ScrollView.java revision 6579b0b4ac0e781efab044aaaf3f66447cf5e067
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 */ 53public class ScrollView extends FrameLayout { 54 static final int ANIMATED_SCROLL_GAP = 250; 55 56 static final float MAX_SCROLL_FACTOR = 0.5f; 57 58 59 private long mLastScroll; 60 61 private final Rect mTempRect = new Rect(); 62 private OverScroller mScroller; 63 64 /** 65 * Flag to indicate that we are moving focus ourselves. This is so the 66 * code that watches for focus changes initiated outside this ScrollView 67 * knows that it does not have to do anything. 68 */ 69 private boolean mScrollViewMovedFocus; 70 71 /** 72 * Position of the last motion event. 73 */ 74 private float mLastMotionY; 75 76 /** 77 * True when the layout has changed but the traversal has not come through yet. 78 * Ideally the view hierarchy would keep track of this for us. 79 */ 80 private boolean mIsLayoutDirty = true; 81 82 /** 83 * The child to give focus to in the event that a child has requested focus while the 84 * layout is dirty. This prevents the scroll from being wrong if the child has not been 85 * laid out before requesting focus. 86 */ 87 private View mChildToScrollTo = null; 88 89 /** 90 * True if the user is currently dragging this ScrollView around. This is 91 * not the same as 'is being flinged', which can be checked by 92 * mScroller.isFinished() (flinging begins when the user lifts his finger). 93 */ 94 private boolean mIsBeingDragged = false; 95 96 /** 97 * Determines speed during touch scrolling 98 */ 99 private VelocityTracker mVelocityTracker; 100 101 /** 102 * When set to true, the scroll view measure its child to make it fill the currently 103 * visible area. 104 */ 105 private boolean mFillViewport; 106 107 /** 108 * Whether arrow scrolling is animated. 109 */ 110 private boolean mSmoothScrollingEnabled = true; 111 112 private int mTouchSlop; 113 private int mMinimumVelocity; 114 private int mMaximumVelocity; 115 116 /** 117 * ID of the active pointer. This is used to retain consistency during 118 * drags/flings if multiple pointers are used. 119 */ 120 private int mActivePointerId = INVALID_POINTER; 121 122 /** 123 * Sentinel value for no current active pointer. 124 * Used by {@link #mActivePointerId}. 125 */ 126 private static final int INVALID_POINTER = -1; 127 128 public ScrollView(Context context) { 129 this(context, null); 130 } 131 132 public ScrollView(Context context, AttributeSet attrs) { 133 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 134 } 135 136 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 137 super(context, attrs, defStyle); 138 initScrollView(); 139 140 TypedArray a = 141 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 142 143 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 144 145 a.recycle(); 146 } 147 148 @Override 149 protected float getTopFadingEdgeStrength() { 150 if (getChildCount() == 0) { 151 return 0.0f; 152 } 153 154 final int length = getVerticalFadingEdgeLength(); 155 if (mScrollY < length) { 156 return mScrollY / (float) length; 157 } 158 159 return 1.0f; 160 } 161 162 @Override 163 protected float getBottomFadingEdgeStrength() { 164 if (getChildCount() == 0) { 165 return 0.0f; 166 } 167 168 final int length = getVerticalFadingEdgeLength(); 169 final int bottomEdge = getHeight() - mPaddingBottom; 170 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 171 if (span < length) { 172 return span / (float) length; 173 } 174 175 return 1.0f; 176 } 177 178 /** 179 * @return The maximum amount this scroll view will scroll in response to 180 * an arrow event. 181 */ 182 public int getMaxScrollAmount() { 183 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 184 } 185 186 187 private void initScrollView() { 188 mScroller = new OverScroller(getContext()); 189 setFocusable(true); 190 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 191 setWillNotDraw(false); 192 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 193 mTouchSlop = configuration.getScaledTouchSlop(); 194 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 195 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 196 } 197 198 @Override 199 public void addView(View child) { 200 if (getChildCount() > 0) { 201 throw new IllegalStateException("ScrollView can host only one direct child"); 202 } 203 204 super.addView(child); 205 } 206 207 @Override 208 public void addView(View child, int index) { 209 if (getChildCount() > 0) { 210 throw new IllegalStateException("ScrollView can host only one direct child"); 211 } 212 213 super.addView(child, index); 214 } 215 216 @Override 217 public void addView(View child, ViewGroup.LayoutParams params) { 218 if (getChildCount() > 0) { 219 throw new IllegalStateException("ScrollView can host only one direct child"); 220 } 221 222 super.addView(child, params); 223 } 224 225 @Override 226 public void addView(View child, int index, ViewGroup.LayoutParams params) { 227 if (getChildCount() > 0) { 228 throw new IllegalStateException("ScrollView can host only one direct child"); 229 } 230 231 super.addView(child, index, params); 232 } 233 234 /** 235 * @return Returns true this ScrollView can be scrolled 236 */ 237 private boolean canScroll() { 238 View child = getChildAt(0); 239 if (child != null) { 240 int childHeight = child.getHeight(); 241 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 242 } 243 return false; 244 } 245 246 /** 247 * Indicates whether this ScrollView's content is stretched to fill the viewport. 