ScrollView.java revision 83d570cb3f1cc59d5a72e608b04d8f666db327a7
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 View child = getChildAt(0); 374 return !(y < child.getTop() 375 || y >= child.getBottom() 376 || x < child.getLeft() 377 || x >= child.getRight()); 378 } 379 return false; 380 } 381 382 @Override 383 public boolean onInterceptTouchEvent(MotionEvent ev) { 384 /* 385 * This method JUST determines whether we want to intercept the motion. 386 * If we return true, onMotionEvent will be called and we do the actual 387 * scrolling there. 388 */ 389 390 /* 391 * Shortcut the most recurring case: the user is in the dragging 392 * state and he is moving his finger. We want to intercept this 393 * motion. 394 */ 395 final int action = ev.getAction(); 396 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 397 return true; 398 } 399 400 switch (action & MotionEvent.ACTION_MASK) { 401 case MotionEvent.ACTION_MOVE: { 402 /* 403 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 404 * whether the user has moved far enough from his original down touch. 405 */ 406 407 /* 408 * Locally do absolute value. mLastMotionY is set to the y value 409 * of the down event. 410 */ 411 final int pointerIndex = ev.findPointerIndex(mActivePointerId); 412 final float y = ev.getY(pointerIndex); 413 final int yDiff = (int) Math.abs(y - mLastMotionY); 414 if (yDiff > mTouchSlop) { 415 mIsBeingDragged = true; 416 mLastMotionY = y; 417 } 418 break; 419 } 420 421 case MotionEvent.ACTION_DOWN: { 422 final float y = ev.getY(); 423 if (!inChild((int) ev.getX(), (int) y)) { 424 mIsBeingDragged = false; 425 break; 426 } 427 428 /* 429 * Remember location of down touch. 430 * ACTION_DOWN always refers to pointer index 0. 431 */ 432 mLastMotionY = y; 433 mActivePointerId = ev.getPointerId(0); 434 435 /* 436 * If being flinged and user touches the screen, initiate drag; 437 * otherwise don't. mScroller.isFinished should be false when 438 * being flinged. 439 */ 440 mIsBeingDragged = !mScroller.isFinished(); 441 break; 442 } 443 444 case MotionEvent.ACTION_CANCEL: 445 case MotionEvent.ACTION_UP: 446 /* Release the drag */ 447 mIsBeingDragged = false; 448 mActivePointerId = INVALID_POINTER; 449 break; 450 case MotionEvent.ACTION_POINTER_UP: 451 onSecondaryPointerUp(ev); 452 break; 453 } 454 455 /* 456 * The only time we want to intercept motion events is if we are in the 457 * drag mode. 458 */ 459 return mIsBeingDragged; 460 } 461 462 @Override 463 public boolean onTouchEvent(MotionEvent ev) { 464 465 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 466 // Don't handle edge touches immediately -- they may actually belong to one of our 467 // descendants. 468 return false; 469 } 470 471 if (mVelocityTracker == null) { 472 mVelocityTracker = VelocityTracker.obtain(); 473 } 474 mVelocityTracker.addMovement(ev); 475 476 final int action = ev.getAction(); 477 478 switch (action & MotionEvent.ACTION_MASK) { 479 case MotionEvent.ACTION_DOWN: { 480 /* 481 * If being flinged and user touches, stop the fling. isFinished 482 * will be false if being flinged. 483 */ 484 if (!mScroller.isFinished()) { 485 mScroller.abortAnimation(); 486 } 487 488 final float y = ev.getY(); 489 if (!(mIsBeingDragged = inChild((int) ev.getX(), (int) y))) { 490 return false; 491 } 492 493 // Remember where the motion event started 494 mLastMotionY = y; 495 mActivePointerId = ev.getPointerId(0); 496 break; 497 } 498 case MotionEvent.ACTION_MOVE: 499 if (mIsBeingDragged) { 500 // Scroll to follow the motion event 501 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 502 final float y = ev.getY(activePointerIndex); 503 final int deltaY = (int) (mLastMotionY - y); 504 mLastMotionY = y; 505 506 final int oldX = mScrollX; 507 final int oldY = mScrollY; 508 overscrollBy(0, deltaY, 0, mScrollY, 0, getScrollRange(), 509 0, getOverscrollMax(), true); 510 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 511 } 512 break; 513 case MotionEvent.ACTION_UP: 514 if (mIsBeingDragged) { 515 final VelocityTracker velocityTracker = mVelocityTracker; 516 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 517 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 518 519 if (getChildCount() > 0) { 520 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 521 fling(-initialVelocity); 522 } else { 523 final int bottom = getScrollRange(); 