroll = event.getAxisValue(MotionEvent.AXIS_VSCROLL); 729 if (vscroll != 0) { 730 final int delta = (int) (vscroll * getVerticalScrollFactor()); 731 final int range = getScrollRange(); 732 int oldScrollY = mScrollY; 733 int newScrollY = oldScrollY - delta; 734 if (newScrollY < 0) { 735 newScrollY = 0; 736 } else if (newScrollY > range) { 737 newScrollY = range; 738 } 739 if (newScrollY != oldScrollY) { 740 super.scrollTo(mScrollX, newScrollY); 741 return true; 742 } 743 } 744 } 745 } 746 } 747 } 748 return super.onGenericMotionEvent(event); 749 } 750 751 @Override onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY)752 protected void onOverScrolled(int scrollX, int scrollY, 753 boolean clampedX, boolean clampedY) { 754 // Treat animating scrolls differently; see #computeScroll() for why. 755 if (!mScroller.isFinished()) { 756 mScrollX = scrollX; 757 mScrollY = scrollY; 758 invalidateParentIfNeeded(); 759 if (clampedY) { 760 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 761 } 762 } else { 763 super.scrollTo(scrollX, scrollY); 764 } 765 766 awakenScrollBars(); 767 } 768 769 @Override performAccessibilityAction(int action, Bundle arguments)770 public boolean performAccessibilityAction(int action, Bundle arguments) { 771 if (super.performAccessibilityAction(action, arguments)) { 772 return true; 773 } 774 if (!isEnabled()) { 775 return false; 776 } 777 switch (action) { 778 case AccessibilityNodeInfo.ACTION_SCROLL_FORWARD: { 779 final int viewportHeight = getHeight() - mPaddingBottom - mPaddingTop; 780 final int targetScrollY = Math.min(mScrollY + viewportHeight, getScrollRange()); 781 if (targetScrollY != mScrollY) { 782 smoothScrollTo(0, targetScrollY); 783 return true; 784 } 785 } return false; 786 case AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD: { 787 final int viewportHeight = getHeight() - mPaddingBottom - mPaddingTop; 788 final int targetScrollY = Math.max(mScrollY - viewportHeight, 0); 789 if (targetScrollY != mScrollY) { 790 smoothScrollTo(0, targetScrollY); 791 return true; 792 } 793 } return false; 794 } 795 return false; 796 } 797 798 @Override onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info)799 public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) { 800 super.onInitializeAccessibilityNodeInfo(info); 801 info.setClassName(ScrollView.class.getName()); 802 if (isEnabled()) { 803 final int scrollRange = getScrollRange(); 804 if (scrollRange > 0) { 805 info.setScrollable(true); 806 if (mScrollY > 0) { 807 info.addAction(AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD); 808 } 809 if (mScrollY < scrollRange) { 810 info.addAction(AccessibilityNodeInfo.ACTION_SCROLL_FORWARD); 811 } 812 } 813 } 814 } 815 816 @Override onInitializeAccessibilityEvent(AccessibilityEvent event)817 public void onInitializeAccessibilityEvent(AccessibilityEvent event) { 818 super.onInitializeAccessibilityEvent(event); 819 event.setClassName(ScrollView.class.getName()); 820 final boolean scrollable = getScrollRange() > 0; 821 event.setScrollable(scrollable); 822 event.setScrollX(mScrollX); 823 event.setScrollY(mScrollY); 824 event.setMaxScrollX(mScrollX); 825 event.setMaxScrollY(getScrollRange()); 826 } 827 getScrollRange()828 private int getScrollRange() { 829 int scrollRange = 0; 830 if (getChildCount() > 0) { 831 View child = getChildAt(0); 832 scrollRange = Math.max(0, 833 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); 834 } 835 return scrollRange; 836 } 837 838 /** 839 * <p> 840 * Finds the next focusable component that fits in the specified bounds. 841 * </p> 842 * 843 * @param topFocus look for a candidate is the one at the top of the bounds 844 * if topFocus is true, or at the bottom of the bounds if topFocus is 845 * false 846 * @param top the top offset of the bounds in which a focusable must be 847 * found 848 * @param bottom the bottom offset of the bounds in which a focusable must 849 * be found 850 * @return the next focusable component in the bounds or null if none can 851 * be found 852 */ findFocusableViewInBounds(boolean topFocus, int top, int bottom)853 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 854 855 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 856 View focusCandidate = null; 857 858 /* 859 * A fully contained focusable is one where its top is below the bound's 860 * top, and its bottom is above the bound's bottom. A partially 861 * contained focusable is one where some part of it is within the 862 * bounds, but it also has some part that is not within bounds. A fully contained 863 * focusable is preferred to a partially contained focusable. 