ScrollView.java revision 9d32d24dbd8a015c9d5c44ed4901d5a666eb8e7f
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 Scroller 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 Scroller(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 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 final float y = ev.getY(); 488 if (!(mIsBeingDragged = inChild((int) ev.getX(), (int) y))) { 489 return false; 490 } 491 492 /* 493 * If being flinged and user touches, stop the fling. isFinished 494 * will be false if being flinged. 495 */ 496 if (!mScroller.isFinished()) { 497 mScroller.abortAnimation(); 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 scrollBy(0, deltaY); 514 } 515 break; 516 case MotionEvent.ACTION_UP: 517 if (mIsBeingDragged) { 518 final VelocityTracker velocityTracker = mVelocityTracker; 519 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 520 int initialVelocity = (int) velocityTracker.getYVelocity(mActivePointerId); 521 522 if (getChildCount() > 0 && Math.abs(initialVelocity) > mMinimumVelocity) { 523 fling(-initialVelocity); 524 } 525 526 mActivePointerId = INVALID_POINTER; 527 mIsBeingDragged = false; 528 529 if (mVelocityTracker != null) { 530 mVelocityTracker.recycle(); 531 mVelocityTracker = null; 532 } 533 } 534 break; 535 case MotionEvent.ACTION_CANCEL: 536 if (mIsBeingDragged && getChildCount() > 0) { 537 mActivePointerId = INVALID_POINTER; 538 mIsBeingDragged = false; 539 if (mVelocityTracker != null) { 540 mVelocityTracker.recycle(); 541 mVelocityTracker = null; 542 } 543 } 544 break; 545 case MotionEvent.ACTION_POINTER_UP: 546 onSecondaryPointerUp(ev); 547 break; 548 } 549 return true; 550 } 551 552 private void onSecondaryPointerUp(MotionEvent ev) { 553 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 554 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 555 final int pointerId = ev.getPointerId(pointerIndex); 556 if (pointerId == mActivePointerId) { 557 // This was our active pointer going up. Choose a new 558 // active pointer and adjust accordingly. 559 // TODO: Make this decision more intelligent. 560 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 561 mLastMotionY = ev.getY(newPointerIndex); 562 mActivePointerId = ev.getPointerId(newPointerIndex); 563 if (mVelocityTracker != null) { 564 mVelocityTracker.clear(); 565 } 566 } 567 } 568 569 private int getScrollRange() { 570 int scrollRange = 0; 571 if (getChildCount() > 0) { 572 View child = getChildAt(0); 573 scrollRange = Math.max(0, 574 child.getHeight() - getHeight() - mPaddingBottom - mPaddingTop); 575 } 576 return scrollRange; 577 } 578 579 /** 580 * <p> 581 * Finds the next focusable component that fits in this View's bounds 582 * (excluding fading edges) pretending that this View's top is located at 583 * the parameter top. 584 * </p> 585 * 586 * @param topFocus look for a candidate is the one at the top of the bounds 587 * if topFocus is true, or at the bottom of the bounds if topFocus is 588 * false 589 * @param top the top offset of the bounds in which a focusable must be 590 * found (the fading edge is assumed to start at this position) 591 * @param preferredFocusable the View that has highest priority and will be 592 * returned if it is within my bounds (null is valid) 593 * @return the next focusable component in the bounds or null if none can be 594 * found 595 */ 596 private View findFocusableViewInMyBounds(final boolean topFocus, 597 final int top, View preferredFocusable) { 598 /* 599 * The fading edge's transparent side should be considered for focus 600 * since it's mostly visible, so we divide the actual fading edge length 601 * by 2. 602 */ 603 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 604 final int topWithoutFadingEdge = top + fadingEdgeLength; 605 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 606 607 if ((preferredFocusable != null) 608 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 609 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 610 return preferredFocusable; 611 } 612 613 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 614 bottomWithoutFadingEdge); 615 } 616 617 /** 618 * <p> 619 * Finds the next focusable component that fits in the specified bounds. 