ScrollView.java revision fdbf484be1eca388553d97a13a9500b98b18b474
1/* 2 * Copyright (C) 2006 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 com.android.internal.R; 20 21import android.content.Context; 22import android.content.res.TypedArray; 23import android.graphics.Rect; 24import android.util.AttributeSet; 25import android.view.FocusFinder; 26import android.view.KeyEvent; 27import android.view.MotionEvent; 28import android.view.VelocityTracker; 29import android.view.View; 30import android.view.ViewConfiguration; 31import android.view.ViewGroup; 32import android.view.ViewParent; 33import android.view.animation.AnimationUtils; 34 35import java.util.List; 36 37/** 38 * Layout container for a view hierarchy that can be scrolled by the user, 39 * allowing it to be larger than the physical display. A ScrollView 40 * is a {@link FrameLayout}, meaning you should place one child in it 41 * containing the entire contents to scroll; this child may itself be a layout 42 * manager with a complex hierarchy of objects. A child that is often used 43 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 44 * array of top-level items that the user can scroll through. 45 * 46 * <p>The {@link TextView} class also 47 * takes care of its own scrolling, so does not require a ScrollView, but 48 * using the two together is possible to achieve the effect of a text view 49 * within a larger container. 50 * 51 * <p>ScrollView only supports vertical scrolling. 52 * 53 * @attr ref android.R.styleable#ScrollView_fillViewport 54 */ 55public class ScrollView extends FrameLayout { 56 static final int ANIMATED_SCROLL_GAP = 250; 57 58 static final float MAX_SCROLL_FACTOR = 0.5f; 59 60 61 private long mLastScroll; 62 63 private final Rect mTempRect = new Rect(); 64 private Scroller mScroller; 65 66 /** 67 * Flag to indicate that we are moving focus ourselves. This is so the 68 * code that watches for focus changes initiated outside this ScrollView 69 * knows that it does not have to do anything. 70 */ 71 private boolean mScrollViewMovedFocus; 72 73 /** 74 * Position of the last motion event. 75 */ 76 private float mLastMotionY; 77 78 /** 79 * True when the layout has changed but the traversal has not come through yet. 80 * Ideally the view hierarchy would keep track of this for us. 81 */ 82 private boolean mIsLayoutDirty = true; 83 84 /** 85 * The child to give focus to in the event that a child has requested focus while the 86 * layout is dirty. This prevents the scroll from being wrong if the child has not been 87 * laid out before requesting focus. 88 */ 89 private View mChildToScrollTo = null; 90 91 /** 92 * True if the user is currently dragging this ScrollView around. This is 93 * not the same as 'is being flinged', which can be checked by 94 * mScroller.isFinished() (flinging begins when the user lifts his finger). 95 */ 96 private boolean mIsBeingDragged = false; 97 98 /** 99 * Determines speed during touch scrolling 100 */ 101 private VelocityTracker mVelocityTracker; 102 103 /** 104 * When set to true, the scroll view measure its child to make it fill the currently 105 * visible area. 106 */ 107 private boolean mFillViewport; 108 109 /** 110 * Whether arrow scrolling is animated. 111 */ 112 private boolean mSmoothScrollingEnabled = true; 113 114 private int mTouchSlop; 115 private int mMinimumVelocity; 116 private int mMaximumVelocity; 117 118 /** 119 * ID of the active pointer. This is used to retain consistency during 120 * drags/flings if multiple pointers are used. 121 */ 122 private int mActivePointerId = INVALID_POINTER; 123 124 /** 125 * Sentinel value for no current active pointer. 126 * Used by {@link #mActivePointerId}. 127 */ 128 private static final int INVALID_POINTER = -1; 129 130 public ScrollView(Context context) { 131 this(context, null); 132 } 133 134 public ScrollView(Context context, AttributeSet attrs) { 135 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 136 } 137 138 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 139 super(context, attrs, defStyle); 140 initScrollView(); 141 142 TypedArray a = 143 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 144 145 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 146 147 a.recycle(); 148 } 149 150 @Override 151 protected float getTopFadingEdgeStrength() { 152 if (getChildCount() == 0) { 153 return 0.0f; 154 } 155 156 final int length = getVerticalFadingEdgeLength(); 157 if (mScrollY < length) { 158 return mScrollY / (float) length; 159 } 160 161 return 1.0f; 162 } 163 164 @Override 165 protected float getBottomFadingEdgeStrength() { 166 if (getChildCount() == 0) { 167 return 0.0f; 168 } 169 170 final int length = getVerticalFadingEdgeLength(); 171 final int bottomEdge = getHeight() - mPaddingBottom; 172 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 173 if (span < length) { 174 return span / (float) length; 175 } 176 177 return 1.0f; 178 } 179 180 /** 181 * @return The maximum amount this scroll view will scroll in response to 182 * an arrow event. 