HorizontalScrollView.java revision 3dec7d563a2f3e1eb967ce2054a00b6620e3558c
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.util.AttributeSet; 20import android.graphics.Rect; 21import android.view.View; 22import android.view.VelocityTracker; 23import android.view.ViewConfiguration; 24import android.view.ViewGroup; 25import android.view.KeyEvent; 26import android.view.FocusFinder; 27import android.view.MotionEvent; 28import android.view.ViewParent; 29import android.view.animation.AnimationUtils; 30import android.content.Context; 31import android.content.res.TypedArray; 32 33import java.util.List; 34 35/** 36 * Layout container for a view hierarchy that can be scrolled by the user, 37 * allowing it to be larger than the physical display. A HorizontalScrollView 38 * is a {@link FrameLayout}, meaning you should place one child in it 39 * containing the entire contents to scroll; this child may itself be a layout 40 * manager with a complex hierarchy of objects. A child that is often used 41 * is a {@link LinearLayout} in a horizontal orientation, presenting a horizontal 42 * array of top-level items that the user can scroll through. 43 * 44 * <p>You should never use a HorizontalScrollView with a {@link ListView}, since 45 * ListView takes care of its own scrolling. Most importantly, doing this 46 * defeats all of the important optimizations in ListView for dealing with 47 * large lists, since it effectively forces the ListView to display its entire 48 * list of items to fill up the infinite container supplied by HorizontalScrollView. 49 * 50 * <p>The {@link TextView} class also 51 * takes care of its own scrolling, so does not require a ScrollView, but 52 * using the two together is possible to achieve the effect of a text view 53 * within a larger container. 54 * 55 * <p>HorizontalScrollView only supports horizontal scrolling. 56 */ 57public class HorizontalScrollView extends FrameLayout { 58 private static final int ANIMATED_SCROLL_GAP = ScrollView.ANIMATED_SCROLL_GAP; 59 60 private static final float MAX_SCROLL_FACTOR = ScrollView.MAX_SCROLL_FACTOR; 61 62 63 private long mLastScroll; 64 65 private final Rect mTempRect = new Rect(); 66 private Scroller mScroller; 67 68 /** 69 * Flag to indicate that we are moving focus ourselves. This is so the 70 * code that watches for focus changes initiated outside this ScrollView 71 * knows that it does not have to do anything. 72 */ 73 private boolean mScrollViewMovedFocus; 74 75 /** 76 * Position of the last motion event. 77 */ 78 private float mLastMotionX; 79 80 /** 81 * True when the layout has changed but the traversal has not come through yet. 82 * Ideally the view hierarchy would keep track of this for us. 83 */ 84 private boolean mIsLayoutDirty = true; 85 86 /** 87 * The child to give focus to in the event that a child has requested focus while the 88 * layout is dirty. This prevents the scroll from being wrong if the child has not been 89 * laid out before requesting focus. 90 */ 91 private View mChildToScrollTo = null; 92 93 /** 94 * True if the user is currently dragging this ScrollView around. This is 95 * not the same as 'is being flinged', which can be checked by 96 * mScroller.isFinished() (flinging begins when the user lifts his finger). 97 */ 98 private boolean mIsBeingDragged = false; 99 100 /** 101 * Determines speed during touch scrolling 102 */ 103 private VelocityTracker mVelocityTracker; 104 105 /** 106 * When set to true, the scroll view measure its child to make it fill the currently 107 * visible area. 108 */ 109 private boolean mFillViewport; 110 111 /** 112 * Whether arrow scrolling is animated. 113 */ 114 private boolean mSmoothScrollingEnabled = true; 115 116 private int mTouchSlop; 117 118 public HorizontalScrollView(Context context) { 119 this(context, null); 120 } 121 122 public HorizontalScrollView(Context context, AttributeSet attrs) { 123 this(context, attrs, com.android.internal.R.attr.horizontalScrollViewStyle); 124 } 125 126 public HorizontalScrollView(Context context, AttributeSet attrs, int defStyle) { 127 super(context, attrs, defStyle); 128 initScrollView(); 129 130 TypedArray a = context.obtainStyledAttributes(attrs, 131 android.R.styleable.HorizontalScrollView, defStyle, 0); 132 133 setFillViewport(a.getBoolean(android.R.styleable.HorizontalScrollView_fillViewport, false)); 134 135 a.recycle(); 136 } 137 138 @Override 139 protected float getLeftFadingEdgeStrength() { 140 if (getChildCount() == 0) { 141 return 0.0f; 142 } 143 144 final int length = getHorizontalFadingEdgeLength(); 145 if (mScrollX < length) { 146 return mScrollX / (float) length; 147 } 148 149 return 1.0f; 150 } 151 152 @Override 153 protected float getRightFadingEdgeStrength() { 154 if (getChildCount() == 0) { 155 return 0.0f; 156 } 157 158 final int length = getHorizontalFadingEdgeLength(); 159 final int rightEdge = getWidth() - mPaddingRight; 160 final int span = getChildAt(0).getRight() - mScrollX - rightEdge; 161 if (span < length) { 162 return span / (float) length; 163 } 164 165 return 1.0f; 166 } 167 168 /** 169 * @return The maximum amount this scroll view will scroll in response to 170 * an arrow event. 