620 * </p> 621 * 622 * @param topFocus look for a candidate is the one at the top of the bounds 623 * if topFocus is true, or at the bottom of the bounds if topFocus is 624 * false 625 * @param top the top offset of the bounds in which a focusable must be 626 * found 627 * @param bottom the bottom offset of the bounds in which a focusable must 628 * be found 629 * @return the next focusable component in the bounds or null if none can 630 * be found 631 */ 632 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 633 634 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 635 View focusCandidate = null; 636 637 /* 638 * A fully contained focusable is one where its top is below the bound's 639 * top, and its bottom is above the bound's bottom. A partially 640 * contained focusable is one where some part of it is within the 641 * bounds, but it also has some part that is not within bounds. A fully contained 642 * focusable is preferred to a partially contained focusable. 643 */ 644 boolean foundFullyContainedFocusable = false; 645 646 int count = focusables.size(); 647 for (int i = 0; i < count; i++) { 648 View view = focusables.get(i); 649 int viewTop = view.getTop(); 650 int viewBottom = view.getBottom(); 651 652 if (top < viewBottom && viewTop < bottom) { 653 /* 654 * the focusable is in the target area, it is a candidate for 655 * focusing 656 */ 657 658 final boolean viewIsFullyContained = (top < viewTop) && 659 (viewBottom < bottom); 660 661 if (focusCandidate == null) { 662 /* No candidate, take this one */ 663 focusCandidate = view; 664 foundFullyContainedFocusable = viewIsFullyContained; 665 } else { 666 final boolean viewIsCloserToBoundary = 667 (topFocus && viewTop < focusCandidate.getTop()) || 668 (!topFocus && viewBottom > focusCandidate 669 .getBottom()); 670 671 if (foundFullyContainedFocusable) { 672 if (viewIsFullyContained && viewIsCloserToBoundary) { 673 /* 674 * We're dealing with only fully contained views, so 675 * it has to be closer to the boundary to beat our 676 * candidate 677 */ 678 focusCandidate = view; 679 } 680 } else { 681 if (viewIsFullyContained) { 682 /* Any fully contained view beats a partially contained view */ 683 focusCandidate = view; 684 foundFullyContainedFocusable = true; 685 } else if (viewIsCloserToBoundary) { 686 /* 687 * Partially contained view beats another partially 688 * contained view if it's closer 689 */ 690 focusCandidate = view; 691 } 692 } 693 } 694 } 695 } 696 697 return focusCandidate; 698 } 699 700 /** 701 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 702 * method will scroll the view by one page up or down and give the focus 703 * to the topmost/bottommost component in the new visible area. If no 704 * component is a good candidate for focus, this scrollview reclaims the 705 * focus.</p> 706 * 707 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 708 * to go one page up or 709 * {@link android.view.View#FOCUS_DOWN} to go one page down 710 * @return true if the key event is consumed by this method, false otherwise 711 */ 712 public boolean pageScroll(int direction) { 713 boolean down = direction == View.FOCUS_DOWN; 714 int height = getHeight(); 715 716 if (down) { 717 mTempRect.top = getScrollY() + height; 718 int count = getChildCount(); 719 if (count > 0) { 720 View view = getChildAt(count - 1); 721 if (mTempRect.top + height > view.getBottom()) { 722 mTempRect.top = view.getBottom() - height; 723 } 724 } 725 } else { 726 mTempRect.top = getScrollY() - height; 727 if (mTempRect.top < 0) { 728 mTempRect.top = 0; 729 } 730 } 731 mTempRect.bottom = mTempRect.top + height; 732 733 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 734 } 735 736 /** 737 * <p>Handles scrolling in response to a "home/end" shortcut press. This 738 * method will scroll the view to the top or bottom and give the focus 739 * to the topmost/bottommost component in the new visible area. If no 740 * component is a good candidate for focus, this scrollview reclaims the 741 * focus.