HorizontalScrollView.java revision 4296fc4d326447875c26a925f12b3935632f13bb
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 private int mMinimumVelocity; 118 private int mMaximumVelocity; 119 120 public HorizontalScrollView(Context context) { 121 this(context, null); 122 } 123 124 public HorizontalScrollView(Context context, AttributeSet attrs) { 125 this(context, attrs, com.android.internal.R.attr.horizontalScrollViewStyle); 126 } 127 128 public HorizontalScrollView(Context context, AttributeSet attrs, int defStyle) { 129 super(context, attrs, defStyle); 130 initScrollView(); 131 132 TypedArray a = context.obtainStyledAttributes(attrs, 133 android.R.styleable.HorizontalScrollView, defStyle, 0); 134 135 setFillViewport(a.getBoolean(android.R.styleable.HorizontalScrollView_fillViewport, false)); 136 137 a.recycle(); 138 } 139 140 @Override 141 protected float getLeftFadingEdgeStrength() { 142 if (getChildCount() == 0) { 143 return 0.0f; 144 } 145 146 final int length = getHorizontalFadingEdgeLength(); 147 if (mScrollX < length) { 148 return mScrollX / (float) length; 149 } 150 151 return 1.0f; 152 } 153 154 @Override 155 protected float getRightFadingEdgeStrength() { 156 if (getChildCount() == 0) { 157 return 0.0f; 158 } 159 160 final int length = getHorizontalFadingEdgeLength(); 161 final int rightEdge = getWidth() - mPaddingRight; 162 final int span = getChildAt(0).getRight() - mScrollX - rightEdge; 163 if (span < length) { 164 return span / (float) length; 165 } 166 167 return 1.0f; 168 } 169 170 /** 171 * @return The maximum amount this scroll view will scroll in response to 172 * an arrow event. 173 */ 174 public int getMaxScrollAmount() { 175 return (int) (MAX_SCROLL_FACTOR * (mRight - mLeft)); 176 } 177 178 179 private void initScrollView() { 180 mScroller = new Scroller(getContext()); 181 setFocusable(true); 182 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 183 setWillNotDraw(false); 184 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 185 mTouchSlop = configuration.getScaledTouchSlop(); 186 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 187 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 188 } 189 190 @Override 191 public void addView(View child) { 192 if (getChildCount() > 0) { 193 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 194 } 195 196 super.addView(child); 197 } 198 199 @Override 200 public void addView(View child, int index) { 201 if (getChildCount() > 0) { 202 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 203 } 204 205 super.addView(child, index); 206 } 207 208 @Override 209 public void addView(View child, ViewGroup.LayoutParams params) { 210 if (getChildCount() > 0) { 211 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 212 } 213 214 super.addView(child, params); 215 } 216 217 @Override 218 public void addView(View child, int index, ViewGroup.LayoutParams params) { 219 if (getChildCount() > 0) { 220 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 221 } 222 223 super.addView(child, index, params); 224 } 225 226 /** 227 * @return Returns true this HorizontalScrollView can be scrolled 228 */ 229 private boolean canScroll() { 230 View child = getChildAt(0); 231 if (child != null) { 232 int childWidth = child.getWidth(); 233 return getWidth() < childWidth + mPaddingLeft + mPaddingRight ; 234 } 235 return false; 236 } 237 238 /** 239 * Indicates whether this ScrollView's content is stretched to fill the viewport. 240 * 241 * @return True if the content fills the viewport, false otherwise. 242 */ 243 public boolean isFillViewport() { 244 return mFillViewport; 245 } 246 247 /** 248 * Indicates this ScrollView whether it should stretch its content width to fill 249 * the viewport or not. 250 * 251 * @param fillViewport True to stretch the content's width to the viewport's 252 * boundaries, false otherwise. 253 */ 254 public void setFillViewport(boolean fillViewport) { 255 if (fillViewport != mFillViewport) { 256 mFillViewport = fillViewport; 257 requestLayout(); 258 } 259 } 260 261 /** 262 * @return Whether arrow scrolling will animate its transition. 