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 android.annotation.NonNull; 20 import android.os.Build; 21 import android.os.Build.VERSION_CODES; 22 import android.os.Parcel; 23 import android.os.Parcelable; 24 import com.android.internal.R; 25 26 import android.content.Context; 27 import android.content.res.TypedArray; 28 import android.graphics.Canvas; 29 import android.graphics.Rect; 30 import android.os.Bundle; 31 import android.os.StrictMode; 32 import android.util.AttributeSet; 33 import android.util.Log; 34 import android.view.FocusFinder; 35 import android.view.InputDevice; 36 import android.view.KeyEvent; 37 import android.view.MotionEvent; 38 import android.view.VelocityTracker; 39 import android.view.View; 40 import android.view.ViewConfiguration; 41 import android.view.ViewDebug; 42 import android.view.ViewGroup; 43 import android.view.ViewHierarchyEncoder; 44 import android.view.ViewParent; 45 import android.view.accessibility.AccessibilityEvent; 46 import android.view.accessibility.AccessibilityNodeInfo; 47 import android.view.animation.AnimationUtils; 48 49 import java.util.List; 50 51 /** 52 * Layout container for a view hierarchy that can be scrolled by the user, 53 * allowing it to be larger than the physical display. A ScrollView 54 * is a {@link FrameLayout}, meaning you should place one child in it 55 * containing the entire contents to scroll; this child may itself be a layout 56 * manager with a complex hierarchy of objects. A child that is often used 57 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 58 * array of top-level items that the user can scroll through. 59 * <p>You should never use a ScrollView with a {@link ListView}, because 60 * ListView takes care of its own vertical scrolling. Most importantly, doing this 61 * defeats all of the important optimizations in ListView for dealing with 62 * large lists, since it effectively forces the ListView to display its entire 63 * list of items to fill up the infinite container supplied by ScrollView. 64 * <p>The {@link TextView} class also 65 * takes care of its own scrolling, so does not require a ScrollView, but 66 * using the two together is possible to achieve the effect of a text view 67 * within a larger container. 68 * 69 * <p>ScrollView only supports vertical scrolling. For horizontal scrolling, 70 * use {@link HorizontalScrollView}. 71 * 72 * @attr ref android.R.styleable#ScrollView_fillViewport 73 */ 74 public class ScrollView extends FrameLayout { 75 static final int ANIMATED_SCROLL_GAP = 250; 76 77 static final float MAX_SCROLL_FACTOR = 0.5f; 78 79 private static final String TAG = "ScrollView"; 80 81 private long mLastScroll; 82 83 private final Rect mTempRect = new Rect(); 84 private OverScroller mScroller; 85 private EdgeEffect mEdgeGlowTop; 86 private EdgeEffect mEdgeGlowBottom; 87 88 /** 89 * Position of the last motion event. 90 */ 91 private int mLastMotionY; 92 93 /** 94 * True when the layout has changed but the traversal has not come through yet. 95 * Ideally the view hierarchy would keep track of this for us. 96 */ 97 private boolean mIsLayoutDirty = true; 98 99 /** 100 * The child to give focus to in the event that a child has requested focus while the 101 * layout is dirty. This prevents the scroll from being wrong if the child has not been 102 * laid out before requesting focus. 103 */ 104 private View mChildToScrollTo = null; 105 106 /** 107 * True if the user is currently dragging this ScrollView around. This is 108 * not the same as 'is being flinged', which can be checked by 109 * mScroller.isFinished() (flinging begins when the user lifts his finger). 110 */ 111 private boolean mIsBeingDragged = false; 112 113 /** 114 * Determines speed during touch scrolling 115 */ 116 private VelocityTracker mVelocityTracker; 117 118 /** 119 * When set to true, the scroll view measure its child to make it fill the currently 120 * visible area. 121 */ 122 @ViewDebug.ExportedProperty(category = "layout") 123 private boolean mFillViewport; 124 125 /** 126 * Whether arrow scrolling is animated. 127 */ 128 private boolean mSmoothScrollingEnabled = true; 129 130 private int mTouchSlop; 131 private int mMinimumVelocity; 132 private int mMaximumVelocity; 133 134 private int mOverscrollDistance; 135 private int mOverflingDistance; 136 137 /** 138 * ID of the active pointer. This is used to retain consistency during 139 * drags/flings if multiple pointers are used. 140 */ 141 private int mActivePointerId = INVALID_POINTER; 142 143 /** 144 * Used during scrolling to retrieve the new offset within the window. 145 */ 146 private final int[] mScrollOffset = new int[2]; 147 private final int[] mScrollConsumed = new int[2]; 148 private int mNestedYOffset; 149 150 /** 151 * The StrictMode "critical time span" objects to catch animation 152 * stutters. Non-null when a time-sensitive animation is 153 * in-flight. Must call finish() on them when done animating. 154 * These are no-ops on user builds. 155 */ 156 private StrictMode.Span mScrollStrictSpan = null; // aka "drag" 157 private StrictMode.Span mFlingStrictSpan = null; 158 159 /** 160 * Sentinel value for no current active pointer. 161 * Used by {@link #mActivePointerId}. 162 */ 163 private static final int INVALID_POINTER = -1; 164 165 private SavedState mSavedState; 166 167 public ScrollView(Context context) { 168 this(context, null); 169 } 170 171 public ScrollView(Context context, AttributeSet attrs) { 172 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 173 } 174 175 public ScrollView(Context context, AttributeSet attrs, int defStyleAttr) { 176 this(context, attrs, defStyleAttr, 0); 177 } 178 179 public ScrollView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { 180 super(context, attrs, defStyleAttr, defStyleRes); 181 initScrollView(); 182 183 final TypedArray a = context.obtainStyledAttributes( 184 attrs, com.android.internal.R.styleable.ScrollView, defStyleAttr, defStyleRes); 185 186 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 187 188 a.recycle(); 189 } 190 191 @Override 192 public boolean shouldDelayChildPressedState() { 193 return true; 194 } 195 196 @Override 197 protected float getTopFadingEdgeStrength() { 198 if (getChildCount() == 0) { 199 return 0.0f; 200 } 201 202 final int length = getVerticalFadingEdgeLength(); 203 if (mScrollY < length) { 204 return mScrollY / (float) length; 205 } 206 207 return 1.0f; 208 } 209 210 @Override 211 protected float getBottomFadingEdgeStrength() { 212 if (getChildCount() == 0) { 213 return 0.0f; 214 } 215 216 final int length = getVerticalFadingEdgeLength(); 217 final int bottomEdge = getHeight() - mPaddingBottom; 218 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 219 if (span < length) { 220 return span / (float) length; 221 } 222 223 return 1.0f; 224 } 225 226 /** 227 * @return The maximum amount this scroll view will scroll in response to 228 * an arrow event. 