HorizontalScrollView.java revision fb1e80a247221ee7e8f5c5deba04812021d9d07e
1/* 2 * Copyright (C) 2009 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package android.widget; 18 19import android.content.Context; 20import android.content.res.TypedArray; 21import android.graphics.Canvas; 22import android.graphics.Rect; 23import android.os.Bundle; 24import android.util.AttributeSet; 25import android.view.FocusFinder; 26import android.view.InputDevice; 27import android.view.KeyEvent; 28import android.view.MotionEvent; 29import android.view.VelocityTracker; 30import android.view.View; 31import android.view.ViewConfiguration; 32import android.view.ViewDebug; 33import android.view.ViewGroup; 34import android.view.ViewParent; 35import android.view.accessibility.AccessibilityEvent; 36import android.view.accessibility.AccessibilityNodeInfo; 37import android.view.animation.AnimationUtils; 38 39import java.util.List; 40 41/** 42 * Layout container for a view hierarchy that can be scrolled by the user, 43 * allowing it to be larger than the physical display. A HorizontalScrollView 44 * is a {@link FrameLayout}, meaning you should place one child in it 45 * containing the entire contents to scroll; this child may itself be a layout 46 * manager with a complex hierarchy of objects. A child that is often used 47 * is a {@link LinearLayout} in a horizontal orientation, presenting a horizontal 48 * array of top-level items that the user can scroll through. 49 * 50 * <p>You should never use a HorizontalScrollView with a {@link ListView}, since 51 * ListView takes care of its own scrolling. Most importantly, doing this 52 * defeats all of the important optimizations in ListView for dealing with 53 * large lists, since it effectively forces the ListView to display its entire 54 * list of items to fill up the infinite container supplied by HorizontalScrollView. 55 * 56 * <p>The {@link TextView} class also 57 * takes care of its own scrolling, so does not require a ScrollView, but 58 * using the two together is possible to achieve the effect of a text view 59 * within a larger container. 60 * 61 * <p>HorizontalScrollView only supports horizontal scrolling. 62 * 63 * @attr ref android.R.styleable#HorizontalScrollView_fillViewport 64 */ 65public class HorizontalScrollView extends FrameLayout { 66 private static final int ANIMATED_SCROLL_GAP = ScrollView.ANIMATED_SCROLL_GAP; 67 68 private static final float MAX_SCROLL_FACTOR = ScrollView.MAX_SCROLL_FACTOR; 69 70 71 private long mLastScroll; 72 73 private final Rect mTempRect = new Rect(); 74 private OverScroller mScroller; 75 private EdgeEffect mEdgeGlowLeft; 76 private EdgeEffect mEdgeGlowRight; 77 78 /** 79 * Position of the last motion event. 80 */ 81 private int mLastMotionX; 82 83 /** 84 * True when the layout has changed but the traversal has not come through yet. 85 * Ideally the view hierarchy would keep track of this for us. 86 */ 87 private boolean mIsLayoutDirty = true; 88 89 /** 90 * The child to give focus to in the event that a child has requested focus while the 91 * layout is dirty. This prevents the scroll from being wrong if the child has not been 92 * laid out before requesting focus. 93 */ 94 private View mChildToScrollTo = null; 95 96 /** 97 * True if the user is currently dragging this ScrollView around. This is 98 * not the same as 'is being flinged', which can be checked by 99 * mScroller.isFinished() (flinging begins when the user lifts his finger). 100 */ 101 private boolean mIsBeingDragged = false; 102 103 /** 104 * Determines speed during touch scrolling 105 */ 106 private VelocityTracker mVelocityTracker; 107 108 /** 109 * When set to true, the scroll view measure its child to make it fill the currently 110 * visible area. 111 */ 112 @ViewDebug.ExportedProperty(category = "layout") 113 private boolean mFillViewport; 114 115 /** 116 * Whether arrow scrolling is animated. 117 */ 118 private boolean mSmoothScrollingEnabled = true; 119 120 private int mTouchSlop; 121 private int mMinimumVelocity; 122 private int mMaximumVelocity; 123 124 private int mOverscrollDistance; 125 private int mOverflingDistance; 126 127 /** 128 * ID of the active pointer. This is used to retain consistency during 129 * drags/flings if multiple pointers are used. 130 */ 131 private int mActivePointerId = INVALID_POINTER; 132 133 /** 134 * Sentinel value for no current active pointer. 135 * Used by {@link #mActivePointerId}. 136 */ 137 private static final int INVALID_POINTER = -1; 138 139 public HorizontalScrollView(Context context) { 140 this(context, null); 141 } 142 143 public HorizontalScrollView(Context context, AttributeSet attrs) { 144 this(context, attrs, com.android.internal.R.attr.horizontalScrollViewStyle); 145 } 146 147 public HorizontalScrollView(Context context, AttributeSet attrs, int defStyle) { 148 super(context, attrs, defStyle); 149 initScrollView(); 150 151 TypedArray a = context.obtainStyledAttributes(attrs, 152 android.R.styleable.HorizontalScrollView, defStyle, 0); 153 154 setFillViewport(a.getBoolean(android.R.styleable.HorizontalScrollView_fillViewport, false)); 155 156 a.recycle(); 157 } 158 159 @Override 160 protected float getLeftFadingEdgeStrength() { 161 if (getChildCount() == 0) { 162 return 0.0f; 163 } 164 165 final int length = getHorizontalFadingEdgeLength(); 166 if (mScrollX < length) { 167 return mScrollX / (float) length; 168 } 169 170 return 1.0f; 171 } 172 173 @Override 174 protected float getRightFadingEdgeStrength() { 175 if (getChildCount() == 0) { 176 return 0.0f; 177 } 178 179 final int length = getHorizontalFadingEdgeLength(); 180 final int rightEdge = getWidth() - mPaddingRight; 181 final int span = getChildAt(0).getRight() - mScrollX - rightEdge; 182 if (span < length) { 183 return span / (float) length; 184 } 185 186 return 1.0f; 187 } 188 189 /** 190 * @return The maximum amount this scroll view will scroll in response to 191 * an arrow event. 