263 */ 264 public boolean isSmoothScrollingEnabled() { 265 return mSmoothScrollingEnabled; 266 } 267 268 /** 269 * Set whether arrow scrolling will animate its transition. 270 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 271 */ 272 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 273 mSmoothScrollingEnabled = smoothScrollingEnabled; 274 } 275 276 @Override 277 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 278 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 279 280 if (!mFillViewport) { 281 return; 282 } 283 284 final int widthMode = MeasureSpec.getMode(widthMeasureSpec); 285 if (widthMode == MeasureSpec.UNSPECIFIED) { 286 return; 287 } 288 289 final View child = getChildAt(0); 290 int width = getMeasuredWidth(); 291 if (child.getMeasuredWidth() < width) { 292 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 293 294 int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec, mPaddingTop 295 + mPaddingBottom, lp.height); 296 width -= mPaddingLeft; 297 width -= mPaddingRight; 298 int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY); 299 300 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 301 } 302 } 303 304 @Override 305 public boolean dispatchKeyEvent(KeyEvent event) { 306 // Let the focused view and/or our descendants get the key first 307 boolean handled = super.dispatchKeyEvent(event); 308 if (handled) { 309 return true; 310 } 311 return executeKeyEvent(event); 312 } 313 314 /** 315 * You can call this function yourself to have the scroll view perform 316 * scrolling from a key event, just as if the event had been dispatched to 317 * it by the view hierarchy. 318 * 319 * @param event The key event to execute. 320 * @return Return true if the event was handled, else false. 321 */ 322 public boolean executeKeyEvent(KeyEvent event) { 323 mTempRect.setEmpty(); 324 325 if (!canScroll()) { 326 if (isFocused()) { 327 View currentFocused = findFocus(); 328 if (currentFocused == this) currentFocused = null; 329 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 330 currentFocused, View.FOCUS_RIGHT); 331 return nextFocused != null && nextFocused != this && 332 nextFocused.requestFocus(View.FOCUS_RIGHT); 333 } 334 return false; 335 } 336 337 boolean handled = false; 338 if (event.getAction() == KeyEvent.ACTION_DOWN) { 339 switch (event.getKeyCode()) { 340 case KeyEvent.KEYCODE_DPAD_LEFT: 341 if (!event.isAltPressed()) { 342 handled = arrowScroll(View.FOCUS_LEFT); 343 } else { 344 handled = fullScroll(View.FOCUS_LEFT); 345 } 346 break; 347 case KeyEvent.KEYCODE_DPAD_RIGHT: 348 if (!event.isAltPressed()) { 349 handled = arrowScroll(View.FOCUS_RIGHT); 350 } else { 351 handled = fullScroll(View.FOCUS_RIGHT); 352 } 353 break; 354 case KeyEvent.KEYCODE_SPACE: 355 pageScroll(event.isShiftPressed() ? View.FOCUS_LEFT : View.FOCUS_RIGHT); 356 break; 357 } 358 } 359 360 return handled; 361 } 362 363 @Override 364 public boolean onInterceptTouchEvent(MotionEvent ev) { 365 /* 366 * This method JUST determines whether we want to intercept the motion. 367 * If we return true, onMotionEvent will be called and we do the actual 368 * scrolling there. 369 */ 370 371 /* 372 * Shortcut the most recurring case: the user is in the dragging 373 * state and he is moving his finger. We want to intercept this 374 * motion. 375 */ 376 final int action = ev.getAction(); 377 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 378 return true; 379 } 380 381 if (!canScroll()) { 382 mIsBeingDragged = false; 383 return false; 384 } 385 386 final float x = ev.getX(); 387 388 switch (action) { 389 case MotionEvent.ACTION_MOVE: 390 /* 391 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 392 * whether the user has moved far enough from his original down touch. 393 */ 394 395 /* 396 * Locally do absolute value. mLastMotionX is set to the x value 397 * of the down event. 398 */ 399 final int xDiff = (int) Math.abs(x - mLastMotionX); 400 if (xDiff > mTouchSlop) { 401 mIsBeingDragged = true; 402 if (mParent != null) mParent.requestDisallowInterceptTouchEvent(true); 403 } 404 break; 405 406 case MotionEvent.ACTION_DOWN: 407 /* Remember location of down touch */ 408 mLastMotionX = x; 409 410 /* 411 * If being flinged and user touches the screen, initiate drag; 412 * otherwise don't. mScroller.isFinished should be false when 413 * being flinged. 