HorizontalScrollView.java revision 4cd47702f00a2fd6d6bc16c5398edb884d98bdca
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 boolean handled = super.dispatchKeyEvent(event); 322 if (handled) { 323 return true; 324 } 325 return executeKeyEvent(event); 326 } 327 328 /** 329 * You can call this function yourself to have the scroll view perform 330 * scrolling from a key event, just as if the event had been dispatched to 331 * it by the view hierarchy. 332 * 333 * @param event The key event to execute. 334 * @return Return true if the event was handled, else false. 335 */ 336 public boolean executeKeyEvent(KeyEvent event) { 337 mTempRect.setEmpty(); 338 339 if (!canScroll()) { 340 if (isFocused()) { 341 View currentFocused = findFocus(); 342 if (currentFocused == this) currentFocused = null; 343 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 344 currentFocused, View.FOCUS_RIGHT); 345 return nextFocused != null && nextFocused != this && 346 nextFocused.requestFocus(View.FOCUS_RIGHT); 347 } 348 return false; 349 } 350 351 boolean handled = false; 352 if (event.getAction() == KeyEvent.ACTION_DOWN) { 353 switch (event.getKeyCode()) { 354 case KeyEvent.KEYCODE_DPAD_LEFT: 355 if (!event.isAltPressed()) { 356 handled = arrowScroll(View.FOCUS_LEFT); 357 } else { 358 handled = fullScroll(View.FOCUS_LEFT); 359 } 360 break; 361 case KeyEvent.KEYCODE_DPAD_RIGHT: 362 if (!event.isAltPressed()) { 363 handled = arrowScroll(View.FOCUS_RIGHT); 364 } else { 365 handled = fullScroll(View.FOCUS_RIGHT); 366 } 367 break; 368 case KeyEvent.KEYCODE_SPACE: 369 pageScroll(event.isShiftPressed() ? View.FOCUS_LEFT : View.FOCUS_RIGHT); 370 break; 371 } 372 } 373 374 return handled; 375 } 376 377 private boolean inChild(int x, int y) { 378 if (getChildCount() > 0) { 379 final View child = getChildAt(0); 380 return !(y < child.getTop() 381 || y >= child.getBottom() 382 || x < child.getLeft() 383 || x >= child.getRight()); 384 } 385 return false; 386 } 387 388 @Override 389 public boolean onInterceptTouchEvent(MotionEvent ev) { 390 /* 391 * This method JUST determines whether we want to intercept the motion. 392 * If we return true, onMotionEvent will be called and we do the actual 393 * scrolling there. 394 */ 395 396 /* 397 * Shortcut the most recurring case: the user is in the dragging 398 * state and he is moving his finger. We want to intercept this 399 * motion. 400 */ 401 final int action = ev.getAction(); 402 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 403 return true; 404 } 405 406 switch (action & MotionEvent.ACTION_MASK) { 407 case MotionEvent.ACTION_MOVE: { 408 /* 409 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 410 * whether the user has moved far enough from his original down touch. 411 */ 412 413 /* 414 * Locally do absolute value. mLastMotionX is set to the x value 415 * of the down event. 416 */ 417 final int pointerIndex = ev.findPointerIndex(mActivePointerId); 418 final float x = ev.getX(pointerIndex); 419 final int xDiff = (int) Math.abs(x - mLastMotionX); 420 if (xDiff > mTouchSlop) { 421 mIsBeingDragged = true; 422 mLastMotionX = x; 423 if (mParent != null) mParent.requestDisallowInterceptTouchEvent(true); 424 } 425 break; 426 } 427 428 case MotionEvent.ACTION_DOWN: { 429 final float x = ev.getX(); 430 if (!inChild((int) x, (int) ev.getY())) { 431 mIsBeingDragged = false; 432 break; 433 } 434 435 /* 436 * Remember location of down touch. 437 * ACTION_DOWN always refers to pointer index 0. 438 */ 439 mLastMotionX = x; 440 mActivePointerId = ev.getPointerId(0); 441 442 /* 443 * If being flinged and user touches the screen, initiate drag; 444 * otherwise don't. mScroller.isFinished should be false when 445 * being flinged. 