864 */ 865 boolean foundFullyContainedFocusable = false; 866 867 int count = focusables.size(); 868 for (int i = 0; i < count; i++) { 869 View view = focusables.get(i); 870 int viewTop = view.getTop(); 871 int viewBottom = view.getBottom(); 872 873 if (top < viewBottom && viewTop < bottom) { 874 /* 875 * the focusable is in the target area, it is a candidate for 876 * focusing 877 */ 878 879 final boolean viewIsFullyContained = (top < viewTop) && 880 (viewBottom < bottom); 881 882 if (focusCandidate == null) { 883 /* No candidate, take this one */ 884 focusCandidate = view; 885 foundFullyContainedFocusable = viewIsFullyContained; 886 } else { 887 final boolean viewIsCloserToBoundary = 888 (topFocus && viewTop < focusCandidate.getTop()) || 889 (!topFocus && viewBottom > focusCandidate 890 .getBottom()); 891 892 if (foundFullyContainedFocusable) { 893 if (viewIsFullyContained && viewIsCloserToBoundary) { 894 /* 895 * We're dealing with only fully contained views, so 896 * it has to be closer to the boundary to beat our 897 * candidate 898 */ 899 focusCandidate = view; 900 } 901 } else { 902 if (viewIsFullyContained) { 903 /* Any fully contained view beats a partially contained view */ 904 focusCandidate = view; 905 foundFullyContainedFocusable = true; 906 } else if (viewIsCloserToBoundary) { 907 /* 908 * Partially contained view beats another partially 909 * contained view if it's closer 910 */ 911 focusCandidate = view; 912 } 913 } 914 } 915 } 916 } 917 918 return focusCandidate; 919 } 920 921 /** 922 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 923 * method will scroll the view by one page up or down and give the focus 924 * to the topmost/bottommost component in the new visible area. If no 925 * component is a good candidate for focus, this scrollview reclaims the 926 * focus.</p> 927 * 928 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 929 * to go one page up or 930 * {@link android.view.View#FOCUS_DOWN} to go one page down 931 * @return true if the key event is consumed by this method, false otherwise 932 */ pageScroll(int direction)933 public boolean pageScroll(int direction) { 934 boolean down = direction == View.FOCUS_DOWN; 935 int height = getHeight(); 936 937 if (down) { 938 mTempRect.top = getScrollY() + height; 939 int count = getChildCount(); 940 if (count > 0) { 941 View view = getChildAt(count - 1); 942 if (mTempRect.top + height > view.getBottom()) { 943 mTempRect.top = view.getBottom() - height; 944 } 945 } 946 } else { 947 mTempRect.top = getScrollY() - height; 948 if (mTempRect.top < 0) { 949 mTempRect.top = 0; 950 } 951 } 952 mTempRect.bottom = mTempRect.top + height; 953 954 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 955 } 956 957 /** 958 * <p>Handles scrolling in response to a "home/end" shortcut press. This 959 * method will scroll the view to the top or bottom and give the focus 960 * to the topmost/bottommost component in the new visible area. If no 961 * component is a good candidate for focus, this scrollview reclaims the 962 * focus.</p> 963 * 964 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 965 * to go the top of the view or 966 * {@link android.view.View#FOCUS_DOWN} to go the bottom 967 * @return true if the key event is consumed by this method, false otherwise 968 */ fullScroll(int direction)969 public boolean fullScroll(int direction) { 970 boolean down = direction == View.FOCUS_DOWN; 971 int height = getHeight(); 972 973 mTempRect.top = 0; 974 mTempRect.bottom = height; 975 976 if (down) { 977 int count = getChildCount(); 978 if (count > 0) { 979 View view = getChildAt(count - 1); 980 mTempRect.bottom = view.getBottom() + mPaddingBottom; 981 mTempRect.top = mTempRect.bottom - height; 982 } 983 } 984 985 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 986 } 987 988 /** 989 * <p>Scrolls the view to make the area defined by <code>top</code> and 990 * <code>bottom</code> visible. This method attempts to give the focus 991 * to a component visible in this area. If no component can be focused in 992 * the new visible area, the focus is reclaimed by this ScrollView.