ScrollView.java revision bc4e7533b9c6a6e45e3cf4a889bcb913b8feefc5
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.util.Log; 26import android.view.FocusFinder; 27import android.view.KeyEvent; 28import android.view.MotionEvent; 29import android.view.VelocityTracker; 30import android.view.View; 31import android.view.ViewConfiguration; 32import android.view.ViewGroup; 33import android.view.ViewParent; 34import android.view.animation.AnimationUtils; 35 36import java.util.List; 37 38/** 39 * Layout container for a view hierarchy that can be scrolled by the user, 40 * allowing it to be larger than the physical display. A ScrollView 41 * is a {@link FrameLayout}, meaning you should place one child in it 42 * containing the entire contents to scroll; this child may itself be a layout 43 * manager with a complex hierarchy of objects. A child that is often used 44 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 45 * array of top-level items that the user can scroll through. 46 * 47 * <p>The {@link TextView} class also 48 * takes care of its own scrolling, so does not require a ScrollView, but 49 * using the two together is possible to achieve the effect of a text view 50 * within a larger container. 51 * 52 * <p>ScrollView only supports vertical scrolling. 53 */ 54public class ScrollView extends FrameLayout { 55 private static final String TAG = "ScrollView"; 56 57 static final int ANIMATED_SCROLL_GAP = 250; 58 59 static final float MAX_SCROLL_FACTOR = 0.5f; 60 61 62 private long mLastScroll; 63 64 private final Rect mTempRect = new Rect(); 65 private OverScroller mScroller; 66 67 /** 68 * Flag to indicate that we are moving focus ourselves. This is so the 69 * code that watches for focus changes initiated outside this ScrollView 70 * knows that it does not have to do anything. 71 */ 72 private boolean mScrollViewMovedFocus; 73 74 /** 75 * Position of the last motion event. 76 */ 77 private float mLastMotionY; 78 79 /** 80 * True when the layout has changed but the traversal has not come through yet. 81 * Ideally the view hierarchy would keep track of this for us. 82 */ 83 private boolean mIsLayoutDirty = true; 84 85 /** 86 * The child to give focus to in the event that a child has requested focus while the 87 * layout is dirty. This prevents the scroll from being wrong if the child has not been 88 * laid out before requesting focus. 89 */ 90 private View mChildToScrollTo = null; 91 92 /** 93 * True if the user is currently dragging this ScrollView around. This is 94 * not the same as 'is being flinged', which can be checked by 95 * mScroller.isFinished() (flinging begins when the user lifts his finger). 96 */ 97 private boolean mIsBeingDragged = false; 98 99 /** 100 * Determines speed during touch scrolling 101 */ 102 private VelocityTracker mVelocityTracker; 103 104 /** 105 * When set to true, the scroll view measure its child to make it fill the currently 106 * visible area. 107 */ 108 private boolean mFillViewport; 109 110 /** 111 * Whether arrow scrolling is animated. 112 */ 113 private boolean mSmoothScrollingEnabled = true; 114 115 private int mTouchSlop; 116 private int mMinimumVelocity; 117 private int mMaximumVelocity; 118 119 /** 120 * ID of the active pointer. This is used to retain consistency during 121 * drags/flings if multiple pointers are used. 122 */ 123 private int mActivePointerId = INVALID_POINTER; 124 125 /** 126 * Sentinel value for no current active pointer. 127 * Used by {@link #mActivePointerId}. 128 */ 129 private static final int INVALID_POINTER = -1; 130 131 public ScrollView(Context context) { 132 this(context, null); 133 } 134 135 public ScrollView(Context context, AttributeSet attrs) { 136 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 137 } 138 139 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 140 super(context, attrs, defStyle); 141 initScrollView(); 142 143 TypedArray a = 144 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 145 146 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 147 148 a.recycle(); 149 } 150 151 @Override 152 protected float getTopFadingEdgeStrength() { 153 if (getChildCount() == 0) { 154 return 0.0f; 155 } 156 157 final int length = getVerticalFadingEdgeLength(); 158 if (mScrollY < length) { 159 return mScrollY / (float) length; 160 } 161 162 return 1.0f; 163 } 164 165 @Override 166 protected float getBottomFadingEdgeStrength() { 167 if (getChildCount() == 0) { 168 return 0.0f; 169 } 170 171 final int length = getVerticalFadingEdgeLength(); 172 final int bottomEdge = getHeight() - mPaddingBottom; 173 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 174 if (span < length) { 175 return span / (float) length; 176 } 177 178 return 1.0f; 179 } 180 181 /** 182 * @return The maximum amount this scroll view will scroll in response to 183 * an arrow event. 