248 * 249 * @return True if the content fills the viewport, false otherwise. 250 */ 251 public boolean isFillViewport() { 252 return mFillViewport; 253 } 254 255 /** 256 * Indicates this ScrollView whether it should stretch its content height to fill 257 * the viewport or not. 258 * 259 * @param fillViewport True to stretch the content's height to the viewport's 260 * boundaries, false otherwise. 261 */ 262 public void setFillViewport(boolean fillViewport) { 263 if (fillViewport != mFillViewport) { 264 mFillViewport = fillViewport; 265 requestLayout(); 266 } 267 } 268 269 /** 270 * @return Whether arrow scrolling will animate its transition. 271 */ 272 public boolean isSmoothScrollingEnabled() { 273 return mSmoothScrollingEnabled; 274 } 275 276 /** 277 * Set whether arrow scrolling will animate its transition. 278 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 279 */ 280 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 281 mSmoothScrollingEnabled = smoothScrollingEnabled; 282 } 283 284 @Override 285 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 286 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 287 288 if (!mFillViewport) { 289 return; 290 } 291 292 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 293 if (heightMode == MeasureSpec.UNSPECIFIED) { 294 return; 295 } 296 297 if (getChildCount() > 0) { 298 final View child = getChildAt(0); 299 int height = getMeasuredHeight(); 300 if (child.getMeasuredHeight() < height) { 301 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 302 303 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 304 + mPaddingRight, lp.width); 305 height -= mPaddingTop; 306 height -= mPaddingBottom; 307 int childHeightMeasureSpec = 308 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 309 310 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 311 } 312 } 313 } 314 315 @Override 316 public boolean dispatchKeyEvent(KeyEvent event) { 317 // Let the focused view and/or our descendants get the key first 318 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 319 } 320 321 /** 322 * You can call this function yourself to have the scroll view perform 323 * scrolling from a key event, just as if the event had been dispatched to 324 * it by the view hierarchy. 325 * 326 * @param event The key event to execute. 327 * @return Return true if the event was handled, else false. 328 */ 329 public boolean executeKeyEvent(KeyEvent event) { 330 mTempRect.setEmpty(); 331 332 if (!canScroll()) { 333 if (isFocused()) { 334 View currentFocused = findFocus(); 335 if (currentFocused == this) currentFocused = null; 336 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 337 currentFocused, View.FOCUS_DOWN); 338 return nextFocused != null 339 && nextFocused != this 340 && nextFocused.requestFocus(View.FOCUS_DOWN); 341 } 342 return false; 343 } 344 345 boolean handled = false; 346 if (event.getAction() == KeyEvent.ACTION_DOWN) { 347 switch (event.getKeyCode()) { 348 case KeyEvent.KEYCODE_DPAD_UP: 349 if (!event.isAltPressed()) { 350 handled = arrowScroll(View.FOCUS_UP); 351 } else { 352 handled = fullScroll(View.FOCUS_UP); 353 } 354 break; 355 case KeyEvent.KEYCODE_DPAD_DOWN: 356 if (!event.isAltPressed()) { 357 handled = arrowScroll(View.FOCUS_DOWN); 358 } else { 359 handled = fullScroll(View.FOCUS_DOWN); 360 } 361 break; 362 case KeyEvent.KEYCODE_SPACE: 363 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 364 break; 365 } 366 } 367 368 return handled; 369 } 370 371 private boolean inChild(int x, int y) { 372 if (getChildCount() > 0) { 373 final int scrollY = mScrollY; 374 final View child = getChildAt(0); 375 return !(y < child.getTop() - scrollY 376 || y >= child.getBottom() - scrollY 377 || x < child.getLeft() 378 || x >= child.getRight()); 379 } 380 return false; 381 } 382 383 @Override 384 public boolean onInterceptTouchEvent(MotionEvent ev) { 385 /* 386 * This method JUST determines whether we want to intercept the motion. 387 * If we return true, onMotionEvent will be called and we do the actual 388 * scrolling there. 389 */ 390 391 /* 392 * Shortcut the most recurring case: the user is in the dragging 393 * state and he is moving his finger. We want to intercept this 394 * motion. 