183 */ 184 public int getMaxScrollAmount() { 185 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 186 } 187 188 189 private void initScrollView() { 190 mScroller = new Scroller(getContext()); 191 setFocusable(true); 192 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 193 setWillNotDraw(false); 194 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 195 mTouchSlop = configuration.getScaledTouchSlop(); 196 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 197 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 198 } 199 200 @Override 201 public void addView(View child) { 202 if (getChildCount() > 0) { 203 throw new IllegalStateException("ScrollView can host only one direct child"); 204 } 205 206 super.addView(child); 207 } 208 209 @Override 210 public void addView(View child, int index) { 211 if (getChildCount() > 0) { 212 throw new IllegalStateException("ScrollView can host only one direct child"); 213 } 214 215 super.addView(child, index); 216 } 217 218 @Override 219 public void addView(View child, ViewGroup.LayoutParams params) { 220 if (getChildCount() > 0) { 221 throw new IllegalStateException("ScrollView can host only one direct child"); 222 } 223 224 super.addView(child, params); 225 } 226 227 @Override 228 public void addView(View child, int index, ViewGroup.LayoutParams params) { 229 if (getChildCount() > 0) { 230 throw new IllegalStateException("ScrollView can host only one direct child"); 231 } 232 233 super.addView(child, index, params); 234 } 235 236 /** 237 * @return Returns true this ScrollView can be scrolled 238 */ 239 private boolean canScroll() { 240 View child = getChildAt(0); 241 if (child != null) { 242 int childHeight = child.getHeight(); 243 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 244 } 245 return false; 246 } 247 248 /** 249 * Indicates whether this ScrollView's content is stretched to fill the viewport. 250 * 251 * @return True if the content fills the viewport, false otherwise. 252 * 253 * @attr ref android.R.styleable#ScrollView_fillViewport 254 */ 255 public boolean isFillViewport() { 256 return mFillViewport; 257 } 258 259 /** 260 * Indicates this ScrollView whether it should stretch its content height to fill 261 * the viewport or not. 262 * 263 * @param fillViewport True to stretch the content's height to the viewport's 264 * boundaries, false otherwise. 265 * 266 * @attr ref android.R.styleable#ScrollView_fillViewport 267 */ 268 public void setFillViewport(boolean fillViewport) { 269 if (fillViewport != mFillViewport) { 270 mFillViewport = fillViewport; 271 requestLayout(); 272 } 273 } 274 275 /** 276 * @return Whether arrow scrolling will animate its transition. 277 */ 278 public boolean isSmoothScrollingEnabled() { 279 return mSmoothScrollingEnabled; 280 } 281 282 /** 283 * Set whether arrow scrolling will animate its transition. 284 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 285 */ 286 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 287 mSmoothScrollingEnabled = smoothScrollingEnabled; 288 } 289 290 @Override 291 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 292 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 293 294 if (!mFillViewport) { 295 return; 296 } 297 298 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 299 if (heightMode == MeasureSpec.UNSPECIFIED) { 300 return; 301 } 302 303 if (getChildCount() > 0) { 304 final View child = getChildAt(0); 305 int height = getMeasuredHeight(); 306 if (child.getMeasuredHeight() < height) { 307 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 308 309 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 310 + mPaddingRight, lp.width); 311 height -= mPaddingTop; 312 height -= mPaddingBottom; 313 int childHeightMeasureSpec = 314 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 315 316 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 317 } 318 } 319 } 320 321 @Override 322 public boolean dispatchKeyEvent(KeyEvent event) { 323 // Let the focused view and/or our descendants get the key first 324 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 325 } 326 327 /** 328 * You can call this function yourself to have the scroll view perform 329 * scrolling from a key event, just as if the event had been dispatched to 330 * it by the view hierarchy. 331 * 332 * @param event The key event to execute. 333 * @return Return true if the event was handled, else false. 