HorizontalScrollView.java revision 6579b0b4ac0e781efab044aaaf3f66447cf5e067
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 OverScroller 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 /** 121 * ID of the active pointer. This is used to retain consistency during 122 * drags/flings if multiple pointers are used. 123 */ 124 private int mActivePointerId = INVALID_POINTER; 125 126 /** 127 * Sentinel value for no current active pointer. 128 * Used by {@link #mActivePointerId}. 129 */ 130 private static final int INVALID_POINTER = -1; 131 132 public HorizontalScrollView(Context context) { 133 this(context, null); 134 } 135 136 public HorizontalScrollView(Context context, AttributeSet attrs) { 137 this(context, attrs, com.android.internal.R.attr.horizontalScrollViewStyle); 138 } 139 140 public HorizontalScrollView(Context context, AttributeSet attrs, int defStyle) { 141 super(context, attrs, defStyle); 142 initScrollView(); 143 144 TypedArray a = context.obtainStyledAttributes(attrs, 145 android.R.styleable.HorizontalScrollView, defStyle, 0); 146 147 setFillViewport(a.getBoolean(android.R.styleable.HorizontalScrollView_fillViewport, false)); 148 149 a.recycle(); 150 } 151 152 @Override 153 protected float getLeftFadingEdgeStrength() { 154 if (getChildCount() == 0) { 155 return 0.0f; 156 } 157 158 final int length = getHorizontalFadingEdgeLength(); 159 if (mScrollX < length) { 160 return mScrollX / (float) length; 161 } 162 163 return 1.0f; 164 } 165 166 @Override 167 protected float getRightFadingEdgeStrength() { 168 if (getChildCount() == 0) { 169 return 0.0f; 170 } 171 172 final int length = getHorizontalFadingEdgeLength(); 173 final int rightEdge = getWidth() - mPaddingRight; 174 final int span = getChildAt(0).getRight() - mScrollX - rightEdge; 175 if (span < length) { 176 return span / (float) length; 177 } 178 179 return 1.0f; 180 } 181 182 /** 183 * @return The maximum amount this scroll view will scroll in response to 184 * an arrow event. 185 */ 186 public int getMaxScrollAmount() { 187 return (int) (MAX_SCROLL_FACTOR * (mRight - mLeft)); 188 } 189 190 191 private void initScrollView() { 192 mScroller = new OverScroller(getContext()); 193 setFocusable(true); 194 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 195 setWillNotDraw(false); 196 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 197 mTouchSlop = configuration.getScaledTouchSlop(); 198 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 199 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 200 } 201 202 @Override 203 public void addView(View child) { 204 if (getChildCount() > 0) { 205 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 206 } 207 208 super.addView(child); 209 } 210 211 @Override 212 public void addView(View child, int index) { 213 if (getChildCount() > 0) { 214 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 215 } 216 217 super.addView(child, index); 218 } 219 220 @Override 221 public void addView(View child, ViewGroup.LayoutParams params) { 222 if (getChildCount() > 0) { 223 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 224 } 225 226 super.addView(child, params); 227 } 228 229 @Override 230 public void addView(View child, int index, ViewGroup.LayoutParams params) { 231 if (getChildCount() > 0) { 232 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 233 } 234 235 super.addView(child, index, params); 236 } 237 238 /** 239 * @return Returns true this HorizontalScrollView can be scrolled 240 */ 241 private boolean canScroll() { 242 View child = getChildAt(0); 243 if (child != null) { 244 int childWidth = child.getWidth(); 245 return getWidth() < childWidth + mPaddingLeft + mPaddingRight ; 246 } 247 return false; 248 } 249 250 /** 251 * Indicates whether this ScrollView's content is stretched to fill the viewport. 252 * 253 * @return True if the content fills the viewport, false otherwise. 254 */ 255 public boolean isFillViewport() { 256 return mFillViewport; 257 } 258 259 /** 260 * Indicates this ScrollView whether it should stretch its content width to fill 261 * the viewport or not. 262 * 263 * @param fillViewport True to stretch the content's width to the viewport's 264 * boundaries, false otherwise. 265 */ 266 public void setFillViewport(boolean fillViewport) { 267 if (fillViewport != mFillViewport) { 268 mFillViewport = fillViewport; 269 requestLayout(); 270 } 271 } 272 273 /** 274 * @return Whether arrow scrolling will animate its transition. 275 */ 276 public boolean isSmoothScrollingEnabled() { 277 return mSmoothScrollingEnabled; 278 } 279 280 /** 281 * Set whether arrow scrolling will animate its transition. 