524 if (mScroller.springback(mScrollX, mScrollY, 0, 0, 0, bottom)) { 525 invalidate(); 526 } 527 } 528 } 529 530 mActivePointerId = INVALID_POINTER; 531 mIsBeingDragged = false; 532 533 if (mVelocityTracker != null) { 534 mVelocityTracker.recycle(); 535 mVelocityTracker = null; 536 } 537 } 538 break; 539 case MotionEvent.ACTION_POINTER_UP: 540 onSecondaryPointerUp(ev); 541 break; 542 } 543 return true; 544 } 545 546 private void onSecondaryPointerUp(MotionEvent ev) { 547 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 548 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 549 final int pointerId = ev.getPointerId(pointerIndex); 550 if (pointerId == mActivePointerId) { 551 // This was our active pointer going up. Choose a new 552 // active pointer and adjust accordingly. 553 // TODO: Make this decision more intelligent. 554 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 555 mLastMotionY = ev.getY(newPointerIndex); 556 mActivePointerId = ev.getPointerId(newPointerIndex); 557 if (mVelocityTracker != null) { 558 mVelocityTracker.clear(); 559 } 560 } 561 } 562 563 @Override 564 protected void onOverscrolled(int scrollX, int scrollY, 565 boolean clampedX, boolean clampedY) { 566 // Treat animating scrolls differently; see #computeScroll() for why. 567 if (!mScroller.isFinished()) { 568 mScrollX = scrollX; 569 mScrollY = scrollY; 570 if (clampedY) { 571 mScroller.springback(mScrollX, mScrollY, 0, 0, 0, getScrollRange()); 572 } 573 } else { 574 super.scrollTo(scrollX, scrollY); 575 } 576 awakenScrollBars(); 577 } 578 579 private int getOverscrollMax() { 580 int childCount = getChildCount(); 581 int containerOverscroll = (getHeight() - mPaddingBottom - mPaddingTop) / 3; 582 if (childCount > 0) { 583 return Math.min(containerOverscroll, getChildAt(0).getHeight() / 3); 584 } else { 585 return containerOverscroll; 586 } 587 } 588 589 private int getScrollRange() { 590 int scrollRange = 0; 591 if (getChildCount() > 0) { 592 View child = getChildAt(0); 593 scrollRange = Math.max(0, 594 child.getHeight() - getHeight() - mPaddingBottom - mPaddingTop); 595 } 596 return scrollRange; 597 } 598 599 /** 600 * <p> 601 * Finds the next focusable component that fits in this View's bounds 602 * (excluding fading edges) pretending that this View's top is located at 603 * the parameter top. 604 * </p> 605 * 606 * @param topFocus look for a candidate is the one at the top of the bounds 607 * if topFocus is true, or at the bottom of the bounds if topFocus is 608 * false 609 * @param top the top offset of the bounds in which a focusable must be 610 * found (the fading edge is assumed to start at this position) 611 * @param preferredFocusable the View that has highest priority and will be 612 * returned if it is within my bounds (null is valid) 613 * @return the next focusable component in the bounds or null if none can be 614 * found 615 */ 616 private View findFocusableViewInMyBounds(final boolean topFocus, 617 final int top, View preferredFocusable) { 618 /* 619 * The fading edge's transparent side should be considered for focus 620 * since it's mostly visible, so we divide the actual fading edge length 621 * by 2. 622 */ 623 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 624 final int topWithoutFadingEdge = top + fadingEdgeLength; 625 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 626 627 if ((preferredFocusable != null) 628 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 629 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 630 return preferredFocusable; 631 } 632 633 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 634 bottomWithoutFadingEdge); 635 } 636 637 /** 638 * <p> 639 * Finds the next focusable component that fits in the specified bounds. 640 * </p> 641 * 642 * @param topFocus look for a candidate is the one at the top of the bounds 643 * if topFocus is true, or at the bottom of the bounds if topFocus is 644 * false 645 * @param top the top offset of the bounds in which a focusable must be 646 * found 647 * @param bottom the bottom offset of the bounds in which a focusable must 648 * be found 649 * @return the next focusable component in the bounds or null if none can 650 * be found 651 */ 652 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 653 654 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 655 View focusCandidate = null; 656 657 /* 658 * A fully contained focusable is one where its top is below the bound's 659 * top, and its bottom is above the bound's bottom. A partially 660 * contained focusable is one where some part of it is within the 661 * bounds, but it also has some part that is not within bounds. A fully contained 662 * focusable is preferred to a partially contained focusable. 