414 */ 415 mIsBeingDragged = !mScroller.isFinished(); 416 break; 417 418 case MotionEvent.ACTION_CANCEL: 419 case MotionEvent.ACTION_UP: 420 /* Release the drag */ 421 mIsBeingDragged = false; 422 break; 423 } 424 425 /* 426 * The only time we want to intercept motion events is if we are in the 427 * drag mode. 428 */ 429 return mIsBeingDragged; 430 } 431 432 @Override 433 public boolean onTouchEvent(MotionEvent ev) { 434 435 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 436 // Don't handle edge touches immediately -- they may actually belong to one of our 437 // descendants. 438 return false; 439 } 440 441 if (!canScroll()) { 442 return false; 443 } 444 445 if (mVelocityTracker == null) { 446 mVelocityTracker = VelocityTracker.obtain(); 447 } 448 mVelocityTracker.addMovement(ev); 449 450 final int action = ev.getAction(); 451 final float x = ev.getX(); 452 453 switch (action) { 454 case MotionEvent.ACTION_DOWN: 455 /* 456 * If being flinged and user touches, stop the fling. isFinished 457 * will be false if being flinged. 458 */ 459 if (!mScroller.isFinished()) { 460 mScroller.abortAnimation(); 461 } 462 463 // Remember where the motion event started 464 mLastMotionX = x; 465 break; 466 case MotionEvent.ACTION_MOVE: 467 // Scroll to follow the motion event 468 final int deltaX = (int) (mLastMotionX - x); 469 mLastMotionX = x; 470 471 if (deltaX < 0) { 472 if (mScrollX > 0) { 473 scrollBy(deltaX, 0); 474 } 475 } else if (deltaX > 0) { 476 final int rightEdge = getWidth() - mPaddingRight; 477 final int availableToScroll = getChildAt(0).getRight() - mScrollX - rightEdge; 478 if (availableToScroll > 0) { 479 scrollBy(Math.min(availableToScroll, deltaX), 0); 480 } 481 } 482 break; 483 case MotionEvent.ACTION_UP: 484 final VelocityTracker velocityTracker = mVelocityTracker; 485 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 486 int initialVelocity = (int) velocityTracker.getXVelocity(); 487 488 if ((Math.abs(initialVelocity) > mMinimumVelocity) && getChildCount() > 0) { 489 fling(-initialVelocity); 490 } 491 492 if (mVelocityTracker != null) { 493 mVelocityTracker.recycle(); 494 mVelocityTracker = null; 495 } 496 } 497 return true; 498 } 499 500 /** 501 * <p> 502 * Finds the next focusable component that fits in this View's bounds 503 * (excluding fading edges) pretending that this View's left is located at 504 * the parameter left. 505 * </p> 506 * 507 * @param leftFocus look for a candidate is the one at the left of the bounds 508 * if leftFocus is true, or at the right of the bounds if leftFocus 509 * is false 510 * @param left the left offset of the bounds in which a focusable must be 511 * found (the fading edge is assumed to start at this position) 512 * @param preferredFocusable the View that has highest priority and will be 513 * returned if it is within my bounds (null is valid) 514 * @return the next focusable component in the bounds or null if none can be found 515 */ 516 private View findFocusableViewInMyBounds(final boolean leftFocus, 517 final int left, View preferredFocusable) { 518 /* 519 * The fading edge's transparent side should be considered for focus 520 * since it's mostly visible, so we divide the actual fading edge length 521 * by 2. 522 */ 523 final int fadingEdgeLength = getHorizontalFadingEdgeLength() / 2; 524 final int leftWithoutFadingEdge = left + fadingEdgeLength; 525 final int rightWithoutFadingEdge = left + getWidth() - fadingEdgeLength; 526 527 if ((preferredFocusable != null) 528 && (preferredFocusable.getLeft() < rightWithoutFadingEdge) 529 && (preferredFocusable.getRight() > leftWithoutFadingEdge)) { 530 return preferredFocusable; 531 } 532 533 return findFocusableViewInBounds(leftFocus, leftWithoutFadingEdge, 534 rightWithoutFadingEdge); 535 } 536 537 /** 538 * <p> 539 * Finds the next focusable component that fits in the specified bounds. 