</p> 993 * 994 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 995 * to go upward, {@link android.view.View#FOCUS_DOWN} to downward 996 * @param top the top offset of the new area to be made visible 997 * @param bottom the bottom offset of the new area to be made visible 998 * @return true if the key event is consumed by this method, false otherwise 999 */ scrollAndFocus(int direction, int top, int bottom)1000 private boolean scrollAndFocus(int direction, int top, int bottom) { 1001 boolean handled = true; 1002 1003 int height = getHeight(); 1004 int containerTop = getScrollY(); 1005 int containerBottom = containerTop + height; 1006 boolean up = direction == View.FOCUS_UP; 1007 1008 View newFocused = findFocusableViewInBounds(up, top, bottom); 1009 if (newFocused == null) { 1010 newFocused = this; 1011 } 1012 1013 if (top >= containerTop && bottom <= containerBottom) { 1014 handled = false; 1015 } else { 1016 int delta = up ? (top - containerTop) : (bottom - containerBottom); 1017 doScrollY(delta); 1018 } 1019 1020 if (newFocused != findFocus()) newFocused.requestFocus(direction); 1021 1022 return handled; 1023 } 1024 1025 /** 1026 * Handle scrolling in response to an up or down arrow click. 1027 * 1028 * @param direction The direction corresponding to the arrow key that was 1029 * pressed 1030 * @return True if we consumed the event, false otherwise 1031 */ arrowScroll(int direction)1032 public boolean arrowScroll(int direction) { 1033 1034 View currentFocused = findFocus(); 1035 if (currentFocused == this) currentFocused = null; 1036 1037 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 1038 1039 final int maxJump = getMaxScrollAmount(); 1040 1041 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 1042 nextFocused.getDrawingRect(mTempRect); 1043 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 1044 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1045 doScrollY(scrollDelta); 1046 nextFocused.requestFocus(direction); 1047 } else { 1048 // no new focus 1049 int scrollDelta = maxJump; 1050 1051 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 1052 scrollDelta = getScrollY(); 1053 } else if (direction == View.FOCUS_DOWN) { 1054 if (getChildCount() > 0) { 1055 int daBottom = getChildAt(0).getBottom(); 1056 int screenBottom = getScrollY() + getHeight() - mPaddingBottom; 1057 if (daBottom - screenBottom < maxJump) { 1058 scrollDelta = daBottom - screenBottom; 1059 } 1060 } 1061 } 1062 if (scrollDelta == 0) { 1063 return false; 1064 } 1065 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 1066 } 1067 1068 if (currentFocused != null && currentFocused.isFocused() 1069 && isOffScreen(currentFocused)) { 1070 // previously focused item still has focus and is off screen, give 1071 // it up (take it back to ourselves) 1072 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 1073 // sure to 1074 // get it) 1075 final int descendantFocusability = getDescendantFocusability(); // save 1076 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 1077 requestFocus(); 1078 setDescendantFocusability(descendantFocusability); // restore 1079 } 1080 return true; 1081 } 1082 1083 /** 1084 * @return whether the descendant of this scroll view is scrolled off 1085 * screen. 1086 */ isOffScreen(View descendant)1087 private boolean isOffScreen(View descendant) { 1088 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 1089 } 1090 1091 /** 1092 * @return whether the descendant of this scroll view is within delta 1093 * pixels of being on the screen. 