282 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 283 */ 284 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 285 mSmoothScrollingEnabled = smoothScrollingEnabled; 286 } 287 288 @Override 289 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 290 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 291 292 if (!mFillViewport) { 293 return; 294 } 295 296 final int widthMode = MeasureSpec.getMode(widthMeasureSpec); 297 if (widthMode == MeasureSpec.UNSPECIFIED) { 298 return; 299 } 300 301 if (getChildCount() > 0) { 302 final View child = getChildAt(0); 303 int width = getMeasuredWidth(); 304 if (child.getMeasuredWidth() < width) { 305 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 306 307 int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec, mPaddingTop 308 + mPaddingBottom, lp.height); 309 width -= mPaddingLeft; 310 width -= mPaddingRight; 311 int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY); 312 313 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 314 } 315 } 316 } 317 318 @Override 319 public boolean dispatchKeyEvent(KeyEvent event) { 320 // Let the focused view and/or our descendants get the key first 321 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 322 } 323 324 /** 325 * You can call this function yourself to have the scroll view perform 326 * scrolling from a key event, just as if the event had been dispatched to 327 * it by the view hierarchy. 328 * 329 * @param event The key event to execute. 330 * @return Return true if the event was handled, else false. 331 */ 332 public boolean executeKeyEvent(KeyEvent event) { 333 mTempRect.setEmpty(); 334 335 if (!canScroll()) { 336 if (isFocused()) { 337 View currentFocused = findFocus(); 338 if (currentFocused == this) currentFocused = null; 339 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 340 currentFocused, View.FOCUS_RIGHT); 341 return nextFocused != null && nextFocused != this && 342 nextFocused.requestFocus(View.FOCUS_RIGHT); 343 } 344 return false; 345 } 346 347 boolean handled = false; 348 if (event.getAction() == KeyEvent.ACTION_DOWN) { 349 switch (event.getKeyCode()) { 350 case KeyEvent.KEYCODE_DPAD_LEFT: 351 if (!event.isAltPressed()) { 352 handled = arrowScroll(View.FOCUS_LEFT); 353 } else { 354 handled = fullScroll(View.FOCUS_LEFT); 355 } 356 break; 357 case KeyEvent.KEYCODE_DPAD_RIGHT: 358 if (!event.isAltPressed()) { 359 handled = arrowScroll(View.FOCUS_RIGHT); 360 } else { 361 handled = fullScroll(View.FOCUS_RIGHT); 362 } 363 break; 364 case KeyEvent.KEYCODE_SPACE: 365 pageScroll(event.isShiftPressed() ? View.FOCUS_LEFT : View.FOCUS_RIGHT); 366 break; 367 } 368 } 369 370 return handled; 371 } 372 373 private boolean inChild(int x, int y) { 374 if (getChildCount() > 0) { 375 final int scrollX = mScrollX; 376 final View child = getChildAt(0); 377 return !(y < child.getTop() 378 || y >= child.getBottom() 379 || x < child.getLeft() - scrollX 380 || x >= child.getRight() - scrollX); 381 } 382 return false; 383 } 384 385 @Override 386 public boolean onInterceptTouchEvent(MotionEvent ev) { 387 /* 388 * This method JUST determines whether we want to intercept the motion. 389 * If we return true, onMotionEvent will be called and we do the actual 390 * scrolling there. 391 */ 392 393 /* 394 * Shortcut the most recurring case: the user is in the dragging 395 * state and he is moving his finger. We want to intercept this 396 * motion. 397 */ 398 final int action = ev.getAction(); 399 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 400 return true; 401 } 402 403 switch (action & MotionEvent.ACTION_MASK) { 404 case MotionEvent.ACTION_MOVE: { 405 /* 406 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 407 * whether the user has moved far enough from his original down touch. 408 */ 409 410 /* 411 * Locally do absolute value. mLastMotionX is set to the x value 412 * of the down event. 413 */ 414 final int activePointerId = mActivePointerId; 415 if (activePointerId == INVALID_POINTER) { 416 // If we don't have a valid id, the touch down wasn't on content. 417 break; 418 } 419 420 final int pointerIndex = ev.findPointerIndex(activePointerId); 421 final float x = ev.getX(pointerIndex); 422 final int xDiff = (int) Math.abs(x - mLastMotionX); 423 if (xDiff > mTouchSlop) { 424 mIsBeingDragged = true; 425 mLastMotionX = x; 426 if (mParent != null) mParent.requestDisallowInterceptTouchEvent(true); 427 } 428 break; 429 } 430 431 case MotionEvent.ACTION_DOWN: { 432 final float x = ev.getX(); 433 if (!inChild((int) x, (int) ev.getY())) { 434 mIsBeingDragged = false; 435 break; 436 } 437 438 /* 439 * Remember location of down touch. 440 * ACTION_DOWN always refers to pointer index 0. 441 */ 442 mLastMotionX = x; 443 mActivePointerId = ev.getPointerId(0); 444 445 /* 446 * If being flinged and user touches the screen, initiate drag; 447 * otherwise don't. mScroller.isFinished should be false when 448 * being flinged. 