334 */ 335 public boolean executeKeyEvent(KeyEvent event) { 336 mTempRect.setEmpty(); 337 338 if (!canScroll()) { 339 if (isFocused() && event.getKeyCode() != KeyEvent.KEYCODE_BACK) { 340 View currentFocused = findFocus(); 341 if (currentFocused == this) currentFocused = null; 342 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 343 currentFocused, View.FOCUS_DOWN); 344 return nextFocused != null 345 && nextFocused != this 346 && nextFocused.requestFocus(View.FOCUS_DOWN); 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_UP: 355 if (!event.isAltPressed()) { 356 handled = arrowScroll(View.FOCUS_UP); 357 } else { 358 handled = fullScroll(View.FOCUS_UP); 359 } 360 break; 361 case KeyEvent.KEYCODE_DPAD_DOWN: 362 if (!event.isAltPressed()) { 363 handled = arrowScroll(View.FOCUS_DOWN); 364 } else { 365 handled = fullScroll(View.FOCUS_DOWN); 366 } 367 break; 368 case KeyEvent.KEYCODE_SPACE: 369 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 370 break; 371 } 372 } 373 374 return handled; 375 } 376 377 private boolean inChild(int x, int y) { 378 if (getChildCount() > 0) { 379 final int scrollY = mScrollY; 380 final View child = getChildAt(0); 381 return !(y < child.getTop() - scrollY 382 || y >= child.getBottom() - scrollY 383 || x < child.getLeft() 384 || x >= child.getRight()); 385 } 386 return false; 387 } 388 389 @Override 390 public boolean onInterceptTouchEvent(MotionEvent ev) { 391 /* 392 * This method JUST determines whether we want to intercept the motion. 393 * If we return true, onMotionEvent will be called and we do the actual 394 * scrolling there. 395 */ 396 397 /* 398 * Shortcut the most recurring case: the user is in the dragging 399 * state and he is moving his finger. We want to intercept this 400 * motion. 401 */ 402 final int action = ev.getAction(); 403 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 404 return true; 405 } 406 407 switch (action & MotionEvent.ACTION_MASK) { 408 case MotionEvent.ACTION_MOVE: { 409 /* 410 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 411 * whether the user has moved far enough from his original down touch. 412 */ 413 414 /* 415 * Locally do absolute value. mLastMotionY is set to the y value 416 * of the down event. 417 */ 418 final int activePointerId = mActivePointerId; 419 if (activePointerId == INVALID_POINTER) { 420 // If we don't have a valid id, the touch down wasn't on content. 421 break; 422 } 423 424 final int pointerIndex = ev.findPointerIndex(activePointerId); 425 final float y = ev.getY(pointerIndex); 426 final int yDiff = (int) Math.abs(y - mLastMotionY); 427 if (yDiff > mTouchSlop) { 428 mIsBeingDragged = true; 429 mLastMotionY = y; 430 } 431 break; 432 } 433 434 case MotionEvent.ACTION_DOWN: { 435 final float y = ev.getY(); 436 if (!inChild((int) ev.getX(), (int) y)) { 437 mIsBeingDragged = false; 438 break; 439 } 440 441 /* 442 * Remember location of down touch. 443 * ACTION_DOWN always refers to pointer index 0. 444 */ 445 mLastMotionY = y; 446 mActivePointerId = ev.getPointerId(0); 447 448 /* 449 * If being flinged and user touches the screen, initiate drag; 450 * otherwise don't. mScroller.isFinished should be false when 451 * being flinged. 452 */ 453 mIsBeingDragged = !mScroller.isFinished(); 454 break; 455 } 456 457 case MotionEvent.ACTION_CANCEL: 458 case MotionEvent.ACTION_UP: 459 /* Release the drag */ 460 mIsBeingDragged = false; 461 mActivePointerId = INVALID_POINTER; 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 y = ev.getY(); 494 if (!(mIsBeingDragged = inChild((int) ev.getX(), (int) y))) { 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 mLastMotionY = y; 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 y = ev.getY(activePointerIndex); 516 final int deltaY = (int) (mLastMotionY - y); 517 mLastMotionY = y; 518 519 scrollBy(0, deltaY); 520 } 521 break; 522 case MotionEvent.ACTION_UP: 523 if (mIsBeingDragged) { 524 final VelocityTracker velocityTracker = mVelocityTracker; 525 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 526 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 527 528 if (getChildCount() > 0 && Math.abs(initialVelocity) > mMinimumVelocity) { 529 fling(-initialVelocity); 530 } 531 532 mActivePointerId = INVALID_POINTER; 533 mIsBeingDragged = false; 534 535 if (mVelocityTracker != null) { 536 mVelocityTracker.recycle(); 537 mVelocityTracker = null; 538 } 539 } 540 break; 541 case MotionEvent.ACTION_CANCEL: 542 if (mIsBeingDragged && getChildCount() > 0) { 543 mActivePointerId = INVALID_POINTER; 544 mIsBeingDragged = false; 545 if (mVelocityTracker != null) { 546 mVelocityTracker.recycle(); 547 mVelocityTracker = null; 548 } 549 } 550 break; 551 case MotionEvent.ACTION_POINTER_UP: 552 onSecondaryPointerUp(ev); 553 break; 554 } 555 return true; 556 } 557 558 private void onSecondaryPointerUp(MotionEvent ev) { 559 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 560 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 561 final int pointerId = ev.getPointerId(pointerIndex); 562 if (pointerId == mActivePointerId) { 563 // This was our active pointer going up. Choose a new 564 // active pointer and adjust accordingly. 