229 */ 230 public int getMaxScrollAmount() { 231 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 232 } 233 234 235 private void initScrollView() { 236 mScroller = new OverScroller(getContext()); 237 setFocusable(true); 238 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 239 setWillNotDraw(false); 240 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 241 mTouchSlop = configuration.getScaledTouchSlop(); 242 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 243 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 244 mOverscrollDistance = configuration.getScaledOverscrollDistance(); 245 mOverflingDistance = configuration.getScaledOverflingDistance(); 246 } 247 248 @Override 249 public void addView(View child) { 250 if (getChildCount() > 0) { 251 throw new IllegalStateException("ScrollView can host only one direct child"); 252 } 253 254 super.addView(child); 255 } 256 257 @Override 258 public void addView(View child, int index) { 259 if (getChildCount() > 0) { 260 throw new IllegalStateException("ScrollView can host only one direct child"); 261 } 262 263 super.addView(child, index); 264 } 265 266 @Override 267 public void addView(View child, ViewGroup.LayoutParams params) { 268 if (getChildCount() > 0) { 269 throw new IllegalStateException("ScrollView can host only one direct child"); 270 } 271 272 super.addView(child, params); 273 } 274 275 @Override 276 public void addView(View child, int index, ViewGroup.LayoutParams params) { 277 if (getChildCount() > 0) { 278 throw new IllegalStateException("ScrollView can host only one direct child"); 279 } 280 281 super.addView(child, index, params); 282 } 283 284 /** 285 * @return Returns true this ScrollView can be scrolled 286 */ 287 private boolean canScroll() { 288 View child = getChildAt(0); 289 if (child != null) { 290 int childHeight = child.getHeight(); 291 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 292 } 293 return false; 294 } 295 296 /** 297 * Indicates whether this ScrollView's content is stretched to fill the viewport. 298 * 299 * @return True if the content fills the viewport, false otherwise. 300 * 301 * @attr ref android.R.styleable#ScrollView_fillViewport 302 */ 303 public boolean isFillViewport() { 304 return mFillViewport; 305 } 306 307 /** 308 * Indicates this ScrollView whether it should stretch its content height to fill 309 * the viewport or not. 310 * 311 * @param fillViewport True to stretch the content's height to the viewport's 312 * boundaries, false otherwise. 313 * 314 * @attr ref android.R.styleable#ScrollView_fillViewport 315 */ 316 public void setFillViewport(boolean fillViewport) { 317 if (fillViewport != mFillViewport) { 318 mFillViewport = fillViewport; 319 requestLayout(); 320 } 321 } 322 323 /** 324 * @return Whether arrow scrolling will animate its transition. 325 */ 326 public boolean isSmoothScrollingEnabled() { 327 return mSmoothScrollingEnabled; 328 } 329 330 /** 331 * Set whether arrow scrolling will animate its transition. 332 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 333 */ 334 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 335 mSmoothScrollingEnabled = smoothScrollingEnabled; 336 } 337 338 @Override 339 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 340 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 341 342 if (!mFillViewport) { 343 return; 344 } 345 346 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 347 if (heightMode == MeasureSpec.UNSPECIFIED) { 348 return; 349 } 350 351 if (getChildCount() > 0) { 352 final View child = getChildAt(0); 353 final int height = getMeasuredHeight(); 354 if (child.getMeasuredHeight() < height) { 355 final int widthPadding; 356 final int heightPadding; 357 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 358 final int targetSdkVersion = getContext().getApplicationInfo().targetSdkVersion; 359 if (targetSdkVersion >= VERSION_CODES.M) { 360 widthPadding = mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin; 361 heightPadding = mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin; 362 } else { 363 widthPadding = mPaddingLeft + mPaddingRight; 364 heightPadding = mPaddingTop + mPaddingBottom; 365 } 366 367 final int childWidthMeasureSpec = getChildMeasureSpec( 368 widthMeasureSpec, widthPadding, lp.width); 369 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 370 height - heightPadding, MeasureSpec.EXACTLY); 371 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 372 } 373 } 374 } 375 376 @Override 377 public boolean dispatchKeyEvent(KeyEvent event) { 378 // Let the focused view and/or our descendants get the key first 379 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 380 } 381 382 /** 383 * You can call this function yourself to have the scroll view perform 384 * scrolling from a key event, just as if the event had been dispatched to 385 * it by the view hierarchy. 386 * 387 * @param event The key event to execute. 388 * @return Return true if the event was handled, else false. 389 */ 390 public boolean executeKeyEvent(KeyEvent event) { 391 mTempRect.setEmpty(); 392 393 if (!canScroll()) { 394 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { 395 View currentFocused = findFocus(); 396 if (currentFocused == this) currentFocused = null; 397 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 398 currentFocused, View.FOCUS_DOWN); 399 return nextFocused != null 400 && nextFocused != this 401 && nextFocused.requestFocus(View.FOCUS_DOWN); 402 } 403 return false; 404 } 405 406 boolean handled = false; 407 if (event.getAction() == KeyEvent.ACTION_DOWN) { 408 switch (event.getKeyCode()) { 409 case KeyEvent.KEYCODE_DPAD_UP: 410 if (!event.isAltPressed()) { 411 handled = arrowScroll(View.FOCUS_UP); 412 } else { 413 handled = fullScroll(View.FOCUS_UP); 414 } 415 break; 416 case KeyEvent.KEYCODE_DPAD_DOWN: 417 if (!event.isAltPressed()) { 418 handled = arrowScroll(View.FOCUS_DOWN); 419 } else { 420 handled = fullScroll(View.FOCUS_DOWN); 421 } 422 break; 423 case KeyEvent.KEYCODE_SPACE: 424 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 425 break; 426 } 427 } 428 429 return handled; 430 } 431 432 private boolean inChild(int x, int y) { 433 if (getChildCount() > 0) { 434 final int scrollY = mScrollY; 435 final View child = getChildAt(0); 436 return !(y < child.getTop() - scrollY 437 || y >= child.getBottom() - scrollY 438 || x < child.getLeft() 439 || x >= child.getRight()); 440 } 441 return false; 442 } 443 444 private void initOrResetVelocityTracker() { 445 if (mVelocityTracker == null) { 446 mVelocityTracker = VelocityTracker.obtain(); 447 } else { 448 mVelocityTracker.clear(); 449 } 450 } 451 452 private void initVelocityTrackerIfNotExists() { 453 if (mVelocityTracker == null) { 454 mVelocityTracker = VelocityTracker.obtain(); 455 } 456 } 457 458 private void recycleVelocityTracker() { 459 if (mVelocityTracker != null) { 460 mVelocityTracker.recycle(); 461 mVelocityTracker = null; 462 } 463 } 464 465 @Override 466 public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) { 467 if (disallowIntercept) { 468 recycleVelocityTracker(); 469 } 470 super.requestDisallowInterceptTouchEvent(disallowIntercept); 471 } 472 473 474 @Override 475 public boolean onInterceptTouchEvent(MotionEvent ev) { 476 /* 477 * This method JUST determines whether we want to intercept the motion. 478 * If we return true, onMotionEvent will be called and we do the actual 479 * scrolling there. 