192 */ 193 public int getMaxScrollAmount() { 194 return (int) (MAX_SCROLL_FACTOR * (mRight - mLeft)); 195 } 196 197 198 private void initScrollView() { 199 mScroller = new OverScroller(getContext()); 200 setFocusable(true); 201 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 202 setWillNotDraw(false); 203 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 204 mTouchSlop = configuration.getScaledTouchSlop(); 205 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 206 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 207 mOverscrollDistance = configuration.getScaledOverscrollDistance(); 208 mOverflingDistance = configuration.getScaledOverflingDistance(); 209 } 210 211 @Override 212 public void addView(View child) { 213 if (getChildCount() > 0) { 214 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 215 } 216 217 super.addView(child); 218 } 219 220 @Override 221 public void addView(View child, int index) { 222 if (getChildCount() > 0) { 223 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 224 } 225 226 super.addView(child, index); 227 } 228 229 @Override 230 public void addView(View child, ViewGroup.LayoutParams params) { 231 if (getChildCount() > 0) { 232 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 233 } 234 235 super.addView(child, params); 236 } 237 238 @Override 239 public void addView(View child, int index, ViewGroup.LayoutParams params) { 240 if (getChildCount() > 0) { 241 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 242 } 243 244 super.addView(child, index, params); 245 } 246 247 /** 248 * @return Returns true this HorizontalScrollView can be scrolled 249 */ 250 private boolean canScroll() { 251 View child = getChildAt(0); 252 if (child != null) { 253 int childWidth = child.getWidth(); 254 return getWidth() < childWidth + mPaddingLeft + mPaddingRight ; 255 } 256 return false; 257 } 258 259 /** 260 * Indicates whether this HorizontalScrollView's content is stretched to 261 * fill the viewport. 262 * 263 * @return True if the content fills the viewport, false otherwise. 264 * 265 * @attr ref android.R.styleable#HorizontalScrollView_fillViewport 266 */ 267 public boolean isFillViewport() { 268 return mFillViewport; 269 } 270 271 /** 272 * Indicates this HorizontalScrollView whether it should stretch its content width 273 * to fill the viewport or not. 274 * 275 * @param fillViewport True to stretch the content's width to the viewport's 276 * boundaries, false otherwise. 277 * 278 * @attr ref android.R.styleable#HorizontalScrollView_fillViewport 279 */ 280 public void setFillViewport(boolean fillViewport) { 281 if (fillViewport != mFillViewport) { 282 mFillViewport = fillViewport; 283 requestLayout(); 284 } 285 } 286 287 /** 288 * @return Whether arrow scrolling will animate its transition. 289 */ 290 public boolean isSmoothScrollingEnabled() { 291 return mSmoothScrollingEnabled; 292 } 293 294 /** 295 * Set whether arrow scrolling will animate its transition. 296 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 297 */ 298 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 299 mSmoothScrollingEnabled = smoothScrollingEnabled; 300 } 301 302 @Override 303 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 304 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 305 306 if (!mFillViewport) { 307 return; 308 } 309 310 final int widthMode = MeasureSpec.getMode(widthMeasureSpec); 311 if (widthMode == MeasureSpec.UNSPECIFIED) { 312 return; 313 } 314 315 if (getChildCount() > 0) { 316 final View child = getChildAt(0); 317 int width = getMeasuredWidth(); 318 if (child.getMeasuredWidth() < width) { 319 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 320 321 int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec, mPaddingTop 322 + mPaddingBottom, lp.height); 323 width -= mPaddingLeft; 324 width -= mPaddingRight; 325 int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY); 326 327 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 328 } 329 } 330 } 331 332 @Override 333 public boolean dispatchKeyEvent(KeyEvent event) { 334 // Let the focused view and/or our descendants get the key first 335 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 336 } 337 338 /** 339 * You can call this function yourself to have the scroll view perform 340 * scrolling from a key event, just as if the event had been dispatched to 341 * it by the view hierarchy. 342 * 343 * @param event The key event to execute. 344 * @return Return true if the event was handled, else false. 345 */ 346 public boolean executeKeyEvent(KeyEvent event) { 347 mTempRect.setEmpty(); 348 349 if (!canScroll()) { 350 if (isFocused()) { 351 View currentFocused = findFocus(); 352 if (currentFocused == this) currentFocused = null; 353 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 354 currentFocused, View.FOCUS_RIGHT); 355 return nextFocused != null && nextFocused != this && 356 nextFocused.requestFocus(View.FOCUS_RIGHT); 357 } 358 return false; 359 } 360 361 boolean handled = false; 362 if (event.getAction() == KeyEvent.ACTION_DOWN) { 363 switch (event.getKeyCode()) { 364 case KeyEvent.KEYCODE_DPAD_LEFT: 365 if (!event.isAltPressed()) { 366 handled = arrowScroll(View.FOCUS_LEFT); 367 } else { 368 handled = fullScroll(View.FOCUS_LEFT); 369 } 370 break; 371 case KeyEvent.KEYCODE_DPAD_RIGHT: 372 if (!event.isAltPressed()) { 373 handled = arrowScroll(View.FOCUS_RIGHT); 374 } else { 375 handled = fullScroll(View.FOCUS_RIGHT); 376 } 377 break; 378 case KeyEvent.KEYCODE_SPACE: 379 pageScroll(event.isShiftPressed() ? View.FOCUS_LEFT : View.FOCUS_RIGHT); 380 break; 381 } 382 } 383 384 return handled; 385 } 386 387 private boolean inChild(int x, int y) { 388 if (getChildCount() > 0) { 389 final int scrollX = mScrollX; 390 final View child = getChildAt(0); 391 return !(y < child.getTop() 392 || y >= child.getBottom() 393 || x < child.getLeft() - scrollX 394 || x >= child.getRight() - scrollX); 395 } 396 return false; 397 } 398 399 private void initOrResetVelocityTracker() { 400 if (mVelocityTracker == null) { 401 mVelocityTracker = VelocityTracker.obtain(); 402 } else { 403 mVelocityTracker.clear(); 404 } 405 } 406 407 private void initVelocityTrackerIfNotExists() { 408 if (mVelocityTracker == null) { 409 mVelocityTracker = VelocityTracker.obtain(); 410 } 411 } 412 413 private void recycleVelocityTracker() { 414 if (mVelocityTracker != null) { 415 mVelocityTracker.recycle(); 416 mVelocityTracker = null; 417 } 418 } 419 420 @Override 421 public void requestDisallowInterceptTouchEvent(boolean disallowIntercept) { 422 if (disallowIntercept) { 423 recycleVelocityTracker(); 424 } 425 super.requestDisallowInterceptTouchEvent(disallowIntercept); 426 } 427 428 @Override 429 public boolean onInterceptTouchEvent(MotionEvent ev) { 430 /* 431 * This method JUST determines whether we want to intercept the motion. 