1094 */ isWithinDeltaOfScreen(View descendant, int delta, int height)1095 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 1096 descendant.getDrawingRect(mTempRect); 1097 offsetDescendantRectToMyCoords(descendant, mTempRect); 1098 1099 return (mTempRect.bottom + delta) >= getScrollY() 1100 && (mTempRect.top - delta) <= (getScrollY() + height); 1101 } 1102 1103 /** 1104 * Smooth scroll by a Y delta 1105 * 1106 * @param delta the number of pixels to scroll by on the Y axis 1107 */ doScrollY(int delta)1108 private void doScrollY(int delta) { 1109 if (delta != 0) { 1110 if (mSmoothScrollingEnabled) { 1111 smoothScrollBy(0, delta); 1112 } else { 1113 scrollBy(0, delta); 1114 } 1115 } 1116 } 1117 1118 /** 1119 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 1120 * 1121 * @param dx the number of pixels to scroll by on the X axis 1122 * @param dy the number of pixels to scroll by on the Y axis 1123 */ smoothScrollBy(int dx, int dy)1124 public final void smoothScrollBy(int dx, int dy) { 1125 if (getChildCount() == 0) { 1126 // Nothing to do. 1127 return; 1128 } 1129 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 1130 if (duration > ANIMATED_SCROLL_GAP) { 1131 final int height = getHeight() - mPaddingBottom - mPaddingTop; 1132 final int bottom = getChildAt(0).getHeight(); 1133 final int maxY = Math.max(0, bottom - height); 1134 final int scrollY = mScrollY; 1135 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 1136 1137 mScroller.startScroll(mScrollX, scrollY, 0, dy); 1138 postInvalidateOnAnimation(); 1139 } else { 1140 if (!mScroller.isFinished()) { 1141 mScroller.abortAnimation(); 1142 if (mFlingStrictSpan != null) { 1143 mFlingStrictSpan.finish(); 1144 mFlingStrictSpan = null; 1145 } 1146 } 1147 scrollBy(dx, dy); 1148 } 1149 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1150 } 1151 1152 /** 1153 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1154 * 1155 * @param x the position where to scroll on the X axis 1156 * @param y the position where to scroll on the Y axis 1157 */ smoothScrollTo(int x, int y)1158 public final void smoothScrollTo(int x, int y) { 1159 smoothScrollBy(x - mScrollX, y - mScrollY); 1160 } 1161 1162 /** 1163 * <p>The scroll range of a scroll view is the overall height of all of its 1164 * children.</p> 1165 */ 1166 @Override computeVerticalScrollRange()1167 protected int computeVerticalScrollRange() { 1168 final int count = getChildCount(); 1169 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1170 if (count == 0) { 1171 return contentHeight; 1172 } 1173 1174 int scrollRange = getChildAt(0).getBottom(); 1175 final int scrollY = mScrollY; 1176 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1177 if (scrollY < 0) { 1178 scrollRange -= scrollY; 1179 } else if (scrollY > overscrollBottom) { 1180 scrollRange += scrollY - overscrollBottom; 1181 } 1182 1183 return scrollRange; 1184 } 1185 1186 @Override computeVerticalScrollOffset()1187 protected int computeVerticalScrollOffset() { 1188 return Math.max(0, super.computeVerticalScrollOffset()); 1189 } 1190 1191 @Override measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec)1192 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1193 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1194 1195 int childWidthMeasureSpec; 1196 int childHeightMeasureSpec; 1197 1198 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1199 + mPaddingRight, lp.width); 1200 1201 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1202 1203 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1204 } 1205 1206 @Override measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed)1207 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1208 int parentHeightMeasureSpec, int heightUsed) { 1209 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1210 1211 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1212 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1213 + widthUsed, lp.width); 1214 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1215 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1216 1217 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1218 } 1219 1220 @Override computeScroll()1221 public void computeScroll() { 1222 if (mScroller.computeScrollOffset()) { 1223 // This is called at drawing time by ViewGroup. We don't want to 1224 // re-show the scrollbars at this point, which scrollTo will do, 1225 // so we replicate most of scrollTo here. 1226 // 1227 // It's a little odd to call onScrollChanged from inside the drawing. 