184 */ 185 public int getMaxScrollAmount() { 186 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 187 } 188 189 190 private void initScrollView() { 191 mScroller = new OverScroller(getContext()); 192 setFocusable(true); 193 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 194 setWillNotDraw(false); 195 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 196 mTouchSlop = configuration.getScaledTouchSlop(); 197 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 198 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 199 } 200 201 @Override 202 public void addView(View child) { 203 if (getChildCount() > 0) { 204 throw new IllegalStateException("ScrollView can host only one direct child"); 205 } 206 207 super.addView(child); 208 } 209 210 @Override 211 public void addView(View child, int index) { 212 if (getChildCount() > 0) { 213 throw new IllegalStateException("ScrollView can host only one direct child"); 214 } 215 216 super.addView(child, index); 217 } 218 219 @Override 220 public void addView(View child, ViewGroup.LayoutParams params) { 221 if (getChildCount() > 0) { 222 throw new IllegalStateException("ScrollView can host only one direct child"); 223 } 224 225 super.addView(child, params); 226 } 227 228 @Override 229 public void addView(View child, int index, ViewGroup.LayoutParams params) { 230 if (getChildCount() > 0) { 231 throw new IllegalStateException("ScrollView can host only one direct child"); 232 } 233 234 super.addView(child, index, params); 235 } 236 237 /** 238 * @return Returns true this ScrollView can be scrolled 239 */ 240 private boolean canScroll() { 241 View child = getChildAt(0); 242 if (child != null) { 243 int childHeight = child.getHeight(); 244 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 245 } 246 return false; 247 } 248 249 /** 250 * Indicates whether this ScrollView's content is stretched to fill the viewport. 251 * 252 * @return True if the content fills the viewport, false otherwise. 253 */ 254 public boolean isFillViewport() { 255 return mFillViewport; 256 } 257 258 /** 259 * Indicates this ScrollView whether it should stretch its content height to fill 260 * the viewport or not. 261 * 262 * @param fillViewport True to stretch the content's height to the viewport's 263 * boundaries, false otherwise. 264 */ 265 public void setFillViewport(boolean fillViewport) { 266 if (fillViewport != mFillViewport) { 267 mFillViewport = fillViewport; 268 requestLayout(); 269 } 270 } 271 272 /** 273 * @return Whether arrow scrolling will animate its transition. 274 */ 275 public boolean isSmoothScrollingEnabled() { 276 return mSmoothScrollingEnabled; 277 } 278 279 /** 280 * Set whether arrow scrolling will animate its transition. 281 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 282 */ 283 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 284 mSmoothScrollingEnabled = smoothScrollingEnabled; 285 } 286 287 @Override 288 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 289 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 290 291 if (!mFillViewport) { 292 return; 293 } 294 295 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 296 if (heightMode == MeasureSpec.UNSPECIFIED) { 297 return; 298 } 299 300 if (getChildCount() > 0) { 301 final View child = getChildAt(0); 302 int height = getMeasuredHeight(); 303 if (child.getMeasuredHeight() < height) { 304 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 305 306 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 307 + mPaddingRight, lp.width); 308 height -= mPaddingTop; 309 height -= mPaddingBottom; 310 int childHeightMeasureSpec = 311 MeasureSpec.makeMeasureSpec(height, 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_DOWN); 345 return nextFocused != null 346 && nextFocused != this 347 && nextFocused.requestFocus(View.FOCUS_DOWN); 348 } 349 return false; 350 } 351 352 boolean handled = false; 353 if (event.getAction() == KeyEvent.ACTION_DOWN) { 354 switch (event.getKeyCode()) { 355 case KeyEvent.KEYCODE_DPAD_UP: 356 if (!event.isAltPressed()) { 357 handled = arrowScroll(View.FOCUS_UP); 358 } else { 359 handled = fullScroll(View.FOCUS_UP); 360 } 361 break; 362 case KeyEvent.KEYCODE_DPAD_DOWN: 363 if (!event.isAltPressed()) { 364 handled = arrowScroll(View.FOCUS_DOWN); 365 } else { 366 handled = fullScroll(View.FOCUS_DOWN); 367 } 368 break; 369 case KeyEvent.KEYCODE_SPACE: 370 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 371 break; 372 } 373 } 374 375 return handled; 376 } 377 378 private boolean inChild(int x, int y) { 379 if (getChildCount() > 0) { 380 final View child = getChildAt(0); 381 return !