449 */ 450 mIsBeingDragged = !mScroller.isFinished(); 451 break; 452 } 453 454 case MotionEvent.ACTION_CANCEL: 455 case MotionEvent.ACTION_UP: 456 /* Release the drag */ 457 mIsBeingDragged = false; 458 mActivePointerId = INVALID_POINTER; 459 if (mScroller.springback(mScrollX, mScrollY, 0, getScrollRange(), 0, 0)) { 460 invalidate(); 461 } 462 break; 463 case MotionEvent.ACTION_POINTER_UP: 464 onSecondaryPointerUp(ev); 465 break; 466 } 467 468 /* 469 * The only time we want to intercept motion events is if we are in the 470 * drag mode. 471 */ 472 return mIsBeingDragged; 473 } 474 475 @Override 476 public boolean onTouchEvent(MotionEvent ev) { 477 478 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 479 // Don't handle edge touches immediately -- they may actually belong to one of our 480 // descendants. 481 return false; 482 } 483 484 if (mVelocityTracker == null) { 485 mVelocityTracker = VelocityTracker.obtain(); 486 } 487 mVelocityTracker.addMovement(ev); 488 489 final int action = ev.getAction(); 490 491 switch (action & MotionEvent.ACTION_MASK) { 492 case MotionEvent.ACTION_DOWN: { 493 final float x = ev.getX(); 494 if (!(mIsBeingDragged = inChild((int) x, (int) ev.getY()))) { 495 return false; 496 } 497 498 /* 499 * If being flinged and user touches, stop the fling. isFinished 500 * will be false if being flinged. 501 */ 502 if (!mScroller.isFinished()) { 503 mScroller.abortAnimation(); 504 } 505 506 // Remember where the motion event started 507 mLastMotionX = x; 508 mActivePointerId = ev.getPointerId(0); 509 break; 510 } 511 case MotionEvent.ACTION_MOVE: 512 if (mIsBeingDragged) { 513 // Scroll to follow the motion event 514 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 515 final float x = ev.getX(activePointerIndex); 516 final int deltaX = (int) (mLastMotionX - x); 517 mLastMotionX = x; 518 519 final int oldX = mScrollX; 520 final int oldY = mScrollY; 521 overscrollBy(deltaX, 0, mScrollX, 0, getScrollRange(), 0, 522 getOverscrollMax(), 0, true); 523 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 524 } 525 break; 526 case MotionEvent.ACTION_UP: 527 if (mIsBeingDragged) { 528 final VelocityTracker velocityTracker = mVelocityTracker; 529 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 530 int initialVelocity = (int) velocityTracker.getXVelocity(mActivePointerId); 531 532 if (getChildCount() > 0) { 533 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 534 fling(-initialVelocity); 535 } else { 536 final int right = getScrollRange(); 537 if (mScroller.springback(mScrollX, mScrollY, 0, right, 0, 0)) { 538 invalidate(); 539 } 540 } 541 } 542 543 mActivePointerId = INVALID_POINTER; 544 mIsBeingDragged = false; 545 546 if (mVelocityTracker != null) { 547 mVelocityTracker.recycle(); 548 mVelocityTracker = null; 549 } 550 } 551 break; 552 case MotionEvent.ACTION_CANCEL: 553 if (mIsBeingDragged && getChildCount() > 0) { 554 if (mScroller.springback(mScrollX, mScrollY, 0, getScrollRange(), 0, 0)) { 555 invalidate(); 556 } 557 mActivePointerId = INVALID_POINTER; 558 mIsBeingDragged = false; 559 if (mVelocityTracker != null) { 560 mVelocityTracker.recycle(); 561 mVelocityTracker = null; 562 } 563 } 564 break; 565 case MotionEvent.ACTION_POINTER_UP: 566 onSecondaryPointerUp(ev); 567 break; 568 } 569 return true; 570 } 571 572 private void onSecondaryPointerUp(MotionEvent ev) { 573 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 574 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 575 final int pointerId = ev.getPointerId(pointerIndex); 576 if (pointerId == mActivePointerId) { 577 // This was our active pointer going up. Choose a new 578 // active pointer and adjust accordingly. 579 // TODO: Make this decision more intelligent. 580 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 581 mLastMotionX = ev.getX(newPointerIndex); 582 mActivePointerId = ev.getPointerId(newPointerIndex); 583 if (mVelocityTracker != null) { 584 mVelocityTracker.clear(); 585 } 586 } 587 } 588 589 @Override 590 protected void onOverscrolled(int scrollX, int scrollY, 591 boolean clampedX, boolean clampedY) { 592 // Treat animating scrolls differently; see #computeScroll() for why. 593 if (!mScroller.isFinished()) { 594 mScrollX = scrollX; 595 mScrollY = scrollY; 596 if (clampedX) { 597 mScroller.springback(mScrollX, mScrollY, 0, getScrollRange(), 0, 0); 598 } 599 } else { 600 super.scrollTo(scrollX, scrollY); 601 } 602 awakenScrollBars(); 603 } 604 605 private int getOverscrollMax() { 606 int childCount = getChildCount(); 607 int containerOverscroll = (getWidth() - mPaddingLeft - mPaddingRight) / 3; 608 if (childCount > 0) { 609 return Math.min(containerOverscroll, getChildAt(0).getWidth() / 3); 610 } else { 611 return