480 */ 481 482 /* 483 * Shortcut the most recurring case: the user is in the dragging 484 * state and he is moving his finger. We want to intercept this 485 * motion. 486 */ 487 final int action = ev.getAction(); 488 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 489 return true; 490 } 491 492 /* 493 * Don't try to intercept touch if we can't scroll anyway. 494 */ 495 if (getScrollY() == 0 && !canScrollVertically(1)) { 496 return false; 497 } 498 499 switch (action & MotionEvent.ACTION_MASK) { 500 case MotionEvent.ACTION_MOVE: { 501 /* 502 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 503 * whether the user has moved far enough from his original down touch. 504 */ 505 506 /* 507 * Locally do absolute value. mLastMotionY is set to the y value 508 * of the down event. 509 */ 510 final int activePointerId = mActivePointerId; 511 if (activePointerId == INVALID_POINTER) { 512 // If we don't have a valid id, the touch down wasn't on content. 513 break; 514 } 515 516 final int pointerIndex = ev.findPointerIndex(activePointerId); 517 if (pointerIndex == -1) { 518 Log.e(TAG, "Invalid pointerId=" + activePointerId 519 + " in onInterceptTouchEvent"); 520 break; 521 } 522 523 final int y = (int) ev.getY(pointerIndex); 524 final int yDiff = Math.abs(y - mLastMotionY); 525 if (yDiff > mTouchSlop && (getNestedScrollAxes() & SCROLL_AXIS_VERTICAL) == 0) { 526 mIsBeingDragged = true; 527 mLastMotionY = y; 528 initVelocityTrackerIfNotExists(); 529 mVelocityTracker.addMovement(ev); 530 mNestedYOffset = 0; 531 if (mScrollStrictSpan == null) { 532 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 533 } 534 final ViewParent parent = getParent(); 535 if (parent != null) { 536 parent.requestDisallowInterceptTouchEvent(true); 537 } 538 } 539 break; 540 } 541 542 case MotionEvent.ACTION_DOWN: { 543 final int y = (int) ev.getY(); 544 if (!inChild((int) ev.getX(), (int) y)) { 545 mIsBeingDragged = false; 546 recycleVelocityTracker(); 547 break; 548 } 549 550 /* 551 * Remember location of down touch. 552 * ACTION_DOWN always refers to pointer index 0. 553 */ 554 mLastMotionY = y; 555 mActivePointerId = ev.getPointerId(0); 556 557 initOrResetVelocityTracker(); 558 mVelocityTracker.addMovement(ev); 559 /* 560 * If being flinged and user touches the screen, initiate drag; 561 * otherwise don't. mScroller.isFinished should be false when 562 * being flinged. 563 */ 564 mIsBeingDragged = !mScroller.isFinished(); 565 if (mIsBeingDragged && mScrollStrictSpan == null) { 566 mScrollStrictSpan = StrictMode.enterCriticalSpan("ScrollView-scroll"); 567 } 568 startNestedScroll(SCROLL_AXIS_VERTICAL); 569 break; 570 } 571 572 case MotionEvent.ACTION_CANCEL: 573 case MotionEvent.ACTION_UP: 574 /* Release the drag */ 575 mIsBeingDragged = false; 576 mActivePointerId = INVALID_POINTER; 577 recycleVelocityTracker(); 578 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 579 postInvalidateOnAnimation(); 580 } 581 stopNestedScroll(); 582 break; 583 case MotionEvent.ACTION_POINTER_UP: 584 onSecondaryPointerUp(ev); 585 break; 586 } 587 588 /* 589 * The only time we want to intercept motion events is if we are in the 590 * drag mode. 591 */ 592 return mIsBeingDragged; 593 } 594 595 @Override 596 public boolean onTouchEvent(MotionEvent ev) { 597 initVelocityTrackerIfNotExists(); 598 599 MotionEvent vtev = MotionEvent.obtain(ev); 600 601 final int actionMasked = ev.getActionMasked(); 602 603 if (actionMasked == MotionEvent.ACTION_DOWN) { 604 mNestedYOffset = 0; 605 } 606 vtev.offsetLocation(0, mNestedYOffset); 607 608 switch (actionMasked) { 609 case MotionEvent.ACTION_DOWN: { 610 if (getChildCount() == 0) { 611 return false; 612 } 613 if ((mIsBeingDragged = !mScroller.isFinished())) { 614 final ViewParent parent = getParent(); 615 if (parent != null) { 616 parent.requestDisallowInterceptTouchEvent(true); 617 } 618 } 619 620 /* 621 * If being flinged and user touches, stop the fling. isFinished 622 * will be false if being flinged. 623 */ 624 if (!mScroller.isFinished()) { 625 mScroller.abortAnimation(); 626 if (mFlingStrictSpan != null) { 627 mFlingStrictSpan.finish(); 628 mFlingStrictSpan = null; 629 } 630 } 631 632 // Remember where the motion event started 633 mLastMotionY = (int) ev.getY(); 634 mActivePointerId = ev.getPointerId(0); 635 startNestedScroll(SCROLL_AXIS_VERTICAL); 636 break; 637 } 638 case MotionEvent.ACTION_MOVE: 639 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 640 if (activePointerIndex == -1) { 641 Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent"); 642 break; 643 } 644 645 final int y = (int) ev.getY(activePointerIndex); 646 int deltaY = mLastMotionY - y; 647 if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) { 648 deltaY -= mScrollConsumed[1]; 649 vtev.offsetLocation(0, mScrollOffset[1]); 650 mNestedYOffset += mScrollOffset[1]; 651 } 652 if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) { 653 final ViewParent parent = getParent(); 654 if (parent != null) { 655 parent.requestDisallowInterceptTouchEvent(true); 656 } 657 mIsBeingDragged = true; 658 if (deltaY > 0) { 659 deltaY -= mTouchSlop; 660 } else { 661 deltaY += mTouchSlop; 662 } 663 } 664 if (mIsBeingDragged) { 665 // Scroll to follow the motion event 666 mLastMotionY = y - mScrollOffset[1]; 667 668 final int oldY = mScrollY; 669 final int range = getScrollRange(); 670 final int overscrollMode = getOverScrollMode(); 671 boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || 672 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 673 674 // Calling overScrollBy will call onOverScrolled, which 675 // calls onScrollChanged if applicable. 676 if (overScrollBy(0, deltaY, 0, mScrollY, 0, range, 0, mOverscrollDistance, true) 677 && !hasNestedScrollingParent()) { 678 // Break our velocity if we hit a scroll barrier. 679 mVelocityTracker.clear(); 680 } 681 682 final int scrolledDeltaY = mScrollY - oldY; 683 final int unconsumedY = deltaY - scrolledDeltaY; 684 if (dispatchNestedScroll(0, scrolledDeltaY, 0, unconsumedY, mScrollOffset)) { 685 mLastMotionY -= mScrollOffset[1]; 686 vtev.offsetLocation(0, mScrollOffset[1]); 687 mNestedYOffset += mScrollOffset[1]; 688 } else if (canOverscroll) { 689 final int pulledToY = oldY + deltaY; 690 if (pulledToY < 0) { 691 mEdgeGlowTop.onPull((float) deltaY / getHeight(), 692 ev.getX(activePointerIndex) / getWidth()); 693 if (!mEdgeGlowBottom.isFinished()) { 694 mEdgeGlowBottom.onRelease(); 695 } 696 } else if (pulledToY > range) { 697 mEdgeGlowBottom.onPull((float) deltaY / getHeight(), 698 1.f - ev.getX(activePointerIndex) / getWidth()); 699 if (!mEdgeGlowTop.isFinished()) { 700 mEdgeGlowTop.onRelease(); 701 } 702 } 703 if (mEdgeGlowTop != null 704 && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) { 705 postInvalidateOnAnimation(); 706 } 707 } 708 } 709 break; 710 case MotionEvent.ACTION_UP: 711 if (mIsBeingDragged) { 712 final VelocityTracker velocityTracker = mVelocityTracker; 713 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 714 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 715 716 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 717 flingWithNestedDispatch(-initialVelocity); 718 } else if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, 719 