(y < child.getTop() 382 || y >= child.getBottom() 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 pointerIndex = ev.findPointerIndex(mActivePointerId); 419 final float y = ev.getY(pointerIndex); 420 final int yDiff = (int) Math.abs(y - mLastMotionY); 421 if (yDiff > mTouchSlop) { 422 mIsBeingDragged = true; 423 mLastMotionY = y; 424 } 425 break; 426 } 427 428 case MotionEvent.ACTION_DOWN: { 429 final float y = ev.getY(); 430 if (!inChild((int)ev.getX(), (int)y)) { 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 mLastMotionY = y; 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 y = ev.getY(); 496 if (!(mIsBeingDragged = inChild((int)ev.getX(), (int)y))) { 497 return false; 498 } 499 500 // Remember where the motion event started 501 mLastMotionY = y; 502 mActivePointerId = ev.getPointerId(0); 503 break; 504 } 505 case MotionEvent.ACTION_MOVE: 506 if (mIsBeingDragged) { 507 // Scroll to follow the motion event 508 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 509 final float y = ev.getY(activePointerIndex); 510 final int deltaY = (int) (mLastMotionY - y); 511 mLastMotionY = y; 512 513 overscrollBy(0, deltaY, 0, mScrollY, 0, getScrollRange(), 514 0, getOverscrollMax()); 515 } 516 break; 517 case MotionEvent.ACTION_UP: 518 if (mIsBeingDragged) { 519 final VelocityTracker velocityTracker = mVelocityTracker; 520 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 521 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 522 523 if (getChildCount() > 0) { 524 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 525 fling(-initialVelocity); 526 } else { 527 final int bottom = getScrollRange(); 528 if (mScroller.springback(mScrollX, mScrollY, 0, 0, 0, bottom)) { 529 invalidate(); 530 } 531 } 532 } 533 534 mActivePointerId = INVALID_POINTER; 535 mIsBeingDragged = false; 536 537 if (mVelocityTracker != null) { 538 mVelocityTracker.recycle(); 539 mVelocityTracker = null; 540 } 541 } 542 break; 543 case MotionEvent.ACTION_POINTER_UP: 544 onSecondaryPointerUp(ev); 545 break; 546 } 547 return true; 548 } 549 550 private void onSecondaryPointerUp(MotionEvent ev) { 551 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 552 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 553 final int pointerId = ev.getPointerId(pointerIndex); 554 if (pointerId == mActivePointerId) { 555 // This was our active pointer going up. Choose a new 556 // active pointer and adjust accordingly. 557 // TODO: Make this decision more intelligent. 558 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 559 mLastMotionY = ev.getY(newPointerIndex); 560 mActivePointerId = ev.getPointerId(newPointerIndex); 561 if (mVelocityTracker != null) { 562 mVelocityTracker.clear(); 563 } 564 } 565 } 566 567 @Override 568 protected void onOverscrolled(int scrollX, int scrollY, 569 boolean clampedX, boolean clampedY) { 570 // Treat animating scrolls differently; see #computeScroll() for why. 571 if (!mScroller.isFinished()) { 572 mScrollX = scrollX; 573 mScrollY = scrollY; 574 if (clampedY) { 575 mScroller.springback(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 576 } 577 } else { 578 super.scrollTo(scrollX, scrollY); 579 } 580 } 581 582 private int getOverscrollMax() { 583 int childCount = getChildCount(); 584 int containerOverscroll = (getHeight() - mPaddingBottom - mPaddingTop) / 3; 585 if (childCount > 0) { 586 return Math.min(containerOverscroll, getChildAt(0).getHeight() / 3); 587 } else { 588 return containerOverscroll; 589 } 590 } 591 592 private int getScrollRange() { 593 int scrollRange = 0; 594 if (getChildCount() > 0) { 595 View child = getChildAt(0); 596 scrollRange = Math.max(0, 597 child.getHeight() - getHeight() - mPaddingBottom - mPaddingTop); 598 } 599 return scrollRange; 600 } 601 602 /** 603 * <p> 604 * Finds the next focusable component that fits in this View's bounds 605 * (excluding fading edges) pretending that this View's top is located at 606 * the parameter top. 607 * </p> 608 * 609 * @param topFocus look for a candidate is the one at the top of the bounds 610 * if topFocus is true, or at the bottom of the bounds if topFocus is 611 * false 612 * @param top the top offset of the bounds in which a focusable must be 613 * found (the fading edge is assumed to start at this position) 614 * @param preferredFocusable the View that has highest priority and will be 615 * returned if it is within my bounds (null is valid) 616 * @return the next focusable component in the bounds or null if none can be 617 * found 618 */ 619 private View findFocusableViewInMyBounds(final boolean topFocus, 620 final int top, View preferredFocusable) { 621 /* 622 * The fading edge's transparent side should be considered for focus 623 * since it's mostly visible, so we divide the actual fading edge length 624 * by 2. 