containerOverscroll; 612 } 613 } 614 615 private int getScrollRange() { 616 int scrollRange = 0; 617 if (getChildCount() > 0) { 618 View child = getChildAt(0); 619 scrollRange = Math.max(0, 620 child.getWidth() - getWidth() - mPaddingLeft - mPaddingRight); 621 } 622 return scrollRange; 623 } 624 625 /** 626 * <p> 627 * Finds the next focusable component that fits in this View's bounds 628 * (excluding fading edges) pretending that this View's left is located at 629 * the parameter left. 630 * </p> 631 * 632 * @param leftFocus look for a candidate is the one at the left of the bounds 633 * if leftFocus is true, or at the right of the bounds if leftFocus 634 * is false 635 * @param left the left offset of the bounds in which a focusable must be 636 * found (the fading edge is assumed to start at this position) 637 * @param preferredFocusable the View that has highest priority and will be 638 * returned if it is within my bounds (null is valid) 639 * @return the next focusable component in the bounds or null if none can be found 640 */ 641 private View findFocusableViewInMyBounds(final boolean leftFocus, 642 final int left, View preferredFocusable) { 643 /* 644 * The fading edge's transparent side should be considered for focus 645 * since it's mostly visible, so we divide the actual fading edge length 646 * by 2. 647 */ 648 final int fadingEdgeLength = getHorizontalFadingEdgeLength() / 2; 649 final int leftWithoutFadingEdge = left + fadingEdgeLength; 650 final int rightWithoutFadingEdge = left + getWidth() - fadingEdgeLength; 651 652 if ((preferredFocusable != null) 653 && (preferredFocusable.getLeft() < rightWithoutFadingEdge) 654 && (preferredFocusable.getRight() > leftWithoutFadingEdge)) { 655 return preferredFocusable; 656 } 657 658 return findFocusableViewInBounds(leftFocus, leftWithoutFadingEdge, 659 rightWithoutFadingEdge); 660 } 661 662 /** 663 * <p> 664 * Finds the next focusable component that fits in the specified bounds. 665 * </p> 666 * 667 * @param leftFocus look for a candidate is the one at the left of the bounds 668 * if leftFocus is true, or at the right of the bounds if 669 * leftFocus is false 670 * @param left the left offset of the bounds in which a focusable must be 671 * found 672 * @param right the right offset of the bounds in which a focusable must 673 * be found 674 * @return the next focusable component in the bounds or null if none can 675 * be found 676 */ 677 private View findFocusableViewInBounds(boolean leftFocus, int left, int right) { 678 679 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 680 View focusCandidate = null; 681 682 /* 683 * A fully contained focusable is one where its left is below the bound's 684 * left, and its right is above the bound's right. A partially 685 * contained focusable is one where some part of it is within the 686 * bounds, but it also has some part that is not within bounds. A fully contained 687 * focusable is preferred to a partially contained focusable. 688 */ 689 boolean foundFullyContainedFocusable = false; 690 691 int count = focusables.size(); 692 for (int i = 0; i < count; i++) { 693 View view = focusables.get(i); 694 int viewLeft = view.getLeft(); 695 int viewRight = view.getRight(); 696 697 if (left < viewRight && viewLeft < right) { 698 /* 699 * the focusable is in the target area, it is a candidate for 700 * focusing 701 */ 702 703 final boolean viewIsFullyContained = (left < viewLeft) && 704 (viewRight < right); 705 706 if (focusCandidate == null) { 707 /* No candidate, take this one */ 708 focusCandidate = view; 709 foundFullyContainedFocusable = viewIsFullyContained; 710 } else { 711 final boolean viewIsCloserToBoundary = 712 (leftFocus && viewLeft < focusCandidate.getLeft()) || 713 (!leftFocus && viewRight > focusCandidate.getRight()); 714 715 if (foundFullyContainedFocusable) { 716 if (viewIsFullyContained && viewIsCloserToBoundary) { 717 /* 718 * We're dealing with only fully contained views, so 719 * it has to be closer to the boundary to beat our 720 * candidate 721 */ 722 focusCandidate = view; 723 } 724 } else { 725 if (viewIsFullyContained) { 726 /* Any fully contained view beats a partially contained view */ 727 focusCandidate = view; 728 foundFullyContainedFocusable = true; 729 } else if (viewIsCloserToBoundary) { 730 /* 731 * Partially contained view beats another partially 732 * contained view if it's closer 733 */ 734 focusCandidate = view; 735 } 736 } 737 } 738 } 739 } 740 741 return focusCandidate; 742 } 743 744 /** 745 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 746 * method will scroll the view by one page left or right and give the focus 747 * to the leftmost/rightmost component in the new visible area. If no 748 * component is a good candidate for focus, this scrollview reclaims the 749 * focus.