663 */ 664 boolean foundFullyContainedFocusable = false; 665 666 int count = focusables.size(); 667 for (int i = 0; i < count; i++) { 668 View view = focusables.get(i); 669 int viewTop = view.getTop(); 670 int viewBottom = view.getBottom(); 671 672 if (top < viewBottom && viewTop < bottom) { 673 /* 674 * the focusable is in the target area, it is a candidate for 675 * focusing 676 */ 677 678 final boolean viewIsFullyContained = (top < viewTop) && 679 (viewBottom < bottom); 680 681 if (focusCandidate == null) { 682 /* No candidate, take this one */ 683 focusCandidate = view; 684 foundFullyContainedFocusable = viewIsFullyContained; 685 } else { 686 final boolean viewIsCloserToBoundary = 687 (topFocus && viewTop < focusCandidate.getTop()) || 688 (!topFocus && viewBottom > focusCandidate 689 .getBottom()); 690 691 if (foundFullyContainedFocusable) { 692 if (viewIsFullyContained && viewIsCloserToBoundary) { 693 /* 694 * We're dealing with only fully contained views, so 695 * it has to be closer to the boundary to beat our 696 * candidate 697 */ 698 focusCandidate = view; 699 } 700 } else { 701 if (viewIsFullyContained) { 702 /* Any fully contained view beats a partially contained view */ 703 focusCandidate = view; 704 foundFullyContainedFocusable = true; 705 } else if (viewIsCloserToBoundary) { 706 /* 707 * Partially contained view beats another partially 708 * contained view if it's closer 709 */ 710 focusCandidate = view; 711 } 712 } 713 } 714 } 715 } 716 717 return focusCandidate; 718 } 719 720 /** 721 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 722 * method will scroll the view by one page up or down and give the focus 723 * to the topmost/bottommost component in the new visible area. If no 724 * component is a good candidate for focus, this scrollview reclaims the 725 * focus.</p> 726 * 727 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 728 * to go one page up or 729 * {@link android.view.View#FOCUS_DOWN} to go one page down 730 * @return true if the key event is consumed by this method, false otherwise 731 */ 732 public boolean pageScroll(int direction) { 733 boolean down = direction == View.FOCUS_DOWN; 734 int height = getHeight(); 735 736 if (down) { 737 mTempRect.top = getScrollY() + height; 738 int count = getChildCount(); 739 if (count > 0) { 740 View view = getChildAt(count - 1); 741 if (mTempRect.top + height > view.getBottom()) { 742 mTempRect.top = view.getBottom() - height; 743 } 744 } 745 } else { 746 mTempRect.top = getScrollY() - height; 747 if (mTempRect.top < 0) { 748 mTempRect.top = 0; 749 } 750 } 751 mTempRect.bottom = mTempRect.top + height; 752 753 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 754 } 755 756 /** 757 * <p>Handles scrolling in response to a "home/end" shortcut press. This 758 * method will scroll the view to the top or bottom and give the focus 759 * to the topmost/bottommost component in the new visible area. If no 760 * component is a good candidate for focus, this scrollview reclaims the 761 * focus.</p> 762 * 763 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 764 * to go the top of the view or 765 * {@link android.view.View#FOCUS_DOWN} to go the bottom 766 * @return true if the key event is consumed by this method, false otherwise 767 */ 768 public boolean fullScroll(int direction) { 769 boolean down = direction == View.FOCUS_DOWN; 770 int height = getHeight(); 771 772 mTempRect.top = 0; 773 mTempRect.bottom = height; 774 775 if (down) { 776 int count = getChildCount(); 777 if (count > 0) { 778 View view = getChildAt(count - 1); 779 mTempRect.bottom = view.getBottom(); 780 mTempRect.top = mTempRect.bottom - height; 781 } 782 } 783 784 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 785 } 786 787 /** 788 * <p>Scrolls the view to make the area defined by <code>top</code> and 789 * <code>bottom</code> visible. This method attempts to give the focus 790 * to a component visible in this area. If no component can be focused in 791 * the new visible area, the focus is reclaimed by this scrollview.