getScrollRange())) { 720 postInvalidateOnAnimation(); 721 } 722 723 mActivePointerId = INVALID_POINTER; 724 endDrag(); 725 } 726 break; 727 case MotionEvent.ACTION_CANCEL: 728 if (mIsBeingDragged && getChildCount() > 0) { 729 if (mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 730 postInvalidateOnAnimation(); 731 } 732 mActivePointerId = INVALID_POINTER; 733 endDrag(); 734 } 735 break; 736 case MotionEvent.ACTION_POINTER_DOWN: { 737 final int index = ev.getActionIndex(); 738 mLastMotionY = (int) ev.getY(index); 739 mActivePointerId = ev.getPointerId(index); 740 break; 741 } 742 case MotionEvent.ACTION_POINTER_UP: 743 onSecondaryPointerUp(ev); 744 mLastMotionY = (int) ev.getY(ev.findPointerIndex(mActivePointerId)); 745 break; 746 } 747 748 if (mVelocityTracker != null) { 749 mVelocityTracker.addMovement(vtev); 750 } 751 vtev.recycle(); 752 return true; 753 } 754 755 private void onSecondaryPointerUp(MotionEvent ev) { 756 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 757 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 758 final int pointerId = ev.getPointerId(pointerIndex); 759 if (pointerId == mActivePointerId) { 760 // This was our active pointer going up. Choose a new 761 // active pointer and adjust accordingly. 762 // TODO: Make this decision more intelligent. 763 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 764 mLastMotionY = (int) ev.getY(newPointerIndex); 765 mActivePointerId = ev.getPointerId(newPointerIndex); 766 if (mVelocityTracker != null) { 767 mVelocityTracker.clear(); 768 } 769 } 770 } 771 772 @Override 773 public boolean onGenericMotionEvent(MotionEvent event) { 774 if ((event.getSource() & InputDevice.SOURCE_CLASS_POINTER) != 0) { 775 switch (event.getAction()) { 776 case MotionEvent.ACTION_SCROLL: { 777 if (!mIsBeingDragged) { 778 final float vscroll = event.getAxisValue(MotionEvent.AXIS_VSCROLL); 779 if (vscroll != 0) { 780 final int delta = (int) (vscroll * getVerticalScrollFactor()); 781 final int range = getScrollRange(); 782 int oldScrollY = mScrollY; 783 int newScrollY = oldScrollY - delta; 784 if (newScrollY < 0) { 785 newScrollY = 0; 786 } else if (newScrollY > range) { 787 newScrollY = range; 788 } 789 if (newScrollY != oldScrollY) { 790 super.scrollTo(mScrollX, newScrollY); 791 return true; 792 } 793 } 794 } 795 } 796 } 797 } 798 return super.onGenericMotionEvent(event); 799 } 800 801 @Override 802 protected void onOverScrolled(int scrollX, int scrollY, 803 boolean clampedX, boolean clampedY) { 804 // Treat animating scrolls differently; see #computeScroll() for why. 805 if (!mScroller.isFinished()) { 806 final int oldX = mScrollX; 807 final int oldY = mScrollY; 808 mScrollX = scrollX; 809 mScrollY = scrollY; 810 invalidateParentIfNeeded(); 811 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 812 if (clampedY) { 813 mScroller.springBack(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 814 } 815 } else { 816 super.scrollTo(scrollX, scrollY); 817 } 818 819 awakenScrollBars(); 820 } 821 822 /** @hide */ 823 @Override 824 public boolean performAccessibilityActionInternal(int action, Bundle arguments) { 825 if (super.performAccessibilityActionInternal(action, arguments)) { 826 return true; 827 } 828 if (!isEnabled()) { 829 return false; 830 } 831 switch (action) { 832 case AccessibilityNodeInfo.ACTION_SCROLL_FORWARD: 833 case R.id.accessibilityActionScrollDown: { 834 final int viewportHeight = getHeight() - mPaddingBottom - mPaddingTop; 835 final int targetScrollY = Math.min(mScrollY + viewportHeight, getScrollRange()); 836 if (targetScrollY != mScrollY) { 837 smoothScrollTo(0, targetScrollY); 838 return true; 839 } 840 } return false; 841 case AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD: 842 case R.id.accessibilityActionScrollUp: { 843 final int viewportHeight = getHeight() - mPaddingBottom - mPaddingTop; 844 final int targetScrollY = Math.max(mScrollY - viewportHeight, 0); 845 if (targetScrollY != mScrollY) { 846 smoothScrollTo(0, targetScrollY); 847 return true; 848 } 849 } return false; 850 } 851 return false; 852 } 853 854 @Override 855 public CharSequence getAccessibilityClassName() { 856 return ScrollView.class.getName(); 857 } 858 859 /** @hide */ 860 @Override 861 public void onInitializeAccessibilityNodeInfoInternal(AccessibilityNodeInfo info) { 862 super.onInitializeAccessibilityNodeInfoInternal(info); 863 if (isEnabled()) { 864 final int scrollRange = getScrollRange(); 865 if (scrollRange > 0) { 866 info.setScrollable(true); 867 if (mScrollY > 0) { 868 info.addAction( 869 AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_BACKWARD); 870 info.addAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_UP); 871 } 872 if (mScrollY < scrollRange) { 873 info.addAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_FORWARD); 874 info.addAction(AccessibilityNodeInfo.AccessibilityAction.ACTION_SCROLL_DOWN); 875 } 876 } 877 } 878 } 879 880 /** @hide */ 881 @Override 882 public void onInitializeAccessibilityEventInternal(AccessibilityEvent event) { 883 super.onInitializeAccessibilityEventInternal(event); 884 final boolean scrollable = getScrollRange() > 0; 885 event.setScrollable(scrollable); 886 event.setScrollX(mScrollX); 887 event.setScrollY(mScrollY); 888 event.setMaxScrollX(mScrollX); 889 event.setMaxScrollY(getScrollRange()); 890 } 891 892 private int getScrollRange() { 893 int scrollRange = 0; 894 if (getChildCount() > 0) { 895 View child = getChildAt(0); 896 scrollRange = Math.max(0, 897 child.getHeight() - (getHeight() - mPaddingBottom - mPaddingTop)); 898 } 899 return scrollRange; 900 } 901 902 /** 903 * <p> 904 * Finds the next focusable component that fits in the specified bounds. 905 * </p> 906 * 907 * @param topFocus look for a candidate is the one at the top of the bounds 908 * if topFocus is true, or at the bottom of the bounds if topFocus is 909 * false 910 * @param top the top offset of the bounds in which a focusable must be 911 * found 912 * @param bottom the bottom offset of the bounds in which a focusable must 913 * be found 914 * @return the next focusable component in the bounds or null if none can 915 * be found 916 */ 917 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 918 919 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 920 View focusCandidate = null; 921 922 /* 923 * A fully contained focusable is one where its top is below the bound's 924 * top, and its bottom is above the bound's bottom. A partially 925 * contained focusable is one where some part of it is within the 926 * bounds, but it also has some part that is not within bounds. A fully contained 927 * focusable is preferred to a partially contained focusable. 