625 */ 626 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 627 final int topWithoutFadingEdge = top + fadingEdgeLength; 628 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 629 630 if ((preferredFocusable != null) 631 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 632 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 633 return preferredFocusable; 634 } 635 636 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 637 bottomWithoutFadingEdge); 638 } 639 640 /** 641 * <p> 642 * Finds the next focusable component that fits in the specified bounds. 643 * </p> 644 * 645 * @param topFocus look for a candidate is the one at the top of the bounds 646 * if topFocus is true, or at the bottom of the bounds if topFocus is 647 * false 648 * @param top the top offset of the bounds in which a focusable must be 649 * found 650 * @param bottom the bottom offset of the bounds in which a focusable must 651 * be found 652 * @return the next focusable component in the bounds or null if none can 653 * be found 654 */ 655 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 656 657 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 658 View focusCandidate = null; 659 660 /* 661 * A fully contained focusable is one where its top is below the bound's 662 * top, and its bottom is above the bound's bottom. A partially 663 * contained focusable is one where some part of it is within the 664 * bounds, but it also has some part that is not within bounds. A fully contained 665 * focusable is preferred to a partially contained focusable. 666 */ 667 boolean foundFullyContainedFocusable = false; 668 669 int count = focusables.size(); 670 for (int i = 0; i < count; i++) { 671 View view = focusables.get(i); 672 int viewTop = view.getTop(); 673 int viewBottom = view.getBottom(); 674 675 if (top < viewBottom && viewTop < bottom) { 676 /* 677 * the focusable is in the target area, it is a candidate for 678 * focusing 679 */ 680 681 final boolean viewIsFullyContained = (top < viewTop) && 682 (viewBottom < bottom); 683 684 if (focusCandidate == null) { 685 /* No candidate, take this one */ 686 focusCandidate = view; 687 foundFullyContainedFocusable = viewIsFullyContained; 688 } else { 689 final boolean viewIsCloserToBoundary = 690 (topFocus && viewTop < focusCandidate.getTop()) || 691 (!topFocus && viewBottom > focusCandidate 692 .getBottom()); 693 694 if (foundFullyContainedFocusable) { 695 if (viewIsFullyContained && viewIsCloserToBoundary) { 696 /* 697 * We're dealing with only fully contained views, so 698 * it has to be closer to the boundary to beat our 699 * candidate 700 */ 701 focusCandidate = view; 702 } 703 } else { 704 if (viewIsFullyContained) { 705 /* Any fully contained view beats a partially contained view */ 706 focusCandidate = view; 707 foundFullyContainedFocusable = true; 708 } else if (viewIsCloserToBoundary) { 709 /* 710 * Partially contained view beats another partially 711 * contained view if it's closer 712 */ 713 focusCandidate = view; 714 } 715 } 716 } 717 } 718 } 719 720 return focusCandidate; 721 } 722 723 /** 724 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 725 * method will scroll the view by one page up or down and give the focus 726 * to the topmost/bottommost component in the new visible area. If no 727 * component is a good candidate for focus, this scrollview reclaims the 728 * focus.</p> 729 * 730 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 731 * to go one page up or 732 * {@link android.view.View#FOCUS_DOWN} to go one page down 733 * @return true if the key event is consumed by this method, false otherwise 734 */ 735 public boolean pageScroll(int direction) { 736 boolean down = direction == View.FOCUS_DOWN; 737 int height = getHeight(); 738 739 if (down) { 740 mTempRect.top = getScrollY() + height; 741 int count = getChildCount(); 742 if (count > 0) { 743 View view = getChildAt(count - 1); 744 if (mTempRect.top + height > view.getBottom()) { 745 mTempRect.top = view.getBottom() - height; 746 } 747 } 748 } else { 749 mTempRect.top = getScrollY() - height; 750 if (mTempRect.top < 0) { 751 mTempRect.top = 0; 752 } 753 } 754 mTempRect.bottom = mTempRect.top + height; 755 756 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 757 } 758 759 /** 760 * <p>Handles scrolling in response to a "home/end" shortcut press. This 761 * method will scroll the view to the top or bottom and give the focus 762 * to the topmost/bottommost component in the new visible area. If no 763 * component is a good candidate for focus, this scrollview reclaims the 764 * focus.