540 * </p> 541 * 542 * @param leftFocus look for a candidate is the one at the left of the bounds 543 * if leftFocus is true, or at the right of the bounds if 544 * leftFocus is false 545 * @param left the left offset of the bounds in which a focusable must be 546 * found 547 * @param right the right offset of the bounds in which a focusable must 548 * be found 549 * @return the next focusable component in the bounds or null if none can 550 * be found 551 */ 552 private View findFocusableViewInBounds(boolean leftFocus, int left, int right) { 553 554 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 555 View focusCandidate = null; 556 557 /* 558 * A fully contained focusable is one where its left is below the bound's 559 * left, and its right is above the bound's right. A partially 560 * contained focusable is one where some part of it is within the 561 * bounds, but it also has some part that is not within bounds. A fully contained 562 * focusable is preferred to a partially contained focusable. 563 */ 564 boolean foundFullyContainedFocusable = false; 565 566 int count = focusables.size(); 567 for (int i = 0; i < count; i++) { 568 View view = focusables.get(i); 569 int viewLeft = view.getLeft(); 570 int viewRight = view.getRight(); 571 572 if (left < viewRight && viewLeft < right) { 573 /* 574 * the focusable is in the target area, it is a candidate for 575 * focusing 576 */ 577 578 final boolean viewIsFullyContained = (left < viewLeft) && 579 (viewRight < right); 580 581 if (focusCandidate == null) { 582 /* No candidate, take this one */ 583 focusCandidate = view; 584 foundFullyContainedFocusable = viewIsFullyContained; 585 } else { 586 final boolean viewIsCloserToBoundary = 587 (leftFocus && viewLeft < focusCandidate.getLeft()) || 588 (!leftFocus && viewRight > focusCandidate.getRight()); 589 590 if (foundFullyContainedFocusable) { 591 if (viewIsFullyContained && viewIsCloserToBoundary) { 592 /* 593 * We're dealing with only fully contained views, so 594 * it has to be closer to the boundary to beat our 595 * candidate 596 */ 597 focusCandidate = view; 598 } 599 } else { 600 if (viewIsFullyContained) { 601 /* Any fully contained view beats a partially contained view */ 602 focusCandidate = view; 603 foundFullyContainedFocusable = true; 604 } else if (viewIsCloserToBoundary) { 605 /* 606 * Partially contained view beats another partially 607 * contained view if it's closer 608 */ 609 focusCandidate = view; 610 } 611 } 612 } 613 } 614 } 615 616 return focusCandidate; 617 } 618 619 /** 620 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 621 * method will scroll the view by one page left or right and give the focus 622 * to the leftmost/rightmost component in the new visible area. If no 623 * component is a good candidate for focus, this scrollview reclaims the 624 * focus.</p> 625 * 626 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 627 * to go one page left or {@link android.view.View#FOCUS_RIGHT} 628 * to go one page right 629 * @return true if the key event is consumed by this method, false otherwise 630 */ 631 public boolean pageScroll(int direction) { 632 boolean right = direction == View.FOCUS_RIGHT; 633 int width = getWidth(); 634 635 if (right) { 636 mTempRect.left = getScrollX() + width; 637 int count = getChildCount(); 638 if (count > 0) { 639 View view = getChildAt(count - 1); 640 if (mTempRect.left + width > view.getRight()) { 641 mTempRect.left = view.getRight() - width; 642 } 643 } 644 } else { 645 mTempRect.left = getScrollX() - width; 646 if (mTempRect.left < 0) { 647 mTempRect.left = 0; 648 } 649 } 650 mTempRect.right = mTempRect.left + width; 651 652 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 653 } 654 655 /** 656 * <p>Handles scrolling in response to a "home/end" shortcut press. This 657 * method will scroll the view to the left or right and give the focus 658 * to the leftmost/rightmost component in the new visible area. If no 659 * component is a good candidate for focus, this scrollview reclaims the 660 * focus.