171 */ 172 public int getMaxScrollAmount() { 173 return (int) (MAX_SCROLL_FACTOR * (mRight - mLeft)); 174 } 175 176 177 private void initScrollView() { 178 mScroller = new Scroller(getContext()); 179 setFocusable(true); 180 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 181 setWillNotDraw(false); 182 mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop(); 183 } 184 185 @Override 186 public void addView(View child) { 187 if (getChildCount() > 0) { 188 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 189 } 190 191 super.addView(child); 192 } 193 194 @Override 195 public void addView(View child, int index) { 196 if (getChildCount() > 0) { 197 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 198 } 199 200 super.addView(child, index); 201 } 202 203 @Override 204 public void addView(View child, ViewGroup.LayoutParams params) { 205 if (getChildCount() > 0) { 206 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 207 } 208 209 super.addView(child, params); 210 } 211 212 @Override 213 public void addView(View child, int index, ViewGroup.LayoutParams params) { 214 if (getChildCount() > 0) { 215 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 216 } 217 218 super.addView(child, index, params); 219 } 220 221 /** 222 * @return Returns true this HorizontalScrollView can be scrolled 223 */ 224 private boolean canScroll() { 225 View child = getChildAt(0); 226 if (child != null) { 227 int childWidth = child.getWidth(); 228 return getWidth() < childWidth + mPaddingLeft + mPaddingRight ; 229 } 230 return false; 231 } 232 233 /** 234 * Indicates whether this ScrollView's content is stretched to fill the viewport. 235 * 236 * @return True if the content fills the viewport, false otherwise. 237 */ 238 public boolean isFillViewport() { 239 return mFillViewport; 240 } 241 242 /** 243 * Indicates this ScrollView whether it should stretch its content width to fill 244 * the viewport or not. 245 * 246 * @param fillViewport True to stretch the content's width to the viewport's 247 * boundaries, false otherwise. 248 */ 249 public void setFillViewport(boolean fillViewport) { 250 if (fillViewport != mFillViewport) { 251 mFillViewport = fillViewport; 252 requestLayout(); 253 } 254 } 255 256 /** 257 * @return Whether arrow scrolling will animate its transition. 258 */ 259 public boolean isSmoothScrollingEnabled() { 260 return mSmoothScrollingEnabled; 261 } 262 263 /** 264 * Set whether arrow scrolling will animate its transition. 265 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 266 */ 267 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 268 mSmoothScrollingEnabled = smoothScrollingEnabled; 269 } 270 271 @Override 272 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 273 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 274 275 if (!mFillViewport) { 276 return; 277 } 278 279 final int widthMode = MeasureSpec.getMode(widthMeasureSpec); 280 if (widthMode == MeasureSpec.UNSPECIFIED) { 281 return; 282 } 283 284 final View child = getChildAt(0); 285 int width = getMeasuredWidth(); 286 if (child.getMeasuredHeight() < width) { 287 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 288 289 int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec, mPaddingTop 290 + mPaddingBottom, lp.height); 291 width -= mPaddingLeft; 292 width -= mPaddingRight; 293 int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY); 294 295 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 296 } 297 } 298 299 @Override 300 public boolean dispatchKeyEvent(KeyEvent event) { 301 // Let the focused view and/or our descendants get the key first 302 boolean handled = super.dispatchKeyEvent(event); 303 if (handled) { 304 return true; 305 } 306 return executeKeyEvent(event); 307 } 308 309 /** 310 * You can call this function yourself to have the scroll view perform 311 * scrolling from a key event, just as if the event had been dispatched to 312 * it by the view hierarchy. 313 * 314 * @param event The key event to execute. 