</p> 742 * 743 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 744 * to go the top of the view or 745 * {@link android.view.View#FOCUS_DOWN} to go the bottom 746 * @return true if the key event is consumed by this method, false otherwise 747 */ 748 public boolean fullScroll(int direction) { 749 boolean down = direction == View.FOCUS_DOWN; 750 int height = getHeight(); 751 752 mTempRect.top = 0; 753 mTempRect.bottom = height; 754 755 if (down) { 756 int count = getChildCount(); 757 if (count > 0) { 758 View view = getChildAt(count - 1); 759 mTempRect.bottom = view.getBottom(); 760 mTempRect.top = mTempRect.bottom - height; 761 } 762 } 763 764 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 765 } 766 767 /** 768 * <p>Scrolls the view to make the area defined by <code>top</code> and 769 * <code>bottom</code> visible. This method attempts to give the focus 770 * to a component visible in this area. If no component can be focused in 771 * the new visible area, the focus is reclaimed by this scrollview.</p> 772 * 773 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 774 * to go upward 775 * {@link android.view.View#FOCUS_DOWN} to downward 776 * @param top the top offset of the new area to be made visible 777 * @param bottom the bottom offset of the new area to be made visible 778 * @return true if the key event is consumed by this method, false otherwise 779 */ 780 private boolean scrollAndFocus(int direction, int top, int bottom) { 781 boolean handled = true; 782 783 int height = getHeight(); 784 int containerTop = getScrollY(); 785 int containerBottom = containerTop + height; 786 boolean up = direction == View.FOCUS_UP; 787 788 View newFocused = findFocusableViewInBounds(up, top, bottom); 789 if (newFocused == null) { 790 newFocused = this; 791 } 792 793 if (top >= containerTop && bottom <= containerBottom) { 794 handled = false; 795 } else { 796 int delta = up ? (top - containerTop) : (bottom - containerBottom); 797 doScrollY(delta); 798 } 799 800 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 801 mScrollViewMovedFocus = true; 802 mScrollViewMovedFocus = false; 803 } 804 805 return handled; 806 } 807 808 /** 809 * Handle scrolling in response to an up or down arrow click. 810 * 811 * @param direction The direction corresponding to the arrow key that was 812 * pressed 813 * @return True if we consumed the event, false otherwise 814 */ 815 public boolean arrowScroll(int direction) { 816 817 View currentFocused = findFocus(); 818 if (currentFocused == this) currentFocused = null; 819 820 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 821 822 final int maxJump = getMaxScrollAmount(); 823 824 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 825 nextFocused.getDrawingRect(mTempRect); 826 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 827 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 828 doScrollY(scrollDelta); 829 nextFocused.requestFocus(direction); 830 } else { 831 // no new focus 832 int scrollDelta = maxJump; 833 834 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 835 scrollDelta = getScrollY(); 836 } else if (direction == View.FOCUS_DOWN) { 837 if (getChildCount() > 0) { 838 int daBottom = getChildAt(0).getBottom(); 839 840 int screenBottom = getScrollY() + getHeight(); 841 842 if (daBottom - screenBottom < maxJump) { 843 scrollDelta = daBottom - screenBottom; 844 } 845 } 846 } 847 if (scrollDelta == 0) { 848 return false; 849 } 850 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 851 } 852 853 if (currentFocused != null && currentFocused.isFocused() 854 && isOffScreen(currentFocused)) { 855 // previously focused item still has focus and is off screen, give 856 // it up (take it back to ourselves) 857 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 858 // sure to 859 // get it) 860 final int descendantFocusability = getDescendantFocusability(); // save 861 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 862 requestFocus(); 863 setDescendantFocusability(descendantFocusability); // restore 864 } 865 return true; 866 } 867 868 /** 869 * @return whether the descendant of this scroll view is scrolled off 870 * screen. 