565 // TODO: Make this decision more intelligent. 566 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 567 mLastMotionY = ev.getY(newPointerIndex); 568 mActivePointerId = ev.getPointerId(newPointerIndex); 569 if (mVelocityTracker != null) { 570 mVelocityTracker.clear(); 571 } 572 } 573 } 574 575 /** 576 * <p> 577 * Finds the next focusable component that fits in this View's bounds 578 * (excluding fading edges) pretending that this View's top is located at 579 * the parameter top. 580 * </p> 581 * 582 * @param topFocus look for a candidate is the one at the top of the bounds 583 * if topFocus is true, or at the bottom of the bounds if topFocus is 584 * false 585 * @param top the top offset of the bounds in which a focusable must be 586 * found (the fading edge is assumed to start at this position) 587 * @param preferredFocusable the View that has highest priority and will be 588 * returned if it is within my bounds (null is valid) 589 * @return the next focusable component in the bounds or null if none can be 590 * found 591 */ 592 private View findFocusableViewInMyBounds(final boolean topFocus, 593 final int top, View preferredFocusable) { 594 /* 595 * The fading edge's transparent side should be considered for focus 596 * since it's mostly visible, so we divide the actual fading edge length 597 * by 2. 598 */ 599 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 600 final int topWithoutFadingEdge = top + fadingEdgeLength; 601 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 602 603 if ((preferredFocusable != null) 604 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 605 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 606 return preferredFocusable; 607 } 608 609 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 610 bottomWithoutFadingEdge); 611 } 612 613 /** 614 * <p> 615 * Finds the next focusable component that fits in the specified bounds. 616 * </p> 617 * 618 * @param topFocus look for a candidate is the one at the top of the bounds 619 * if topFocus is true, or at the bottom of the bounds if topFocus is 620 * false 621 * @param top the top offset of the bounds in which a focusable must be 622 * found 623 * @param bottom the bottom offset of the bounds in which a focusable must 624 * be found 625 * @return the next focusable component in the bounds or null if none can 626 * be found 627 */ 628 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 629 630 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 631 View focusCandidate = null; 632 633 /* 634 * A fully contained focusable is one where its top is below the bound's 635 * top, and its bottom is above the bound's bottom. A partially 636 * contained focusable is one where some part of it is within the 637 * bounds, but it also has some part that is not within bounds. A fully contained 638 * focusable is preferred to a partially contained focusable. 639 */ 640 boolean foundFullyContainedFocusable = false; 641 642 int count = focusables.size(); 643 for (int i = 0; i < count; i++) { 644 View view = focusables.get(i); 645 int viewTop = view.getTop(); 646 int viewBottom = view.getBottom(); 647 648 if (top < viewBottom && viewTop < bottom) { 649 /* 650 * the focusable is in the target area, it is a candidate for 651 * focusing 652 */ 653 654 final boolean viewIsFullyContained = (top < viewTop) && 655 (viewBottom < bottom); 656 657 if (focusCandidate == null) { 658 /* No candidate, take this one */ 659 focusCandidate = view; 660 foundFullyContainedFocusable = viewIsFullyContained; 661 } else { 662 final boolean viewIsCloserToBoundary = 663 (topFocus && viewTop < focusCandidate.getTop()) || 664 (!topFocus && viewBottom > focusCandidate 665 .getBottom()); 666 667 if (foundFullyContainedFocusable) { 668 if (viewIsFullyContained && viewIsCloserToBoundary) { 669 /* 670 * We're dealing with only fully contained views, so 671 * it has to be closer to the boundary to beat our 672 * candidate 673 */ 674 focusCandidate = view; 675 } 676 } else { 677 if (viewIsFullyContained) { 678 /* Any fully contained view beats a partially contained view */ 679 focusCandidate = view; 680 foundFullyContainedFocusable = true; 681 } else if (viewIsCloserToBoundary) { 682 /* 683 * Partially contained view beats another partially 684 * contained view if it's closer 685 */ 686 focusCandidate = view; 687 } 688 } 689 } 690 } 691 } 692 693 return focusCandidate; 694 } 695 696 /** 697 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 698 * method will scroll the view by one page up or down and give the focus 699 * to the topmost/bottommost component in the new visible area. If no 700 * component is a good candidate for focus, this scrollview reclaims the 701 * focus.