315 * @return Return true if the event was handled, else false. 316 */ 317 public boolean executeKeyEvent(KeyEvent event) { 318 mTempRect.setEmpty(); 319 320 if (!canScroll()) { 321 if (isFocused()) { 322 View currentFocused = findFocus(); 323 if (currentFocused == this) currentFocused = null; 324 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 325 currentFocused, View.FOCUS_RIGHT); 326 return nextFocused != null && nextFocused != this && 327 nextFocused.requestFocus(View.FOCUS_RIGHT); 328 } 329 return false; 330 } 331 332 boolean handled = false; 333 if (event.getAction() == KeyEvent.ACTION_DOWN) { 334 switch (event.getKeyCode()) { 335 case KeyEvent.KEYCODE_DPAD_LEFT: 336 if (!event.isAltPressed()) { 337 handled = arrowScroll(View.FOCUS_LEFT); 338 } else { 339 handled = fullScroll(View.FOCUS_LEFT); 340 } 341 break; 342 case KeyEvent.KEYCODE_DPAD_RIGHT: 343 if (!event.isAltPressed()) { 344 handled = arrowScroll(View.FOCUS_RIGHT); 345 } else { 346 handled = fullScroll(View.FOCUS_RIGHT); 347 } 348 break; 349 case KeyEvent.KEYCODE_SPACE: 350 pageScroll(event.isShiftPressed() ? View.FOCUS_LEFT : View.FOCUS_RIGHT); 351 break; 352 } 353 } 354 355 return handled; 356 } 357 358 @Override 359 public boolean onInterceptTouchEvent(MotionEvent ev) { 360 /* 361 * This method JUST determines whether we want to intercept the motion. 362 * If we return true, onMotionEvent will be called and we do the actual 363 * scrolling there. 364 */ 365 366 /* 367 * Shortcut the most recurring case: the user is in the dragging 368 * state and he is moving his finger. We want to intercept this 369 * motion. 370 */ 371 final int action = ev.getAction(); 372 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 373 return true; 374 } 375 376 if (!canScroll()) { 377 mIsBeingDragged = false; 378 return false; 379 } 380 381 final float x = ev.getX(); 382 383 switch (action) { 384 case MotionEvent.ACTION_MOVE: 385 /* 386 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 387 * whether the user has moved far enough from his original down touch. 388 */ 389 390 /* 391 * Locally do absolute value. mLastMotionX is set to the x value 392 * of the down event. 393 */ 394 final int xDiff = (int) Math.abs(x - mLastMotionX); 395 if (xDiff > mTouchSlop) { 396 mIsBeingDragged = true; 397 if (mParent != null) mParent.requestDisallowInterceptTouchEvent(true); 398 } 399 break; 400 401 case MotionEvent.ACTION_DOWN: 402 /* Remember location of down touch */ 403 mLastMotionX = x; 404 405 /* 406 * If being flinged and user touches the screen, initiate drag; 407 * otherwise don't. mScroller.isFinished should be false when 408 * being flinged. 409 */ 410 mIsBeingDragged = !mScroller.isFinished(); 411 break; 412 413 case MotionEvent.ACTION_CANCEL: 414 case MotionEvent.ACTION_UP: 415 /* Release the drag */ 416 mIsBeingDragged = false; 417 break; 418 } 419 420 /* 421 * The only time we want to intercept motion events is if we are in the 422 * drag mode. 423 */ 424 return mIsBeingDragged; 425 } 426 427 @Override 428 public boolean onTouchEvent(MotionEvent ev) { 429 430 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 431 // Don't handle edge touches immediately -- they may actually belong to one of our 432 // descendants. 433 return false; 434 } 435 436 if (!canScroll()) { 437 return false; 438 } 439 440 if (mVelocityTracker == null) { 441 mVelocityTracker = VelocityTracker.obtain(); 442 } 443 mVelocityTracker.addMovement(ev); 444 445 final int action = ev.getAction(); 446 final float x = ev.getX(); 447 448 switch (action) { 449 case MotionEvent.ACTION_DOWN: 450 /* 451 * If being flinged and user touches, stop the fling. isFinished 452 * will be false if being flinged. 453 */ 454 if (!mScroller.isFinished()) { 455 mScroller.abortAnimation(); 456 } 457 458 // Remember where the motion event started 459 mLastMotionX = x; 460 break; 461 case MotionEvent.ACTION_MOVE: 462 // Scroll to follow the motion event 463 final int deltaX = (int) (mLastMotionX - x); 464 mLastMotionX = x; 465 466 if (deltaX < 0) { 467 if (mScrollX > 0) { 468 scrollBy(deltaX, 0); 469 } 470 } else if (deltaX > 0) { 471 final int rightEdge = getWidth() - mPaddingRight; 472 final int availableToScroll = getChildAt(0).getRight() - mScrollX - rightEdge; 473 if (availableToScroll > 0) { 474 scrollBy(Math.min(availableToScroll, deltaX), 0); 475 } 476 } 477 break; 478 case MotionEvent.ACTION_UP: 479 final VelocityTracker velocityTracker = mVelocityTracker; 480 velocityTracker.computeCurrentVelocity(1000); 481 int initialVelocity = (int) velocityTracker.getXVelocity(); 