</p> 765 * 766 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 767 * to go the top of the view or 768 * {@link android.view.View#FOCUS_DOWN} to go the bottom 769 * @return true if the key event is consumed by this method, false otherwise 770 */ 771 public boolean fullScroll(int direction) { 772 boolean down = direction == View.FOCUS_DOWN; 773 int height = getHeight(); 774 775 mTempRect.top = 0; 776 mTempRect.bottom = height; 777 778 if (down) { 779 int count = getChildCount(); 780 if (count > 0) { 781 View view = getChildAt(count - 1); 782 mTempRect.bottom = view.getBottom(); 783 mTempRect.top = mTempRect.bottom - height; 784 } 785 } 786 787 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 788 } 789 790 /** 791 * <p>Scrolls the view to make the area defined by <code>top</code> and 792 * <code>bottom</code> visible. This method attempts to give the focus 793 * to a component visible in this area. If no component can be focused in 794 * the new visible area, the focus is reclaimed by this scrollview.</p> 795 * 796 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 797 * to go upward 798 * {@link android.view.View#FOCUS_DOWN} to downward 799 * @param top the top offset of the new area to be made visible 800 * @param bottom the bottom offset of the new area to be made visible 801 * @return true if the key event is consumed by this method, false otherwise 802 */ 803 private boolean scrollAndFocus(int direction, int top, int bottom) { 804 boolean handled = true; 805 806 int height = getHeight(); 807 int containerTop = getScrollY(); 808 int containerBottom = containerTop + height; 809 boolean up = direction == View.FOCUS_UP; 810 811 View newFocused = findFocusableViewInBounds(up, top, bottom); 812 if (newFocused == null) { 813 newFocused = this; 814 } 815 816 if (top >= containerTop && bottom <= containerBottom) { 817 handled = false; 818 } else { 819 int delta = up ? (top - containerTop) : (bottom - containerBottom); 820 doScrollY(delta); 821 } 822 823 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 824 mScrollViewMovedFocus = true; 825 mScrollViewMovedFocus = false; 826 } 827 828 return handled; 829 } 830 831 /** 832 * Handle scrolling in response to an up or down arrow click. 833 * 834 * @param direction The direction corresponding to the arrow key that was 835 * pressed 836 * @return True if we consumed the event, false otherwise 837 */ 838 public boolean arrowScroll(int direction) { 839 840 View currentFocused = findFocus(); 841 if (currentFocused == this) currentFocused = null; 842 843 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 844 845 final int maxJump = getMaxScrollAmount(); 846 847 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 848 nextFocused.getDrawingRect(mTempRect); 849 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 850 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 851 doScrollY(scrollDelta); 852 nextFocused.requestFocus(direction); 853 } else { 854 // no new focus 855 int scrollDelta = maxJump; 856 857 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 858 scrollDelta = getScrollY(); 859 } else if (direction == View.FOCUS_DOWN) { 860 if (getChildCount() > 0) { 861 int daBottom = getChildAt(0).getBottom(); 862 863 int screenBottom = getScrollY() + getHeight(); 864 865 if (daBottom - screenBottom < maxJump) { 866 scrollDelta = daBottom - screenBottom; 867 } 868 } 869 } 870 if (scrollDelta == 0) { 871 return false; 872 } 873 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 874 } 875 876 if (currentFocused != null && currentFocused.isFocused() 877 && isOffScreen(currentFocused)) { 878 // previously focused item still has focus and is off screen, give 879 // it up (take it back to ourselves) 880 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 881 // sure to 882 // get it) 883 final int descendantFocusability = getDescendantFocusability(); // save 884 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 885 requestFocus(); 886 setDescendantFocusability(descendantFocusability); // restore 887 } 888 return true; 889 } 890 891 /** 892 * @return whether the descendant of this scroll view is scrolled off 893 * screen. 894 */ 895 private boolean isOffScreen(View descendant) { 896 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 897 } 898 899 /** 900 * @return whether the descendant of this scroll view is within delta 901 * pixels of being on the screen. 