</p> 661 * 662 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 663 * to go the left of the view or {@link android.view.View#FOCUS_RIGHT} 664 * to go the right 665 * @return true if the key event is consumed by this method, false otherwise 666 */ 667 public boolean fullScroll(int direction) { 668 boolean right = direction == View.FOCUS_RIGHT; 669 int width = getWidth(); 670 671 mTempRect.left = 0; 672 mTempRect.right = width; 673 674 if (right) { 675 int count = getChildCount(); 676 if (count > 0) { 677 View view = getChildAt(count - 1); 678 mTempRect.right = view.getRight(); 679 mTempRect.left = mTempRect.right - width; 680 } 681 } 682 683 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 684 } 685 686 /** 687 * <p>Scrolls the view to make the area defined by <code>left</code> and 688 * <code>right</code> visible. This method attempts to give the focus 689 * to a component visible in this area. If no component can be focused in 690 * the new visible area, the focus is reclaimed by this scrollview.</p> 691 * 692 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 693 * to go left {@link android.view.View#FOCUS_RIGHT} to right 694 * @param left the left offset of the new area to be made visible 695 * @param right the right offset of the new area to be made visible 696 * @return true if the key event is consumed by this method, false otherwise 697 */ 698 private boolean scrollAndFocus(int direction, int left, int right) { 699 boolean handled = true; 700 701 int width = getWidth(); 702 int containerLeft = getScrollX(); 703 int containerRight = containerLeft + width; 704 boolean goLeft = direction == View.FOCUS_LEFT; 705 706 View newFocused = findFocusableViewInBounds(goLeft, left, right); 707 if (newFocused == null) { 708 newFocused = this; 709 } 710 711 if (left >= containerLeft && right <= containerRight) { 712 handled = false; 713 } else { 714 int delta = goLeft ? (left - containerLeft) : (right - containerRight); 715 doScrollX(delta); 716 } 717 718 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 719 mScrollViewMovedFocus = true; 720 mScrollViewMovedFocus = false; 721 } 722 723 return handled; 724 } 725 726 /** 727 * Handle scrolling in response to a left or right arrow click. 728 * 729 * @param direction The direction corresponding to the arrow key that was 730 * pressed 731 * @return True if we consumed the event, false otherwise 732 */ 733 public boolean arrowScroll(int direction) { 734 735 View currentFocused = findFocus(); 736 if (currentFocused == this) currentFocused = null; 737 738 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 739 740 final int maxJump = getMaxScrollAmount(); 741 742 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 743 nextFocused.getDrawingRect(mTempRect); 744 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 745 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 746 doScrollX(scrollDelta); 747 nextFocused.requestFocus(direction); 748 } else { 749 // no new focus 750 int scrollDelta = maxJump; 751 752 if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) { 753 scrollDelta = getScrollX(); 754 } else if (direction == View.FOCUS_RIGHT) { 755 756 int daRight = getChildAt(getChildCount() - 1).getRight(); 757 758 int screenRight = getScrollX() + getWidth(); 759 760 if (daRight - screenRight < maxJump) { 761 scrollDelta = daRight - screenRight; 762 } 763 } 764 if (scrollDelta == 0) { 765 return false; 766 } 767 doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta); 768 } 769 770 if (currentFocused != null && currentFocused.isFocused() 771 && isOffScreen(currentFocused)) { 772 // previously focused item still has focus and is off screen, give 773 // it up (take it back to ourselves) 774 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 775 // sure to 776 // get it) 777 final int descendantFocusability = getDescendantFocusability(); // save 778 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 779 requestFocus(); 780 setDescendantFocusability(descendantFocusability); // restore 781 } 782 return true; 783 } 784 785 /** 786 * @return whether the descendant of this scroll view is scrolled off 787 * screen. 788 */ 789 private boolean isOffScreen(View descendant) { 790 return !isWithinDeltaOfScreen(descendant, 0); 791 } 792 793 /** 794 * @return whether the descendant of this scroll view is within delta 795 * pixels of being on the screen. 