395 */ 396 final int action = ev.getAction(); 397 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 398 return true; 399 } 400 401 switch (action & MotionEvent.ACTION_MASK) { 402 case MotionEvent.ACTION_MOVE: { 403 /* 404 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 405 * whether the user has moved far enough from his original down touch. 406 */ 407 408 /* 409 * Locally do absolute value. mLastMotionY is set to the y value 410 * of the down event. 411 */ 412 final int activePointerId = mActivePointerId; 413 if (activePointerId == INVALID_POINTER) { 414 // If we don't have a valid id, the touch down wasn't on content. 415 break; 416 } 417 418 final int pointerIndex = ev.findPointerIndex(activePointerId); 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 if (mScroller.springback(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 457 invalidate(); 458 } 459 break; 460 case MotionEvent.ACTION_POINTER_UP: 461 onSecondaryPointerUp(ev); 462 break; 463 } 464 465 /* 466 * The only time we want to intercept motion events is if we are in the 467 * drag mode. 468 */ 469 return mIsBeingDragged; 470 } 471 472 @Override 473 public boolean onTouchEvent(MotionEvent ev) { 474 475 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 476 // Don't handle edge touches immediately -- they may actually belong to one of our 477 // descendants. 478 return false; 479 } 480 481 if (mVelocityTracker == null) { 482 mVelocityTracker = VelocityTracker.obtain(); 483 } 484 mVelocityTracker.addMovement(ev); 485 486 final int action = ev.getAction(); 487 488 switch (action & MotionEvent.ACTION_MASK) { 489 case MotionEvent.ACTION_DOWN: { 490 final float y = ev.getY(); 491 if (!(mIsBeingDragged = inChild((int) ev.getX(), (int) y))) { 492 return false; 493 } 494 495 /* 496 * If being flinged and user touches, stop the fling. isFinished 497 * will be false if being flinged. 498 */ 499 if (!mScroller.isFinished()) { 500 mScroller.abortAnimation(); 501 } 502 503 // Remember where the motion event started 504 mLastMotionY = y; 505 mActivePointerId = ev.getPointerId(0); 506 break; 507 } 508 case MotionEvent.ACTION_MOVE: 509 if (mIsBeingDragged) { 510 // Scroll to follow the motion event 511 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 512 final float y = ev.getY(activePointerIndex); 513 final int deltaY = (int) (mLastMotionY - y); 514 mLastMotionY = y; 515 516 final int oldX = mScrollX; 517 final int oldY = mScrollY; 518 overscrollBy(0, deltaY, 0, mScrollY, 0, getScrollRange(), 519 0, getOverscrollMax(), true); 520 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 521 } 522 break; 523 case MotionEvent.ACTION_UP: 524 if (mIsBeingDragged) { 525 final VelocityTracker velocityTracker = mVelocityTracker; 526 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 527 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 528 529 if (getChildCount() > 0) { 530 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 531 fling(-initialVelocity); 532 } else { 533 final int bottom = getScrollRange(); 534 if (mScroller.springback(mScrollX, mScrollY, 0, 0, 0, bottom)) { 535 invalidate(); 536 } 537 } 538 } 539 540 mActivePointerId = INVALID_POINTER; 541 mIsBeingDragged = false; 542 543 if (mVelocityTracker != null) { 544 mVelocityTracker.recycle(); 545 mVelocityTracker = null; 546 } 547 } 548 break; 549 case MotionEvent.ACTION_CANCEL: 550 if (mIsBeingDragged && getChildCount() > 0) { 551 if (mScroller.springback(mScrollX, mScrollY, 0, 0, 0, getScrollRange())) { 552 invalidate(); 553 } 554 mActivePointerId = INVALID_POINTER; 555 mIsBeingDragged = false; 556 if (mVelocityTracker != null) { 557 mVelocityTracker.recycle(); 558 mVelocityTracker = null; 559 } 560 } 561 break; 562 case MotionEvent.ACTION_POINTER_UP: 563 onSecondaryPointerUp(ev); 564 break; 565 } 566 return true; 567 } 568 569 private void onSecondaryPointerUp(MotionEvent ev) { 570 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 571 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 572 final int pointerId = ev.getPointerId(pointerIndex); 573 if (pointerId == mActivePointerId) { 574 // This was our active pointer going up. Choose a new 575 // active pointer and adjust accordingly. 576 // TODO: Make this decision more intelligent. 