</p> 702 * 703 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 704 * to go one page up or 705 * {@link android.view.View#FOCUS_DOWN} to go one page down 706 * @return true if the key event is consumed by this method, false otherwise 707 */ 708 public boolean pageScroll(int direction) { 709 boolean down = direction == View.FOCUS_DOWN; 710 int height = getHeight(); 711 712 if (down) { 713 mTempRect.top = getScrollY() + height; 714 int count = getChildCount(); 715 if (count > 0) { 716 View view = getChildAt(count - 1); 717 if (mTempRect.top + height > view.getBottom()) { 718 mTempRect.top = view.getBottom() - height; 719 } 720 } 721 } else { 722 mTempRect.top = getScrollY() - height; 723 if (mTempRect.top < 0) { 724 mTempRect.top = 0; 725 } 726 } 727 mTempRect.bottom = mTempRect.top + height; 728 729 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 730 } 731 732 /** 733 * <p>Handles scrolling in response to a "home/end" shortcut press. This 734 * method will scroll the view to the top or bottom and give the focus 735 * to the topmost/bottommost component in the new visible area. If no 736 * component is a good candidate for focus, this scrollview reclaims the 737 * focus.</p> 738 * 739 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 740 * to go the top of the view or 741 * {@link android.view.View#FOCUS_DOWN} to go the bottom 742 * @return true if the key event is consumed by this method, false otherwise 743 */ 744 public boolean fullScroll(int direction) { 745 boolean down = direction == View.FOCUS_DOWN; 746 int height = getHeight(); 747 748 mTempRect.top = 0; 749 mTempRect.bottom = height; 750 751 if (down) { 752 int count = getChildCount(); 753 if (count > 0) { 754 View view = getChildAt(count - 1); 755 mTempRect.bottom = view.getBottom(); 756 mTempRect.top = mTempRect.bottom - height; 757 } 758 } 759 760 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 761 } 762 763 /** 764 * <p>Scrolls the view to make the area defined by <code>top</code> and 765 * <code>bottom</code> visible. This method attempts to give the focus 766 * to a component visible in this area. If no component can be focused in 767 * the new visible area, the focus is reclaimed by this scrollview.</p> 768 * 769 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 770 * to go upward 771 * {@link android.view.View#FOCUS_DOWN} to downward 772 * @param top the top offset of the new area to be made visible 773 * @param bottom the bottom offset of the new area to be made visible 774 * @return true if the key event is consumed by this method, false otherwise 775 */ 776 private boolean scrollAndFocus(int direction, int top, int bottom) { 777 boolean handled = true; 778 779 int height = getHeight(); 780 int containerTop = getScrollY(); 781 int containerBottom = containerTop + height; 782 boolean up = direction == View.FOCUS_UP; 783 784 View newFocused = findFocusableViewInBounds(up, top, bottom); 785 if (newFocused == null) { 786 newFocused = this; 787 } 788 789 if (top >= containerTop && bottom <= containerBottom) { 790 handled = false; 791 } else { 792 int delta = up ? (top - containerTop) : (bottom - containerBottom); 793 doScrollY(delta); 794 } 795 796 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 797 mScrollViewMovedFocus = true; 798 mScrollViewMovedFocus = false; 799 } 800 801 return handled; 802 } 803 804 /** 805 * Handle scrolling in response to an up or down arrow click. 806 * 807 * @param direction The direction corresponding to the arrow key that was 808 * pressed 809 * @return True if we consumed the event, false otherwise 810 */ 811 public boolean arrowScroll(int direction) { 812 813 View currentFocused = findFocus(); 814 if (currentFocused == this) currentFocused = null; 815 816 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 817 818 final int maxJump = getMaxScrollAmount(); 819 820 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 821 nextFocused.getDrawingRect(mTempRect); 822 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 823 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 824 doScrollY(scrollDelta); 825 nextFocused.requestFocus(direction); 826 } else { 827 // no new focus 828 int scrollDelta = maxJump; 829 830 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 831 scrollDelta = getScrollY(); 832 } else if (direction == View.FOCUS_DOWN) { 833 if (getChildCount() > 0) { 834 int daBottom = getChildAt(0).getBottom(); 835 836 int screenBottom = getScrollY() + getHeight(); 837 838 if (daBottom - screenBottom < maxJump) { 839 scrollDelta = daBottom - screenBottom; 840 } 841 } 842 } 843 if (scrollDelta == 0) { 844 return false; 845 } 846 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 847 } 848 849 if (currentFocused != null && currentFocused.isFocused() 850 && isOffScreen(currentFocused)) { 851 // previously focused item still has focus and is off screen, give 852 // it up (take it back to ourselves) 853 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 854 // sure to 855 // get it) 856 final int descendantFocusability = getDescendantFocusability(); // save 857 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 858 requestFocus(); 859 setDescendantFocusability(descendantFocusability); // restore 860 } 861 return true; 862 } 863 864 /** 865 * @return whether the descendant of this scroll view is scrolled off 866 * screen. 