482 483 if ((Math.abs(initialVelocity) > 484 ViewConfiguration.get(mContext).getScaledMinimumFlingVelocity()) && 485 getChildCount() > 0) { 486 fling(-initialVelocity); 487 } 488 489 if (mVelocityTracker != null) { 490 mVelocityTracker.recycle(); 491 mVelocityTracker = null; 492 } 493 } 494 return true; 495 } 496 497 /** 498 * <p> 499 * Finds the next focusable component that fits in this View's bounds 500 * (excluding fading edges) pretending that this View's left is located at 501 * the parameter left. 502 * </p> 503 * 504 * @param leftFocus look for a candidate is the one at the left of the bounds 505 * if leftFocus is true, or at the right of the bounds if leftFocus 506 * is false 507 * @param left the left offset of the bounds in which a focusable must be 508 * found (the fading edge is assumed to start at this position) 509 * @param preferredFocusable the View that has highest priority and will be 510 * returned if it is within my bounds (null is valid) 511 * @return the next focusable component in the bounds or null if none can be found 512 */ 513 private View findFocusableViewInMyBounds(final boolean leftFocus, 514 final int left, View preferredFocusable) { 515 /* 516 * The fading edge's transparent side should be considered for focus 517 * since it's mostly visible, so we divide the actual fading edge length 518 * by 2. 519 */ 520 final int fadingEdgeLength = getHorizontalFadingEdgeLength() / 2; 521 final int leftWithoutFadingEdge = left + fadingEdgeLength; 522 final int rightWithoutFadingEdge = left + getWidth() - fadingEdgeLength; 523 524 if ((preferredFocusable != null) 525 && (preferredFocusable.getLeft() < rightWithoutFadingEdge) 526 && (preferredFocusable.getRight() > leftWithoutFadingEdge)) { 527 return preferredFocusable; 528 } 529 530 return findFocusableViewInBounds(leftFocus, leftWithoutFadingEdge, 531 rightWithoutFadingEdge); 532 } 533 534 /** 535 * <p> 536 * Finds the next focusable component that fits in the specified bounds. 537 * </p> 538 * 539 * @param leftFocus look for a candidate is the one at the left of the bounds 540 * if leftFocus is true, or at the right of the bounds if 541 * leftFocus is false 542 * @param left the left offset of the bounds in which a focusable must be 543 * found 544 * @param right the right offset of the bounds in which a focusable must 545 * be found 546 * @return the next focusable component in the bounds or null if none can 547 * be found 548 */ 549 private View findFocusableViewInBounds(boolean leftFocus, int left, int right) { 550 551 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 552 View focusCandidate = null; 553 554 /* 555 * A fully contained focusable is one where its left is below the bound's 556 * left, and its right is above the bound's right. A partially 557 * contained focusable is one where some part of it is within the 558 * bounds, but it also has some part that is not within bounds. A fully contained 559 * focusable is preferred to a partially contained focusable. 560 */ 561 boolean foundFullyContainedFocusable = false; 562 563 int count = focusables.size(); 564 for (int i = 0; i < count; i++) { 565 View view = focusables.get(i); 566 int viewLeft = view.getLeft(); 567 int viewRight = view.getRight(); 568 569 if (left < viewRight && viewLeft < right) { 570 /* 571 * the focusable is in the target area, it is a candidate for 572 * focusing 573 */ 574 575 final boolean viewIsFullyContained = (left < viewLeft) && 576 (viewRight < right); 577 578 if (focusCandidate == null) { 579 /* No candidate, take this one */ 580 focusCandidate = view; 581 foundFullyContainedFocusable = viewIsFullyContained; 582 } else { 583 final boolean viewIsCloserToBoundary = 584 (leftFocus && viewLeft < focusCandidate.getLeft()) || 585 (!leftFocus && viewRight > focusCandidate.getRight()); 586 587 if (foundFullyContainedFocusable) { 588 if (viewIsFullyContained && viewIsCloserToBoundary) { 589 /* 590 * We're dealing with only fully contained views, so 591 * it has to be closer to the boundary to beat our 592 * candidate 593 */ 594 focusCandidate = view; 595 } 596 } else { 597 if (viewIsFullyContained) { 598 /* Any fully contained view beats a partially contained view */ 599 focusCandidate = view; 600 foundFullyContainedFocusable = true; 601 } else if (viewIsCloserToBoundary) { 602 /* 603 * Partially contained view beats another partially 604 * contained view if it's closer 605 */ 606 focusCandidate = view; 607 } 608 } 609 } 610 } 611 } 612 613 return focusCandidate; 614 } 615 616 /** 617 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 618 * method will scroll the view by one page left or right and give the focus 619 * to the leftmost/rightmost component in the new visible area. If no 620 * component is a good candidate for focus, this scrollview reclaims the 621 * focus.