</p> 750 * 751 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 752 * to go one page left or {@link android.view.View#FOCUS_RIGHT} 753 * to go one page right 754 * @return true if the key event is consumed by this method, false otherwise 755 */ 756 public boolean pageScroll(int direction) { 757 boolean right = direction == View.FOCUS_RIGHT; 758 int width = getWidth(); 759 760 if (right) { 761 mTempRect.left = getScrollX() + width; 762 int count = getChildCount(); 763 if (count > 0) { 764 View view = getChildAt(0); 765 if (mTempRect.left + width > view.getRight()) { 766 mTempRect.left = view.getRight() - width; 767 } 768 } 769 } else { 770 mTempRect.left = getScrollX() - width; 771 if (mTempRect.left < 0) { 772 mTempRect.left = 0; 773 } 774 } 775 mTempRect.right = mTempRect.left + width; 776 777 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 778 } 779 780 /** 781 * <p>Handles scrolling in response to a "home/end" shortcut press. This 782 * method will scroll the view to the left or right and give the focus 783 * to the leftmost/rightmost component in the new visible area. If no 784 * component is a good candidate for focus, this scrollview reclaims the 785 * focus.</p> 786 * 787 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 788 * to go the left of the view or {@link android.view.View#FOCUS_RIGHT} 789 * to go the right 790 * @return true if the key event is consumed by this method, false otherwise 791 */ 792 public boolean fullScroll(int direction) { 793 boolean right = direction == View.FOCUS_RIGHT; 794 int width = getWidth(); 795 796 mTempRect.left = 0; 797 mTempRect.right = width; 798 799 if (right) { 800 int count = getChildCount(); 801 if (count > 0) { 802 View view = getChildAt(0); 803 mTempRect.right = view.getRight(); 804 mTempRect.left = mTempRect.right - width; 805 } 806 } 807 808 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 809 } 810 811 /** 812 * <p>Scrolls the view to make the area defined by <code>left</code> and 813 * <code>right</code> visible. This method attempts to give the focus 814 * to a component visible in this area. If no component can be focused in 815 * the new visible area, the focus is reclaimed by this scrollview.</p> 816 * 817 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 818 * to go left {@link android.view.View#FOCUS_RIGHT} to right 819 * @param left the left offset of the new area to be made visible 820 * @param right the right offset of the new area to be made visible 821 * @return true if the key event is consumed by this method, false otherwise 822 */ 823 private boolean scrollAndFocus(int direction, int left, int right) { 824 boolean handled = true; 825 826 int width = getWidth(); 827 int containerLeft = getScrollX(); 828 int containerRight = containerLeft + width; 829 boolean goLeft = direction == View.FOCUS_LEFT; 830 831 View newFocused = findFocusableViewInBounds(goLeft, left, right); 832 if (newFocused == null) { 833 newFocused = this; 834 } 835 836 if (left >= containerLeft && right <= containerRight) { 837 handled = false; 838 } else { 839 int delta = goLeft ? (left - containerLeft) : (right - containerRight); 840 doScrollX(delta); 841 } 842 843 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 844 mScrollViewMovedFocus = true; 845 mScrollViewMovedFocus = false; 846 } 847 848 return handled; 849 } 850 851 /** 852 * Handle scrolling in response to a left or right arrow click. 853 * 854 * @param direction The direction corresponding to the arrow key that was 855 * pressed 856 * @return True if we consumed the event, false otherwise 857 */ 858 public boolean arrowScroll(int direction) { 859 860 View currentFocused = findFocus(); 861 if (currentFocused == this) currentFocused = null; 862 863 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 864 865 final int maxJump = getMaxScrollAmount(); 866 867 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 868 nextFocused.getDrawingRect(mTempRect); 869 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 870 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 871 doScrollX(scrollDelta); 872 nextFocused.requestFocus(direction); 873 } else { 874 // no new focus 875 int scrollDelta = maxJump; 876 877 if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) { 878 scrollDelta = getScrollX(); 879 } else if (direction == View.FOCUS_RIGHT && getChildCount() > 0) { 880 881 int daRight = getChildAt(0).getRight(); 882 883 int screenRight = getScrollX() + getWidth(); 884 885 if (daRight - screenRight < maxJump) { 886 scrollDelta = daRight - screenRight; 887 } 888 } 889 if (scrollDelta == 0) { 890 return false; 891 } 892 doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta); 893 } 894 895 if (currentFocused != null && currentFocused.isFocused() 896 && isOffScreen(currentFocused)) { 897 // previously focused item still has focus and is off screen, give 898 // it up (take it back to ourselves) 899 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 900 // sure to 901 // get it) 902 final int descendantFocusability = getDescendantFocusability(); // save 903 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 904 requestFocus(); 905 setDescendantFocusability(descendantFocusability); // restore 906 } 907 return true; 908 } 909 910 /** 911 * @return whether the descendant of this scroll view is scrolled off 912 * screen. 