867 */ 868 private boolean isOffScreen(View descendant) { 869 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 870 } 871 872 /** 873 * @return whether the descendant of this scroll view is within delta 874 * pixels of being on the screen. 875 */ 876 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 877 descendant.getDrawingRect(mTempRect); 878 offsetDescendantRectToMyCoords(descendant, mTempRect); 879 880 return (mTempRect.bottom + delta) >= getScrollY() 881 && (mTempRect.top - delta) <= (getScrollY() + height); 882 } 883 884 /** 885 * Smooth scroll by a Y delta 886 * 887 * @param delta the number of pixels to scroll by on the Y axis 888 */ 889 private void doScrollY(int delta) { 890 if (delta != 0) { 891 if (mSmoothScrollingEnabled) { 892 smoothScrollBy(0, delta); 893 } else { 894 scrollBy(0, delta); 895 } 896 } 897 } 898 899 /** 900 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 901 * 902 * @param dx the number of pixels to scroll by on the X axis 903 * @param dy the number of pixels to scroll by on the Y axis 904 */ 905 public final void smoothScrollBy(int dx, int dy) { 906 if (getChildCount() == 0) { 907 // Nothing to do. 908 return; 909 } 910 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 911 if (duration > ANIMATED_SCROLL_GAP) { 912 final int height = getHeight() - mPaddingBottom - mPaddingTop; 913 final int bottom = getChildAt(0).getHeight(); 914 final int maxY = Math.max(0, bottom - height); 915 final int scrollY = mScrollY; 916 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 917 918 mScroller.startScroll(mScrollX, scrollY, 0, dy); 919 invalidate(); 920 } else { 921 if (!mScroller.isFinished()) { 922 mScroller.abortAnimation(); 923 } 924 scrollBy(dx, dy); 925 } 926 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 927 } 928 929 /** 930 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 931 * 932 * @param x the position where to scroll on the X axis 933 * @param y the position where to scroll on the Y axis 934 */ 935 public final void smoothScrollTo(int x, int y) { 936 smoothScrollBy(x - mScrollX, y - mScrollY); 937 } 938 939 /** 940 * <p>The scroll range of a scroll view is the overall height of all of its 941 * children.</p> 942 */ 943 @Override 944 protected int computeVerticalScrollRange() { 945 final int count = getChildCount(); 946 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 947 if (count == 0) { 948 return contentHeight; 949 } 950 951 return getChildAt(0).getBottom(); 952 } 953 954 @Override 955 protected int computeVerticalScrollOffset() { 956 return Math.max(0, super.computeVerticalScrollOffset()); 957 } 958 959 @Override 960 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 961 ViewGroup.LayoutParams lp = child.getLayoutParams(); 962 963 int childWidthMeasureSpec; 964 int childHeightMeasureSpec; 965 966 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 967 + mPaddingRight, lp.width); 968 969 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 970 971 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 972 } 973 974 @Override 975 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 976 int parentHeightMeasureSpec, int heightUsed) { 977 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 978 979 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 980 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 981 + widthUsed, lp.width); 982 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 983 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 984 985 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 986 } 987 988 @Override 989 public void computeScroll() { 990 if (mScroller.computeScrollOffset()) { 991 // This is called at drawing time by ViewGroup. We don't want to 992 // re-show the scrollbars at this point, which scrollTo will do, 993 // so we replicate most of scrollTo here. 994 // 995 // It's a little odd to call onScrollChanged from inside the drawing. 