871 */ 872 private boolean isOffScreen(View descendant) { 873 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 874 } 875 876 /** 877 * @return whether the descendant of this scroll view is within delta 878 * pixels of being on the screen. 879 */ 880 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 881 descendant.getDrawingRect(mTempRect); 882 offsetDescendantRectToMyCoords(descendant, mTempRect); 883 884 return (mTempRect.bottom + delta) >= getScrollY() 885 && (mTempRect.top - delta) <= (getScrollY() + height); 886 } 887 888 /** 889 * Smooth scroll by a Y delta 890 * 891 * @param delta the number of pixels to scroll by on the Y axis 892 */ 893 private void doScrollY(int delta) { 894 if (delta != 0) { 895 if (mSmoothScrollingEnabled) { 896 smoothScrollBy(0, delta); 897 } else { 898 scrollBy(0, delta); 899 } 900 } 901 } 902 903 /** 904 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 905 * 906 * @param dx the number of pixels to scroll by on the X axis 907 * @param dy the number of pixels to scroll by on the Y axis 908 */ 909 public final void smoothScrollBy(int dx, int dy) { 910 if (getChildCount() == 0) { 911 // Nothing to do. 912 return; 913 } 914 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 915 if (duration > ANIMATED_SCROLL_GAP) { 916 final int height = getHeight() - mPaddingBottom - mPaddingTop; 917 final int bottom = getChildAt(0).getHeight(); 918 final int maxY = Math.max(0, bottom - height); 919 final int scrollY = mScrollY; 920 dy = Math.max(0, Math.min(scrollY + dy, maxY)) - scrollY; 921 922 mScroller.startScroll(mScrollX, scrollY, 0, dy); 923 invalidate(); 924 } else { 925 if (!mScroller.isFinished()) { 926 mScroller.abortAnimation(); 927 } 928 scrollBy(dx, dy); 929 } 930 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 931 } 932 933 /** 934 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 935 * 936 * @param x the position where to scroll on the X axis 937 * @param y the position where to scroll on the Y axis 938 */ 939 public final void smoothScrollTo(int x, int y) { 940 smoothScrollBy(x - mScrollX, y - mScrollY); 941 } 942 943 /** 944 * <p>The scroll range of a scroll view is the overall height of all of its 945 * children.</p> 946 */ 947 @Override 948 protected int computeVerticalScrollRange() { 949 final int count = getChildCount(); 950 final int contentHeight = getHeight() - mPaddingBottom - mPaddingTop; 951 if (count == 0) { 952 return contentHeight; 953 } 954 955 return getChildAt(0).getBottom(); 956 } 957 958 @Override 959 protected int computeVerticalScrollOffset() { 960 return Math.max(0, super.computeVerticalScrollOffset()); 961 } 962 963 @Override 964 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 965 ViewGroup.LayoutParams lp = child.getLayoutParams(); 966 967 int childWidthMeasureSpec; 968 int childHeightMeasureSpec; 969 970 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 971 + mPaddingRight, lp.width); 972 973 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 974 975 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 976 } 977 978 @Override 979 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 980 int parentHeightMeasureSpec, int heightUsed) { 981 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 982 983 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 984 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 985 + widthUsed, lp.width); 986 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 987 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 988 989 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 990 } 991 992 @Override 993 public void computeScroll() { 994 if (mScroller.computeScrollOffset()) { 995 // This is called at drawing time by ViewGroup. We don't want to 996 // re-show the scrollbars at this point, which scrollTo will do, 997 // so we replicate most of scrollTo here. 998 // 999 // It's a little odd to call onScrollChanged from inside the drawing. 