1228 // 1229 // It is, except when you remember that computeScroll() is used to 1230 // animate scrolling. So unless we want to defer the onScrollChanged() 1231 // until the end of the animated scrolling, we don't really have a 1232 // choice here. 1233 // 1234 // I agree. The alternative, which I think would be worse, is to post 1235 // something and tell the subclasses later. This is bad because there 1236 // will be a window where mScrollX/Y is different from what the app 1237 // thinks it is. 1238 // 1239 int oldX = mScrollX; 1240 int oldY = mScrollY; 1241 int x = mScroller.getCurrX(); 1242 int y = mScroller.getCurrY(); 1243 1244 if (oldX != x || oldY != y) { 1245 final int range = getScrollRange(); 1246 final int overscrollMode = getOverScrollMode(); 1247 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || 1248 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 1249 1250 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, range, 1251 0, mOverflingDistance, false); 1252 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1253 1254 if (canOverscroll) { 1255 if (y < 0 && oldY >= 0) { 1256 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1257 } else if (y > range && oldY <= range) { 1258 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1259 } 1260 } 1261 } 1262 1263 if (!awakenScrollBars()) { 1264 // Keep on drawing until the animation has finished. 1265 postInvalidateOnAnimation(); 1266 } 1267 } else { 1268 if (mFlingStrictSpan != null) { 1269 mFlingStrictSpan.finish(); 1270 mFlingStrictSpan = null; 1271 } 1272 } 1273 } 1274 1275 /** 1276 * Scrolls the view to the given child. 1277 * 1278 * @param child the View to scroll to 1279 */ scrollToChild(View child)1280 private void scrollToChild(View child) { 1281 child.getDrawingRect(mTempRect); 1282 1283 /* Offset from child's local coordinates to ScrollView coordinates */ 1284 offsetDescendantRectToMyCoords(child, mTempRect); 1285 1286 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1287 1288 if (scrollDelta != 0) { 1289 scrollBy(0, scrollDelta); 1290 } 1291 } 1292 1293 /** 1294 * If rect is off screen, scroll just enough to get it (or at least the 1295 * first screen size chunk of it) on screen. 1296 * 1297 * @param rect The rectangle. 1298 * @param immediate True to scroll immediately without animation 1299 * @return true if scrolling was performed 1300 */ scrollToChildRect(Rect rect, boolean immediate)1301 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1302 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1303 final boolean scroll = delta != 0; 1304 if (scroll) { 1305 if (immediate) { 1306 scrollBy(0, delta); 1307 } else { 1308 smoothScrollBy(0, delta); 1309 } 1310 } 1311 return scroll; 1312 } 1313 1314 /** 1315 * Compute the amount to scroll in the Y direction in order to get 1316 * a rectangle completely on the screen (or, if taller than the screen, 1317 * at least the first screen size chunk of it). 1318 * 1319 * @param rect The rect. 1320 * @return The scroll delta. 1321 */ computeScrollDeltaToGetChildRectOnScreen(Rect rect)1322 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1323 if (getChildCount() == 0) return 0; 1324 1325 int height = getHeight(); 1326 int screenTop = getScrollY(); 1327 int screenBottom = screenTop + height; 1328 1329 int fadingEdge = getVerticalFadingEdgeLength(); 1330 1331 // leave room for top fading edge as long as rect isn't at very top 1332 if (rect.top > 0) { 1333 screenTop += fadingEdge; 1334 } 1335 1336 // leave room for bottom fading edge as long as rect isn't at very bottom 1337 if (rect.bottom < getChildAt(0).getHeight()) { 1338 screenBottom -= fadingEdge; 1339 } 1340 1341 int scrollYDelta = 0; 1342 1343 if (rect.bottom > screenBottom && rect.top > screenTop) { 1344 // need to move down to get it in view: move down just enough so 1345 // that the entire rectangle is in view (or at least the first 1346 // screen size chunk). 1347 1348 if (rect.height() > height) { 1349 // just enough to get screen size chunk on 1350 scrollYDelta += (rect.top - screenTop); 1351 } else { 1352 // get entire rect at bottom of screen 1353 scrollYDelta += (rect.bottom - screenBottom); 1354 } 1355 1356 // make sure we aren't scrolling beyond the end of our content 1357 int bottom = getChildAt(0).getBottom(); 1358 int distanceToBottom = bottom - screenBottom; 1359 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1360 1361 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1362 // need to move up to get it in view: move up just enough so that 1363 // entire rectangle is in view (or at least the first screen 1364 // size chunk of it). 