432 * If we return true, onMotionEvent will be called and we do the actual 433 * scrolling there. 434 */ 435 436 /* 437 * Shortcut the most recurring case: the user is in the dragging 438 * state and he is moving his finger. We want to intercept this 439 * motion. 440 */ 441 final int action = ev.getAction(); 442 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 443 return true; 444 } 445 446 switch (action & MotionEvent.ACTION_MASK) { 447 case MotionEvent.ACTION_MOVE: { 448 /* 449 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 450 * whether the user has moved far enough from his original down touch. 451 */ 452 453 /* 454 * Locally do absolute value. mLastMotionX is set to the x value 455 * of the down event. 456 */ 457 final int activePointerId = mActivePointerId; 458 if (activePointerId == INVALID_POINTER) { 459 // If we don't have a valid id, the touch down wasn't on content. 460 break; 461 } 462 463 final int pointerIndex = ev.findPointerIndex(activePointerId); 464 final int x = (int) ev.getX(pointerIndex); 465 final int xDiff = (int) Math.abs(x - mLastMotionX); 466 if (xDiff > mTouchSlop) { 467 mIsBeingDragged = true; 468 mLastMotionX = x; 469 initVelocityTrackerIfNotExists(); 470 mVelocityTracker.addMovement(ev); 471 if (mParent != null) mParent.requestDisallowInterceptTouchEvent(true); 472 } 473 break; 474 } 475 476 case MotionEvent.ACTION_DOWN: { 477 final int x = (int) ev.getX(); 478 if (!inChild((int) x, (int) ev.getY())) { 479 mIsBeingDragged = false; 480 recycleVelocityTracker(); 481 break; 482 } 483 484 /* 485 * Remember location of down touch. 486 * ACTION_DOWN always refers to pointer index 0. 487 */ 488 mLastMotionX = x; 489 mActivePointerId = ev.getPointerId(0); 490 491 initOrResetVelocityTracker(); 492 mVelocityTracker.addMovement(ev); 493 494 /* 495 * If being flinged and user touches the screen, initiate drag; 496 * otherwise don't. mScroller.isFinished should be false when 497 * being flinged. 498 */ 499 mIsBeingDragged = !mScroller.isFinished(); 500 break; 501 } 502 503 case MotionEvent.ACTION_CANCEL: 504 case MotionEvent.ACTION_UP: 505 /* Release the drag */ 506 mIsBeingDragged = false; 507 mActivePointerId = INVALID_POINTER; 508 if (mScroller.springBack(mScrollX, mScrollY, 0, getScrollRange(), 0, 0)) { 509 postInvalidateOnAnimation(); 510 } 511 break; 512 case MotionEvent.ACTION_POINTER_DOWN: { 513 final int index = ev.getActionIndex(); 514 mLastMotionX = (int) ev.getX(index); 515 mActivePointerId = ev.getPointerId(index); 516 break; 517 } 518 case MotionEvent.ACTION_POINTER_UP: 519 onSecondaryPointerUp(ev); 520 mLastMotionX = (int) ev.getX(ev.findPointerIndex(mActivePointerId)); 521 break; 522 } 523 524 /* 525 * The only time we want to intercept motion events is if we are in the 526 * drag mode. 527 */ 528 return mIsBeingDragged; 529 } 530 531 @Override 532 public boolean onTouchEvent(MotionEvent ev) { 533 initVelocityTrackerIfNotExists(); 534 mVelocityTracker.addMovement(ev); 535 536 final int action = ev.getAction(); 537 538 switch (action & MotionEvent.ACTION_MASK) { 539 case MotionEvent.ACTION_DOWN: { 540 if (getChildCount() == 0) { 541 return false; 542 } 543 if ((mIsBeingDragged = !mScroller.isFinished())) { 544 final ViewParent parent = getParent(); 545 if (parent != null) { 546 parent.requestDisallowInterceptTouchEvent(true); 547 } 548 } 549 550 /* 551 * If being flinged and user touches, stop the fling. isFinished 552 * will be false if being flinged. 553 */ 554 if (!mScroller.isFinished()) { 555 mScroller.abortAnimation(); 556 } 557 558 // Remember where the motion event started 559 mLastMotionX = (int) ev.getX(); 560 mActivePointerId = ev.getPointerId(0); 561 break; 562 } 563 case MotionEvent.ACTION_MOVE: 564 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 565 final int x = (int) ev.getX(activePointerIndex); 566 int deltaX = mLastMotionX - x; 567 if (!mIsBeingDragged && Math.abs(deltaX) > mTouchSlop) { 568 final ViewParent parent = getParent(); 569 if (parent != null) { 570 parent.requestDisallowInterceptTouchEvent(true); 571 } 572 mIsBeingDragged = true; 573 if (deltaX > 0) { 574 deltaX -= mTouchSlop; 575 } else { 576 deltaX += mTouchSlop; 577 } 578 } 579 if (mIsBeingDragged) { 580 // Scroll to follow the motion event 581 mLastMotionX = x; 582 583 final int oldX = mScrollX; 584 final int oldY = mScrollY; 585 final int range = getScrollRange(); 586 final int overscrollMode = getOverScrollMode(); 587 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || 588 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 589 590 if (overScrollBy(deltaX, 0, mScrollX, 0, range, 0, 591 mOverscrollDistance, 0, true)) { 592 // Break our velocity if we hit a scroll barrier. 593 mVelocityTracker.clear(); 594 } 595 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 596 597 if (canOverscroll) { 598 final int pulledToX = oldX + deltaX; 599 if (pulledToX < 0) { 600 mEdgeGlowLeft.onPull((float) deltaX / getWidth()); 601 if (!mEdgeGlowRight.isFinished()) { 602 mEdgeGlowRight.onRelease(); 603 } 604 } else if (pulledToX > range) { 605 mEdgeGlowRight.onPull((float) deltaX / getWidth()); 606 if (!mEdgeGlowLeft.isFinished()) { 607 mEdgeGlowLeft.onRelease(); 608 } 609 } 610 if (mEdgeGlowLeft != null 611 && (!mEdgeGlowLeft.isFinished() || !mEdgeGlowRight.isFinished())) { 612 postInvalidateOnAnimation(); 613 } 614 } 615 } 616 break; 617 case MotionEvent.ACTION_UP: 618 if (mIsBeingDragged) { 619 final VelocityTracker velocityTracker = mVelocityTracker; 620 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 621 int initialVelocity = (int) velocityTracker.getXVelocity(mActivePointerId); 622 623 if (getChildCount() > 0) { 624 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 625 fling(-initialVelocity); 626 } else { 627 if (mScroller.springBack(mScrollX, mScrollY, 0, 628 getScrollRange(), 0, 0)) { 629 postInvalidateOnAnimation(); 630 } 631 } 632 } 633 634 mActivePointerId = INVALID_POINTER; 635 mIsBeingDragged = false; 636 recycleVelocityTracker(); 637 638 if (mEdgeGlowLeft != null) { 639 mEdgeGlowLeft.onRelease(); 640 mEdgeGlowRight.onRelease(); 641 } 642 } 643 break; 644 case MotionEvent.ACTION_CANCEL: 645 if (mIsBeingDragged && getChildCount() > 0) { 646 if (mScroller.springBack(mScrollX, mScrollY, 0, getScrollRange(), 0, 0)) { 647 postInvalidateOnAnimation(); 648 } 649 mActivePointerId = INVALID_POINTER; 650 mIsBeingDragged = false; 651 recycleVelocityTracker(); 652 653 if (mEdgeGlowLeft != null) { 654 mEdgeGlowLeft.onRelease(); 655 mEdgeGlowRight.onRelease(); 656 } 657 } 658 break; 659 case MotionEvent.ACTION_POINTER_UP: 660 onSecondaryPointerUp(ev); 661 break; 662 } 663 return true; 664 } 665 666 private void onSecondaryPointerUp(MotionEvent ev) { 667 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 668 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 669 final int pointerId = ev.getPointerId(pointerIndex); 670 if (pointerId == mActivePointerId) { 671 // This was our active pointer going up. Choose a new 672 // active pointer and adjust accordingly. 673 // TODO: Make this decision more intelligent. 674 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 675 mLastMotionX = (int) ev.getX(newPointerIndex); 676 mActivePointerId = ev.getPointerId(newPointerIndex); 677 if (mVelocityTracker != null) { 678 mVelocityTracker.clear(); 679 } 680 } 681 } 682 683 @Override 684 public boolean onGenericMotionEvent(MotionEvent event) { 685 if ((event.getSource() & InputDevice.SOURCE_CLASS_POINTER) != 0) { 686 switch (event.getAction()) { 687 case MotionEvent.ACTION_SCROLL: { 688 if (!mIsBeingDragged) { 689 final float hscroll; 690 if ((event.getMetaState() & KeyEvent.META_SHIFT_ON) != 0) { 691 hscroll = -event.getAxisValue(MotionEvent.AXIS_VSCROLL); 692 } else { 693 hscroll = event.getAxisValue(MotionEvent.AXIS_HSCROLL); 694 } 695 if (hscroll != 0) { 696 final int delta = (int) (hscroll * getHorizontalScrollFactor()); 697 final int range = getScrollRange(); 698 int oldScrollX = mScrollX; 699 int newScrollX = oldScrollX + delta; 700 if (newScrollX < 0) { 701 newScrollX = 0; 702 } else if (newScrollX > range) { 703 newScrollX = range; 704 } 705 if (newScrollX != oldScrollX) { 706 super.scrollTo(newScrollX, mScrollY); 707 return true; 708 } 709 } 710 } 711 } 712 } 713 } 714 return super.onGenericMotionEvent(event); 715 } 716 717 @Override 718 public boolean shouldDelayChildPressedState() { 719 return true; 720 } 721 722 @Override 723 protected void onOverScrolled(int scrollX, int scrollY, 724 boolean clampedX, boolean clampedY) { 725 // Treat animating scrolls differently; see #computeScroll() for why. 726 if (!mScroller.isFinished()) { 727 mScrollX = scrollX; 728 mScrollY = scrollY; 729 invalidateParentIfNeeded(); 730 if (clampedX) { 731 mScroller.springBack(mScrollX, mScrollY, 0, getScrollRange(), 0, 0); 732 } 733 } else { 734 super.scrollTo(scrollX, scrollY); 735 } 736 737 awakenScrollBars(); 738 } 739 740 @Override 741 public boolean performAccessibilityAction(int action, Bundle arguments) { 742 if (super.performAccessibilityAction(action, arguments)) { 743 return true; 744 } 745 switch (action) { 746 case AccessibilityNodeInfo.ACTION_SCROLL_FORWARD: { 747 if (!isEnabled()) { 748 return false; 749 } 750 final int viewportWidth = getWidth() - mPaddingLeft - mPaddingRight; 751 final int targetScrollX = Math.min(mScrollX + viewportWidth, getScrollRange()); 752 if (targetScrollX != mScrollX) { 753 smoothScrollTo(targetScrollX, 0); 754 return true; 755 } 756 } return false; 757 case AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD: { 758 if (!isEnabled()) { 759 return false; 760 } 761 final int viewportWidth = getWidth() - mPaddingLeft - mPaddingRight; 762 final int targetScrollX = Math.max(0, mScrollX - viewportWidth); 763 if (targetScrollX != mScrollX) { 764 smoothScrollTo(targetScrollX, 0); 765 return true; 766 } 767 } return false; 768 } 769 return false; 770 } 771 772 @Override 773 public void onInitializeAccessibilityNodeInfo(AccessibilityNodeInfo info) { 774 super.onInitializeAccessibilityNodeInfo(info); 775 info.setClassName(HorizontalScrollView.class.getName()); 776 final int scrollRange = getScrollRange(); 777 if (scrollRange > 0) { 778 info.setScrollable(true); 779 if (isEnabled() && mScrollX > 0) { 780 info.addAction(AccessibilityNodeInfo.ACTION_SCROLL_BACKWARD); 781 } 782 if (isEnabled() && mScrollX < scrollRange) { 783 info.addAction(AccessibilityNodeInfo.ACTION_SCROLL_FORWARD); 784 } 785 } 786 } 787 788 @Override 789 public void onInitializeAccessibilityEvent(AccessibilityEvent event) { 790 super.onInitializeAccessibilityEvent(event); 791 event.setClassName(HorizontalScrollView.class.getName()); 792 event.setScrollable(getScrollRange() > 0); 793 event.setScrollX(mScrollX); 794 event.setScrollY(mScrollY); 795 event.setMaxScrollX(getScrollRange()); 796 event.setMaxScrollY(mScrollY); 797 } 798 799 private int getScrollRange() { 800 int scrollRange = 0; 801 if (getChildCount() > 0) { 802 View child = getChildAt(0); 803 scrollRange = Math.max(0, 804 child.getWidth() - (getWidth() - mPaddingLeft - mPaddingRight)); 805 } 806 return scrollRange; 807 } 808 809 /** 810 * <p> 811 * Finds the next focusable component that fits in this View's bounds 812 * (excluding fading edges) pretending that this View's left is located at 813 * the parameter left. 814 * </p> 815 * 816 * @param leftFocus look for a candidate is the one at the left of the bounds 817 * if leftFocus is true, or at the right of the bounds if leftFocus 818 * is false 819 * @param left the left offset of the bounds in which a focusable must be 820 * found (the fading edge is assumed to start at this position) 821 * @param preferredFocusable the View that has highest priority and will be 822 * returned if it is within my bounds (null is valid) 823 * @return the next focusable component in the bounds or null if none can be found 824 */ 825 private View findFocusableViewInMyBounds(final boolean leftFocus, 826 final int left, View preferredFocusable) { 827 /* 828 * The fading edge's transparent side should be considered for focus 829 * since it's mostly visible, so we divide the actual fading edge length 830 * by 2. 