928 */ 929 boolean foundFullyContainedFocusable = false; 930 931 int count = focusables.size(); 932 for (int i = 0; i < count; i++) { 933 View view = focusables.get(i); 934 int viewTop = view.getTop(); 935 int viewBottom = view.getBottom(); 936 937 if (top < viewBottom && viewTop < bottom) { 938 /* 939 * the focusable is in the target area, it is a candidate for 940 * focusing 941 */ 942 943 final boolean viewIsFullyContained = (top < viewTop) && 944 (viewBottom < bottom); 945 946 if (focusCandidate == null) { 947 /* No candidate, take this one */ 948 focusCandidate = view; 949 foundFullyContainedFocusable = viewIsFullyContained; 950 } else { 951 final boolean viewIsCloserToBoundary = 952 (topFocus && viewTop < focusCandidate.getTop()) || 953 (!topFocus && viewBottom > focusCandidate 954 .getBottom()); 955 956 if (foundFullyContainedFocusable) { 957 if (viewIsFullyContained && viewIsCloserToBoundary) { 958 /* 959 * We're dealing with only fully contained views, so 960 * it has to be closer to the boundary to beat our 961 * candidate 962 */ 963 focusCandidate = view; 964 } 965 } else { 966 if (viewIsFullyContained) { 967 /* Any fully contained view beats a partially contained view */ 968 focusCandidate = view; 969 foundFullyContainedFocusable = true; 970 } else if (viewIsCloserToBoundary) { 971 /* 972 * Partially contained view beats another partially 973 * contained view if it's closer 974 */ 975 focusCandidate = view; 976 } 977 } 978 } 979 } 980 } 981 982 return focusCandidate; 983 } 984 985 /** 986 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 987 * method will scroll the view by one page up or down and give the focus 988 * to the topmost/bottommost component in the new visible area. If no 989 * component is a good candidate for focus, this scrollview reclaims the 990 * focus.</p> 991 * 992 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 993 * to go one page up or 994 * {@link android.view.View#FOCUS_DOWN} to go one page down 995 * @return true if the key event is consumed by this method, false otherwise 996 */ 997 public boolean pageScroll(int direction) { 998 boolean down = direction == View.FOCUS_DOWN; 999 int height = getHeight(); 1000 1001 if (down) { 1002 mTempRect.top = getScrollY() + height; 1003 int count = getChildCount(); 1004 if (count > 0) { 1005 View view = getChildAt(count - 1); 1006 if (mTempRect.top + height > view.getBottom()) { 1007 mTempRect.top = view.getBottom() - height; 1008 } 1009 } 1010 } else { 1011 mTempRect.top = getScrollY() - height; 1012 if (mTempRect.top < 0) { 1013 mTempRect.top = 0; 1014 } 1015 } 1016 mTempRect.bottom = mTempRect.top + height; 1017 1018 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 1019 } 1020 1021 /** 1022 * <p>Handles scrolling in response to a "home/end" shortcut press. This 1023 * method will scroll the view to the top or bottom and give the focus 1024 * to the topmost/bottommost component in the new visible area. If no 1025 * component is a good candidate for focus, this scrollview reclaims the 1026 * focus.</p> 1027 * 1028 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 1029 * to go the top of the view or 1030 * {@link android.view.View#FOCUS_DOWN} to go the bottom 1031 * @return true if the key event is consumed by this method, false otherwise 1032 */ 1033 public boolean fullScroll(int direction) { 1034 boolean down = direction == View.FOCUS_DOWN; 1035 int height = getHeight(); 1036 1037 mTempRect.top = 0; 1038 mTempRect.bottom = height; 1039 1040 if (down) { 1041 int count = getChildCount(); 1042 if (count > 0) { 1043 View view = getChildAt(count - 1); 1044 mTempRect.bottom = view.getBottom() + mPaddingBottom; 1045 mTempRect.top = mTempRect.bottom - height; 1046 } 1047 } 1048 1049 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 1050 } 1051 1052 /** 1053 * <p>Scrolls the view to make the area defined by <code>top</code> and 1054 * <code>bottom</code> visible. This method attempts to give the focus 1055 * to a component visible in this area. If no component can be focused in 1056 * the new visible area, the focus is reclaimed by this ScrollView.</p> 1057 * 1058 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 1059 * to go upward, {@link android.view.View#FOCUS_DOWN} to downward 1060 * @param top the top offset of the new area to be made visible 1061 * @param bottom the bottom offset of the new area to be made visible 1062 * @return true if the key event is consumed by this method, false otherwise 1063 */ 1064 private boolean scrollAndFocus(int direction, int top, int bottom) { 1065 boolean handled = true; 1066 1067 int height = getHeight(); 1068 int containerTop = getScrollY(); 1069 int containerBottom = containerTop + height; 1070 boolean up = direction == View.FOCUS_UP; 1071 1072 View newFocused = findFocusableViewInBounds(up, top, bottom); 1073 if (newFocused == null) { 1074 newFocused = this; 1075 } 1076 1077 if (top >= containerTop && bottom <= containerBottom) { 1078 handled = false; 1079 } else { 1080 int delta = up ? (top - containerTop) : (bottom - containerBottom); 1081 doScrollY(delta); 1082 } 1083 1084 if (newFocused != findFocus()) newFocused.requestFocus(direction); 1085 1086 return handled; 1087 } 1088 1089 /** 1090 * Handle scrolling in response to an up or down arrow click. 1091 * 1092 * @param direction The direction corresponding to the arrow key that was 1093 * pressed 1094 * @return True if we consumed the event, false otherwise 1095 */ 1096 public boolean arrowScroll(int direction) { 1097 1098 View currentFocused = findFocus(); 1099 if (currentFocused == this) currentFocused = null; 1100 1101 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 1102 1103 final int maxJump = getMaxScrollAmount(); 1104 1105 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 1106 nextFocused.getDrawingRect(mTempRect); 1107 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 1108 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1109 doScrollY(scrollDelta); 1110 nextFocused.requestFocus(direction); 1111 } else { 1112 // no new focus 1113 int scrollDelta = maxJump; 1114 1115 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 1116 scrollDelta = getScrollY(); 1117 } else if (direction == View.FOCUS_DOWN) { 1118 if (getChildCount() > 0) { 1119 int daBottom = getChildAt(0).getBottom(); 1120 int screenBottom = getScrollY() + getHeight() - mPaddingBottom; 1121 if (daBottom - screenBottom < maxJump) { 1122 scrollDelta = daBottom - screenBottom; 1123 } 1124 } 1125 } 1126 if (scrollDelta == 0) { 1127 return false; 1128 } 1129 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 1130 } 1131 1132 if (currentFocused != null && currentFocused.isFocused() 1133 && isOffScreen(currentFocused)) { 1134 // previously focused item still has focus and is off screen, give 1135 // it up (take it back to ourselves) 1136 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 1137 // sure to 1138 // get it) 1139 final int descendantFocusability = getDescendantFocusability(); // save 1140 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 1141 requestFocus(); 1142 setDescendantFocusability(descendantFocusability); // restore 1143 } 1144 return true; 1145 } 1146 1147 /** 1148 * @return whether the descendant of this scroll view is scrolled off 1149 * screen. 1150 */ 1151 private boolean isOffScreen(View descendant) { 1152 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 1153 } 1154 1155 /** 1156 * @return whether the descendant of this scroll view is within delta 1157 * pixels of being on the screen. 