1365 1366 if (rect.height() > height) { 1367 // screen size chunk 1368 scrollYDelta -= (screenBottom - rect.bottom); 1369 } else { 1370 // entire rect at top 1371 scrollYDelta -= (screenTop - rect.top); 1372 } 1373 1374 // make sure we aren't scrolling any further than the top our content 1375 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1376 } 1377 return scrollYDelta; 1378 } 1379 1380 @Override requestChildFocus(View child, View focused)1381 public void requestChildFocus(View child, View focused) { 1382 if (!mIsLayoutDirty) { 1383 scrollToChild(focused); 1384 } else { 1385 // The child may not be laid out yet, we can't compute the scroll yet 1386 mChildToScrollTo = focused; 1387 } 1388 super.requestChildFocus(child, focused); 1389 } 1390 1391 1392 /** 1393 * When looking for focus in children of a scroll view, need to be a little 1394 * more careful not to give focus to something that is scrolled off screen. 1395 * 1396 * This is more expensive than the default {@link android.view.ViewGroup} 1397 * implementation, otherwise this behavior might have been made the default. 1398 */ 1399 @Override onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect)1400 protected boolean onRequestFocusInDescendants(int direction, 1401 Rect previouslyFocusedRect) { 1402 1403 // convert from forward / backward notation to up / down / left / right 1404 // (ugh). 1405 if (direction == View.FOCUS_FORWARD) { 1406 direction = View.FOCUS_DOWN; 1407 } else if (direction == View.FOCUS_BACKWARD) { 1408 direction = View.FOCUS_UP; 1409 } 1410 1411 final View nextFocus = previouslyFocusedRect == null ? 1412 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1413 FocusFinder.getInstance().findNextFocusFromRect(this, 1414 previouslyFocusedRect, direction); 1415 1416 if (nextFocus == null) { 1417 return false; 1418 } 1419 1420 if (isOffScreen(nextFocus)) { 1421 return false; 1422 } 1423 1424 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1425 } 1426 1427 @Override requestChildRectangleOnScreen(View child, Rect rectangle, boolean immediate)1428 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1429 boolean immediate) { 1430 // offset into coordinate space of this scroll view 1431 rectangle.offset(child.getLeft() - child.getScrollX(), 1432 child.getTop() - child.getScrollY()); 1433 1434 return scrollToChildRect(rectangle, immediate); 1435 } 1436 1437 @Override requestLayout()1438 public void requestLayout() { 1439 mIsLayoutDirty = true; 1440 super.requestLayout(); 1441 } 1442 1443 @Override onDetachedFromWindow()1444 protected void onDetachedFromWindow() { 1445 super.onDetachedFromWindow(); 1446 1447 if (mScrollStrictSpan != null) { 1448 mScrollStrictSpan.finish(); 1449 mScrollStrictSpan = null; 1450 } 1451 if (mFlingStrictSpan != null) { 1452 mFlingStrictSpan.finish(); 1453 mFlingStrictSpan = null; 1454 } 1455 } 1456 1457 @Override onLayout(boolean changed, int l, int t, int r, int b)1458 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1459 super.onLayout(changed, l, t, r, b); 1460 mIsLayoutDirty = false; 1461 // Give a child focus if it needs it 1462 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1463 scrollToChild(mChildToScrollTo); 1464 } 1465 mChildToScrollTo = null; 1466 1467 // Calling this with the present values causes it to re-claim them 1468 scrollTo(mScrollX, mScrollY); 1469 } 1470 1471 @Override onSizeChanged(int w, int h, int oldw, int oldh)1472 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1473 super.onSizeChanged(w, h, oldw, oldh); 1474 1475 View currentFocused = findFocus(); 1476 if (null == currentFocused || this == currentFocused) 1477 return; 1478 1479 // If the currently-focused view was visible on the screen when the 1480 // screen was at the old height, then scroll the screen to make that 1481 // view visible with the new screen height. 1482 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1483 currentFocused.getDrawingRect(mTempRect); 1484 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1485 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1486 doScrollY(scrollDelta); 1487 } 1488 } 1489 1490 /** 1491 * Return true if child is a descendant of parent, (or equal to the parent). 