1000 // 1001 // It is, except when you remember that computeScroll() is used to 1002 // animate scrolling. So unless we want to defer the onScrollChanged() 1003 // until the end of the animated scrolling, we don't really have a 1004 // choice here. 1005 // 1006 // I agree. The alternative, which I think would be worse, is to post 1007 // something and tell the subclasses later. This is bad because there 1008 // will be a window where mScrollX/Y is different from what the app 1009 // thinks it is. 1010 // 1011 int oldX = mScrollX; 1012 int oldY = mScrollY; 1013 int x = mScroller.getCurrX(); 1014 int y = mScroller.getCurrY(); 1015 1016 if (getChildCount() > 0) { 1017 View child = getChildAt(0); 1018 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1019 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1020 if (x != oldX || y != oldY) { 1021 mScrollX = x; 1022 mScrollY = y; 1023 onScrollChanged(x, y, oldX, oldY); 1024 } 1025 } 1026 1027 // Keep on drawing until the animation has finished. 1028 postInvalidate(); 1029 } 1030 } 1031 1032 /** 1033 * Scrolls the view to the given child. 1034 * 1035 * @param child the View to scroll to 1036 */ 1037 private void scrollToChild(View child) { 1038 child.getDrawingRect(mTempRect); 1039 1040 /* Offset from child's local coordinates to ScrollView coordinates */ 1041 offsetDescendantRectToMyCoords(child, mTempRect); 1042 1043 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1044 1045 if (scrollDelta != 0) { 1046 scrollBy(0, scrollDelta); 1047 } 1048 } 1049 1050 /** 1051 * If rect is off screen, scroll just enough to get it (or at least the 1052 * first screen size chunk of it) on screen. 1053 * 1054 * @param rect The rectangle. 1055 * @param immediate True to scroll immediately without animation 1056 * @return true if scrolling was performed 1057 */ 1058 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1059 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1060 final boolean scroll = delta != 0; 1061 if (scroll) { 1062 if (immediate) { 1063 scrollBy(0, delta); 1064 } else { 1065 smoothScrollBy(0, delta); 1066 } 1067 } 1068 return scroll; 1069 } 1070 1071 /** 1072 * Compute the amount to scroll in the Y direction in order to get 1073 * a rectangle completely on the screen (or, if taller than the screen, 1074 * at least the first screen size chunk of it). 1075 * 1076 * @param rect The rect. 1077 * @return The scroll delta. 1078 */ 1079 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1080 if (getChildCount() == 0) return 0; 1081 1082 int height = getHeight(); 1083 int screenTop = getScrollY(); 1084 int screenBottom = screenTop + height; 1085 1086 int fadingEdge = getVerticalFadingEdgeLength(); 1087 1088 // leave room for top fading edge as long as rect isn't at very top 1089 if (rect.top > 0) { 1090 screenTop += fadingEdge; 1091 } 1092 1093 // leave room for bottom fading edge as long as rect isn't at very bottom 1094 if (rect.bottom < getChildAt(0).getHeight()) { 1095 screenBottom -= fadingEdge; 1096 } 1097 1098 int scrollYDelta = 0; 1099 1100 if (rect.bottom > screenBottom && rect.top > screenTop) { 1101 // need to move down to get it in view: move down just enough so 1102 // that the entire rectangle is in view (or at least the first 1103 // screen size chunk). 1104 1105 if (rect.height() > height) { 1106 // just enough to get screen size chunk on 1107 scrollYDelta += (rect.top - screenTop); 1108 } else { 1109 // get entire rect at bottom of screen 1110 scrollYDelta += (rect.bottom - screenBottom); 1111 } 1112 1113 // make sure we aren't scrolling beyond the end of our content 1114 int bottom = getChildAt(0).getBottom(); 1115 int distanceToBottom = bottom - screenBottom; 1116 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1117 1118 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1119 // need to move up to get it in view: move up just enough so that 1120 // entire rectangle is in view (or at least the first screen 1121 // size chunk of it). 