831 */ 832 final int fadingEdgeLength = getHorizontalFadingEdgeLength() / 2; 833 final int leftWithoutFadingEdge = left + fadingEdgeLength; 834 final int rightWithoutFadingEdge = left + getWidth() - fadingEdgeLength; 835 836 if ((preferredFocusable != null) 837 && (preferredFocusable.getLeft() < rightWithoutFadingEdge) 838 && (preferredFocusable.getRight() > leftWithoutFadingEdge)) { 839 return preferredFocusable; 840 } 841 842 return findFocusableViewInBounds(leftFocus, leftWithoutFadingEdge, 843 rightWithoutFadingEdge); 844 } 845 846 /** 847 * <p> 848 * Finds the next focusable component that fits in the specified bounds. 849 * </p> 850 * 851 * @param leftFocus look for a candidate is the one at the left of the bounds 852 * if leftFocus is true, or at the right of the bounds if 853 * leftFocus is false 854 * @param left the left offset of the bounds in which a focusable must be 855 * found 856 * @param right the right offset of the bounds in which a focusable must 857 * be found 858 * @return the next focusable component in the bounds or null if none can 859 * be found 860 */ 861 private View findFocusableViewInBounds(boolean leftFocus, int left, int right) { 862 863 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 864 View focusCandidate = null; 865 866 /* 867 * A fully contained focusable is one where its left is below the bound's 868 * left, and its right is above the bound's right. A partially 869 * contained focusable is one where some part of it is within the 870 * bounds, but it also has some part that is not within bounds. A fully contained 871 * focusable is preferred to a partially contained focusable. 872 */ 873 boolean foundFullyContainedFocusable = false; 874 875 int count = focusables.size(); 876 for (int i = 0; i < count; i++) { 877 View view = focusables.get(i); 878 int viewLeft = view.getLeft(); 879 int viewRight = view.getRight(); 880 881 if (left < viewRight && viewLeft < right) { 882 /* 883 * the focusable is in the target area, it is a candidate for 884 * focusing 885 */ 886 887 final boolean viewIsFullyContained = (left < viewLeft) && 888 (viewRight < right); 889 890 if (focusCandidate == null) { 891 /* No candidate, take this one */ 892 focusCandidate = view; 893 foundFullyContainedFocusable = viewIsFullyContained; 894 } else { 895 final boolean viewIsCloserToBoundary = 896 (leftFocus && viewLeft < focusCandidate.getLeft()) || 897 (!leftFocus && viewRight > focusCandidate.getRight()); 898 899 if (foundFullyContainedFocusable) { 900 if (viewIsFullyContained && viewIsCloserToBoundary) { 901 /* 902 * We're dealing with only fully contained views, so 903 * it has to be closer to the boundary to beat our 904 * candidate 905 */ 906 focusCandidate = view; 907 } 908 } else { 909 if (viewIsFullyContained) { 910 /* Any fully contained view beats a partially contained view */ 911 focusCandidate = view; 912 foundFullyContainedFocusable = true; 913 } else if (viewIsCloserToBoundary) { 914 /* 915 * Partially contained view beats another partially 916 * contained view if it's closer 917 */ 918 focusCandidate = view; 919 } 920 } 921 } 922 } 923 } 924 925 return focusCandidate; 926 } 927 928 /** 929 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 930 * method will scroll the view by one page left or right and give the focus 931 * to the leftmost/rightmost component in the new visible area. If no 932 * component is a good candidate for focus, this scrollview reclaims the 933 * focus.</p> 934 * 935 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 936 * to go one page left or {@link android.view.View#FOCUS_RIGHT} 937 * to go one page right 938 * @return true if the key event is consumed by this method, false otherwise 939 */ 940 public boolean pageScroll(int direction) { 941 boolean right = direction == View.FOCUS_RIGHT; 942 int width = getWidth(); 943 944 if (right) { 945 mTempRect.left = getScrollX() + width; 946 int count = getChildCount(); 947 if (count > 0) { 948 View view = getChildAt(0); 949 if (mTempRect.left + width > view.getRight()) { 950 mTempRect.left = view.getRight() - width; 951 } 952 } 953 } else { 954 mTempRect.left = getScrollX() - width; 955 if (mTempRect.left < 0) { 956 mTempRect.left = 0; 957 } 958 } 959 mTempRect.right = mTempRect.left + width; 960 961 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 962 } 963 964 /** 965 * <p>Handles scrolling in response to a "home/end" shortcut press. This 966 * method will scroll the view to the left or right and give the focus 967 * to the leftmost/rightmost component in the new visible area. If no 968 * component is a good candidate for focus, this scrollview reclaims the 969 * focus.</p> 970 * 971 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 972 * to go the left of the view or {@link android.view.View#FOCUS_RIGHT} 973 * to go the right 974 * @return true if the key event is consumed by this method, false otherwise 975 */ 976 public boolean fullScroll(int direction) { 977 boolean right = direction == View.FOCUS_RIGHT; 978 int width = getWidth(); 979 980 mTempRect.left = 0; 981 mTempRect.right = width; 982 983 if (right) { 984 int count = getChildCount(); 985 if (count > 0) { 986 View view = getChildAt(0); 987 mTempRect.right = view.getRight(); 988 mTempRect.left = mTempRect.right - width; 989 } 990 } 991 992 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 993 } 994 995 /** 996 * <p>Scrolls the view to make the area defined by <code>left</code> and 997 * <code>right</code> visible. This method attempts to give the focus 998 * to a component visible in this area. If no component can be focused in 999 * the new visible area, the focus is reclaimed by this scrollview.