446 */ 447 mIsBeingDragged = !mScroller.isFinished(); 448 break; 449 } 450 451 case MotionEvent.ACTION_CANCEL: 452 case MotionEvent.ACTION_UP: 453 /* Release the drag */ 454 mIsBeingDragged = false; 455 mActivePointerId = INVALID_POINTER; 456 break; 457 case MotionEvent.ACTION_POINTER_UP: 458 onSecondaryPointerUp(ev); 459 break; 460 } 461 462 /* 463 * The only time we want to intercept motion events is if we are in the 464 * drag mode. 465 */ 466 return mIsBeingDragged; 467 } 468 469 @Override 470 public boolean onTouchEvent(MotionEvent ev) { 471 472 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 473 // Don't handle edge touches immediately -- they may actually belong to one of our 474 // descendants. 475 return false; 476 } 477 478 if (mVelocityTracker == null) { 479 mVelocityTracker = VelocityTracker.obtain(); 480 } 481 mVelocityTracker.addMovement(ev); 482 483 final int action = ev.getAction(); 484 485 switch (action & MotionEvent.ACTION_MASK) { 486 case MotionEvent.ACTION_DOWN: { 487 /* 488 * If being flinged and user touches, stop the fling. isFinished 489 * will be false if being flinged. 490 */ 491 if (!mScroller.isFinished()) { 492 mScroller.abortAnimation(); 493 } 494 495 final float x = ev.getX(); 496 if (!(mIsBeingDragged = inChild((int) x, (int) ev.getY()))) { 497 return false; 498 } 499 500 // Remember where the motion event started 501 mLastMotionX = x; 502 break; 503 } 504 case MotionEvent.ACTION_MOVE: 505 if (mIsBeingDragged) { 506 // Scroll to follow the motion event 507 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 508 final float x = ev.getX(activePointerIndex); 509 final int deltaX = (int) (mLastMotionX - x); 510 mLastMotionX = x; 511 512 overscrollBy(deltaX, 0, mScrollX, 0, getScrollRange(), 0, 513 getOverscrollMax(), 0); 514 } 515 break; 516 case MotionEvent.ACTION_UP: 517 if (mIsBeingDragged) { 518 final VelocityTracker velocityTracker = mVelocityTracker; 519 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 520 int initialVelocity = (int) velocityTracker.getXVelocity(mActivePointerId); 521 522 if (getChildCount() > 0) { 523 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 524 fling(-initialVelocity); 525 } else { 526 final int right = getScrollRange(); 527 if (mScroller.springback(mScrollX, mScrollY, 0, 0, right, 0)) { 528 invalidate(); 529 } 530 } 531 } 532 533 mActivePointerId = INVALID_POINTER; 534 mIsBeingDragged = false; 535 536 if (mVelocityTracker != null) { 537 mVelocityTracker.recycle(); 538 mVelocityTracker = null; 539 } 540 } 541 break; 542 case MotionEvent.ACTION_POINTER_UP: 543 onSecondaryPointerUp(ev); 544 break; 545 } 546 return true; 547 } 548 549 private void onSecondaryPointerUp(MotionEvent ev) { 550 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 551 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 552 final int pointerId = ev.getPointerId(pointerIndex); 553 if (pointerId == mActivePointerId) { 554 // This was our active pointer going up. Choose a new 555 // active pointer and adjust accordingly. 556 // TODO: Make this decision more intelligent. 557 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 558 mLastMotionX = ev.getX(newPointerIndex); 559 mActivePointerId = ev.getPointerId(newPointerIndex); 560 if (mVelocityTracker != null) { 561 mVelocityTracker.clear(); 562 } 563 } 564 } 565 566 @Override 567 protected void onOverscrolled(int scrollX, int scrollY, 568 boolean clampedX, boolean clampedY) { 569 // Treat animating scrolls differently; see #computeScroll() for why. 570 if (!mScroller.isFinished()) { 571 mScrollX = scrollX; 572 mScrollY = scrollY; 573 if (clampedX) { 574 mScroller.springback(mScrollX, mScrollY, 0, getScrollRange(), 0, 0); 575 } 576 } else { 577 super.scrollTo(scrollX, scrollY); 578 } 579 } 580 581 private int getOverscrollMax() { 582 int childCount = getChildCount(); 583 int containerOverscroll = (getWidth() - mPaddingLeft - mPaddingRight) / 3; 584 if (childCount > 0) { 585 return Math.min(containerOverscroll, getChildAt(0).getWidth() / 3); 586 } else { 587 return containerOverscroll; 588 } 589 } 590 591 private int getScrollRange() { 592 int scrollRange = 0; 593 if (getChildCount() > 0) { 594 View child = getChildAt(0); 595 scrollRange = Math.max(0, 596 child.getWidth() - getWidth() - mPaddingLeft - mPaddingRight); 597 } 598 return scrollRange; 599 } 600 601 /** 602 * <p> 603 * Finds the next focusable component that fits in this View's bounds 604 * (excluding fading edges) pretending that this View's left is located at 605 * the parameter left. 606 * </p> 607 * 608 * @param leftFocus look for a candidate is the one at the left of the bounds 609 * if leftFocus is true, or at the right of the bounds if leftFocus 610 * is false 611 * @param left the left offset of the bounds in which a focusable must be 612 * found (the fading edge is assumed to start at this position) 613 * @param preferredFocusable the View that has highest priority and will be 614 * returned if it is within my bounds (null is valid) 615 * @return the next focusable component in the bounds or null if none can be found 616 */ 617 private View findFocusableViewInMyBounds(final boolean leftFocus, 618 final int left, View preferredFocusable) { 619 /* 620 * The fading edge's transparent side should be considered for focus 621 * since it's mostly visible, so we divide the actual fading edge length 622 * by 2. 623 */ 624 final int fadingEdgeLength = getHorizontalFadingEdgeLength() / 2; 625 final int leftWithoutFadingEdge = left + fadingEdgeLength; 626 final int rightWithoutFadingEdge = left + getWidth() - fadingEdgeLength; 627 628 if ((preferredFocusable != null) 629 && (preferredFocusable.getLeft() < rightWithoutFadingEdge) 630 && (preferredFocusable.getRight() > leftWithoutFadingEdge)) { 631 return preferredFocusable; 632 } 633 634 return findFocusableViewInBounds(leftFocus, leftWithoutFadingEdge, 635 rightWithoutFadingEdge); 636 } 637 638 /** 639 * <p> 640 * Finds the next focusable component that fits in the specified bounds. 641 * </p> 642 * 643 * @param leftFocus look for a candidate is the one at the left of the bounds 644 * if leftFocus is true, or at the right of the bounds if 645 * leftFocus is false 646 * @param left the left offset of the bounds in which a focusable must be 647 * found 648 * @param right the right offset of the bounds in which a focusable must 649 * be found 650 * @return the next focusable component in the bounds or null if none can 651 * be found 652 */ 653 private View findFocusableViewInBounds(boolean leftFocus, int left, int right) { 654 655 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 656 View focusCandidate = null; 657 658 /* 659 * A fully contained focusable is one where its left is below the bound's 660 * left, and its right is above the bound's right. A partially 661 * contained focusable is one where some part of it is within the 662 * bounds, but it also has some part that is not within bounds. A fully contained 663 * focusable is preferred to a partially contained focusable. 664 */ 665 boolean foundFullyContainedFocusable = false; 666 667 int count = focusables.size(); 668 for (int i = 0; i < count; i++) { 669 View view = focusables.get(i); 670 int viewLeft = view.getLeft(); 671 int viewRight = view.getRight(); 672 673 if (left < viewRight && viewLeft < right) { 674 /* 675 * the focusable is in the target area, it is a candidate for 676 * focusing 677 */ 678 679 final boolean viewIsFullyContained = (left < viewLeft) && 680 (viewRight < right); 681 682 if (focusCandidate == null) { 683 /* No candidate, take this one */ 684 focusCandidate = view; 685 foundFullyContainedFocusable = viewIsFullyContained; 686 } else { 687 final boolean viewIsCloserToBoundary = 688 (leftFocus && viewLeft < focusCandidate.getLeft()) || 689 (!leftFocus && viewRight > focusCandidate.getRight()); 690 691 if (foundFullyContainedFocusable) { 692 if (viewIsFullyContained && viewIsCloserToBoundary) { 693 /* 694 * We're dealing with only fully contained views, so 695 * it has to be closer to the boundary to beat our 696 * candidate 697 */ 698 focusCandidate = view; 699 } 700 } else { 701 if (viewIsFullyContained) { 702 /* Any fully contained view beats a partially contained view */ 703 focusCandidate = view; 704 foundFullyContainedFocusable = true; 705 } else if (viewIsCloserToBoundary) { 706 /* 707 * Partially contained view beats another partially 708 * contained view if it's closer 709 */ 710 focusCandidate = view; 711 } 712 } 713 } 714 } 715 } 716 717 return focusCandidate; 718 } 719 720 /** 721 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 722 * method will scroll the view by one page left or right and give the focus 723 * to the leftmost/rightmost component in the new visible area. If no 724 * component is a good candidate for focus, this scrollview reclaims the 725 * focus.</p> 726 * 727 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 728 * to go one page left or {@link android.view.View#FOCUS_RIGHT} 729 * to go one page right 730 * @return true if the key event is consumed by this method, false otherwise 731 */ 732 public boolean pageScroll(int direction) { 733 boolean right = direction == View.FOCUS_RIGHT; 734 int width = getWidth(); 735 736 if (right) { 737 mTempRect.left = getScrollX() + width; 738 int count = getChildCount(); 739 if (count > 0) { 740 View view = getChildAt(0); 741 if (mTempRect.left + width > view.getRight()) { 742 mTempRect.left = view.getRight() - width; 743 } 744 } 745 } else { 746 mTempRect.left = getScrollX() - width; 747 if (mTempRect.left < 0) { 748 mTempRect.left = 0; 749 } 750 } 751 mTempRect.right = mTempRect.left + width; 752 753 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 754 } 755 756 /** 757 * <p>Handles scrolling in response to a "home/end" shortcut press. This 758 * method will scroll the view to the left or right and give the focus 759 * to the leftmost/rightmost component in the new visible area. If no 760 * component is a good candidate for focus, this scrollview reclaims the 761 * focus.</p> 762 * 763 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 764 * to go the left of the view or {@link android.view.View#FOCUS_RIGHT} 765 * to go the right 766 * @return true if the key event is consumed by this method, false otherwise 767 */ 768 public boolean fullScroll(int direction) { 769 boolean right = direction == View.FOCUS_RIGHT; 770 int width = getWidth(); 771 772 mTempRect.left = 0; 773 mTempRect.right = width; 774 775 if (right) { 776 int count = getChildCount(); 777 if (count > 0) { 778 View view = getChildAt(0); 779 mTempRect.right = view.getRight(); 780 mTempRect.left = mTempRect.right - width; 781 } 782 } 783 784 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 785 } 786 787 /** 788 * <p>Scrolls the view to make the area defined by <code>left</code> and 789 * <code>right</code> visible. This method attempts to give the focus 790 * to a component visible in this area. If no component can be focused in 791 * the new visible area, the focus is reclaimed by this scrollview.</p> 792 * 793 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 794 * to go left {@link android.view.View#FOCUS_RIGHT} to right 795 * @param left the left offset of the new area to be made visible 796 * @param right the right offset of the new area to be made visible 797 * @return true if the key event is consumed by this method, false otherwise 798 */ 799 private boolean scrollAndFocus(int direction, int left, int right) { 800 boolean handled = true; 801 802 int width = getWidth(); 803 int containerLeft = getScrollX(); 804 int containerRight = containerLeft + width; 805 boolean goLeft = direction == View.FOCUS_LEFT; 806 807 View newFocused = findFocusableViewInBounds(goLeft, left, right); 808 if (newFocused == null) { 809 newFocused = this; 810 } 811 812 if (left >= containerLeft && right <= containerRight) { 813 handled = false; 814 } else { 815 int delta = goLeft ? (left - containerLeft) : (right - containerRight); 816 doScrollX(delta); 817 } 818 819 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 820 mScrollViewMovedFocus = true; 821 mScrollViewMovedFocus = false; 822 } 823 824 return handled; 825 } 826 827 /** 828 * Handle scrolling in response to a left or right arrow click. 