1158 */ 1159 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 1160 descendant.getDrawingRect(mTempRect); 1161 offsetDescendantRectToMyCoords(descendant, mTempRect); 1162 1163 return (mTempRect.bottom + delta) >= getScrollY() 1164 && (mTempRect.top - delta) <= (getScrollY() + height); 1165 } 1166 1167 /** 1168 * Smooth scroll by a Y delta 1169 * 1170 * @param delta the number of pixels to scroll by on the Y axis 1171 */ 1172 private void doScrollY(int delta) { 1173 if (delta != 0) { 1174 if (mSmoothScrollingEnabled) { 1175 smoothScrollBy(0, delta); 1176 } else { 1177 scrollBy(0, delta); 1178 } 1179 } 1180 } 1181 1182 /** 1183 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 1184 * 1185 * @param dx the number of pixels to scroll by on the X axis 1186 * @param dy the number of pixels to scroll by on the Y axis 1187 */ 1188 public final void smoothScrollBy(int dx, int dy) { 1189 if (getChildCount() == 0) { 1190 // Nothing to do. 1191 return; 1192 } 1193 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 1194 if (duration > ANIMATED_SCROLL_GAP) { 1195 final int height = getHeight() - mPaddingBottom - mPaddingTop; 1196 final int bottom = getChildAt(0).getHeight(); 1197 final int maxY = Math.max(0, bottom - height); 1198 final int scrollY = mScrollY; 1199 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 1200 1201 mScroller.startScroll(mScrollX, scrollY, 0, dy); 1202 postInvalidateOnAnimation(); 1203 } else { 1204 if (!mScroller.isFinished()) { 1205 mScroller.abortAnimation(); 1206 if (mFlingStrictSpan != null) { 1207 mFlingStrictSpan.finish(); 1208 mFlingStrictSpan = null; 1209 } 1210 } 1211 scrollBy(dx, dy); 1212 } 1213 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1214 } 1215 1216 /** 1217 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1218 * 1219 * @param x the position where to scroll on the X axis 1220 * @param y the position where to scroll on the Y axis 1221 */ 1222 public final void smoothScrollTo(int x, int y) { 1223 smoothScrollBy(x - mScrollX, y - mScrollY); 1224 } 1225 1226 /** 1227 * <p>The scroll range of a scroll view is the overall height of all of its 1228 * children.</p> 1229 */ 1230 @Override 1231 protected int computeVerticalScrollRange() { 1232 final int count = getChildCount(); 1233 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 1234 if (count == 0) { 1235 return contentHeight; 1236 } 1237 1238 int scrollRange = getChildAt(0).getBottom(); 1239 final int scrollY = mScrollY; 1240 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1241 if (scrollY < 0) { 1242 scrollRange -= scrollY; 1243 } else if (scrollY > overscrollBottom) { 1244 scrollRange += scrollY - overscrollBottom; 1245 } 1246 1247 return scrollRange; 1248 } 1249 1250 @Override 1251 protected int computeVerticalScrollOffset() { 1252 return Math.max(0, super.computeVerticalScrollOffset()); 1253 } 1254 1255 @Override 1256 protected void measureChild(View child, int parentWidthMeasureSpec, 1257 int parentHeightMeasureSpec) { 1258 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1259 1260 int childWidthMeasureSpec; 1261 int childHeightMeasureSpec; 1262 1263 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1264 + mPaddingRight, lp.width); 1265 1266 childHeightMeasureSpec = MeasureSpec.makeSafeMeasureSpec( 1267 MeasureSpec.getSize(parentHeightMeasureSpec), MeasureSpec.UNSPECIFIED); 1268 1269 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1270 } 1271 1272 @Override 1273 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1274 int parentHeightMeasureSpec, int heightUsed) { 1275 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1276 1277 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1278 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1279 + widthUsed, lp.width); 1280 final int childHeightMeasureSpec = MeasureSpec.makeSafeMeasureSpec( 1281 MeasureSpec.getSize(parentHeightMeasureSpec), MeasureSpec.UNSPECIFIED); 1282 1283 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1284 } 1285 1286 @Override 1287 public void computeScroll() { 1288 if (mScroller.computeScrollOffset()) { 1289 // This is called at drawing time by ViewGroup. We don't want to 1290 // re-show the scrollbars at this point, which scrollTo will do, 1291 // so we replicate most of scrollTo here. 1292 // 1293 // It's a little odd to call onScrollChanged from inside the drawing. 1294 // 1295 // It is, except when you remember that computeScroll() is used to 1296 // animate scrolling. So unless we want to defer the onScrollChanged() 1297 // until the end of the animated scrolling, we don't really have a 1298 // choice here. 1299 // 1300 // I agree. The alternative, which I think would be worse, is to post 1301 // something and tell the subclasses later. This is bad because there 1302 // will be a window where mScrollX/Y is different from what the app 1303 // thinks it is. 1304 // 1305 int oldX = mScrollX; 1306 int oldY = mScrollY; 1307 int x = mScroller.getCurrX(); 1308 int y = mScroller.getCurrY(); 1309 1310 if (oldX != x || oldY != y) { 1311 final int range = getScrollRange(); 1312 final int overscrollMode = getOverScrollMode(); 1313 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || 1314 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 1315 1316 overScrollBy(x - oldX, y - oldY, oldX, oldY, 0, range, 1317 0, mOverflingDistance, false); 1318 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1319 1320 if (canOverscroll) { 1321 if (y < 0 && oldY >= 0) { 1322 mEdgeGlowTop.onAbsorb((int) mScroller.getCurrVelocity()); 1323 } else if (y > range && oldY <= range) { 1324 mEdgeGlowBottom.onAbsorb((int) mScroller.getCurrVelocity()); 1325 } 1326 } 1327 } 1328 1329 if (!awakenScrollBars()) { 1330 // Keep on drawing until the animation has finished. 1331 postInvalidateOnAnimation(); 1332 } 1333 } else { 1334 if (mFlingStrictSpan != null) { 1335 mFlingStrictSpan.finish(); 1336 mFlingStrictSpan = null; 1337 } 1338 } 1339 } 1340 1341 /** 1342 * Scrolls the view to the given child. 1343 * 1344 * @param child the View to scroll to 1345 */ 1346 private void scrollToChild(View child) { 1347 child.getDrawingRect(mTempRect); 1348 1349 /* Offset from child's local coordinates to ScrollView coordinates */ 1350 offsetDescendantRectToMyCoords(child, mTempRect); 1351 1352 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1353 1354 if (scrollDelta != 0) { 1355 scrollBy(0, scrollDelta); 1356 } 1357 } 1358 1359 /** 1360 * If rect is off screen, scroll just enough to get it (or at least the 1361 * first screen size chunk of it) on screen. 1362 * 1363 * @param rect The rectangle. 1364 * @param immediate True to scroll immediately without animation 1365 * @return true if scrolling was performed 1366 */ 1367 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1368 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1369 final boolean scroll = delta != 0; 1370 if (scroll) { 1371 if (immediate) { 1372 scrollBy(0, delta); 1373 } else { 1374 smoothScrollBy(0, delta); 1375 } 1376 } 1377 return scroll; 1378 } 1379 1380 /** 1381 * Compute the amount to scroll in the Y direction in order to get 1382 * a rectangle completely on the screen (or, if taller than the screen, 1383 * at least the first screen size chunk of it). 1384 * 1385 * @param rect The rect. 1386 * @return The scroll delta. 