902 */ 903 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 904 descendant.getDrawingRect(mTempRect); 905 offsetDescendantRectToMyCoords(descendant, mTempRect); 906 907 return (mTempRect.bottom + delta) >= getScrollY() 908 && (mTempRect.top - delta) <= (getScrollY() + height); 909 } 910 911 /** 912 * Smooth scroll by a Y delta 913 * 914 * @param delta the number of pixels to scroll by on the Y axis 915 */ 916 private void doScrollY(int delta) { 917 if (delta != 0) { 918 if (mSmoothScrollingEnabled) { 919 smoothScrollBy(0, delta); 920 } else { 921 scrollBy(0, delta); 922 } 923 } 924 } 925 926 /** 927 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 928 * 929 * @param dx the number of pixels to scroll by on the X axis 930 * @param dy the number of pixels to scroll by on the Y axis 931 */ 932 public final void smoothScrollBy(int dx, int dy) { 933 if (getChildCount() == 0) { 934 // Nothing to do. 935 return; 936 } 937 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 938 if (duration > ANIMATED_SCROLL_GAP) { 939 final int height = getHeight() - mPaddingBottom - mPaddingTop; 940 final int bottom = getChildAt(0).getHeight(); 941 final int maxY = Math.max(0, bottom - height); 942 final int scrollY = mScrollY; 943 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 944 945 mScroller.startScroll(mScrollX, scrollY, 0, dy); 946 awakenScrollBars(mScroller.getDuration()); 947 invalidate(); 948 } else { 949 if (!mScroller.isFinished()) { 950 mScroller.abortAnimation(); 951 } 952 scrollBy(dx, dy); 953 } 954 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 955 } 956 957 /** 958 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 959 * 960 * @param x the position where to scroll on the X axis 961 * @param y the position where to scroll on the Y axis 962 */ 963 public final void smoothScrollTo(int x, int y) { 964 smoothScrollBy(x - mScrollX, y - mScrollY); 965 } 966 967 /** 968 * <p>The scroll range of a scroll view is the overall height of all of its 969 * children.</p> 970 */ 971 @Override 972 protected int computeVerticalScrollRange() { 973 final int count = getChildCount(); 974 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 975 if (count == 0) { 976 return contentHeight; 977 } 978 979 int scrollRange = getChildAt(0).getBottom(); 980 final int scrollY = mScrollY; 981 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 982 if (scrollY < 0) { 983 scrollRange -= scrollY; 984 } else if (scrollY > overscrollBottom) { 985 scrollRange += scrollY - overscrollBottom; 986 } 987 988 return scrollRange; 989 } 990 991 @Override 992 protected int computeVerticalScrollOffset() { 993 return Math.max(0, super.computeVerticalScrollOffset()); 994 } 995 996 @Override 997 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 998 ViewGroup.LayoutParams lp = child.getLayoutParams(); 999 1000 int childWidthMeasureSpec; 1001 int childHeightMeasureSpec; 1002 1003 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1004 + mPaddingRight, lp.width); 1005 1006 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1007 1008 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1009 } 1010 1011 @Override 1012 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1013 int parentHeightMeasureSpec, int heightUsed) { 1014 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1015 1016 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1017 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1018 + widthUsed, lp.width); 1019 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1020 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1021 1022 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1023 } 1024 1025 @Override 1026 public void computeScroll() { 1027 if (mScroller.computeScrollOffset()) { 1028 // This is called at drawing time by ViewGroup. We don't want to 1029 // re-show the scrollbars at this point, which scrollTo will do, 1030 // so we replicate most of scrollTo here. 1031 // 1032 // It's a little odd to call onScrollChanged from inside the drawing. 1033 // 1034 // It is, except when you remember that computeScroll() is used to 1035 // animate scrolling. So unless we want to defer the onScrollChanged() 1036 // until the end of the animated scrolling, we don't really have a 1037 // choice here. 1038 // 1039 // I agree. The alternative, which I think would be worse, is to post 1040 // something and tell the subclasses later. This is bad because there 1041 // will be a window where mScrollX/Y is different from what the app 1042 // thinks it is. 1043 // 1044 int oldX = mScrollX; 1045 int oldY = mScrollY; 1046 int x = mScroller.getCurrX(); 1047 int y = mScroller.getCurrY(); 1048 1049 if (oldX != x || oldY != y) { 1050 overscrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 1051 0, getOverscrollMax()); 1052 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1053 } 1054 1055 // Keep on drawing until the animation has finished. 