</p> 792 * 793 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 794 * to go upward 795 * {@link android.view.View#FOCUS_DOWN} to downward 796 * @param top the top offset of the new area to be made visible 797 * @param bottom the bottom offset of the new area to be made visible 798 * @return true if the key event is consumed by this method, false otherwise 799 */ 800 private boolean scrollAndFocus(int direction, int top, int bottom) { 801 boolean handled = true; 802 803 int height = getHeight(); 804 int containerTop = getScrollY(); 805 int containerBottom = containerTop + height; 806 boolean up = direction == View.FOCUS_UP; 807 808 View newFocused = findFocusableViewInBounds(up, top, bottom); 809 if (newFocused == null) { 810 newFocused = this; 811 } 812 813 if (top >= containerTop && bottom <= containerBottom) { 814 handled = false; 815 } else { 816 int delta = up ? (top - containerTop) : (bottom - containerBottom); 817 doScrollY(delta); 818 } 819 820 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 821 mScrollViewMovedFocus = true; 822 mScrollViewMovedFocus = false; 823 } 824 825 return handled; 826 } 827 828 /** 829 * Handle scrolling in response to an up or down arrow click. 830 * 831 * @param direction The direction corresponding to the arrow key that was 832 * pressed 833 * @return True if we consumed the event, false otherwise 834 */ 835 public boolean arrowScroll(int direction) { 836 837 View currentFocused = findFocus(); 838 if (currentFocused == this) currentFocused = null; 839 840 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 841 842 final int maxJump = getMaxScrollAmount(); 843 844 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 845 nextFocused.getDrawingRect(mTempRect); 846 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 847 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 848 doScrollY(scrollDelta); 849 nextFocused.requestFocus(direction); 850 } else { 851 // no new focus 852 int scrollDelta = maxJump; 853 854 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 855 scrollDelta = getScrollY(); 856 } else if (direction == View.FOCUS_DOWN) { 857 if (getChildCount() > 0) { 858 int daBottom = getChildAt(0).getBottom(); 859 860 int screenBottom = getScrollY() + getHeight(); 861 862 if (daBottom - screenBottom < maxJump) { 863 scrollDelta = daBottom - screenBottom; 864 } 865 } 866 } 867 if (scrollDelta == 0) { 868 return false; 869 } 870 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 871 } 872 873 if (currentFocused != null && currentFocused.isFocused() 874 && isOffScreen(currentFocused)) { 875 // previously focused item still has focus and is off screen, give 876 // it up (take it back to ourselves) 877 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 878 // sure to 879 // get it) 880 final int descendantFocusability = getDescendantFocusability(); // save 881 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 882 requestFocus(); 883 setDescendantFocusability(descendantFocusability); // restore 884 } 885 return true; 886 } 887 888 /** 889 * @return whether the descendant of this scroll view is scrolled off 890 * screen. 891 */ 892 private boolean isOffScreen(View descendant) { 893 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 894 } 895 896 /** 897 * @return whether the descendant of this scroll view is within delta 898 * pixels of being on the screen. 899 */ 900 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 901 descendant.getDrawingRect(mTempRect); 902 offsetDescendantRectToMyCoords(descendant, mTempRect); 903 904 return (mTempRect.bottom + delta) >= getScrollY() 905 && (mTempRect.top - delta) <= (getScrollY() + height); 906 } 907 908 /** 909 * Smooth scroll by a Y delta 910 * 911 * @param delta the number of pixels to scroll by on the Y axis 912 */ 913 private void doScrollY(int delta) { 914 if (delta != 0) { 915 if (mSmoothScrollingEnabled) { 916 smoothScrollBy(0, delta); 917 } else { 918 scrollBy(0, delta); 919 } 920 } 921 } 922 923 /** 924 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 925 * 926 * @param dx the number of pixels to scroll by on the X axis 927 * @param dy the number of pixels to scroll by on the Y axis 928 */ 929 public final void smoothScrollBy(int dx, int dy) { 930 if (getChildCount() == 0) { 931 // Nothing to do. 932 return; 933 } 934 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 935 if (duration > ANIMATED_SCROLL_GAP) { 936 final int height = getHeight() - mPaddingBottom - mPaddingTop; 937 final int bottom = getChildAt(0).getHeight(); 938 final int maxY = Math.max(0, bottom - height); 939 final int scrollY = mScrollY; 940 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 941 942 mScroller.startScroll(mScrollX, scrollY, 0, dy); 943 awakenScrollBars(mScroller.getDuration()); 944 invalidate(); 945 } else { 946 if (!mScroller.isFinished()) { 947 mScroller.abortAnimation(); 948 } 949 scrollBy(dx, dy); 950 } 951 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 952 } 953 954 /** 955 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 956 * 957 * @param x the position where to scroll on the X axis 958 * @param y the position where to scroll on the Y axis 959 */ 960 public final void smoothScrollTo(int x, int y) { 961 smoothScrollBy(x - mScrollX, y - mScrollY); 962 } 963 964 /** 965 * <p>The scroll range of a scroll view is the overall height of all of its 966 * children.</p> 967 */ 968 @Override 969 protected int computeVerticalScrollRange() { 970 final int count = getChildCount(); 971 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 972 if (count == 0) { 973 return contentHeight; 974 } 975 976 int scrollRange = getChildAt(0).getBottom(); 977 final int scrollY = mScrollY; 978 final int overscrollBottom = Math.max(0, scrollRange - contentHeight); 979 if (scrollY < 0) { 980 scrollRange -= scrollY; 981 } else if (scrollY > overscrollBottom) { 982 scrollRange += scrollY - overscrollBottom; 983 } 984 985 return scrollRange; 986 } 987 988 @Override 989 protected int computeVerticalScrollOffset() { 990 return Math.max(0, super.computeVerticalScrollOffset()); 991 } 992 993 @Override 994 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 995 ViewGroup.LayoutParams lp = child.getLayoutParams(); 996 997 int childWidthMeasureSpec; 998 int childHeightMeasureSpec; 999 1000 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 1001 + mPaddingRight, lp.width); 1002 1003 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1004 1005 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1006 } 1007 1008 @Override 1009 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1010 int parentHeightMeasureSpec, int heightUsed) { 1011 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1012 1013 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 1014 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 1015 + widthUsed, lp.width); 1016 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 1017 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 1018 1019 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1020 } 1021 1022 @Override 1023 public void computeScroll() { 1024 if (mScroller.computeScrollOffset()) { 1025 // This is called at drawing time by ViewGroup. We don't want to 1026 // re-show the scrollbars at this point, which scrollTo will do, 1027 // so we replicate most of scrollTo here. 1028 // 1029 // It's a little odd to call onScrollChanged from inside the drawing. 1030 // 1031 // It is, except when you remember that computeScroll() is used to 1032 // animate scrolling. So unless we want to defer the onScrollChanged() 1033 // until the end of the animated scrolling, we don't really have a 1034 // choice here. 1035 // 1036 // I agree. The alternative, which I think would be worse, is to post 1037 // something and tell the subclasses later. This is bad because there 1038 // will be a window where mScrollX/Y is different from what the app 1039 // thinks it is. 1040 // 1041 int oldX = mScrollX; 1042 int oldY = mScrollY; 1043 int x = mScroller.getCurrX(); 1044 int y = mScroller.getCurrY(); 1045 1046 if (oldX != x || oldY != y) { 1047 overscrollBy(x - oldX, y - oldY, oldX, oldY, 0, getScrollRange(), 1048 0, getOverscrollMax(), false); 1049 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1050 } 1051 1052 // Keep on drawing until the animation has finished. 1053 postInvalidate(); 1054 } 1055 } 1056 1057 /** 1058 * Scrolls the view to the given child. 