</p> 622 * 623 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 624 * to go one page left or {@link android.view.View#FOCUS_RIGHT} 625 * to go one page right 626 * @return true if the key event is consumed by this method, false otherwise 627 */ 628 public boolean pageScroll(int direction) { 629 boolean right = direction == View.FOCUS_RIGHT; 630 int width = getWidth(); 631 632 if (right) { 633 mTempRect.left = getScrollX() + width; 634 int count = getChildCount(); 635 if (count > 0) { 636 View view = getChildAt(count - 1); 637 if (mTempRect.left + width > view.getRight()) { 638 mTempRect.left = view.getRight() - width; 639 } 640 } 641 } else { 642 mTempRect.left = getScrollX() - width; 643 if (mTempRect.left < 0) { 644 mTempRect.left = 0; 645 } 646 } 647 mTempRect.right = mTempRect.left + width; 648 649 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 650 } 651 652 /** 653 * <p>Handles scrolling in response to a "home/end" shortcut press. This 654 * method will scroll the view to the left or right and give the focus 655 * to the leftmost/rightmost component in the new visible area. If no 656 * component is a good candidate for focus, this scrollview reclaims the 657 * focus.</p> 658 * 659 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 660 * to go the left of the view or {@link android.view.View#FOCUS_RIGHT} 661 * to go the right 662 * @return true if the key event is consumed by this method, false otherwise 663 */ 664 public boolean fullScroll(int direction) { 665 boolean right = direction == View.FOCUS_RIGHT; 666 int width = getWidth(); 667 668 mTempRect.left = 0; 669 mTempRect.right = width; 670 671 if (right) { 672 int count = getChildCount(); 673 if (count > 0) { 674 View view = getChildAt(count - 1); 675 mTempRect.right = view.getRight(); 676 mTempRect.left = mTempRect.right - width; 677 } 678 } 679 680 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 681 } 682 683 /** 684 * <p>Scrolls the view to make the area defined by <code>left</code> and 685 * <code>right</code> visible. This method attempts to give the focus 686 * to a component visible in this area. If no component can be focused in 687 * the new visible area, the focus is reclaimed by this scrollview.</p> 688 * 689 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 690 * to go left {@link android.view.View#FOCUS_RIGHT} to right 691 * @param left the left offset of the new area to be made visible 692 * @param right the right offset of the new area to be made visible 693 * @return true if the key event is consumed by this method, false otherwise 694 */ 695 private boolean scrollAndFocus(int direction, int left, int right) { 696 boolean handled = true; 697 698 int width = getWidth(); 699 int containerLeft = getScrollX(); 700 int containerRight = containerLeft + width; 701 boolean goLeft = direction == View.FOCUS_LEFT; 702 703 View newFocused = findFocusableViewInBounds(goLeft, left, right); 704 if (newFocused == null) { 705 newFocused = this; 706 } 707 708 if (left >= containerLeft && right <= containerRight) { 709 handled = false; 710 } else { 711 int delta = goLeft ? (left - containerLeft) : (right - containerRight); 712 doScrollX(delta); 713 } 714 715 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 716 mScrollViewMovedFocus = true; 717 mScrollViewMovedFocus = false; 718 } 719 720 return handled; 721 } 722 723 /** 724 * Handle scrolling in response to a left or right arrow click. 725 * 726 * @param direction The direction corresponding to the arrow key that was 727 * pressed 728 * @return True if we consumed the event, false otherwise 729 */ 730 public boolean arrowScroll(int direction) { 731 732 View currentFocused = findFocus(); 733 if (currentFocused == this) currentFocused = null; 734 735 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 736 737 final int maxJump = getMaxScrollAmount(); 738 739 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 740 nextFocused.getDrawingRect(mTempRect); 741 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 742 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 743 doScrollX(scrollDelta); 744 nextFocused.requestFocus(direction); 745 } else { 746 // no new focus 747 int scrollDelta = maxJump; 748 749 if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) { 750 scrollDelta = getScrollX(); 751 } else if (direction == View.FOCUS_RIGHT) { 752 753 int daRight = getChildAt(getChildCount() - 1).getRight(); 754 755 int screenRight = getScrollX() + getWidth(); 756 757 if (daRight - screenRight < maxJump) { 758 scrollDelta = daRight - screenRight; 759 } 760 } 761 if (scrollDelta == 0) { 762 return false; 763 } 764 doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta); 765 } 766 767 if (currentFocused != null && currentFocused.isFocused() 768 && isOffScreen(currentFocused)) { 769 // previously focused item still has focus and is off screen, give 770 // it up (take it back to ourselves) 771 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 772 // sure to 773 // get it) 774 final int descendantFocusability = getDescendantFocusability(); // save 775 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 776 requestFocus(); 777 setDescendantFocusability(descendantFocusability); // restore 778 } 779 return true; 780 } 781 782 /** 783 * @return whether the descendant of this scroll view is scrolled off 784 * screen. 785 */ 786 private boolean isOffScreen(View descendant) { 787 return !isWithinDeltaOfScreen(descendant, 0); 788 } 789 790 /** 791 * @return whether the descendant of this scroll view is within delta 792 * pixels of being on the screen. 793 */ 794 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 795 descendant.getDrawingRect(mTempRect); 796 offsetDescendantRectToMyCoords(descendant, mTempRect); 797 798 return (mTempRect.right + delta) >= getScrollX() 799 && (mTempRect.left - delta) <= (getScrollX() + getWidth()); 800 } 801 802 /** 803 * Smooth scroll by a X delta 804 * 805 * @param delta the number of pixels to scroll by on the X axis 806 */ 807 private void doScrollX(int delta) { 808 if (delta != 0) { 809 if (mSmoothScrollingEnabled) { 810 smoothScrollBy(delta, 0); 811 } else { 812 scrollBy(delta, 0); 813 } 814 } 815 } 816 817 /** 818 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 819 * 820 * @param dx the number of pixels to scroll by on the X axis 821 * @param dy the number of pixels to scroll by on the Y axis 822 */ 823 public final void smoothScrollBy(int dx, int dy) { 824 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 825 if (duration > ANIMATED_SCROLL_GAP) { 826 mScroller.startScroll(mScrollX, mScrollY, dx, dy); 827 invalidate(); 828 } else { 829 if (!mScroller.isFinished()) { 830 mScroller.abortAnimation(); 831 } 832 scrollBy(dx, dy); 833 } 834 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 835 } 836 837 /** 838 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 839 * 840 * @param x the position where to scroll on the X axis 841 * @param y the position where to scroll on the Y axis 842 */ 843 public final void smoothScrollTo(int x, int y) { 844 smoothScrollBy(x - mScrollX, y - mScrollY); 845 } 846 847 /** 848 * <p>The scroll range of a scroll view is the overall width of all of its 849 * children.</p> 850 */ 851 @Override 852 protected int computeHorizontalScrollRange() { 853 int count = getChildCount(); 854 return count == 0 ? getWidth() : getChildAt(0).getRight(); 855 } 856 857 858 @Override 859 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 860 ViewGroup.LayoutParams lp = child.getLayoutParams(); 861 862 int childWidthMeasureSpec; 863 int childHeightMeasureSpec; 864 865 childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop 866 + mPaddingBottom, lp.height); 867 868 childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 869 870 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 871 } 872 873 @Override 874 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 875 int parentHeightMeasureSpec, int heightUsed) { 876 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 877 878 final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, 879 mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin 880 + heightUsed, lp.height); 881 final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( 882 lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); 883 884 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 885 } 886 887 @Override 888 public void computeScroll() { 889 if (mScroller.computeScrollOffset()) { 890 // This is called at drawing time by ViewGroup. We don't want to 891 // re-show the scrollbars at this point, which scrollTo will do, 892 // so we replicate most of scrollTo here. 893 // 894 // It's a little odd to call onScrollChanged from inside the drawing. 