1056 postInvalidate(); 1057 } 1058 } 1059 1060 /** 1061 * Scrolls the view to the given child. 1062 * 1063 * @param child the View to scroll to 1064 */ 1065 private void scrollToChild(View child) { 1066 child.getDrawingRect(mTempRect); 1067 1068 /* Offset from child's local coordinates to ScrollView coordinates */ 1069 offsetDescendantRectToMyCoords(child, mTempRect); 1070 1071 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1072 1073 if (scrollDelta != 0) { 1074 scrollBy(0, scrollDelta); 1075 } 1076 } 1077 1078 /** 1079 * If rect is off screen, scroll just enough to get it (or at least the 1080 * first screen size chunk of it) on screen. 1081 * 1082 * @param rect The rectangle. 1083 * @param immediate True to scroll immediately without animation 1084 * @return true if scrolling was performed 1085 */ 1086 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1087 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1088 final boolean scroll = delta != 0; 1089 if (scroll) { 1090 if (immediate) { 1091 scrollBy(0, delta); 1092 } else { 1093 smoothScrollBy(0, delta); 1094 } 1095 } 1096 return scroll; 1097 } 1098 1099 /** 1100 * Compute the amount to scroll in the Y direction in order to get 1101 * a rectangle completely on the screen (or, if taller than the screen, 1102 * at least the first screen size chunk of it). 1103 * 1104 * @param rect The rect. 1105 * @return The scroll delta. 1106 */ 1107 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1108 if (getChildCount() == 0) return 0; 1109 1110 int height = getHeight(); 1111 int screenTop = getScrollY(); 1112 int screenBottom = screenTop + height; 1113 1114 int fadingEdge = getVerticalFadingEdgeLength(); 1115 1116 // leave room for top fading edge as long as rect isn't at very top 1117 if (rect.top > 0) { 1118 screenTop += fadingEdge; 1119 } 1120 1121 // leave room for bottom fading edge as long as rect isn't at very bottom 1122 if (rect.bottom < getChildAt(0).getHeight()) { 1123 screenBottom -= fadingEdge; 1124 } 1125 1126 int scrollYDelta = 0; 1127 1128 if (rect.bottom > screenBottom && rect.top > screenTop) { 1129 // need to move down to get it in view: move down just enough so 1130 // that the entire rectangle is in view (or at least the first 1131 // screen size chunk). 1132 1133 if (rect.height() > height) { 1134 // just enough to get screen size chunk on 1135 scrollYDelta += (rect.top - screenTop); 1136 } else { 1137 // get entire rect at bottom of screen 1138 scrollYDelta += (rect.bottom - screenBottom); 1139 } 1140 1141 // make sure we aren't scrolling beyond the end of our content 1142 int bottom = getChildAt(0).getBottom(); 1143 int distanceToBottom = bottom - screenBottom; 1144 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1145 1146 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1147 // need to move up to get it in view: move up just enough so that 1148 // entire rectangle is in view (or at least the first screen 1149 // size chunk of it). 1150 1151 if (rect.height() > height) { 1152 // screen size chunk 1153 scrollYDelta -= (screenBottom - rect.bottom); 1154 } else { 1155 // entire rect at top 1156 scrollYDelta -= (screenTop - rect.top); 1157 } 1158 1159 // make sure we aren't scrolling any further than the top our content 1160 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1161 } 1162 return scrollYDelta; 1163 } 1164 1165 @Override 1166 public void requestChildFocus(View child, View focused) { 1167 if (!mScrollViewMovedFocus) { 1168 if (!mIsLayoutDirty) { 1169 scrollToChild(focused); 1170 } else { 1171 // The child may not be laid out yet, we can't compute the scroll yet 1172 mChildToScrollTo = focused; 1173 } 1174 } 1175 super.requestChildFocus(child, focused); 1176 } 1177 1178 1179 /** 1180 * When looking for focus in children of a scroll view, need to be a little 1181 * more careful not to give focus to something that is scrolled off screen. 1182 * 1183 * This is more expensive than the default {@link android.view.ViewGroup} 1184 * implementation, otherwise this behavior might have been made the default. 1185 */ 1186 @Override 1187 protected boolean onRequestFocusInDescendants(int direction, 1188 Rect previouslyFocusedRect) { 1189 1190 // convert from forward / backward notation to up / down / left / right 1191 // (ugh). 