1492 */ isViewDescendantOf(View child, View parent)1493 private static boolean isViewDescendantOf(View child, View parent) { 1494 if (child == parent) { 1495 return true; 1496 } 1497 1498 final ViewParent theParent = child.getParent(); 1499 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1500 } 1501 1502 /** 1503 * Fling the scroll view 1504 * 1505 * @param velocityY The initial velocity in the Y direction. Positive 1506 * numbers mean that the finger/cursor is moving down the screen, 1507 * which means we want to scroll towards the top. 1508 */ fling(int velocityY)1509 public void fling(int velocityY) { 1510 if (getChildCount() > 0) { 1511 int height = getHeight() - mPaddingBottom - mPaddingTop; 1512 int bottom = getChildAt(0).getHeight(); 1513 1514 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1515 Math.max(0, bottom - height), 0, height/2); 1516 1517 if (mFlingStrictSpan == null) { 1518 mFlingStrictSpan = StrictMode.enterCriticalSpan("ScrollView-fling"); 1519 } 1520 1521 postInvalidateOnAnimation(); 1522 } 1523 } 1524 endDrag()1525 private void endDrag() { 1526 mIsBeingDragged = false; 1527 1528 recycleVelocityTracker(); 1529 1530 if (mEdgeGlowTop != null) { 1531 mEdgeGlowTop.onRelease(); 1532 mEdgeGlowBottom.onRelease(); 1533 } 1534 1535 if (mScrollStrictSpan != null) { 1536 mScrollStrictSpan.finish(); 1537 mScrollStrictSpan = null; 1538 } 1539 } 1540 1541 /** 1542 * {@inheritDoc} 1543 * 1544 * <p>This version also clamps the scrolling to the bounds of our child. 1545 */ 1546 @Override scrollTo(int x, int y)1547 public void scrollTo(int x, int y) { 1548 // we rely on the fact the View.scrollBy calls scrollTo. 1549 if (getChildCount() > 0) { 1550 View child = getChildAt(0); 1551 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1552 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1553 if (x != mScrollX || y != mScrollY) { 1554 super.scrollTo(x, y); 1555 } 1556 } 1557 } 1558 1559 @Override setOverScrollMode(int mode)1560 public void setOverScrollMode(int mode) { 1561 if (mode != OVER_SCROLL_NEVER) { 1562 if (mEdgeGlowTop == null) { 1563 Context context = getContext(); 1564 mEdgeGlowTop = new EdgeEffect(context); 1565 mEdgeGlowBottom = new EdgeEffect(context); 1566 } 1567 } else { 1568 mEdgeGlowTop = null; 1569 mEdgeGlowBottom = null; 1570 } 1571 super.setOverScrollMode(mode); 1572 } 1573 1574 @Override draw(Canvas canvas)1575 public void draw(Canvas canvas) { 1576 super.draw(canvas); 1577 if (mEdgeGlowTop != null) { 1578 final int scrollY = mScrollY; 1579 if (!mEdgeGlowTop.isFinished()) { 1580 final int restoreCount = canvas.save(); 1581 final int width = getWidth() - mPaddingLeft - mPaddingRight; 1582 1583 canvas.translate(mPaddingLeft, Math.min(0, scrollY)); 1584 mEdgeGlowTop.setSize(width, getHeight()); 1585 if (mEdgeGlowTop.draw(canvas)) { 1586 postInvalidateOnAnimation(); 1587 } 1588 canvas.restoreToCount(restoreCount); 1589 } 1590 if (!mEdgeGlowBottom.isFinished()) { 1591 final int restoreCount = canvas.save(); 1592 final int width = getWidth() - mPaddingLeft - mPaddingRight; 1593 final int height = getHeight(); 1594 1595 canvas.translate(-width + mPaddingLeft, 1596 Math.max(getScrollRange(), scrollY) + height); 1597 canvas.rotate(180, width, 0); 1598 mEdgeGlowBottom.setSize(width, height); 1599 if (mEdgeGlowBottom.draw(canvas)) { 1600 postInvalidateOnAnimation(); 1601 } 1602 canvas.restoreToCount(restoreCount); 1603 } 1604 } 1605 } 1606 clamp(int n, int my, int child)1607 private static int clamp(int n, int my, int child) { 1608 if (my >= child || n < 0) { 1609 /* my >= child is this case: 1610 * |--------------- me ---------------| 1611 * |------ child ------| 1612 * or 1613 * |--------------- me ---------------| 1614 * |------ child ------| 1615 * or 1616 * |--------------- me ---------------| 1617 * |------ child ------| 1618 * 1619 * n < 0 is this case: 1620 * |------ me ------| 1621 * |-------- child --------| 1622 * |-- mScrollX --| 1623 */ 1624 return 0; 1625 } 1626 if ((my+n) > child) { 1627 /* this case: 1628 * |------ me ------| 1629 * |------ child ------| 1630 * |-- mScrollX --| 1631 */ 1632 return child-my; 1633 } 1634 return n; 1635 } 1636 } 1637