577 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 578 mLastMotionY = ev.getY(newPointerIndex); 579 mActivePointerId = ev.getPointerId(newPointerIndex); 580 if (mVelocityTracker != null) { 581 mVelocityTracker.clear(); 582 } 583 } 584 } 585 586 @Override 587 protected void onOverscrolled(int scrollX, int scrollY, 588 boolean clampedX, boolean clampedY) { 589 // Treat animating scrolls differently; see #computeScroll() for why. 590 if (!mScroller.isFinished()) { 591 mScrollX = scrollX; 592 mScrollY = scrollY; 593 if (clampedY) { 594 mScroller.springback(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 595 } 596 } else { 597 super.scrollTo(scrollX, scrollY); 598 } 599 awakenScrollBars(); 600 } 601 602 private int getOverscrollMax() { 603 int childCount = getChildCount(); 604 int containerOverscroll = (getHeight() - mPaddingBottom - mPaddingTop) / 3; 605 if (childCount > 0) { 606 return Math.min(containerOverscroll, getChildAt(0).getHeight() / 3); 607 } else { 608 return containerOverscroll; 609 } 610 } 611 612 private int getScrollRange() { 613 int scrollRange = 0; 614 if (getChildCount() > 0) { 615 View child = getChildAt(0); 616 scrollRange = Math.max(0, 617 child.getHeight() - getHeight() - mPaddingBottom - mPaddingTop); 618 } 619 return scrollRange; 620 } 621 622 /** 623 * <p> 624 * Finds the next focusable component that fits in this View's bounds 625 * (excluding fading edges) pretending that this View's top is located at 626 * the parameter top. 627 * </p> 628 * 629 * @param topFocus look for a candidate is the one at the top of the bounds 630 * if topFocus is true, or at the bottom of the bounds if topFocus is 631 * false 632 * @param top the top offset of the bounds in which a focusable must be 633 * found (the fading edge is assumed to start at this position) 634 * @param preferredFocusable the View that has highest priority and will be 635 * returned if it is within my bounds (null is valid) 636 * @return the next focusable component in the bounds or null if none can be 637 * found 638 */ 639 private View findFocusableViewInMyBounds(final boolean topFocus, 640 final int top, View preferredFocusable) { 641 /* 642 * The fading edge's transparent side should be considered for focus 643 * since it's mostly visible, so we divide the actual fading edge length 644 * by 2. 645 */ 646 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 647 final int topWithoutFadingEdge = top + fadingEdgeLength; 648 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 649 650 if ((preferredFocusable != null) 651 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 652 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 653 return preferredFocusable; 654 } 655 656 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 657 bottomWithoutFadingEdge); 658 } 659 660 /** 661 * <p> 662 * Finds the next focusable component that fits in the specified bounds. 663 * </p> 664 * 665 * @param topFocus look for a candidate is the one at the top of the bounds 666 * if topFocus is true, or at the bottom of the bounds if topFocus is 667 * false 668 * @param top the top offset of the bounds in which a focusable must be 669 * found 670 * @param bottom the bottom offset of the bounds in which a focusable must 671 * be found 672 * @return the next focusable component in the bounds or null if none can 673 * be found 674 */ 675 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 676 677 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 678 View focusCandidate = null; 679 680 /* 681 * A fully contained focusable is one where its top is below the bound's 682 * top, and its bottom is above the bound's bottom. A partially 683 * contained focusable is one where some part of it is within the 684 * bounds, but it also has some part that is not within bounds. A fully contained 685 * focusable is preferred to a partially contained focusable. 686 */ 687 boolean foundFullyContainedFocusable = false; 688 689 int count = focusables.size(); 690 for (int i = 0; i < count; i++) { 691 View view = focusables.get(i); 692 int viewTop = view.getTop(); 693 int viewBottom = view.getBottom(); 694 695 if (top < viewBottom && viewTop < bottom) { 696 /* 697 * the focusable is in the target area, it is a candidate for 698 * focusing 699 */ 700 701 final boolean viewIsFullyContained = (top < viewTop) && 702 (viewBottom < bottom); 703 704 if (focusCandidate == null) { 705 /* No candidate, take this one */ 706 focusCandidate = view; 707 foundFullyContainedFocusable = viewIsFullyContained; 708 } else { 709 final boolean viewIsCloserToBoundary = 710 (topFocus && viewTop < focusCandidate.getTop()) || 711 (!topFocus && viewBottom > focusCandidate 712 .getBottom()); 713 714 if (foundFullyContainedFocusable) { 715 if (viewIsFullyContained && viewIsCloserToBoundary) { 716 /* 717 * We're dealing with only fully contained views, so 718 * it has to be closer to the boundary to beat our 719 * candidate 720 */ 721 focusCandidate = view; 722 } 723 } else { 724 if (viewIsFullyContained) { 725 /* Any fully contained view beats a partially contained view */ 726 focusCandidate = view; 727 foundFullyContainedFocusable = true; 728 } else if (viewIsCloserToBoundary) { 729 /* 730 * Partially contained view beats another partially 731 * contained view if it's closer 732 */ 733 focusCandidate = view; 734 } 735 } 736 } 737 } 738 } 739 740 return focusCandidate; 741 } 742 743 /** 744 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 745 * method will scroll the view by one page up or down and give the focus 746 * to the topmost/bottommost component in the new visible area. If no 747 * component is a good candidate for focus, this scrollview reclaims the 748 * focus.