1192 if (direction == View.FOCUS_FORWARD) { 1193 direction = View.FOCUS_DOWN; 1194 } else if (direction == View.FOCUS_BACKWARD) { 1195 direction = View.FOCUS_UP; 1196 } 1197 1198 final View nextFocus = previouslyFocusedRect == null ? 1199 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1200 FocusFinder.getInstance().findNextFocusFromRect(this, 1201 previouslyFocusedRect, direction); 1202 1203 if (nextFocus == null) { 1204 return false; 1205 } 1206 1207 if (isOffScreen(nextFocus)) { 1208 return false; 1209 } 1210 1211 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1212 } 1213 1214 @Override 1215 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1216 boolean immediate) { 1217 // offset into coordinate space of this scroll view 1218 rectangle.offset(child.getLeft() - child.getScrollX(), 1219 child.getTop() - child.getScrollY()); 1220 1221 return scrollToChildRect(rectangle, immediate); 1222 } 1223 1224 @Override 1225 public void requestLayout() { 1226 mIsLayoutDirty = true; 1227 super.requestLayout(); 1228 } 1229 1230 @Override 1231 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1232 super.onLayout(changed, l, t, r, b); 1233 mIsLayoutDirty = false; 1234 // Give a child focus if it needs it 1235 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1236 scrollToChild(mChildToScrollTo); 1237 } 1238 mChildToScrollTo = null; 1239 1240 // Calling this with the present values causes it to re-clam them 1241 scrollTo(mScrollX, mScrollY); 1242 } 1243 1244 @Override 1245 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1246 super.onSizeChanged(w, h, oldw, oldh); 1247 1248 View currentFocused = findFocus(); 1249 if (null == currentFocused || this == currentFocused) 1250 return; 1251 1252 // If the currently-focused view was visible on the screen when the 1253 // screen was at the old height, then scroll the screen to make that 1254 // view visible with the new screen height. 1255 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1256 currentFocused.getDrawingRect(mTempRect); 1257 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1258 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1259 doScrollY(scrollDelta); 1260 } 1261 } 1262 1263 /** 1264 * Return true if child is an descendant of parent, (or equal to the parent). 1265 */ 1266 private boolean isViewDescendantOf(View child, View parent) { 1267 if (child == parent) { 1268 return true; 1269 } 1270 1271 final ViewParent theParent = child.getParent(); 1272 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1273 } 1274 1275 /** 1276 * Fling the scroll view 1277 * 1278 * @param velocityY The initial velocity in the Y direction. Positive 1279 * numbers mean that the finger/curor is moving down the screen, 1280 * which means we want to scroll towards the top. 1281 */ 1282 public void fling(int velocityY) { 1283 if (getChildCount() > 0) { 1284 int height = getHeight() - mPaddingBottom - mPaddingTop; 1285 int bottom = getChildAt(0).getHeight(); 1286 1287 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1288 Math.max(0, bottom - height), 0, height/2); 1289 1290 final boolean movingDown = velocityY > 0; 1291 1292 View newFocused = 1293 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1294 if (newFocused == null) { 1295 newFocused = this; 1296 } 1297 1298 if (newFocused != findFocus() 1299 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1300 mScrollViewMovedFocus = true; 1301 mScrollViewMovedFocus = false; 1302 } 1303 1304 awakenScrollBars(mScroller.getDuration()); 1305 invalidate(); 1306 } 1307 } 1308 1309 /** 1310 * {@inheritDoc} 1311 * 1312 * <p>This version also clamps the scrolling to the bounds of our child. 1313 */ 1314 public void scrollTo(int x, int y) { 1315 // we rely on the fact the View.scrollBy calls scrollTo. 1316 if (getChildCount() > 0) { 1317 View child = getChildAt(0); 1318 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1319 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1320 if (x != mScrollX || y != mScrollY) { 1321 super.scrollTo(x, y); 1322 } 1323 } 1324 } 1325 1326 private int clamp(int n, int my, int child) { 1327 if (my >= child || n < 0) { 1328 /* my >= child is this case: 1329 * |--------------- me ---------------| 1330 * |------ child ------| 1331 * or 1332 * |--------------- me ---------------| 1333 * |------ child ------| 1334 * or 1335 * |--------------- me ---------------| 1336 * |------ child ------| 1337 * 1338 * n < 0 is this case: 1339 * |------ me ------| 1340 * |-------- child --------| 1341 * |-- mScrollX --| 1342 */ 1343 return 0; 1344 } 1345 if ((my+n) > child) { 1346 /* this case: 1347 * |------ me ------| 1348 * |------ child ------| 1349 * |-- mScrollX --| 1350 */ 1351 return child-my; 1352 } 1353 return n; 1354 } 1355} 1356