</p> 1000 * 1001 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 1002 * to go left {@link android.view.View#FOCUS_RIGHT} to right 1003 * @param left the left offset of the new area to be made visible 1004 * @param right the right offset of the new area to be made visible 1005 * @return true if the key event is consumed by this method, false otherwise 1006 */ 1007 private boolean scrollAndFocus(int direction, int left, int right) { 1008 boolean handled = true; 1009 1010 int width = getWidth(); 1011 int containerLeft = getScrollX(); 1012 int containerRight = containerLeft + width; 1013 boolean goLeft = direction == View.FOCUS_LEFT; 1014 1015 View newFocused = findFocusableViewInBounds(goLeft, left, right); 1016 if (newFocused == null) { 1017 newFocused = this; 1018 } 1019 1020 if (left >= containerLeft && right <= containerRight) { 1021 handled = false; 1022 } else { 1023 int delta = goLeft ? (left - containerLeft) : (right - containerRight); 1024 doScrollX(delta); 1025 } 1026 1027 if (newFocused != findFocus()) newFocused.requestFocus(direction); 1028 1029 return handled; 1030 } 1031 1032 /** 1033 * Handle scrolling in response to a left or right arrow click. 1034 * 1035 * @param direction The direction corresponding to the arrow key that was 1036 * pressed 1037 * @return True if we consumed the event, false otherwise 1038 */ 1039 public boolean arrowScroll(int direction) { 1040 1041 View currentFocused = findFocus(); 1042 if (currentFocused == this) currentFocused = null; 1043 1044 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 1045 1046 final int maxJump = getMaxScrollAmount(); 1047 1048 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 1049 nextFocused.getDrawingRect(mTempRect); 1050 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 1051 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1052 doScrollX(scrollDelta); 1053 nextFocused.requestFocus(direction); 1054 } else { 1055 // no new focus 1056 int scrollDelta = maxJump; 1057 1058 if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) { 1059 scrollDelta = getScrollX(); 1060 } else if (direction == View.FOCUS_RIGHT && getChildCount() > 0) { 1061 1062 int daRight = getChildAt(0).getRight(); 1063 1064 int screenRight = getScrollX() + getWidth(); 1065 1066 if (daRight - screenRight < maxJump) { 1067 scrollDelta = daRight - screenRight; 1068 } 1069 } 1070 if (scrollDelta == 0) { 1071 return false; 1072 } 1073 doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta); 1074 } 1075 1076 if (currentFocused != null && currentFocused.isFocused() 1077 && isOffScreen(currentFocused)) { 1078 // previously focused item still has focus and is off screen, give 1079 // it up (take it back to ourselves) 1080 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 1081 // sure to 1082 // get it) 1083 final int descendantFocusability = getDescendantFocusability(); // save 1084 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 1085 requestFocus(); 1086 setDescendantFocusability(descendantFocusability); // restore 1087 } 1088 return true; 1089 } 1090 1091 /** 1092 * @return whether the descendant of this scroll view is scrolled off 1093 * screen. 1094 */ 1095 private boolean isOffScreen(View descendant) { 1096 return !isWithinDeltaOfScreen(descendant, 0); 1097 } 1098 1099 /** 1100 * @return whether the descendant of this scroll view is within delta 1101 * pixels of being on the screen. 1102 */ 1103 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 1104 descendant.getDrawingRect(mTempRect); 1105 offsetDescendantRectToMyCoords(descendant, mTempRect); 1106 1107 return (mTempRect.right + delta) >= getScrollX() 1108 && (mTempRect.left - delta) <= (getScrollX() + getWidth()); 1109 } 1110 1111 /** 1112 * Smooth scroll by a X delta 1113 * 1114 * @param delta the number of pixels to scroll by on the X axis 1115 */ 1116 private void doScrollX(int delta) { 1117 if (delta != 0) { 1118 if (mSmoothScrollingEnabled) { 1119 smoothScrollBy(delta, 0); 1120 } else { 1121 scrollBy(delta, 0); 1122 } 1123 } 1124 } 1125 1126 /** 1127 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 1128 * 1129 * @param dx the number of pixels to scroll by on the X axis 1130 * @param dy the number of pixels to scroll by on the Y axis 1131 */ 1132 public final void smoothScrollBy(int dx, int dy) { 1133 if (getChildCount() == 0) { 1134 // Nothing to do. 1135 return; 1136 } 1137 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 1138 if (duration > ANIMATED_SCROLL_GAP) { 1139 final int width = getWidth() - mPaddingRight - mPaddingLeft; 1140 final int right = getChildAt(0).getWidth(); 1141 final int maxX = Math.max(0, right - width); 1142 final int scrollX = mScrollX; 1143 dx = Math.max(0, Math.min(scrollX + dx, maxX)) - scrollX; 1144 1145 mScroller.startScroll(scrollX, mScrollY, dx, 0); 1146 postInvalidateOnAnimation(); 1147 } else { 1148 if (!mScroller.isFinished()) { 1149 mScroller.abortAnimation(); 1150 } 1151 scrollBy(dx, dy); 1152 } 1153 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 1154 } 1155 1156 /** 1157 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 1158 * 1159 * @param x the position where to scroll on the X axis 1160 * @param y the position where to scroll on the Y axis 1161 */ 1162 public final void smoothScrollTo(int x, int y) { 1163 smoothScrollBy(x - mScrollX, y - mScrollY); 1164 } 1165 1166 /** 1167 * <p>The scroll range of a scroll view is the overall width of all of its 1168 * children.</p> 1169 */ 1170 @Override 1171 protected int computeHorizontalScrollRange() { 1172 final int count = getChildCount(); 1173 final int contentWidth = getWidth() - mPaddingLeft - mPaddingRight; 1174 if (count == 0) { 1175 return contentWidth; 1176 } 1177 1178 int scrollRange = getChildAt(0).getRight(); 1179 final int scrollX = mScrollX; 1180 final int overscrollRight = Math.max(0, scrollRange - contentWidth); 1181 if (scrollX < 0) { 1182 scrollRange -= scrollX; 1183 } else if (scrollX > overscrollRight) { 1184 scrollRange += scrollX - overscrollRight; 1185 } 1186 1187 return scrollRange; 1188 } 1189 1190 @Override 1191 protected int computeHorizontalScrollOffset() { 1192 return Math.max(0, super.computeHorizontalScrollOffset()); 1193 } 1194 1195 @Override 1196 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1197 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1198 1199 int childWidthMeasureSpec; 1200 int childHeightMeasureSpec; 1201 1202 childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop 1203 + mPaddingBottom, lp.height); 