</p> 749 * 750 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 751 * to go one page up or 752 * {@link android.view.View#FOCUS_DOWN} to go one page down 753 * @return true if the key event is consumed by this method, false otherwise 754 */ 755 public boolean pageScroll(int direction) { 756 boolean down = direction == View.FOCUS_DOWN; 757 int height = getHeight(); 758 759 if (down) { 760 mTempRect.top = getScrollY() + height; 761 int count = getChildCount(); 762 if (count > 0) { 763 View view = getChildAt(count - 1); 764 if (mTempRect.top + height > view.getBottom()) { 765 mTempRect.top = view.getBottom() - height; 766 } 767 } 768 } else { 769 mTempRect.top = getScrollY() - height; 770 if (mTempRect.top < 0) { 771 mTempRect.top = 0; 772 } 773 } 774 mTempRect.bottom = mTempRect.top + height; 775 776 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 777 } 778 779 /** 780 * <p>Handles scrolling in response to a "home/end" shortcut press. This 781 * method will scroll the view to the top or bottom and give the focus 782 * to the topmost/bottommost component in the new visible area. If no 783 * component is a good candidate for focus, this scrollview reclaims the 784 * focus.</p> 785 * 786 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 787 * to go the top of the view or 788 * {@link android.view.View#FOCUS_DOWN} to go the bottom 789 * @return true if the key event is consumed by this method, false otherwise 790 */ 791 public boolean fullScroll(int direction) { 792 boolean down = direction == View.FOCUS_DOWN; 793 int height = getHeight(); 794 795 mTempRect.top = 0; 796 mTempRect.bottom = height; 797 798 if (down) { 799 int count = getChildCount(); 800 if (count > 0) { 801 View view = getChildAt(count - 1); 802 mTempRect.bottom = view.getBottom(); 803 mTempRect.top = mTempRect.bottom - height; 804 } 805 } 806 807 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 808 } 809 810 /** 811 * <p>Scrolls the view to make the area defined by <code>top</code> and 812 * <code>bottom</code> visible. This method attempts to give the focus 813 * to a component visible in this area. If no component can be focused in 814 * the new visible area, the focus is reclaimed by this scrollview.</p> 815 * 816 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 817 * to go upward 818 * {@link android.view.View#FOCUS_DOWN} to downward 819 * @param top the top offset of the new area to be made visible 820 * @param bottom the bottom offset of the new area to be made visible 821 * @return true if the key event is consumed by this method, false otherwise 822 */ 823 private boolean scrollAndFocus(int direction, int top, int bottom) { 824 boolean handled = true; 825 826 int height = getHeight(); 827 int containerTop = getScrollY(); 828 int containerBottom = containerTop + height; 829 boolean up = direction == View.FOCUS_UP; 830 831 View newFocused = findFocusableViewInBounds(up, top, bottom); 832 if (newFocused == null) { 833 newFocused = this; 834 } 835 836 if (top >= containerTop && bottom <= containerBottom) { 837 handled = false; 838 } else { 839 int delta = up ? (top - containerTop) : (bottom - containerBottom); 840 doScrollY(delta); 841 } 842 843 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 844 mScrollViewMovedFocus = true; 845 mScrollViewMovedFocus = false; 846 } 847 848 return handled; 849 } 850 851 /** 852 * Handle scrolling in response to an up or down arrow click. 853 * 854 * @param direction The direction corresponding to the arrow key that was 855 * pressed 856 * @return True if we consumed the event, false otherwise 857 */ 858 public boolean arrowScroll(int direction) { 859 860 View currentFocused = findFocus(); 861 if (currentFocused == this) currentFocused = null; 862 863 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 864 865 final int maxJump = getMaxScrollAmount(); 866 867 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 868 nextFocused.getDrawingRect(mTempRect); 869 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 870 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 871 doScrollY(scrollDelta); 872 nextFocused.requestFocus(direction); 873 } else { 874 // no new focus 875 int scrollDelta = maxJump; 876 877 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 878 scrollDelta = getScrollY(); 879 } else if (direction == View.FOCUS_DOWN) { 880 if (getChildCount() > 0) { 881 int daBottom = getChildAt(0).getBottom(); 882 883 int screenBottom = getScrollY() + getHeight(); 884 885 if (daBottom - screenBottom < maxJump) { 886 scrollDelta = daBottom - screenBottom; 887 } 888 } 889 } 890 if (scrollDelta == 0) { 891 return false; 892 } 893 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 894 } 895 896 if (currentFocused != null && currentFocused.isFocused() 897 && isOffScreen(currentFocused)) { 898 // previously focused item still has focus and is off screen, give 899 // it up (take it back to ourselves) 900 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 901 // sure to 902 // get it) 903 final int descendantFocusability = getDescendantFocusability(); // save 904 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 905 requestFocus(); 906 setDescendantFocusability(descendantFocusability); // restore 907 } 908 return true; 909 } 910 911 /** 912 * @return whether the descendant of this scroll view is scrolled off 913 * screen. 