796 */ 797 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 798 descendant.getDrawingRect(mTempRect); 799 offsetDescendantRectToMyCoords(descendant, mTempRect); 800 801 return (mTempRect.right + delta) >= getScrollX() 802 && (mTempRect.left - delta) <= (getScrollX() + getWidth()); 803 } 804 805 /** 806 * Smooth scroll by a X delta 807 * 808 * @param delta the number of pixels to scroll by on the X axis 809 */ 810 private void doScrollX(int delta) { 811 if (delta != 0) { 812 if (mSmoothScrollingEnabled) { 813 smoothScrollBy(delta, 0); 814 } else { 815 scrollBy(delta, 0); 816 } 817 } 818 } 819 820 /** 821 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 822 * 823 * @param dx the number of pixels to scroll by on the X axis 824 * @param dy the number of pixels to scroll by on the Y axis 825 */ 826 public final void smoothScrollBy(int dx, int dy) { 827 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 828 if (duration > ANIMATED_SCROLL_GAP) { 829 mScroller.startScroll(mScrollX, mScrollY, dx, dy); 830 invalidate(); 831 } else { 832 if (!mScroller.isFinished()) { 833 mScroller.abortAnimation(); 834 } 835 scrollBy(dx, dy); 836 } 837 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 838 } 839 840 /** 841 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 842 * 843 * @param x the position where to scroll on the X axis 844 * @param y the position where to scroll on the Y axis 845 */ 846 public final void smoothScrollTo(int x, int y) { 847 smoothScrollBy(x - mScrollX, y - mScrollY); 848 } 849 850 /** 851 * <p>The scroll range of a scroll view is the overall width of all of its 852 * children.</p> 853 */ 854 @Override 855 protected int computeHorizontalScrollRange() { 856 int count = getChildCount(); 857 return count == 0 ? getWidth() : getChildAt(0).getRight(); 858 } 859 860 861 @Override 862 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 863 ViewGroup.LayoutParams lp = child.getLayoutParams(); 864 865 int childWidthMeasureSpec; 866 int childHeightMeasureSpec; 867 868 childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop 869 + mPaddingBottom, lp.height); 870 871 childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 872 873 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 874 } 875 876 @Override 877 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 878 int parentHeightMeasureSpec, int heightUsed) { 879 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 880 881 final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, 882 mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin 883 + heightUsed, lp.height); 884 final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( 885 lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); 886 887 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 888 } 889 890 @Override 891 public void computeScroll() { 892 if (mScroller.computeScrollOffset()) { 893 // This is called at drawing time by ViewGroup. We don't want to 894 // re-show the scrollbars at this point, which scrollTo will do, 895 // so we replicate most of scrollTo here. 896 // 897 // It's a little odd to call onScrollChanged from inside the drawing. 898 // 899 // It is, except when you remember that computeScroll() is used to 900 // animate scrolling. So unless we want to defer the onScrollChanged() 901 // until the end of the animated scrolling, we don't really have a 902 // choice here. 903 // 904 // I agree. The alternative, which I think would be worse, is to post 905 // something and tell the subclasses later. This is bad because there 906 // will be a window where mScrollX/Y is different from what the app 907 // thinks it is. 908 // 909 int oldX = mScrollX; 910 int oldY = mScrollY; 911 int x = mScroller.getCurrX(); 912 int y = mScroller.getCurrY(); 913 if (getChildCount() > 0) { 914 View child = getChildAt(0); 915 mScrollX = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 916 mScrollY = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 917 } else { 918 mScrollX = x; 919 mScrollY = y; 920 } 921 if (oldX != mScrollX || oldY != mScrollY) { 922 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 923 } 924 925 // Keep on drawing until the animation has finished. 