829 * 830 * @param direction The direction corresponding to the arrow key that was 831 * pressed 832 * @return True if we consumed the event, false otherwise 833 */ 834 public boolean arrowScroll(int direction) { 835 836 View currentFocused = findFocus(); 837 if (currentFocused == this) currentFocused = null; 838 839 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 840 841 final int maxJump = getMaxScrollAmount(); 842 843 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 844 nextFocused.getDrawingRect(mTempRect); 845 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 846 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 847 doScrollX(scrollDelta); 848 nextFocused.requestFocus(direction); 849 } else { 850 // no new focus 851 int scrollDelta = maxJump; 852 853 if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) { 854 scrollDelta = getScrollX(); 855 } else if (direction == View.FOCUS_RIGHT && getChildCount() > 0) { 856 857 int daRight = getChildAt(0).getRight(); 858 859 int screenRight = getScrollX() + getWidth(); 860 861 if (daRight - screenRight < maxJump) { 862 scrollDelta = daRight - screenRight; 863 } 864 } 865 if (scrollDelta == 0) { 866 return false; 867 } 868 doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta); 869 } 870 871 if (currentFocused != null && currentFocused.isFocused() 872 && isOffScreen(currentFocused)) { 873 // previously focused item still has focus and is off screen, give 874 // it up (take it back to ourselves) 875 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 876 // sure to 877 // get it) 878 final int descendantFocusability = getDescendantFocusability(); // save 879 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 880 requestFocus(); 881 setDescendantFocusability(descendantFocusability); // restore 882 } 883 return true; 884 } 885 886 /** 887 * @return whether the descendant of this scroll view is scrolled off 888 * screen. 889 */ 890 private boolean isOffScreen(View descendant) { 891 return !isWithinDeltaOfScreen(descendant, 0); 892 } 893 894 /** 895 * @return whether the descendant of this scroll view is within delta 896 * pixels of being on the screen. 897 */ 898 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 899 descendant.getDrawingRect(mTempRect); 900 offsetDescendantRectToMyCoords(descendant, mTempRect); 901 902 return (mTempRect.right + delta) >= getScrollX() 903 && (mTempRect.left - delta) <= (getScrollX() + getWidth()); 904 } 905 906 /** 907 * Smooth scroll by a X delta 908 * 909 * @param delta the number of pixels to scroll by on the X axis 910 */ 911 private void doScrollX(int delta) { 912 if (delta != 0) { 913 if (mSmoothScrollingEnabled) { 914 smoothScrollBy(delta, 0); 915 } else { 916 scrollBy(delta, 0); 917 } 918 } 919 } 920 921 /** 922 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 923 * 924 * @param dx the number of pixels to scroll by on the X axis 925 * @param dy the number of pixels to scroll by on the Y axis 926 */ 927 public final void smoothScrollBy(int dx, int dy) { 928 if (getChildCount() == 0) { 929 // Nothing to do. 930 return; 931 } 932 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 933 if (duration > ANIMATED_SCROLL_GAP) { 934 final int width = getWidth() - mPaddingRight - mPaddingLeft; 935 final int right = getChildAt(0).getWidth(); 936 final int maxX = Math.max(0, right - width); 937 final int scrollX = mScrollX; 938 dx = Math.max(0, Math.min(scrollX + dx, maxX)) - scrollX; 939 940 mScroller.startScroll(scrollX, mScrollY, dx, 0); 941 awakenScrollBars(mScroller.getDuration()); 942 invalidate(); 943 } else { 944 if (!mScroller.isFinished()) { 945 mScroller.abortAnimation(); 946 } 947 scrollBy(dx, dy); 948 } 949 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 950 } 951 952 /** 953 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 954 * 955 * @param x the position where to scroll on the X axis 956 * @param y the position where to scroll on the Y axis 957 */ 958 public final void smoothScrollTo(int x, int y) { 959 smoothScrollBy(x - mScrollX, y - mScrollY); 960 } 961 962 /** 963 * <p>The scroll range of a scroll view is the overall width of all of its 964 * children.