1387 */ 1388 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1389 if (getChildCount() == 0) return 0; 1390 1391 int height = getHeight(); 1392 int screenTop = getScrollY(); 1393 int screenBottom = screenTop + height; 1394 1395 int fadingEdge = getVerticalFadingEdgeLength(); 1396 1397 // leave room for top fading edge as long as rect isn't at very top 1398 if (rect.top > 0) { 1399 screenTop += fadingEdge; 1400 } 1401 1402 // leave room for bottom fading edge as long as rect isn't at very bottom 1403 if (rect.bottom < getChildAt(0).getHeight()) { 1404 screenBottom -= fadingEdge; 1405 } 1406 1407 int scrollYDelta = 0; 1408 1409 if (rect.bottom > screenBottom && rect.top > screenTop) { 1410 // need to move down to get it in view: move down just enough so 1411 // that the entire rectangle is in view (or at least the first 1412 // screen size chunk). 1413 1414 if (rect.height() > height) { 1415 // just enough to get screen size chunk on 1416 scrollYDelta += (rect.top - screenTop); 1417 } else { 1418 // get entire rect at bottom of screen 1419 scrollYDelta += (rect.bottom - screenBottom); 1420 } 1421 1422 // make sure we aren't scrolling beyond the end of our content 1423 int bottom = getChildAt(0).getBottom(); 1424 int distanceToBottom = bottom - screenBottom; 1425 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1426 1427 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1428 // need to move up to get it in view: move up just enough so that 1429 // entire rectangle is in view (or at least the first screen 1430 // size chunk of it). 1431 1432 if (rect.height() > height) { 1433 // screen size chunk 1434 scrollYDelta -= (screenBottom - rect.bottom); 1435 } else { 1436 // entire rect at top 1437 scrollYDelta -= (screenTop - rect.top); 1438 } 1439 1440 // make sure we aren't scrolling any further than the top our content 1441 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1442 } 1443 return scrollYDelta; 1444 } 1445 1446 @Override 1447 public void requestChildFocus(View child, View focused) { 1448 if (!mIsLayoutDirty) { 1449 scrollToChild(focused); 1450 } else { 1451 // The child may not be laid out yet, we can't compute the scroll yet 1452 mChildToScrollTo = focused; 1453 } 1454 super.requestChildFocus(child, focused); 1455 } 1456 1457 1458 /** 1459 * When looking for focus in children of a scroll view, need to be a little 1460 * more careful not to give focus to something that is scrolled off screen. 1461 * 1462 * This is more expensive than the default {@link android.view.ViewGroup} 1463 * implementation, otherwise this behavior might have been made the default. 1464 */ 1465 @Override 1466 protected boolean onRequestFocusInDescendants(int direction, 1467 Rect previouslyFocusedRect) { 1468 1469 // convert from forward / backward notation to up / down / left / right 1470 // (ugh). 1471 if (direction == View.FOCUS_FORWARD) { 1472 direction = View.FOCUS_DOWN; 1473 } else if (direction == View.FOCUS_BACKWARD) { 1474 direction = View.FOCUS_UP; 1475 } 1476 1477 final View nextFocus = previouslyFocusedRect == null ? 1478 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1479 FocusFinder.getInstance().findNextFocusFromRect(this, 1480 previouslyFocusedRect, direction); 1481 1482 if (nextFocus == null) { 1483 return false; 1484 } 1485 1486 if (isOffScreen(nextFocus)) { 1487 return false; 1488 } 1489 1490 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1491 } 1492 1493 @Override 1494 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1495 boolean immediate) { 1496 // offset into coordinate space of this scroll view 1497 rectangle.offset(child.getLeft() - child.getScrollX(), 1498 child.getTop() - child.getScrollY()); 1499 1500 return scrollToChildRect(rectangle, immediate); 1501 } 1502 1503 @Override 1504 public void requestLayout() { 1505 mIsLayoutDirty = true; 1506 super.requestLayout(); 1507 } 1508 1509 @Override 1510 protected void onDetachedFromWindow() { 1511 super.onDetachedFromWindow(); 1512 1513 if (mScrollStrictSpan != null) { 1514 mScrollStrictSpan.finish(); 1515 mScrollStrictSpan = null; 1516 } 1517 if (mFlingStrictSpan != null) { 1518 mFlingStrictSpan.finish(); 1519 mFlingStrictSpan = null; 1520 } 1521 } 1522 1523 @Override 1524 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1525 super.onLayout(changed, l, t, r, b); 1526 mIsLayoutDirty = false; 1527 // Give a child focus if it needs it 1528 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1529 scrollToChild(mChildToScrollTo); 1530 } 1531 mChildToScrollTo = null; 1532 1533 if (!isLaidOut()) { 1534 if (mSavedState != null) { 1535 mScrollY = mSavedState.scrollPosition; 1536 mSavedState = null; 1537 } // mScrollY default value is "0" 1538 1539 final int childHeight = (getChildCount() > 0) ? getChildAt(0).getMeasuredHeight() : 0; 1540 final int scrollRange = Math.max(0, 1541 childHeight - (b - t - mPaddingBottom - mPaddingTop)); 1542 1543 // Don't forget to clamp 1544 if (mScrollY > scrollRange) { 1545 mScrollY = scrollRange; 1546 } else if (mScrollY < 0) { 1547 mScrollY = 0; 1548 } 1549 } 1550 1551 // Calling this with the present values causes it to re-claim them 1552 scrollTo(mScrollX, mScrollY); 1553 } 1554 1555 @Override 1556 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1557 super.onSizeChanged(w, h, oldw, oldh); 1558 1559 View currentFocused = findFocus(); 1560 if (null == currentFocused || this == currentFocused) 1561 return; 1562 1563 // If the currently-focused view was visible on the screen when the 1564 // screen was at the old height, then scroll the screen to make that 1565 // view visible with the new screen height. 1566 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1567 currentFocused.getDrawingRect(mTempRect); 1568 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1569 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1570 doScrollY(scrollDelta); 1571 } 1572 } 1573 1574 /** 1575 * Return true if child is a descendant of parent, (or equal to the parent). 1576 */ 1577 private static boolean isViewDescendantOf(View child, View parent) { 1578 if (child == parent) { 1579 return true; 1580 } 1581 1582 final ViewParent theParent = child.getParent(); 1583 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1584 } 1585 1586 /** 1587 * Fling the scroll view 1588 * 1589 * @param velocityY The initial velocity in the Y direction. Positive 1590 * numbers mean that the finger/cursor is moving down the screen, 1591 * which means we want to scroll towards the top. 1592 */ 1593 public void fling(int velocityY) { 1594 if (getChildCount() > 0) { 1595 int height = getHeight() - mPaddingBottom - mPaddingTop; 1596 int bottom = getChildAt(0).getHeight(); 1597 1598 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1599 Math.max(0, bottom - height), 0, height/2); 1600 1601 if (mFlingStrictSpan == null) { 1602 mFlingStrictSpan = StrictMode.enterCriticalSpan("ScrollView-fling"); 1603 } 1604 1605 postInvalidateOnAnimation(); 1606 } 1607 } 1608 1609 private void flingWithNestedDispatch(int velocityY) { 1610 final boolean canFling = (mScrollY > 0 || velocityY > 0) && 1611 (mScrollY < getScrollRange() || velocityY < 0); 1612 if (!dispatchNestedPreFling(0, velocityY)) { 1613 dispatchNestedFling(0, velocityY, canFling); 1614 if (canFling) { 1615 fling(velocityY); 1616 } 1617 } 1618 } 1619 1620 private void endDrag() { 1621 mIsBeingDragged = false; 1622 1623 recycleVelocityTracker(); 1624 1625 if (mEdgeGlowTop != null) { 1626 mEdgeGlowTop.onRelease(); 1627 mEdgeGlowBottom.onRelease(); 1628 } 1629 1630 if (mScrollStrictSpan != null) { 1631 mScrollStrictSpan.finish(); 1632 mScrollStrictSpan = null; 1633 } 1634 } 1635 1636 /** 1637 * {@inheritDoc} 1638 * 1639 * <p>This version also clamps the scrolling to the bounds of our child. 