996 // 997 // It is, except when you remember that computeScroll() is used to 998 // animate scrolling. So unless we want to defer the onScrollChanged() 999 // until the end of the animated scrolling, we don't really have a 1000 // choice here. 1001 // 1002 // I agree. The alternative, which I think would be worse, is to post 1003 // something and tell the subclasses later. This is bad because there 1004 // will be a window where mScrollX/Y is different from what the app 1005 // thinks it is. 1006 // 1007 int oldX = mScrollX; 1008 int oldY = mScrollY; 1009 int x = mScroller.getCurrX(); 1010 int y = mScroller.getCurrY(); 1011 1012 if (getChildCount() > 0) { 1013 View child = getChildAt(0); 1014 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1015 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1016 if (x != oldX || y != oldY) { 1017 mScrollX = x; 1018 mScrollY = y; 1019 onScrollChanged(x, y, oldX, oldY); 1020 } 1021 } 1022 awakenScrollBars(); 1023 1024 // Keep on drawing until the animation has finished. 1025 postInvalidate(); 1026 } 1027 } 1028 1029 /** 1030 * Scrolls the view to the given child. 1031 * 1032 * @param child the View to scroll to 1033 */ 1034 private void scrollToChild(View child) { 1035 child.getDrawingRect(mTempRect); 1036 1037 /* Offset from child's local coordinates to ScrollView coordinates */ 1038 offsetDescendantRectToMyCoords(child, mTempRect); 1039 1040 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1041 1042 if (scrollDelta != 0) { 1043 scrollBy(0, scrollDelta); 1044 } 1045 } 1046 1047 /** 1048 * If rect is off screen, scroll just enough to get it (or at least the 1049 * first screen size chunk of it) on screen. 1050 * 1051 * @param rect The rectangle. 1052 * @param immediate True to scroll immediately without animation 1053 * @return true if scrolling was performed 1054 */ 1055 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1056 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1057 final boolean scroll = delta != 0; 1058 if (scroll) { 1059 if (immediate) { 1060 scrollBy(0, delta); 1061 } else { 1062 smoothScrollBy(0, delta); 1063 } 1064 } 1065 return scroll; 1066 } 1067 1068 /** 1069 * Compute the amount to scroll in the Y direction in order to get 1070 * a rectangle completely on the screen (or, if taller than the screen, 1071 * at least the first screen size chunk of it). 1072 * 1073 * @param rect The rect. 1074 * @return The scroll delta. 1075 */ 1076 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1077 if (getChildCount() == 0) return 0; 1078 1079 int height = getHeight(); 1080 int screenTop = getScrollY(); 1081 int screenBottom = screenTop + height; 1082 1083 int fadingEdge = getVerticalFadingEdgeLength(); 1084 1085 // leave room for top fading edge as long as rect isn't at very top 1086 if (rect.top > 0) { 1087 screenTop += fadingEdge; 1088 } 1089 1090 // leave room for bottom fading edge as long as rect isn't at very bottom 1091 if (rect.bottom < getChildAt(0).getHeight()) { 1092 screenBottom -= fadingEdge; 1093 } 1094 1095 int scrollYDelta = 0; 1096 1097 if (rect.bottom > screenBottom && rect.top > screenTop) { 1098 // need to move down to get it in view: move down just enough so 1099 // that the entire rectangle is in view (or at least the first 1100 // screen size chunk). 1101 1102 if (rect.height() > height) { 1103 // just enough to get screen size chunk on 1104 scrollYDelta += (rect.top - screenTop); 1105 } else { 1106 // get entire rect at bottom of screen 1107 scrollYDelta += (rect.bottom - screenBottom); 1108 } 1109 1110 // make sure we aren't scrolling beyond the end of our content 1111 int bottom = getChildAt(0).getBottom(); 1112 int distanceToBottom = bottom - screenBottom; 1113 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1114 1115 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1116 // need to move up to get it in view: move up just enough so that 1117 // entire rectangle is in view (or at least the first screen 1118 // size chunk of it). 1119 1120 if (rect.height() > height) { 1121 // screen size chunk 1122 scrollYDelta -= (screenBottom - rect.bottom); 1123 } else { 1124 // entire rect at top 1125 scrollYDelta -= (screenTop - rect.top); 1126 } 1127 1128 // make sure we aren't scrolling any further than the top our content 1129 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1130 } 1131 return scrollYDelta; 1132 } 1133 1134 @Override 1135 public void requestChildFocus(View child, View focused) { 1136 if (!mScrollViewMovedFocus) { 1137 if (!mIsLayoutDirty) { 1138 scrollToChild(focused); 1139 } else { 1140 // The child may not be laid out yet, we can't compute the scroll yet 1141 mChildToScrollTo = focused; 1142 } 1143 } 1144 super.requestChildFocus(child, focused); 1145 } 1146 1147 1148 /** 1149 * When looking for focus in children of a scroll view, need to be a little 1150 * more careful not to give focus to something that is scrolled off screen. 1151 * 1152 * This is more expensive than the default {@link android.view.ViewGroup} 1153 * implementation, otherwise this behavior might have been made the default. 