895 // 896 // It is, except when you remember that computeScroll() is used to 897 // animate scrolling. So unless we want to defer the onScrollChanged() 898 // until the end of the animated scrolling, we don't really have a 899 // choice here. 900 // 901 // I agree. The alternative, which I think would be worse, is to post 902 // something and tell the subclasses later. This is bad because there 903 // will be a window where mScrollX/Y is different from what the app 904 // thinks it is. 905 // 906 int oldX = mScrollX; 907 int oldY = mScrollY; 908 int x = mScroller.getCurrX(); 909 int y = mScroller.getCurrY(); 910 if (getChildCount() > 0) { 911 View child = getChildAt(0); 912 mScrollX = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 913 mScrollY = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 914 } else { 915 mScrollX = x; 916 mScrollY = y; 917 } 918 if (oldX != mScrollX || oldY != mScrollY) { 919 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 920 } 921 922 // Keep on drawing until the animation has finished. 923 postInvalidate(); 924 } 925 } 926 927 /** 928 * Scrolls the view to the given child. 929 * 930 * @param child the View to scroll to 931 */ 932 private void scrollToChild(View child) { 933 child.getDrawingRect(mTempRect); 934 935 /* Offset from child's local coordinates to ScrollView coordinates */ 936 offsetDescendantRectToMyCoords(child, mTempRect); 937 938 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 939 940 if (scrollDelta != 0) { 941 scrollBy(scrollDelta, 0); 942 } 943 } 944 945 /** 946 * If rect is off screen, scroll just enough to get it (or at least the 947 * first screen size chunk of it) on screen. 948 * 949 * @param rect The rectangle. 950 * @param immediate True to scroll immediately without animation 951 * @return true if scrolling was performed 952 */ 953 private boolean scrollToChildRect(Rect rect, boolean immediate) { 954 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 955 final boolean scroll = delta != 0; 956 if (scroll) { 957 if (immediate) { 958 scrollBy(delta, 0); 959 } else { 960 smoothScrollBy(delta, 0); 961 } 962 } 963 return scroll; 964 } 965 966 /** 967 * Compute the amount to scroll in the X direction in order to get 968 * a rectangle completely on the screen (or, if taller than the screen, 969 * at least the first screen size chunk of it). 970 * 971 * @param rect The rect. 972 * @return The scroll delta. 973 */ 974 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 975 976 int width = getWidth(); 977 int screenLeft = getScrollX(); 978 int screenRight = screenLeft + width; 979 980 int fadingEdge = getHorizontalFadingEdgeLength(); 981 982 // leave room for left fading edge as long as rect isn't at very left 983 if (rect.left > 0) { 984 screenLeft += fadingEdge; 985 } 986 987 // leave room for right fading edge as long as rect isn't at very right 988 if (rect.right < getChildAt(0).getWidth()) { 989 screenRight -= fadingEdge; 990 } 991 992 int scrollXDelta = 0; 993 994 if (rect.right > screenRight && rect.left > screenLeft) { 995 // need to move right to get it in view: move right just enough so 996 // that the entire rectangle is in view (or at least the first 997 // screen size chunk). 998 999 if (rect.width() > width) { 1000 // just enough to get screen size chunk on 1001 scrollXDelta += (rect.left - screenLeft); 1002 } else { 1003 // get entire rect at right of screen 1004 scrollXDelta += (rect.right - screenRight); 1005 } 1006 1007 // make sure we aren't scrolling beyond the end of our content 1008 int right = getChildAt(getChildCount() - 1).getRight(); 1009 int distanceToRight = right - screenRight; 1010 scrollXDelta = Math.min(scrollXDelta, distanceToRight); 1011 1012 } else if (rect.left < screenLeft && rect.right < screenRight) { 1013 // need to move right to get it in view: move right just enough so that 1014 // entire rectangle is in view (or at least the first screen 1015 // size chunk of it). 1016 1017 if (rect.width() > width) { 1018 // screen size chunk 1019 scrollXDelta -= (screenRight - rect.right); 1020 } else { 1021 // entire rect at left 1022 scrollXDelta -= (screenLeft - rect.left); 1023 } 1024 1025 // make sure we aren't scrolling any further than the left our content 1026 scrollXDelta = Math.max(scrollXDelta, -getScrollX()); 1027 } 1028 return scrollXDelta; 1029 } 1030 1031 @Override 1032 public void requestChildFocus(View child, View focused) { 1033 if (!mScrollViewMovedFocus) { 1034 if (!mIsLayoutDirty) { 1035 scrollToChild(focused); 1036 } else { 1037 // The child may not be laid out yet, we can't compute the scroll yet 1038 mChildToScrollTo = focused; 1039 } 1040 } 1041 super.requestChildFocus(child, focused); 1042 } 1043 1044 1045 /** 1046 * When looking for focus in children of a scroll view, need to be a little 1047 * more careful not to give focus to something that is scrolled off screen. 