1204 1205 childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1206 1207 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1208 } 1209 1210 @Override 1211 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1212 int parentHeightMeasureSpec, int heightUsed) { 1213 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1214 1215 final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, 1216 mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin 1217 + heightUsed, lp.height); 1218 final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( 1219 lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); 1220 1221 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1222 } 1223 1224 @Override 1225 public void computeScroll() { 1226 if (mScroller.computeScrollOffset()) { 1227 // This is called at drawing time by ViewGroup. We don't want to 1228 // re-show the scrollbars at this point, which scrollTo will do, 1229 // so we replicate most of scrollTo here. 1230 // 1231 // It's a little odd to call onScrollChanged from inside the drawing. 1232 // 1233 // It is, except when you remember that computeScroll() is used to 1234 // animate scrolling. So unless we want to defer the onScrollChanged() 1235 // until the end of the animated scrolling, we don't really have a 1236 // choice here. 1237 // 1238 // I agree. The alternative, which I think would be worse, is to post 1239 // something and tell the subclasses later. This is bad because there 1240 // will be a window where mScrollX/Y is different from what the app 1241 // thinks it is. 1242 // 1243 int oldX = mScrollX; 1244 int oldY = mScrollY; 1245 int x = mScroller.getCurrX(); 1246 int y = mScroller.getCurrY(); 1247 1248 if (oldX != x || oldY != y) { 1249 final int range = getScrollRange(); 1250 final int overscrollMode = getOverScrollMode(); 1251 final boolean canOverscroll = overscrollMode == OVER_SCROLL_ALWAYS || 1252 (overscrollMode == OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0); 1253 1254 overScrollBy(x - oldX, y - oldY, oldX, oldY, range, 0, 1255 mOverflingDistance, 0, false); 1256 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1257 1258 if (canOverscroll) { 1259 if (x < 0 && oldX >= 0) { 1260 mEdgeGlowLeft.onAbsorb((int) mScroller.getCurrVelocity()); 1261 } else if (x > range && oldX <= range) { 1262 mEdgeGlowRight.onAbsorb((int) mScroller.getCurrVelocity()); 1263 } 1264 } 1265 } 1266 1267 if (!awakenScrollBars()) { 1268 postInvalidateOnAnimation(); 1269 } 1270 } 1271 } 1272 1273 /** 1274 * Scrolls the view to the given child. 1275 * 1276 * @param child the View to scroll to 1277 */ 1278 private void scrollToChild(View child) { 1279 child.getDrawingRect(mTempRect); 1280 1281 /* Offset from child's local coordinates to ScrollView coordinates */ 1282 offsetDescendantRectToMyCoords(child, mTempRect); 1283 1284 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1285 1286 if (scrollDelta != 0) { 1287 scrollBy(scrollDelta, 0); 1288 } 1289 } 1290 1291 /** 1292 * If rect is off screen, scroll just enough to get it (or at least the 1293 * first screen size chunk of it) on screen. 1294 * 1295 * @param rect The rectangle. 1296 * @param immediate True to scroll immediately without animation 1297 * @return true if scrolling was performed 1298 */ 1299 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1300 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1301 final boolean scroll = delta != 0; 1302 if (scroll) { 1303 if (immediate) { 1304 scrollBy(delta, 0); 1305 } else { 1306 smoothScrollBy(delta, 0); 1307 } 1308 } 1309 return scroll; 1310 } 1311 1312 /** 1313 * Compute the amount to scroll in the X direction in order to get 1314 * a rectangle completely on the screen (or, if taller than the screen, 1315 * at least the first screen size chunk of it). 1316 * 1317 * @param rect The rect. 1318 * @return The scroll delta. 1319 */ 1320 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1321 if (getChildCount() == 0) return 0; 1322 1323 int width = getWidth(); 1324 int screenLeft = getScrollX(); 1325 int screenRight = screenLeft + width; 1326 1327 int fadingEdge = getHorizontalFadingEdgeLength(); 1328 1329 // leave room for left fading edge as long as rect isn't at very left 1330 if (rect.left > 0) { 1331 screenLeft += fadingEdge; 1332 } 1333 1334 // leave room for right fading edge as long as rect isn't at very right 1335 if (rect.right < getChildAt(0).getWidth()) { 1336 screenRight -= fadingEdge; 1337 } 1338 1339 int scrollXDelta = 0; 1340 1341 if (rect.right > screenRight && rect.left > screenLeft) { 1342 // need to move right to get it in view: move right just enough so 1343 // that the entire rectangle is in view (or at least the first 1344 // screen size chunk). 1345 1346 if (rect.width() > width) { 1347 // just enough to get screen size chunk on 1348 scrollXDelta += (rect.left - screenLeft); 1349 } else { 1350 // get entire rect at right of screen 1351 scrollXDelta += (rect.right - screenRight); 1352 } 1353 1354 // make sure we aren't scrolling beyond the end of our content 1355 int right = getChildAt(0).getRight(); 1356 int distanceToRight = right - screenRight; 1357 scrollXDelta = Math.min(scrollXDelta, distanceToRight); 1358 1359 } else if (rect.left < screenLeft && rect.right < screenRight) { 1360 // need to move right to get it in view: move right just enough so that 1361 // entire rectangle is in view (or at least the first screen 1362 // size chunk of it). 1363 1364 if (rect.width() > width) { 1365 // screen size chunk 1366 scrollXDelta -= (screenRight - rect.right); 1367 } else { 1368 // entire rect at left 1369 scrollXDelta -= (screenLeft - rect.left); 1370 } 1371 1372 // make sure we aren't scrolling any further than the left our content 1373 scrollXDelta = Math.max(scrollXDelta, -getScrollX()); 1374 } 1375 return scrollXDelta; 1376 } 1377 1378 @Override 1379 public void requestChildFocus(View child, View focused) { 1380 if (!mIsLayoutDirty) { 1381 scrollToChild(focused); 1382 } else { 1383 // The child may not be laid out yet, we can't compute the scroll yet 1384 mChildToScrollTo = focused; 1385 } 1386 super.requestChildFocus(child, focused); 1387 } 1388 1389 1390 /** 1391 * When looking for focus in children of a scroll view, need to be a little 1392 * more careful not to give focus to something that is scrolled off screen. 