1059 * 1060 * @param child the View to scroll to 1061 */ 1062 private void scrollToChild(View child) { 1063 child.getDrawingRect(mTempRect); 1064 1065 /* Offset from child's local coordinates to ScrollView coordinates */ 1066 offsetDescendantRectToMyCoords(child, mTempRect); 1067 1068 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1069 1070 if (scrollDelta != 0) { 1071 scrollBy(0, scrollDelta); 1072 } 1073 } 1074 1075 /** 1076 * If rect is off screen, scroll just enough to get it (or at least the 1077 * first screen size chunk of it) on screen. 1078 * 1079 * @param rect The rectangle. 1080 * @param immediate True to scroll immediately without animation 1081 * @return true if scrolling was performed 1082 */ 1083 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1084 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1085 final boolean scroll = delta != 0; 1086 if (scroll) { 1087 if (immediate) { 1088 scrollBy(0, delta); 1089 } else { 1090 smoothScrollBy(0, delta); 1091 } 1092 } 1093 return scroll; 1094 } 1095 1096 /** 1097 * Compute the amount to scroll in the Y direction in order to get 1098 * a rectangle completely on the screen (or, if taller than the screen, 1099 * at least the first screen size chunk of it). 1100 * 1101 * @param rect The rect. 1102 * @return The scroll delta. 1103 */ 1104 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1105 if (getChildCount() == 0) return 0; 1106 1107 int height = getHeight(); 1108 int screenTop = getScrollY(); 1109 int screenBottom = screenTop + height; 1110 1111 int fadingEdge = getVerticalFadingEdgeLength(); 1112 1113 // leave room for top fading edge as long as rect isn't at very top 1114 if (rect.top > 0) { 1115 screenTop += fadingEdge; 1116 } 1117 1118 // leave room for bottom fading edge as long as rect isn't at very bottom 1119 if (rect.bottom < getChildAt(0).getHeight()) { 1120 screenBottom -= fadingEdge; 1121 } 1122 1123 int scrollYDelta = 0; 1124 1125 if (rect.bottom > screenBottom && rect.top > screenTop) { 1126 // need to move down to get it in view: move down just enough so 1127 // that the entire rectangle is in view (or at least the first 1128 // screen size chunk). 1129 1130 if (rect.height() > height) { 1131 // just enough to get screen size chunk on 1132 scrollYDelta += (rect.top - screenTop); 1133 } else { 1134 // get entire rect at bottom of screen 1135 scrollYDelta += (rect.bottom - screenBottom); 1136 } 1137 1138 // make sure we aren't scrolling beyond the end of our content 1139 int bottom = getChildAt(0).getBottom(); 1140 int distanceToBottom = bottom - screenBottom; 1141 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1142 1143 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1144 // need to move up to get it in view: move up just enough so that 1145 // entire rectangle is in view (or at least the first screen 1146 // size chunk of it). 1147 1148 if (rect.height() > height) { 1149 // screen size chunk 1150 scrollYDelta -= (screenBottom - rect.bottom); 1151 } else { 1152 // entire rect at top 1153 scrollYDelta -= (screenTop - rect.top); 1154 } 1155 1156 // make sure we aren't scrolling any further than the top our content 1157 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1158 } 1159 return scrollYDelta; 1160 } 1161 1162 @Override 1163 public void requestChildFocus(View child, View focused) { 1164 if (!mScrollViewMovedFocus) { 1165 if (!mIsLayoutDirty) { 1166 scrollToChild(focused); 1167 } else { 1168 // The child may not be laid out yet, we can't compute the scroll yet 1169 mChildToScrollTo = focused; 1170 } 1171 } 1172 super.requestChildFocus(child, focused); 1173 } 1174 1175 1176 /** 1177 * When looking for focus in children of a scroll view, need to be a little 1178 * more careful not to give focus to something that is scrolled off screen. 1179 * 1180 * This is more expensive than the default {@link android.view.ViewGroup} 1181 * implementation, otherwise this behavior might have been made the default. 1182 */ 1183 @Override 1184 protected boolean onRequestFocusInDescendants(int direction, 1185 Rect previouslyFocusedRect) { 1186 1187 // convert from forward / backward notation to up / down / left / right 1188 // (ugh). 1189 if (direction == View.FOCUS_FORWARD) { 1190 direction = View.FOCUS_DOWN; 1191 } else if (direction == View.FOCUS_BACKWARD) { 1192 direction = View.FOCUS_UP; 1193 } 1194 1195 final View nextFocus = previouslyFocusedRect == null ? 