913 */ 914 private boolean isOffScreen(View descendant) { 915 return !isWithinDeltaOfScreen(descendant, 0); 916 } 917 918 /** 919 * @return whether the descendant of this scroll view is within delta 920 * pixels of being on the screen. 921 */ 922 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 923 descendant.getDrawingRect(mTempRect); 924 offsetDescendantRectToMyCoords(descendant, mTempRect); 925 926 return (mTempRect.right + delta) >= getScrollX() 927 && (mTempRect.left - delta) <= (getScrollX() + getWidth()); 928 } 929 930 /** 931 * Smooth scroll by a X delta 932 * 933 * @param delta the number of pixels to scroll by on the X axis 934 */ 935 private void doScrollX(int delta) { 936 if (delta != 0) { 937 if (mSmoothScrollingEnabled) { 938 smoothScrollBy(delta, 0); 939 } else { 940 scrollBy(delta, 0); 941 } 942 } 943 } 944 945 /** 946 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 947 * 948 * @param dx the number of pixels to scroll by on the X axis 949 * @param dy the number of pixels to scroll by on the Y axis 950 */ 951 public final void smoothScrollBy(int dx, int dy) { 952 if (getChildCount() == 0) { 953 // Nothing to do. 954 return; 955 } 956 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 957 if (duration > ANIMATED_SCROLL_GAP) { 958 final int width = getWidth() - mPaddingRight - mPaddingLeft; 959 final int right = getChildAt(0).getWidth(); 960 final int maxX = Math.max(0, right - width); 961 final int scrollX = mScrollX; 962 dx = Math.max(0, Math.min(scrollX + dx, maxX)) - scrollX; 963 964 mScroller.startScroll(scrollX, mScrollY, dx, 0); 965 invalidate(); 966 } else { 967 if (!mScroller.isFinished()) { 968 mScroller.abortAnimation(); 969 } 970 scrollBy(dx, dy); 971 } 972 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 973 } 974 975 /** 976 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 977 * 978 * @param x the position where to scroll on the X axis 979 * @param y the position where to scroll on the Y axis 980 */ 981 public final void smoothScrollTo(int x, int y) { 982 smoothScrollBy(x - mScrollX, y - mScrollY); 983 } 984 985 /** 986 * <p>The scroll range of a scroll view is the overall width of all of its 987 * children.</p> 988 */ 989 @Override 990 protected int computeHorizontalScrollRange() { 991 final int count = getChildCount(); 992 final int contentWidth = getWidth() - mPaddingLeft - mPaddingRight; 993 if (count == 0) { 994 return contentWidth; 995 } 996 997 int scrollRange = getChildAt(0).getRight(); 998 final int scrollX = mScrollX; 999 final int overscrollRight = Math.max(0, scrollRange - contentWidth); 1000 if (scrollX < 0) { 1001 scrollRange -= scrollX; 1002 } else if (scrollX > overscrollRight) { 1003 scrollRange += scrollX - overscrollRight; 1004 } 1005 1006 return scrollRange; 1007 } 1008 1009 @Override 1010 protected int computeHorizontalScrollOffset() { 1011 return Math.max(0, super.computeHorizontalScrollOffset()); 1012 } 1013 1014 @Override 1015 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1016 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1017 1018 int childWidthMeasureSpec; 1019 int childHeightMeasureSpec; 1020 1021 childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop 1022 + mPaddingBottom, lp.height); 1023 1024 childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1025 1026 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1027 } 1028 1029 @Override 1030 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1031 int parentHeightMeasureSpec, int heightUsed) { 1032 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1033 1034 final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, 1035 mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin 1036 + heightUsed, lp.height); 1037 final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( 1038 lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); 1039 1040 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1041 } 1042 1043 @Override 1044 public void computeScroll() { 1045 if (mScroller.computeScrollOffset()) { 1046 // This is called at drawing time by ViewGroup. We don't want to 1047 // re-show the scrollbars at this point, which scrollTo will do, 1048 // so we replicate most of scrollTo here. 1049 // 1050 // It's a little odd to call onScrollChanged from inside the drawing. 