1393 * 1394 * This is more expensive than the default {@link android.view.ViewGroup} 1395 * implementation, otherwise this behavior might have been made the default. 1396 */ 1397 @Override 1398 protected boolean onRequestFocusInDescendants(int direction, 1399 Rect previouslyFocusedRect) { 1400 1401 // convert from forward / backward notation to up / down / left / right 1402 // (ugh). 1403 if (direction == View.FOCUS_FORWARD) { 1404 direction = View.FOCUS_RIGHT; 1405 } else if (direction == View.FOCUS_BACKWARD) { 1406 direction = View.FOCUS_LEFT; 1407 } 1408 1409 final View nextFocus = previouslyFocusedRect == null ? 1410 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1411 FocusFinder.getInstance().findNextFocusFromRect(this, 1412 previouslyFocusedRect, direction); 1413 1414 if (nextFocus == null) { 1415 return false; 1416 } 1417 1418 if (isOffScreen(nextFocus)) { 1419 return false; 1420 } 1421 1422 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1423 } 1424 1425 @Override 1426 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1427 boolean immediate) { 1428 // offset into coordinate space of this scroll view 1429 rectangle.offset(child.getLeft() - child.getScrollX(), 1430 child.getTop() - child.getScrollY()); 1431 1432 return scrollToChildRect(rectangle, immediate); 1433 } 1434 1435 @Override 1436 public void requestLayout() { 1437 mIsLayoutDirty = true; 1438 super.requestLayout(); 1439 } 1440 1441 @Override 1442 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1443 super.onLayout(changed, l, t, r, b); 1444 mIsLayoutDirty = false; 1445 // Give a child focus if it needs it 1446 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1447 scrollToChild(mChildToScrollTo); 1448 } 1449 mChildToScrollTo = null; 1450 1451 // Calling this with the present values causes it to re-claim them 1452 scrollTo(mScrollX, mScrollY); 1453 } 1454 1455 @Override 1456 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1457 super.onSizeChanged(w, h, oldw, oldh); 1458 1459 View currentFocused = findFocus(); 1460 if (null == currentFocused || this == currentFocused) 1461 return; 1462 1463 final int maxJump = mRight - mLeft; 1464 1465 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1466 currentFocused.getDrawingRect(mTempRect); 1467 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1468 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1469 doScrollX(scrollDelta); 1470 } 1471 } 1472 1473 /** 1474 * Return true if child is a descendant of parent, (or equal to the parent). 1475 */ 1476 private static boolean isViewDescendantOf(View child, View parent) { 1477 if (child == parent) { 1478 return true; 1479 } 1480 1481 final ViewParent theParent = child.getParent(); 1482 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1483 } 1484 1485 /** 1486 * Fling the scroll view 1487 * 1488 * @param velocityX The initial velocity in the X direction. Positive 1489 * numbers mean that the finger/cursor is moving down the screen, 1490 * which means we want to scroll towards the left. 1491 */ 1492 public void fling(int velocityX) { 1493 if (getChildCount() > 0) { 1494 int width = getWidth() - mPaddingRight - mPaddingLeft; 1495 int right = getChildAt(0).getWidth(); 1496 1497 mScroller.fling(mScrollX, mScrollY, velocityX, 0, 0, 1498 Math.max(0, right - width), 0, 0, width/2, 0); 1499 1500 final boolean movingRight = velocityX > 0; 1501 1502 View currentFocused = findFocus(); 1503 View newFocused = findFocusableViewInMyBounds(movingRight, 1504 mScroller.getFinalX(), currentFocused); 1505 1506 if (newFocused == null) { 1507 newFocused = this; 1508 } 1509 1510 if (newFocused != currentFocused) { 1511 newFocused.requestFocus(movingRight ? View.FOCUS_RIGHT : View.FOCUS_LEFT); 1512 } 1513 1514 postInvalidateOnAnimation(); 1515 } 1516 } 1517 1518 /** 1519 * {@inheritDoc} 1520 * 1521 * <p>This version also clamps the scrolling to the bounds of our child. 1522 */ 1523 @Override 1524 public void scrollTo(int x, int y) { 1525 // we rely on the fact the View.scrollBy calls scrollTo. 1526 if (getChildCount() > 0) { 1527 View child = getChildAt(0); 1528 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1529 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1530 if (x != mScrollX || y != mScrollY) { 1531 super.scrollTo(x, y); 1532 } 1533 } 1534 } 1535 1536 @Override 1537 public void setOverScrollMode(int mode) { 1538 if (mode != OVER_SCROLL_NEVER) { 1539 if (mEdgeGlowLeft == null) { 1540 Context context = getContext(); 1541 mEdgeGlowLeft = new EdgeEffect(context); 1542 mEdgeGlowRight = new EdgeEffect(context); 1543 } 1544 } else { 1545 mEdgeGlowLeft = null; 1546 mEdgeGlowRight = null; 1547 } 1548 super.setOverScrollMode(mode); 1549 } 1550 1551 @SuppressWarnings({"SuspiciousNameCombination"}) 1552 @Override 1553 public void draw(Canvas canvas) { 1554 super.draw(canvas); 1555 if (mEdgeGlowLeft != null) { 1556 final int scrollX = mScrollX; 1557 if (!mEdgeGlowLeft.isFinished()) { 1558 final int restoreCount = canvas.save(); 1559 final int height = getHeight() - mPaddingTop - mPaddingBottom; 1560 1561 canvas.rotate(270); 1562 canvas.translate(-height + mPaddingTop, Math.min(0, scrollX)); 1563 mEdgeGlowLeft.setSize(height, getWidth()); 1564 if (mEdgeGlowLeft.draw(canvas)) { 1565 postInvalidateOnAnimation(); 1566 } 1567 canvas.restoreToCount(restoreCount); 1568 } 1569 if (!mEdgeGlowRight.isFinished()) { 1570 final int restoreCount = canvas.save(); 1571 final int width = getWidth(); 1572 final int height = getHeight() - mPaddingTop - mPaddingBottom; 1573 1574 canvas.rotate(90); 1575 canvas.translate(-mPaddingTop, 1576 -(Math.max(getScrollRange(), scrollX) + width)); 1577 mEdgeGlowRight.setSize(height, width); 1578 if (mEdgeGlowRight.draw(canvas)) { 1579 postInvalidateOnAnimation(); 1580 } 1581 canvas.restoreToCount(restoreCount); 1582 } 1583 } 1584 } 1585 1586 private static int clamp(int n, int my, int child) { 1587 if (my >= child || n < 0) { 1588 return 0; 1589 } 1590 if ((my + n) > child) { 1591 return child - my; 1592 } 1593 return n; 1594 } 1595} 1596