1640 */ 1641 @Override 1642 public void scrollTo(int x, int y) { 1643 // we rely on the fact the View.scrollBy calls scrollTo. 1644 if (getChildCount() > 0) { 1645 View child = getChildAt(0); 1646 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1647 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1648 if (x != mScrollX || y != mScrollY) { 1649 super.scrollTo(x, y); 1650 } 1651 } 1652 } 1653 1654 @Override 1655 public void setOverScrollMode(int mode) { 1656 if (mode != OVER_SCROLL_NEVER) { 1657 if (mEdgeGlowTop == null) { 1658 Context context = getContext(); 1659 mEdgeGlowTop = new EdgeEffect(context); 1660 mEdgeGlowBottom = new EdgeEffect(context); 1661 } 1662 } else { 1663 mEdgeGlowTop = null; 1664 mEdgeGlowBottom = null; 1665 } 1666 super.setOverScrollMode(mode); 1667 } 1668 1669 @Override 1670 public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) { 1671 return (nestedScrollAxes & SCROLL_AXIS_VERTICAL) != 0; 1672 } 1673 1674 @Override 1675 public void onNestedScrollAccepted(View child, View target, int axes) { 1676 super.onNestedScrollAccepted(child, target, axes); 1677 startNestedScroll(SCROLL_AXIS_VERTICAL); 1678 } 1679 1680 /** 1681 * @inheritDoc 1682 */ 1683 @Override 1684 public void onStopNestedScroll(View target) { 1685 super.onStopNestedScroll(target); 1686 } 1687 1688 @Override 1689 public void onNestedScroll(View target, int dxConsumed, int dyConsumed, 1690 int dxUnconsumed, int dyUnconsumed) { 1691 final int oldScrollY = mScrollY; 1692 scrollBy(0, dyUnconsumed); 1693 final int myConsumed = mScrollY - oldScrollY; 1694 final int myUnconsumed = dyUnconsumed - myConsumed; 1695 dispatchNestedScroll(0, myConsumed, 0, myUnconsumed, null); 1696 } 1697 1698 /** 1699 * @inheritDoc 1700 */ 1701 @Override 1702 public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) { 1703 if (!consumed) { 1704 flingWithNestedDispatch((int) velocityY); 1705 return true; 1706 } 1707 return false; 1708 } 1709 1710 @Override 1711 public void draw(Canvas canvas) { 1712 super.draw(canvas); 1713 if (mEdgeGlowTop != null) { 1714 final int scrollY = mScrollY; 1715 final boolean clipToPadding = getClipToPadding(); 1716 if (!mEdgeGlowTop.isFinished()) { 1717 final int restoreCount = canvas.save(); 1718 final int width; 1719 final int height; 1720 final float translateX; 1721 final float translateY; 1722 if (clipToPadding) { 1723 width = getWidth() - mPaddingLeft - mPaddingRight; 1724 height = getHeight() - mPaddingTop - mPaddingBottom; 1725 translateX = mPaddingLeft; 1726 translateY = mPaddingTop; 1727 } else { 1728 width = getWidth(); 1729 height = getHeight(); 1730 translateX = 0; 1731 translateY = 0; 1732 } 1733 canvas.translate(translateX, Math.min(0, scrollY) + translateY); 1734 mEdgeGlowTop.setSize(width, height); 1735 if (mEdgeGlowTop.draw(canvas)) { 1736 postInvalidateOnAnimation(); 1737 } 1738 canvas.restoreToCount(restoreCount); 1739 } 1740 if (!mEdgeGlowBottom.isFinished()) { 1741 final int restoreCount = canvas.save(); 1742 final int width; 1743 final int height; 1744 final float translateX; 1745 final float translateY; 1746 if (clipToPadding) { 1747 width = getWidth() - mPaddingLeft - mPaddingRight; 1748 height = getHeight() - mPaddingTop - mPaddingBottom; 1749 translateX = mPaddingLeft; 1750 translateY = mPaddingTop; 1751 } else { 1752 width = getWidth(); 1753 height = getHeight(); 1754 translateX = 0; 1755 translateY = 0; 1756 } 1757 canvas.translate(-width + translateX, 1758 Math.max(getScrollRange(), scrollY) + height + translateY); 1759 canvas.rotate(180, width, 0); 1760 mEdgeGlowBottom.setSize(width, height); 1761 if (mEdgeGlowBottom.draw(canvas)) { 1762 postInvalidateOnAnimation(); 1763 } 1764 canvas.restoreToCount(restoreCount); 1765 } 1766 } 1767 } 1768 1769 private static int clamp(int n, int my, int child) { 1770 if (my >= child || n < 0) { 1771 /* my >= child is this case: 1772 * |--------------- me ---------------| 1773 * |------ child ------| 1774 * or 1775 * |--------------- me ---------------| 1776 * |------ child ------| 1777 * or 1778 * |--------------- me ---------------| 1779 * |------ child ------| 1780 * 1781 * n < 0 is this case: 1782 * |------ me ------| 1783 * |-------- child --------| 1784 * |-- mScrollX --| 1785 */ 1786 return 0; 1787 } 1788 if ((my+n) > child) { 1789 /* this case: 1790 * |------ me ------| 1791 * |------ child ------| 1792 * |-- mScrollX --| 1793 */ 1794 return child-my; 1795 } 1796 return n; 1797 } 1798 1799 @Override 1800 protected void onRestoreInstanceState(Parcelable state) { 1801 if (mContext.getApplicationInfo().targetSdkVersion <= Build.VERSION_CODES.JELLY_BEAN_MR2) { 1802 // Some old apps reused IDs in ways they shouldn't have. 1803 // Don't break them, but they don't get scroll state restoration. 1804 super.onRestoreInstanceState(state); 1805 return; 1806 } 1807 SavedState ss = (SavedState) state; 1808 super.onRestoreInstanceState(ss.getSuperState()); 1809 mSavedState = ss; 1810 requestLayout(); 1811 } 1812 1813 @Override 1814 protected Parcelable onSaveInstanceState() { 1815 if (mContext.getApplicationInfo().targetSdkVersion <= Build.VERSION_CODES.JELLY_BEAN_MR2) { 1816 // Some old apps reused IDs in ways they shouldn't have. 1817 // Don't break them, but they don't get scroll state restoration. 1818 return super.onSaveInstanceState(); 1819 } 1820 Parcelable superState = super.onSaveInstanceState(); 1821 SavedState ss = new SavedState(superState); 1822 ss.scrollPosition = mScrollY; 1823 return ss; 1824 } 1825 1826 /** @hide */ 1827 @Override 1828 protected void encodeProperties(@NonNull ViewHierarchyEncoder encoder) { 1829 super.encodeProperties(encoder); 1830 encoder.addProperty("fillViewport", mFillViewport); 1831 } 1832 1833 static class SavedState extends BaseSavedState { 1834 public int scrollPosition; 1835 1836 SavedState(Parcelable superState) { 1837 super(superState); 1838 } 1839 1840 public SavedState(Parcel source) { 1841 super(source); 1842 scrollPosition = source.readInt(); 1843 } 1844 1845 @Override 1846 public void writeToParcel(Parcel dest, int flags) { 1847 super.writeToParcel(dest, flags); 1848 dest.writeInt(scrollPosition); 1849 } 1850 1851 @Override 1852 public String toString() { 1853 return "HorizontalScrollView.SavedState{" 1854 + Integer.toHexString(System.identityHashCode(this)) 1855 + " scrollPosition=" + scrollPosition + "}"; 1856 } 1857 1858 public static final Parcelable.Creator<SavedState> CREATOR 1859 = new Parcelable.Creator<SavedState>() { 1860 public SavedState createFromParcel(Parcel in) { 1861 return new SavedState(in); 1862 } 1863 1864 public SavedState[] newArray(int size) { 1865 return new SavedState[size]; 1866 } 1867 }; 1868 } 1869 1870 } 1871