1154 */ 1155 @Override 1156 protected boolean onRequestFocusInDescendants(int direction, 1157 Rect previouslyFocusedRect) { 1158 1159 // convert from forward / backward notation to up / down / left / right 1160 // (ugh). 1161 if (direction == View.FOCUS_FORWARD) { 1162 direction = View.FOCUS_DOWN; 1163 } else if (direction == View.FOCUS_BACKWARD) { 1164 direction = View.FOCUS_UP; 1165 } 1166 1167 final View nextFocus = previouslyFocusedRect == null ? 1168 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1169 FocusFinder.getInstance().findNextFocusFromRect(this, 1170 previouslyFocusedRect, direction); 1171 1172 if (nextFocus == null) { 1173 return false; 1174 } 1175 1176 if (isOffScreen(nextFocus)) { 1177 return false; 1178 } 1179 1180 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1181 } 1182 1183 @Override 1184 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1185 boolean immediate) { 1186 // offset into coordinate space of this scroll view 1187 rectangle.offset(child.getLeft() - child.getScrollX(), 1188 child.getTop() - child.getScrollY()); 1189 1190 return scrollToChildRect(rectangle, immediate); 1191 } 1192 1193 @Override 1194 public void requestLayout() { 1195 mIsLayoutDirty = true; 1196 super.requestLayout(); 1197 } 1198 1199 @Override 1200 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1201 super.onLayout(changed, l, t, r, b); 1202 mIsLayoutDirty = false; 1203 // Give a child focus if it needs it 1204 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1205 scrollToChild(mChildToScrollTo); 1206 } 1207 mChildToScrollTo = null; 1208 1209 // Calling this with the present values causes it to re-clam them 1210 scrollTo(mScrollX, mScrollY); 1211 } 1212 1213 @Override 1214 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1215 super.onSizeChanged(w, h, oldw, oldh); 1216 1217 View currentFocused = findFocus(); 1218 if (null == currentFocused || this == currentFocused) 1219 return; 1220 1221 // If the currently-focused view was visible on the screen when the 1222 // screen was at the old height, then scroll the screen to make that 1223 // view visible with the new screen height. 1224 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1225 currentFocused.getDrawingRect(mTempRect); 1226 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1227 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1228 doScrollY(scrollDelta); 1229 } 1230 } 1231 1232 /** 1233 * Return true if child is an descendant of parent, (or equal to the parent). 1234 */ 1235 private boolean isViewDescendantOf(View child, View parent) { 1236 if (child == parent) { 1237 return true; 1238 } 1239 1240 final ViewParent theParent = child.getParent(); 1241 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1242 } 1243 1244 /** 1245 * Fling the scroll view 1246 * 1247 * @param velocityY The initial velocity in the Y direction. Positive 1248 * numbers mean that the finger/cursor is moving down the screen, 1249 * which means we want to scroll towards the top. 1250 */ 1251 public void fling(int velocityY) { 1252 if (getChildCount() > 0) { 1253 int height = getHeight() - mPaddingBottom - mPaddingTop; 1254 int bottom = getChildAt(0).getHeight(); 1255 1256 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1257 Math.max(0, bottom - height)); 1258 1259 final boolean movingDown = velocityY > 0; 1260 1261 View newFocused = 1262 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1263 if (newFocused == null) { 1264 newFocused = this; 1265 } 1266 1267 if (newFocused != findFocus() 1268 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1269 mScrollViewMovedFocus = true; 1270 mScrollViewMovedFocus = false; 1271 } 1272 1273 invalidate(); 1274 } 1275 } 1276 1277 /** 1278 * {@inheritDoc} 1279 * 1280 * <p>This version also clamps the scrolling to the bounds of our child. 1281 */ 1282 @Override 1283 public void scrollTo(int x, int y) { 1284 // we rely on the fact the View.scrollBy calls scrollTo. 1285 if (getChildCount() > 0) { 1286 View child = getChildAt(0); 1287 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1288 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1289 if (x != mScrollX || y != mScrollY) { 1290 super.scrollTo(x, y); 1291 } 1292 } 1293 } 1294 1295 private int clamp(int n, int my, int child) { 1296 if (my >= child || n < 0) { 1297 /* my >= child is this case: 1298 * |--------------- me ---------------| 1299 * |------ child ------| 1300 * or 1301 * |--------------- me ---------------| 1302 * |------ child ------| 1303 * or 1304 * |--------------- me ---------------| 1305 * |------ child ------| 1306 * 1307 * n < 0 is this case: 1308 * |------ me ------| 1309 * |-------- child --------| 1310 * |-- mScrollX --| 1311 */ 1312 return 0; 1313 } 1314 if ((my+n) > child) { 1315 /* this case: 1316 * |------ me ------| 1317 * |------ child ------| 1318 * |-- mScrollX --| 1319 */ 1320 return child-my; 1321 } 1322 return n; 1323 } 1324} 1325