1051 // 1052 // It is, except when you remember that computeScroll() is used to 1053 // animate scrolling. So unless we want to defer the onScrollChanged() 1054 // until the end of the animated scrolling, we don't really have a 1055 // choice here. 1056 // 1057 // I agree. The alternative, which I think would be worse, is to post 1058 // something and tell the subclasses later. This is bad because there 1059 // will be a window where mScrollX/Y is different from what the app 1060 // thinks it is. 1061 // 1062 int oldX = mScrollX; 1063 int oldY = mScrollY; 1064 int x = mScroller.getCurrX(); 1065 int y = mScroller.getCurrY(); 1066 1067 if (oldX != x || oldY != y) { 1068 overscrollBy(x - oldX, y - oldY, oldX, oldY, getScrollRange(), 0, 1069 getOverscrollMax(), 0, false); 1070 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1071 } 1072 1073 // Keep on drawing until the animation has finished. 1074 postInvalidate(); 1075 } 1076 } 1077 1078 /** 1079 * Scrolls the view to the given child. 1080 * 1081 * @param child the View to scroll to 1082 */ 1083 private void scrollToChild(View child) { 1084 child.getDrawingRect(mTempRect); 1085 1086 /* Offset from child's local coordinates to ScrollView coordinates */ 1087 offsetDescendantRectToMyCoords(child, mTempRect); 1088 1089 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1090 1091 if (scrollDelta != 0) { 1092 scrollBy(scrollDelta, 0); 1093 } 1094 } 1095 1096 /** 1097 * If rect is off screen, scroll just enough to get it (or at least the 1098 * first screen size chunk of it) on screen. 1099 * 1100 * @param rect The rectangle. 1101 * @param immediate True to scroll immediately without animation 1102 * @return true if scrolling was performed 1103 */ 1104 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1105 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1106 final boolean scroll = delta != 0; 1107 if (scroll) { 1108 if (immediate) { 1109 scrollBy(delta, 0); 1110 } else { 1111 smoothScrollBy(delta, 0); 1112 } 1113 } 1114 return scroll; 1115 } 1116 1117 /** 1118 * Compute the amount to scroll in the X direction in order to get 1119 * a rectangle completely on the screen (or, if taller than the screen, 1120 * at least the first screen size chunk of it). 1121 * 1122 * @param rect The rect. 1123 * @return The scroll delta. 1124 */ 1125 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1126 if (getChildCount() == 0) return 0; 1127 1128 int width = getWidth(); 1129 int screenLeft = getScrollX(); 1130 int screenRight = screenLeft + width; 1131 1132 int fadingEdge = getHorizontalFadingEdgeLength(); 1133 1134 // leave room for left fading edge as long as rect isn't at very left 1135 if (rect.left > 0) { 1136 screenLeft += fadingEdge; 1137 } 1138 1139 // leave room for right fading edge as long as rect isn't at very right 1140 if (rect.right < getChildAt(0).getWidth()) { 1141 screenRight -= fadingEdge; 1142 } 1143 1144 int scrollXDelta = 0; 1145 1146 if (rect.right > screenRight && rect.left > screenLeft) { 1147 // need to move right to get it in view: move right just enough so 1148 // that the entire rectangle is in view (or at least the first 1149 // screen size chunk). 1150 1151 if (rect.width() > width) { 1152 // just enough to get screen size chunk on 1153 scrollXDelta += (rect.left - screenLeft); 1154 } else { 1155 // get entire rect at right of screen 1156 scrollXDelta += (rect.right - screenRight); 1157 } 1158 1159 // make sure we aren't scrolling beyond the end of our content 1160 int right = getChildAt(0).getRight(); 1161 int distanceToRight = right - screenRight; 1162 scrollXDelta = Math.min(scrollXDelta, distanceToRight); 1163 1164 } else if (rect.left < screenLeft && rect.right < screenRight) { 1165 // need to move right to get it in view: move right just enough so that 1166 // entire rectangle is in view (or at least the first screen 1167 // size chunk of it). 1168 1169 if (rect.width() > width) { 1170 // screen size chunk 1171 scrollXDelta -= (screenRight - rect.right); 1172 } else { 1173 // entire rect at left 1174 scrollXDelta -= (screenLeft - rect.left); 1175 } 1176 1177 // make sure we aren't scrolling any further than the left our content 1178 scrollXDelta = Math.max(scrollXDelta, -getScrollX()); 1179 } 1180 return scrollXDelta; 1181 } 1182 1183 @Override 1184 public void requestChildFocus(View child, View focused) { 1185 if (!mScrollViewMovedFocus) { 1186 if (!mIsLayoutDirty) { 1187 scrollToChild(focused); 1188 } else { 1189 // The child may not be laid out yet, we can't compute the scroll yet 1190 mChildToScrollTo = focused; 1191 } 1192 } 1193 super.requestChildFocus(child, focused); 1194 } 1195 1196 1197 /** 1198 * When looking for focus in children of a scroll view, need to be a little 1199 * more careful not to give focus to something that is scrolled off screen. 