</p> 965 */ 966 @Override 967 protected int computeHorizontalScrollRange() { 968 final int count = getChildCount(); 969 final int contentWidth = getWidth() - mPaddingLeft - mPaddingRight; 970 if (count == 0) { 971 return contentWidth; 972 } 973 974 int scrollRange = getChildAt(0).getRight(); 975 final int scrollX = mScrollX; 976 final int overscrollRight = Math.max(0, scrollRange - contentWidth); 977 if (scrollX < 0) { 978 scrollRange -= scrollX; 979 } else if (scrollX > overscrollRight) { 980 scrollRange += scrollX - overscrollRight; 981 } 982 983 return scrollRange; 984 } 985 986 @Override 987 protected int computeHorizontalScrollOffset() { 988 return Math.max(0, super.computeHorizontalScrollOffset()); 989 } 990 991 @Override 992 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 993 ViewGroup.LayoutParams lp = child.getLayoutParams(); 994 995 int childWidthMeasureSpec; 996 int childHeightMeasureSpec; 997 998 childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop 999 + mPaddingBottom, lp.height); 1000 1001 childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1002 1003 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1004 } 1005 1006 @Override 1007 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1008 int parentHeightMeasureSpec, int heightUsed) { 1009 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1010 1011 final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, 1012 mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin 1013 + heightUsed, lp.height); 1014 final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( 1015 lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); 1016 1017 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1018 } 1019 1020 @Override 1021 public void computeScroll() { 1022 if (mScroller.computeScrollOffset()) { 1023 // This is called at drawing time by ViewGroup. We don't want to 1024 // re-show the scrollbars at this point, which scrollTo will do, 1025 // so we replicate most of scrollTo here. 1026 // 1027 // It's a little odd to call onScrollChanged from inside the drawing. 1028 // 1029 // It is, except when you remember that computeScroll() is used to 1030 // animate scrolling. So unless we want to defer the onScrollChanged() 1031 // until the end of the animated scrolling, we don't really have a 1032 // choice here. 1033 // 1034 // I agree. The alternative, which I think would be worse, is to post 1035 // something and tell the subclasses later. This is bad because there 1036 // will be a window where mScrollX/Y is different from what the app 1037 // thinks it is. 1038 // 1039 int oldX = mScrollX; 1040 int oldY = mScrollY; 1041 int x = mScroller.getCurrX(); 1042 int y = mScroller.getCurrY(); 1043 1044 if (oldX != x || oldY != y) { 1045 overscrollBy(x - oldX, y - oldY, oldX, oldY, getScrollRange(), 0, 1046 getOverscrollMax(), 0); 1047 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1048 } 1049 1050 // Keep on drawing until the animation has finished. 1051 postInvalidate(); 1052 } 1053 } 1054 1055 /** 1056 * Scrolls the view to the given child. 1057 * 1058 * @param child the View to scroll to 1059 */ 1060 private void scrollToChild(View child) { 1061 child.getDrawingRect(mTempRect); 1062 1063 /* Offset from child's local coordinates to ScrollView coordinates */ 1064 offsetDescendantRectToMyCoords(child, mTempRect); 1065 1066 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1067 1068 if (scrollDelta != 0) { 1069 scrollBy(scrollDelta, 0); 1070 } 1071 } 1072 1073 /** 1074 * If rect is off screen, scroll just enough to get it (or at least the 1075 * first screen size chunk of it) on screen. 