1196 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1197 FocusFinder.getInstance().findNextFocusFromRect(this, 1198 previouslyFocusedRect, direction); 1199 1200 if (nextFocus == null) { 1201 return false; 1202 } 1203 1204 if (isOffScreen(nextFocus)) { 1205 return false; 1206 } 1207 1208 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1209 } 1210 1211 @Override 1212 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1213 boolean immediate) { 1214 // offset into coordinate space of this scroll view 1215 rectangle.offset(child.getLeft() - child.getScrollX(), 1216 child.getTop() - child.getScrollY()); 1217 1218 return scrollToChildRect(rectangle, immediate); 1219 } 1220 1221 @Override 1222 public void requestLayout() { 1223 mIsLayoutDirty = true; 1224 super.requestLayout(); 1225 } 1226 1227 @Override 1228 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1229 super.onLayout(changed, l, t, r, b); 1230 mIsLayoutDirty = false; 1231 // Give a child focus if it needs it 1232 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1233 scrollToChild(mChildToScrollTo); 1234 } 1235 mChildToScrollTo = null; 1236 1237 // Calling this with the present values causes it to re-clam them 1238 scrollTo(mScrollX, mScrollY); 1239 } 1240 1241 @Override 1242 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1243 super.onSizeChanged(w, h, oldw, oldh); 1244 1245 View currentFocused = findFocus(); 1246 if (null == currentFocused || this == currentFocused) 1247 return; 1248 1249 // If the currently-focused view was visible on the screen when the 1250 // screen was at the old height, then scroll the screen to make that 1251 // view visible with the new screen height. 1252 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1253 currentFocused.getDrawingRect(mTempRect); 1254 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1255 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1256 doScrollY(scrollDelta); 1257 } 1258 } 1259 1260 /** 1261 * Return true if child is an descendant of parent, (or equal to the parent). 1262 */ 1263 private boolean isViewDescendantOf(View child, View parent) { 1264 if (child == parent) { 1265 return true; 1266 } 1267 1268 final ViewParent theParent = child.getParent(); 1269 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1270 } 1271 1272 /** 1273 * Fling the scroll view 1274 * 1275 * @param velocityY The initial velocity in the Y direction. Positive 1276 * numbers mean that the finger/cursor is moving down the screen, 1277 * which means we want to scroll towards the top. 1278 */ 1279 public void fling(int velocityY) { 1280 if (getChildCount() > 0) { 1281 int height = getHeight() - mPaddingBottom - mPaddingTop; 1282 int bottom = getChildAt(0).getHeight(); 1283 1284 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1285 Math.max(0, bottom - height), 0, height/2); 1286 1287 final boolean movingDown = velocityY > 0; 1288 1289 View newFocused = 1290 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1291 if (newFocused == null) { 1292 newFocused = this; 1293 } 1294 1295 if (newFocused != findFocus() 1296 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1297 mScrollViewMovedFocus = true; 1298 mScrollViewMovedFocus = false; 1299 } 1300 1301 invalidate(); 1302 } 1303 } 1304 1305 /** 1306 * {@inheritDoc} 1307 * 1308 * <p>This version also clamps the scrolling to the bounds of our child. 1309 */ 1310 @Override 1311 public void scrollTo(int x, int y) { 1312 // we rely on the fact the View.scrollBy calls scrollTo. 1313 if (getChildCount() > 0) { 1314 View child = getChildAt(0); 1315 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1316 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1317 if (x != mScrollX || y != mScrollY) { 1318 super.scrollTo(x, y); 1319 } 1320 } 1321 } 1322 1323 private int clamp(int n, int my, int child) { 1324 if (my >= child || n < 0) { 1325 /* my >= child is this case: 1326 * |--------------- me ---------------| 1327 * |------ child ------| 1328 * or 1329 * |--------------- me ---------------| 1330 * |------ child ------| 1331 * or 1332 * |--------------- me ---------------| 1333 * |------ child ------| 1334 * 1335 * n < 0 is this case: 1336 * |------ me ------| 1337 * |-------- child --------| 1338 * |-- mScrollX --| 1339 */ 1340 return 0; 1341 } 1342 if ((my+n) > child) { 1343 /* this case: 1344 * |------ me ------| 1345 * |------ child ------| 1346 * |-- mScrollX --| 1347 */ 1348 return child-my; 1349 } 1350 return n; 1351 } 1352} 1353