914 */ 915 private boolean isOffScreen(View descendant) { 916 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 917 } 918 919 /** 920 * @return whether the descendant of this scroll view is within delta 921 * pixels of being on the screen. 922 */ 923 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 924 descendant.getDrawingRect(mTempRect); 925 offsetDescendantRectToMyCoords(descendant, mTempRect); 926 927 return (mTempRect.bottom + delta) >= getScrollY() 928 && (mTempRect.top - delta) <= (getScrollY() + height); 929 } 930 931 /** 932 * Smooth scroll by a Y delta 933 * 934 * @param delta the number of pixels to scroll by on the Y axis 935 */ 936 private void doScrollY(int delta) { 937 if (delta != 0) { 938 if (mSmoothScrollingEnabled) { 939 smoothScrollBy(0, delta); 940 } else { 941 scrollBy(0, delta); 942 } 943 } 944 } 945 946 /** 947 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 948 * 949 * @param dx the number of pixels to scroll by on the X axis 950 * @param dy the number of pixels to scroll by on the Y axis 951 */ 952 public final void smoothScrollBy(int dx, int dy) { 953 if (getChildCount() == 0) { 954 // Nothing to do. 955 return; 956 } 957 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 958 if (duration > ANIMATED_SCROLL_GAP) { 959 final int height = getHeight() - mPaddingBottom - mPaddingTop; 960 final int bottom = getChildAt(0).getHeight(); 961 final int maxY = Math.max(0, bottom - height); 962 final int scrollY = mScrollY; 963 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 964 965 mScroller.startScroll(mScrollX, scrollY, 0, dy); 966 invalidate(); 967 } else { 968 if (!mScroller.isFinished()) { 969 mScroller.abortAnimation(); 970 } 971 scrollBy(dx, dy); 972 } 973 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 974 } 975 976 /** 977 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 978 * 979 * @param x the position where to scroll on the X axis 980 * @param y the position where to scroll on the Y axis 981 */ 982 public final void smoothScrollTo(int x, int y) { 983 smoothScrollBy(x - mScrollX, y - mScrollY); 984 } 985 986 /** 987 * <p>The scroll range of a scroll view is the overall height of all of its 988 * children.</p> 989 */ 990 @Override 991 protected int computeVerticalScrollRange() { 992 final int count = getChildCount(); 993 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 994 if (count == 0) { 995 return contentHeight; 996 } 997 998 int scrollRange = getChildAt(0).getBottom(); 999 final int scrollY = mScrollY; 1000 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 1001 if (scrollY < 0) { 1002 scrollRange -= scrollY; 1003 } else if (scrollY > overscrollBottom) { 1004 scrollRange += scrollY - overscrollBottom; 1005 } 1006 1007 return scrollRange; 1008 } 1009 1010 @Override 1011 protected int computeVerticalScrollOffset() { 1012 return Math.max(0, super.computeVerticalScrollOffset()); 1013 } 1014 1015 @Override 1016 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 1017 ViewGroup.LayoutParams lp = child.getLayoutParams(); 1018 1019 int childWidthMeasureSpec; 1020 int childHeightMeasureSpec; 1021 1022 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1023 + mPaddingRight, lp.width); 1024 1025 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1026 1027 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1028 } 1029 1030 @Override 1031 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1032 int parentHeightMeasureSpec, int heightUsed) { 1033 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1034 1035 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1036 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1037 + widthUsed, lp.width); 1038 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1039 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1040 1041 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1042 } 1043 1044 @Override 1045 public void computeScroll() { 1046 if (mScroller.computeScrollOffset()) { 1047 // This is called at drawing time by ViewGroup. We don't want to 1048 // re-show the scrollbars at this point, which scrollTo will do, 1049 // so we replicate most of scrollTo here. 1050 // 1051 // It's a little odd to call onScrollChanged from inside the drawing. 