1076 * 1077 * @param rect The rectangle. 1078 * @param immediate True to scroll immediately without animation 1079 * @return true if scrolling was performed 1080 */ 1081 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1082 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1083 final boolean scroll = delta != 0; 1084 if (scroll) { 1085 if (immediate) { 1086 scrollBy(delta, 0); 1087 } else { 1088 smoothScrollBy(delta, 0); 1089 } 1090 } 1091 return scroll; 1092 } 1093 1094 /** 1095 * Compute the amount to scroll in the X direction in order to get 1096 * a rectangle completely on the screen (or, if taller than the screen, 1097 * at least the first screen size chunk of it). 1098 * 1099 * @param rect The rect. 1100 * @return The scroll delta. 1101 */ 1102 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1103 if (getChildCount() == 0) return 0; 1104 1105 int width = getWidth(); 1106 int screenLeft = getScrollX(); 1107 int screenRight = screenLeft + width; 1108 1109 int fadingEdge = getHorizontalFadingEdgeLength(); 1110 1111 // leave room for left fading edge as long as rect isn't at very left 1112 if (rect.left > 0) { 1113 screenLeft += fadingEdge; 1114 } 1115 1116 // leave room for right fading edge as long as rect isn't at very right 1117 if (rect.right < getChildAt(0).getWidth()) { 1118 screenRight -= fadingEdge; 1119 } 1120 1121 int scrollXDelta = 0; 1122 1123 if (rect.right > screenRight && rect.left > screenLeft) { 1124 // need to move right to get it in view: move right just enough so 1125 // that the entire rectangle is in view (or at least the first 1126 // screen size chunk). 1127 1128 if (rect.width() > width) { 1129 // just enough to get screen size chunk on 1130 scrollXDelta += (rect.left - screenLeft); 1131 } else { 1132 // get entire rect at right of screen 1133 scrollXDelta += (rect.right - screenRight); 1134 } 1135 1136 // make sure we aren't scrolling beyond the end of our content 1137 int right = getChildAt(0).getRight(); 1138 int distanceToRight = right - screenRight; 1139 scrollXDelta = Math.min(scrollXDelta, distanceToRight); 1140 1141 } else if (rect.left < screenLeft && rect.right < screenRight) { 1142 // need to move right to get it in view: move right just enough so that 1143 // entire rectangle is in view (or at least the first screen 1144 // size chunk of it). 1145 1146 if (rect.width() > width) { 1147 // screen size chunk 1148 scrollXDelta -= (screenRight - rect.right); 1149 } else { 1150 // entire rect at left 1151 scrollXDelta -= (screenLeft - rect.left); 1152 } 1153 1154 // make sure we aren't scrolling any further than the left our content 1155 scrollXDelta = Math.max(scrollXDelta, -getScrollX()); 1156 } 1157 return scrollXDelta; 1158 } 1159 1160 @Override 1161 public void requestChildFocus(View child, View focused) { 1162 if (!mScrollViewMovedFocus) { 1163 if (!mIsLayoutDirty) { 1164 scrollToChild(focused); 1165 } else { 1166 // The child may not be laid out yet, we can't compute the scroll yet 1167 mChildToScrollTo = focused; 1168 } 1169 } 1170 super.requestChildFocus(child, focused); 1171 } 1172 1173 1174 /** 1175 * When looking for focus in children of a scroll view, need to be a little 1176 * more careful not to give focus to something that is scrolled off screen. 1177 * 1178 * This is more expensive than the default {@link android.view.ViewGroup} 1179 * implementation, otherwise this behavior might have been made the default. 1180 */ 1181 @Override 1182 protected boolean onRequestFocusInDescendants(int direction, 1183 Rect previouslyFocusedRect) { 1184 1185 // convert from forward / backward notation to up / down / left / right 1186 // (ugh). 1187 if (direction == View.FOCUS_FORWARD) { 1188 direction = View.FOCUS_RIGHT; 1189 } else if (direction == View.FOCUS_BACKWARD) { 1190 direction = View.FOCUS_LEFT; 1191 } 1192 1193 final View nextFocus = previouslyFocusedRect == null ? 