1048 * 1049 * This is more expensive than the default {@link android.view.ViewGroup} 1050 * implementation, otherwise this behavior might have been made the default. 1051 */ 1052 @Override 1053 protected boolean onRequestFocusInDescendants(int direction, 1054 Rect previouslyFocusedRect) { 1055 1056 // convert from forward / backward notation to up / down / left / right 1057 // (ugh). 1058 if (direction == View.FOCUS_FORWARD) { 1059 direction = View.FOCUS_RIGHT; 1060 } else if (direction == View.FOCUS_BACKWARD) { 1061 direction = View.FOCUS_LEFT; 1062 } 1063 1064 final View nextFocus = previouslyFocusedRect == null ? 1065 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1066 FocusFinder.getInstance().findNextFocusFromRect(this, 1067 previouslyFocusedRect, direction); 1068 1069 if (nextFocus == null) { 1070 return false; 1071 } 1072 1073 if (isOffScreen(nextFocus)) { 1074 return false; 1075 } 1076 1077 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1078 } 1079 1080 @Override 1081 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1082 boolean immediate) { 1083 // offset into coordinate space of this scroll view 1084 rectangle.offset(child.getLeft() - child.getScrollX(), 1085 child.getTop() - child.getScrollY()); 1086 1087 return scrollToChildRect(rectangle, immediate); 1088 } 1089 1090 @Override 1091 public void requestLayout() { 1092 mIsLayoutDirty = true; 1093 super.requestLayout(); 1094 } 1095 1096 @Override 1097 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1098 super.onLayout(changed, l, t, r, b); 1099 mIsLayoutDirty = false; 1100 // Give a child focus if it needs it 1101 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1102 scrollToChild(mChildToScrollTo); 1103 } 1104 mChildToScrollTo = null; 1105 1106 // Calling this with the present values causes it to re-clam them 1107 scrollTo(mScrollX, mScrollY); 1108 } 1109 1110 @Override 1111 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1112 super.onSizeChanged(w, h, oldw, oldh); 1113 1114 View currentFocused = findFocus(); 1115 if (null == currentFocused || this == currentFocused) 1116 return; 1117 1118 final int maxJump = mRight - mLeft; 1119 1120 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1121 currentFocused.getDrawingRect(mTempRect); 1122 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1123 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1124 doScrollX(scrollDelta); 1125 } 1126 } 1127 1128 /** 1129 * Return true if child is an descendant of parent, (or equal to the parent). 1130 */ 1131 private boolean isViewDescendantOf(View child, View parent) { 1132 if (child == parent) { 1133 return true; 1134 } 1135 1136 final ViewParent theParent = child.getParent(); 1137 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1138 } 1139 1140 /** 1141 * Fling the scroll view 1142 * 1143 * @param velocityX The initial velocity in the X direction. Positive 1144 * numbers mean that the finger/curor is moving down the screen, 1145 * which means we want to scroll towards the left. 1146 */ 1147 public void fling(int velocityX) { 1148 int width = getWidth() - mPaddingRight - mPaddingLeft; 1149 int right = getChildAt(0).getWidth(); 1150 1151 mScroller.fling(mScrollX, mScrollY, velocityX, 0, 0, right - width, 0, 0); 1152 1153 final boolean movingRight = velocityX > 0; 1154 1155 View newFocused = findFocusableViewInMyBounds(movingRight, 1156 mScroller.getFinalX(), findFocus()); 1157 1158 if (newFocused == null) { 1159 newFocused = this; 1160 } 1161 1162 if (newFocused != findFocus() 1163 && newFocused.requestFocus(movingRight ? View.FOCUS_RIGHT : View.FOCUS_LEFT)) { 1164 mScrollViewMovedFocus = true; 1165 mScrollViewMovedFocus = false; 1166 } 1167 1168 invalidate(); 1169 } 1170 1171 /** 1172 * {@inheritDoc} 1173 * 1174 * <p>This version also clamps the scrolling to the bounds of our child. 1175 */ 1176 public void scrollTo(int x, int y) { 1177 // we rely on the fact the View.scrollBy calls scrollTo. 1178 if (getChildCount() > 0) { 1179 View child = getChildAt(0); 1180 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1181 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1182 if (x != mScrollX || y != mScrollY) { 1183 super.scrollTo(x, y); 1184 } 1185 } 1186 } 1187 1188 private int clamp(int n, int my, int child) { 1189 if (my >= child || n < 0) { 1190 return 0; 1191 } 1192 if ((my + n) > child) { 1193 return child - my; 1194 } 1195 return n; 1196 } 1197} 1198