1052 // 1053 // It is, except when you remember that computeScroll() is used to 1054 // animate scrolling. So unless we want to defer the onScrollChanged() 1055 // until the end of the animated scrolling, we don't really have a 1056 // choice here. 1057 // 1058 // I agree. The alternative, which I think would be worse, is to post 1059 // something and tell the subclasses later. This is bad because there 1060 // will be a window where mScrollX/Y is different from what the app 1061 // thinks it is. 1062 // 1063 int oldX = mScrollX; 1064 int oldY = mScrollY; 1065 int x = mScroller.getCurrX(); 1066 int y = mScroller.getCurrY(); 1067 1068 if (oldX != x || oldY != y) { 1069 overscrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 1070 0, getOverscrollMax(), false); 1071 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1072 } 1073 1074 // Keep on drawing until the animation has finished. 1075 postInvalidate(); 1076 } 1077 } 1078 1079 /** 1080 * Scrolls the view to the given child. 1081 * 1082 * @param child the View to scroll to 1083 */ 1084 private void scrollToChild(View child) { 1085 child.getDrawingRect(mTempRect); 1086 1087 /* Offset from child's local coordinates to ScrollView coordinates */ 1088 offsetDescendantRectToMyCoords(child, mTempRect); 1089 1090 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1091 1092 if (scrollDelta != 0) { 1093 scrollBy(0, scrollDelta); 1094 } 1095 } 1096 1097 /** 1098 * If rect is off screen, scroll just enough to get it (or at least the 1099 * first screen size chunk of it) on screen. 1100 * 1101 * @param rect The rectangle. 1102 * @param immediate True to scroll immediately without animation 1103 * @return true if scrolling was performed 1104 */ 1105 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1106 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1107 final boolean scroll = delta != 0; 1108 if (scroll) { 1109 if (immediate) { 1110 scrollBy(0, delta); 1111 } else { 1112 smoothScrollBy(0, delta); 1113 } 1114 } 1115 return scroll; 1116 } 1117 1118 /** 1119 * Compute the amount to scroll in the Y direction in order to get 1120 * a rectangle completely on the screen (or, if taller than the screen, 1121 * at least the first screen size chunk of it). 1122 * 1123 * @param rect The rect. 1124 * @return The scroll delta. 1125 */ 1126 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1127 if (getChildCount() == 0) return 0; 1128 1129 int height = getHeight(); 1130 int screenTop = getScrollY(); 1131 int screenBottom = screenTop + height; 1132 1133 int fadingEdge = getVerticalFadingEdgeLength(); 1134 1135 // leave room for top fading edge as long as rect isn't at very top 1136 if (rect.top > 0) { 1137 screenTop += fadingEdge; 1138 } 1139 1140 // leave room for bottom fading edge as long as rect isn't at very bottom 1141 if (rect.bottom < getChildAt(0).getHeight()) { 1142 screenBottom -= fadingEdge; 1143 } 1144 1145 int scrollYDelta = 0; 1146 1147 if (rect.bottom > screenBottom && rect.top > screenTop) { 1148 // need to move down to get it in view: move down just enough so 1149 // that the entire rectangle is in view (or at least the first 1150 // screen size chunk). 1151 1152 if (rect.height() > height) { 1153 // just enough to get screen size chunk on 1154 scrollYDelta += (rect.top - screenTop); 1155 } else { 1156 // get entire rect at bottom of screen 1157 scrollYDelta += (rect.bottom - screenBottom); 1158 } 1159 1160 // make sure we aren't scrolling beyond the end of our content 1161 int bottom = getChildAt(0).getBottom(); 1162 int distanceToBottom = bottom - screenBottom; 1163 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1164 1165 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1166 // need to move up to get it in view: move up just enough so that 1167 // entire rectangle is in view (or at least the first screen 1168 // size chunk of it). 1169 1170 if (rect.height() > height) { 1171 // screen size chunk 1172 scrollYDelta -= (screenBottom - rect.bottom); 1173 } else { 1174 // entire rect at top 1175 scrollYDelta -= (screenTop - rect.top); 1176 } 1177 1178 // make sure we aren't scrolling any further than the top our content 1179 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1180 } 1181 return scrollYDelta; 1182 } 1183 1184 @Override 1185 public void requestChildFocus(View child, View focused) { 1186 if (!mScrollViewMovedFocus) { 1187 if (!mIsLayoutDirty) { 1188 scrollToChild(focused); 1189 } else { 1190 // The child may not be laid out yet, we can't compute the scroll yet 1191 mChildToScrollTo = focused; 1192 } 1193 } 1194 super.requestChildFocus(child, focused); 1195 } 1196 1197 1198 /** 1199 * When looking for focus in children of a scroll view, need to be a little 1200 * more careful not to give focus to something that is scrolled off screen. 1201 * 1202 * This is more expensive than the default {@link android.view.ViewGroup} 1203 * implementation, otherwise this behavior might have been made the default. 