926 postInvalidate(); 927 } 928 } 929 930 /** 931 * Scrolls the view to the given child. 932 * 933 * @param child the View to scroll to 934 */ 935 private void scrollToChild(View child) { 936 child.getDrawingRect(mTempRect); 937 938 /* Offset from child's local coordinates to ScrollView coordinates */ 939 offsetDescendantRectToMyCoords(child, mTempRect); 940 941 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 942 943 if (scrollDelta != 0) { 944 scrollBy(scrollDelta, 0); 945 } 946 } 947 948 /** 949 * If rect is off screen, scroll just enough to get it (or at least the 950 * first screen size chunk of it) on screen. 951 * 952 * @param rect The rectangle. 953 * @param immediate True to scroll immediately without animation 954 * @return true if scrolling was performed 955 */ 956 private boolean scrollToChildRect(Rect rect, boolean immediate) { 957 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 958 final boolean scroll = delta != 0; 959 if (scroll) { 960 if (immediate) { 961 scrollBy(delta, 0); 962 } else { 963 smoothScrollBy(delta, 0); 964 } 965 } 966 return scroll; 967 } 968 969 /** 970 * Compute the amount to scroll in the X direction in order to get 971 * a rectangle completely on the screen (or, if taller than the screen, 972 * at least the first screen size chunk of it). 973 * 974 * @param rect The rect. 975 * @return The scroll delta. 976 */ 977 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 978 979 int width = getWidth(); 980 int screenLeft = getScrollX(); 981 int screenRight = screenLeft + width; 982 983 int fadingEdge = getHorizontalFadingEdgeLength(); 984 985 // leave room for left fading edge as long as rect isn't at very left 986 if (rect.left > 0) { 987 screenLeft += fadingEdge; 988 } 989 990 // leave room for right fading edge as long as rect isn't at very right 991 if (rect.right < getChildAt(0).getWidth()) { 992 screenRight -= fadingEdge; 993 } 994 995 int scrollXDelta = 0; 996 997 if (rect.right > screenRight && rect.left > screenLeft) { 998 // need to move right to get it in view: move right just enough so 999 // that the entire rectangle is in view (or at least the first 1000 // screen size chunk). 1001 1002 if (rect.width() > width) { 1003 // just enough to get screen size chunk on 1004 scrollXDelta += (rect.left - screenLeft); 1005 } else { 1006 // get entire rect at right of screen 1007 scrollXDelta += (rect.right - screenRight); 1008 } 1009 1010 // make sure we aren't scrolling beyond the end of our content 1011 int right = getChildAt(getChildCount() - 1).getRight(); 1012 int distanceToRight = right - screenRight; 1013 scrollXDelta = Math.min(scrollXDelta, distanceToRight); 1014 1015 } else if (rect.left < screenLeft && rect.right < screenRight) { 1016 // need to move right to get it in view: move right just enough so that 1017 // entire rectangle is in view (or at least the first screen 1018 // size chunk of it). 1019 1020 if (rect.width() > width) { 1021 // screen size chunk 1022 scrollXDelta -= (screenRight - rect.right); 1023 } else { 1024 // entire rect at left 1025 scrollXDelta -= (screenLeft - rect.left); 1026 } 1027 1028 // make sure we aren't scrolling any further than the left our content 1029 scrollXDelta = Math.max(scrollXDelta, -getScrollX()); 1030 } 1031 return scrollXDelta; 1032 } 1033 1034 @Override 1035 public void requestChildFocus(View child, View focused) { 1036 if (!mScrollViewMovedFocus) { 1037 if (!mIsLayoutDirty) { 1038 scrollToChild(focused); 1039 } else { 1040 // The child may not be laid out yet, we can't compute the scroll yet 1041 mChildToScrollTo = focused; 1042 } 1043 } 1044 super.requestChildFocus(child, focused); 1045 } 1046 1047 1048 /** 1049 * When looking for focus in children of a scroll view, need to be a little 1050 * more careful not to give focus to something that is scrolled off screen. 1051 * 1052 * This is more expensive than the default {@link android.view.ViewGroup} 1053 * implementation, otherwise this behavior might have been made the default. 1054 */ 1055 @Override 1056 protected boolean onRequestFocusInDescendants(int direction, 1057 Rect previouslyFocusedRect) { 1058 1059 // convert from forward / backward notation to up / down / left / right 1060 // (ugh). 