1200 * 1201 * This is more expensive than the default {@link android.view.ViewGroup} 1202 * implementation, otherwise this behavior might have been made the default. 1203 */ 1204 @Override 1205 protected boolean onRequestFocusInDescendants(int direction, 1206 Rect previouslyFocusedRect) { 1207 1208 // convert from forward / backward notation to up / down / left / right 1209 // (ugh). 1210 if (direction == View.FOCUS_FORWARD) { 1211 direction = View.FOCUS_RIGHT; 1212 } else if (direction == View.FOCUS_BACKWARD) { 1213 direction = View.FOCUS_LEFT; 1214 } 1215 1216 final View nextFocus = previouslyFocusedRect == null ? 1217 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1218 FocusFinder.getInstance().findNextFocusFromRect(this, 1219 previouslyFocusedRect, direction); 1220 1221 if (nextFocus == null) { 1222 return false; 1223 } 1224 1225 if (isOffScreen(nextFocus)) { 1226 return false; 1227 } 1228 1229 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1230 } 1231 1232 @Override 1233 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1234 boolean immediate) { 1235 // offset into coordinate space of this scroll view 1236 rectangle.offset(child.getLeft() - child.getScrollX(), 1237 child.getTop() - child.getScrollY()); 1238 1239 return scrollToChildRect(rectangle, immediate); 1240 } 1241 1242 @Override 1243 public void requestLayout() { 1244 mIsLayoutDirty = true; 1245 super.requestLayout(); 1246 } 1247 1248 @Override 1249 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1250 super.onLayout(changed, l, t, r, b); 1251 mIsLayoutDirty = false; 1252 // Give a child focus if it needs it 1253 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1254 scrollToChild(mChildToScrollTo); 1255 } 1256 mChildToScrollTo = null; 1257 1258 // Calling this with the present values causes it to re-clam them 1259 scrollTo(mScrollX, mScrollY); 1260 } 1261 1262 @Override 1263 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1264 super.onSizeChanged(w, h, oldw, oldh); 1265 1266 View currentFocused = findFocus(); 1267 if (null == currentFocused || this == currentFocused) 1268 return; 1269 1270 final int maxJump = mRight - mLeft; 1271 1272 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1273 currentFocused.getDrawingRect(mTempRect); 1274 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1275 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1276 doScrollX(scrollDelta); 1277 } 1278 } 1279 1280 /** 1281 * Return true if child is an descendant of parent, (or equal to the parent). 1282 */ 1283 private boolean isViewDescendantOf(View child, View parent) { 1284 if (child == parent) { 1285 return true; 1286 } 1287 1288 final ViewParent theParent = child.getParent(); 1289 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1290 } 1291 1292 /** 1293 * Fling the scroll view 1294 * 1295 * @param velocityX The initial velocity in the X direction. Positive 1296 * numbers mean that the finger/curor is moving down the screen, 1297 * which means we want to scroll towards the left. 1298 */ 1299 public void fling(int velocityX) { 1300 if (getChildCount() > 0) { 1301 int width = getWidth() - mPaddingRight - mPaddingLeft; 1302 int right = getChildAt(0).getWidth(); 1303 1304 mScroller.fling(mScrollX, mScrollY, velocityX, 0, 0, 1305 Math.max(0, right - width), 0, 0, width/2, 0); 1306 1307 final boolean movingRight = velocityX > 0; 1308 1309 View newFocused = findFocusableViewInMyBounds(movingRight, 1310 mScroller.getFinalX(), findFocus()); 1311 1312 if (newFocused == null) { 1313 newFocused = this; 1314 } 1315 1316 if (newFocused != findFocus() 1317 && newFocused.requestFocus(movingRight ? View.FOCUS_RIGHT : View.FOCUS_LEFT)) { 1318 mScrollViewMovedFocus = true; 1319 mScrollViewMovedFocus = false; 1320 } 1321 1322 invalidate(); 1323 } 1324 } 1325 1326 /** 1327 * {@inheritDoc} 1328 * 1329 * <p>This version also clamps the scrolling to the bounds of our child. 1330 */ 1331 public void scrollTo(int x, int y) { 1332 // we rely on the fact the View.scrollBy calls scrollTo. 1333 if (getChildCount() > 0) { 1334 View child = getChildAt(0); 1335 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1336 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1337 if (x != mScrollX || y != mScrollY) { 1338 super.scrollTo(x, y); 1339 } 1340 } 1341 } 1342 1343 private int clamp(int n, int my, int child) { 1344 if (my >= child || n < 0) { 1345 return 0; 1346 } 1347 if ((my + n) > child) { 1348 return child - my; 1349 } 1350 return n; 1351 } 1352} 1353