1204 */ 1205 @Override 1206 protected boolean onRequestFocusInDescendants(int direction, 1207 Rect previouslyFocusedRect) { 1208 1209 // convert from forward / backward notation to up / down / left / right 1210 // (ugh). 1211 if (direction == View.FOCUS_FORWARD) { 1212 direction = View.FOCUS_DOWN; 1213 } else if (direction == View.FOCUS_BACKWARD) { 1214 direction = View.FOCUS_UP; 1215 } 1216 1217 final View nextFocus = previouslyFocusedRect == null ? 1218 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1219 FocusFinder.getInstance().findNextFocusFromRect(this, 1220 previouslyFocusedRect, direction); 1221 1222 if (nextFocus == null) { 1223 return false; 1224 } 1225 1226 if (isOffScreen(nextFocus)) { 1227 return false; 1228 } 1229 1230 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1231 } 1232 1233 @Override 1234 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1235 boolean immediate) { 1236 // offset into coordinate space of this scroll view 1237 rectangle.offset(child.getLeft() - child.getScrollX(), 1238 child.getTop() - child.getScrollY()); 1239 1240 return scrollToChildRect(rectangle, immediate); 1241 } 1242 1243 @Override 1244 public void requestLayout() { 1245 mIsLayoutDirty = true; 1246 super.requestLayout(); 1247 } 1248 1249 @Override 1250 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1251 super.onLayout(changed, l, t, r, b); 1252 mIsLayoutDirty = false; 1253 // Give a child focus if it needs it 1254 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1255 scrollToChild(mChildToScrollTo); 1256 } 1257 mChildToScrollTo = null; 1258 1259 // Calling this with the present values causes it to re-clam them 1260 scrollTo(mScrollX, mScrollY); 1261 } 1262 1263 @Override 1264 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1265 super.onSizeChanged(w, h, oldw, oldh); 1266 1267 View currentFocused = findFocus(); 1268 if (null == currentFocused || this == currentFocused) 1269 return; 1270 1271 // If the currently-focused view was visible on the screen when the 1272 // screen was at the old height, then scroll the screen to make that 1273 // view visible with the new screen height. 1274 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1275 currentFocused.getDrawingRect(mTempRect); 1276 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1277 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1278 doScrollY(scrollDelta); 1279 } 1280 } 1281 1282 /** 1283 * Return true if child is an descendant of parent, (or equal to the parent). 1284 */ 1285 private boolean isViewDescendantOf(View child, View parent) { 1286 if (child == parent) { 1287 return true; 1288 } 1289 1290 final ViewParent theParent = child.getParent(); 1291 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1292 } 1293 1294 /** 1295 * Fling the scroll view 1296 * 1297 * @param velocityY The initial velocity in the Y direction. Positive 1298 * numbers mean that the finger/cursor is moving down the screen, 1299 * which means we want to scroll towards the top. 1300 */ 1301 public void fling(int velocityY) { 1302 if (getChildCount() > 0) { 1303 int height = getHeight() - mPaddingBottom - mPaddingTop; 1304 int bottom = getChildAt(0).getHeight(); 1305 1306 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1307 Math.max(0, bottom - height), 0, height/2); 1308 1309 final boolean movingDown = velocityY > 0; 1310 1311 View newFocused = 1312 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1313 if (newFocused == null) { 1314 newFocused = this; 1315 } 1316 1317 if (newFocused != findFocus() 1318 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1319 mScrollViewMovedFocus = true; 1320 mScrollViewMovedFocus = false; 1321 } 1322 1323 invalidate(); 1324 } 1325 } 1326 1327 /** 1328 * {@inheritDoc} 1329 * 1330 * <p>This version also clamps the scrolling to the bounds of our child. 1331 */ 1332 @Override 1333 public void scrollTo(int x, int y) { 1334 // we rely on the fact the View.scrollBy calls scrollTo. 1335 if (getChildCount() > 0) { 1336 View child = getChildAt(0); 1337 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1338 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1339 if (x != mScrollX || y != mScrollY) { 1340 super.scrollTo(x, y); 1341 } 1342 } 1343 } 1344 1345 private int clamp(int n, int my, int child) { 1346 if (my >= child || n < 0) { 1347 /* my >= child is this case: 1348 * |--------------- me ---------------| 1349 * |------ child ------| 1350 * or 1351 * |--------------- me ---------------| 1352 * |------ child ------| 1353 * or 1354 * |--------------- me ---------------| 1355 * |------ child ------| 1356 * 1357 * n < 0 is this case: 1358 * |------ me ------| 1359 * |-------- child --------| 1360 * |-- mScrollX --| 1361 */ 1362 return 0; 1363 } 1364 if ((my+n) > child) { 1365 /* this case: 1366 * |------ me ------| 1367 * |------ child ------| 1368 * |-- mScrollX --| 1369 */ 1370 return child-my; 1371 } 1372 return n; 1373 } 1374} 1375