1061 if (direction == View.FOCUS_FORWARD) { 1062 direction = View.FOCUS_RIGHT; 1063 } else if (direction == View.FOCUS_BACKWARD) { 1064 direction = View.FOCUS_LEFT; 1065 } 1066 1067 final View nextFocus = previouslyFocusedRect == null ? 1068 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1069 FocusFinder.getInstance().findNextFocusFromRect(this, 1070 previouslyFocusedRect, direction); 1071 1072 if (nextFocus == null) { 1073 return false; 1074 } 1075 1076 if (isOffScreen(nextFocus)) { 1077 return false; 1078 } 1079 1080 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1081 } 1082 1083 @Override 1084 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1085 boolean immediate) { 1086 // offset into coordinate space of this scroll view 1087 rectangle.offset(child.getLeft() - child.getScrollX(), 1088 child.getTop() - child.getScrollY()); 1089 1090 return scrollToChildRect(rectangle, immediate); 1091 } 1092 1093 @Override 1094 public void requestLayout() { 1095 mIsLayoutDirty = true; 1096 super.requestLayout(); 1097 } 1098 1099 @Override 1100 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1101 super.onLayout(changed, l, t, r, b); 1102 mIsLayoutDirty = false; 1103 // Give a child focus if it needs it 1104 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1105 scrollToChild(mChildToScrollTo); 1106 } 1107 mChildToScrollTo = null; 1108 1109 // Calling this with the present values causes it to re-clam them 1110 scrollTo(mScrollX, mScrollY); 1111 } 1112 1113 @Override 1114 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1115 super.onSizeChanged(w, h, oldw, oldh); 1116 1117 View currentFocused = findFocus(); 1118 if (null == currentFocused || this == currentFocused) 1119 return; 1120 1121 final int maxJump = mRight - mLeft; 1122 1123 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1124 currentFocused.getDrawingRect(mTempRect); 1125 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1126 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1127 doScrollX(scrollDelta); 1128 } 1129 } 1130 1131 /** 1132 * Return true if child is an descendant of parent, (or equal to the parent). 1133 */ 1134 private boolean isViewDescendantOf(View child, View parent) { 1135 if (child == parent) { 1136 return true; 1137 } 1138 1139 final ViewParent theParent = child.getParent(); 1140 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1141 } 1142 1143 /** 1144 * Fling the scroll view 1145 * 1146 * @param velocityX The initial velocity in the X direction. Positive 1147 * numbers mean that the finger/curor is moving down the screen, 1148 * which means we want to scroll towards the left. 1149 */ 1150 public void fling(int velocityX) { 1151 int width = getWidth() - mPaddingRight - mPaddingLeft; 1152 int right = getChildAt(0).getWidth(); 1153 1154 mScroller.fling(mScrollX, mScrollY, velocityX, 0, 0, right - width, 0, 0); 1155 1156 final boolean movingRight = velocityX > 0; 1157 1158 View newFocused = findFocusableViewInMyBounds(movingRight, 1159 mScroller.getFinalX(), findFocus()); 1160 1161 if (newFocused == null) { 1162 newFocused = this; 1163 } 1164 1165 if (newFocused != findFocus() 1166 && newFocused.requestFocus(movingRight ? View.FOCUS_RIGHT : View.FOCUS_LEFT)) { 1167 mScrollViewMovedFocus = true; 1168 mScrollViewMovedFocus = false; 1169 } 1170 1171 invalidate(); 1172 } 1173 1174 /** 1175 * {@inheritDoc} 1176 * 1177 * <p>This version also clamps the scrolling to the bounds of our child. 1178 */ 1179 public void scrollTo(int x, int y) { 1180 // we rely on the fact the View.scrollBy calls scrollTo. 1181 if (getChildCount() > 0) { 1182 View child = getChildAt(0); 1183 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1184 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1185 if (x != mScrollX || y != mScrollY) { 1186 super.scrollTo(x, y); 1187 } 1188 } 1189 } 1190 1191 private int clamp(int n, int my, int child) { 1192 if (my >= child || n < 0) { 1193 return 0; 1194 } 1195 if ((my + n) > child) { 1196 return child - my; 1197 } 1198 return n; 1199 } 1200} 1201