1194 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1195 FocusFinder.getInstance().findNextFocusFromRect(this, 1196 previouslyFocusedRect, direction); 1197 1198 if (nextFocus == null) { 1199 return false; 1200 } 1201 1202 if (isOffScreen(nextFocus)) { 1203 return false; 1204 } 1205 1206 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1207 } 1208 1209 @Override 1210 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1211 boolean immediate) { 1212 // offset into coordinate space of this scroll view 1213 rectangle.offset(child.getLeft() - child.getScrollX(), 1214 child.getTop() - child.getScrollY()); 1215 1216 return scrollToChildRect(rectangle, immediate); 1217 } 1218 1219 @Override 1220 public void requestLayout() { 1221 mIsLayoutDirty = true; 1222 super.requestLayout(); 1223 } 1224 1225 @Override 1226 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1227 super.onLayout(changed, l, t, r, b); 1228 mIsLayoutDirty = false; 1229 // Give a child focus if it needs it 1230 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1231 scrollToChild(mChildToScrollTo); 1232 } 1233 mChildToScrollTo = null; 1234 1235 // Calling this with the present values causes it to re-clam them 1236 scrollTo(mScrollX, mScrollY); 1237 } 1238 1239 @Override 1240 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1241 super.onSizeChanged(w, h, oldw, oldh); 1242 1243 View currentFocused = findFocus(); 1244 if (null == currentFocused || this == currentFocused) 1245 return; 1246 1247 final int maxJump = mRight - mLeft; 1248 1249 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1250 currentFocused.getDrawingRect(mTempRect); 1251 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1252 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1253 doScrollX(scrollDelta); 1254 } 1255 } 1256 1257 /** 1258 * Return true if child is an descendant of parent, (or equal to the parent). 1259 */ 1260 private boolean isViewDescendantOf(View child, View parent) { 1261 if (child == parent) { 1262 return true; 1263 } 1264 1265 final ViewParent theParent = child.getParent(); 1266 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1267 } 1268 1269 /** 1270 * Fling the scroll view 1271 * 1272 * @param velocityX The initial velocity in the X direction. Positive 1273 * numbers mean that the finger/curor is moving down the screen, 1274 * which means we want to scroll towards the left. 1275 */ 1276 public void fling(int velocityX) { 1277 if (getChildCount() > 0) { 1278 int width = getWidth() - mPaddingRight - mPaddingLeft; 1279 int right = getChildAt(0).getWidth(); 1280 1281 mScroller.fling(mScrollX, mScrollY, velocityX, 0, 0, 1282 Math.max(0, right - width), 0, 0, width/2, 0); 1283 1284 final boolean movingRight = velocityX > 0; 1285 1286 View newFocused = findFocusableViewInMyBounds(movingRight, 1287 mScroller.getFinalX(), findFocus()); 1288 1289 if (newFocused == null) { 1290 newFocused = this; 1291 } 1292 1293 if (newFocused != findFocus() 1294 && newFocused.requestFocus(movingRight ? View.FOCUS_RIGHT : View.FOCUS_LEFT)) { 1295 mScrollViewMovedFocus = true; 1296 mScrollViewMovedFocus = false; 1297 } 1298 1299 awakenScrollBars(mScroller.getDuration()); 1300 invalidate(); 1301 } 1302 } 1303 1304 /** 1305 * {@inheritDoc} 1306 * 1307 * <p>This version also clamps the scrolling to the bounds of our child. 1308 */ 1309 public void scrollTo(int x, int y) { 1310 // we rely on the fact the View.scrollBy calls scrollTo. 1311 if (getChildCount() > 0) { 1312 View child = getChildAt(0); 1313 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1314 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1315 if (x != mScrollX || y != mScrollY) { 1316 super.scrollTo(x, y); 1317 } 1318 } 1319 } 1320 1321 private int clamp(int n, int my, int child) { 1322 if (my >= child || n < 0) { 1323 return 0; 1324 } 1325 if ((my + n) > child) { 1326 return child - my; 1327 } 1328 return n; 1329 } 1330} 1331