1122 1123 if (rect.height() > height) { 1124 // screen size chunk 1125 scrollYDelta -= (screenBottom - rect.bottom); 1126 } else { 1127 // entire rect at top 1128 scrollYDelta -= (screenTop - rect.top); 1129 } 1130 1131 // make sure we aren't scrolling any further than the top our content 1132 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1133 } 1134 return scrollYDelta; 1135 } 1136 1137 @Override 1138 public void requestChildFocus(View child, View focused) { 1139 if (!mScrollViewMovedFocus) { 1140 if (!mIsLayoutDirty) { 1141 scrollToChild(focused); 1142 } else { 1143 // The child may not be laid out yet, we can't compute the scroll yet 1144 mChildToScrollTo = focused; 1145 } 1146 } 1147 super.requestChildFocus(child, focused); 1148 } 1149 1150 1151 /** 1152 * When looking for focus in children of a scroll view, need to be a little 1153 * more careful not to give focus to something that is scrolled off screen. 1154 * 1155 * This is more expensive than the default {@link android.view.ViewGroup} 1156 * implementation, otherwise this behavior might have been made the default. 1157 */ 1158 @Override 1159 protected boolean onRequestFocusInDescendants(int direction, 1160 Rect previouslyFocusedRect) { 1161 1162 // convert from forward / backward notation to up / down / left / right 1163 // (ugh). 1164 if (direction == View.FOCUS_FORWARD) { 1165 direction = View.FOCUS_DOWN; 1166 } else if (direction == View.FOCUS_BACKWARD) { 1167 direction = View.FOCUS_UP; 1168 } 1169 1170 final View nextFocus = previouslyFocusedRect == null ? 1171 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1172 FocusFinder.getInstance().findNextFocusFromRect(this, 1173 previouslyFocusedRect, direction); 1174 1175 if (nextFocus == null) { 1176 return false; 1177 } 1178 1179 if (isOffScreen(nextFocus)) { 1180 return false; 1181 } 1182 1183 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1184 } 1185 1186 @Override 1187 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1188 boolean immediate) { 1189 // offset into coordinate space of this scroll view 1190 rectangle.offset(child.getLeft() - child.getScrollX(), 1191 child.getTop() - child.getScrollY()); 1192 1193 return scrollToChildRect(rectangle, immediate); 1194 } 1195 1196 @Override 1197 public void requestLayout() { 1198 mIsLayoutDirty = true; 1199 super.requestLayout(); 1200 } 1201 1202 @Override 1203 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1204 super.onLayout(changed, l, t, r, b); 1205 mIsLayoutDirty = false; 1206 // Give a child focus if it needs it 1207 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1208 scrollToChild(mChildToScrollTo); 1209 } 1210 mChildToScrollTo = null; 1211 1212 // Calling this with the present values causes it to re-clam them 1213 scrollTo(mScrollX, mScrollY); 1214 } 1215 1216 @Override 1217 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1218 super.onSizeChanged(w, h, oldw, oldh); 1219 1220 View currentFocused = findFocus(); 1221 if (null == currentFocused || this == currentFocused) 1222 return; 1223 1224 // If the currently-focused view was visible on the screen when the 1225 // screen was at the old height, then scroll the screen to make that 1226 // view visible with the new screen height. 1227 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1228 currentFocused.getDrawingRect(mTempRect); 1229 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1230 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1231 doScrollY(scrollDelta); 1232 } 1233 } 1234 1235 /** 1236 * Return true if child is an descendant of parent, (or equal to the parent). 1237 */ 1238 private boolean isViewDescendantOf(View child, View parent) { 1239 if (child == parent) { 1240 return true; 1241 } 1242 1243 final ViewParent theParent = child.getParent(); 1244 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1245 } 1246 1247 /** 1248 * Fling the scroll view 1249 * 1250 * @param velocityY The initial velocity in the Y direction. Positive 1251 * numbers mean that the finger/cursor is moving down the screen, 1252 * which means we want to scroll towards the top. 1253 */ 1254 public void fling(int velocityY) { 1255 if (getChildCount() > 0) { 1256 int height = getHeight() - mPaddingBottom - mPaddingTop; 1257 int bottom = getChildAt(0).getHeight(); 1258 1259 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, 1260 Math.max(0, bottom - height)); 1261 1262 final boolean movingDown = velocityY > 0; 1263 1264 View newFocused = 1265 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1266 if (newFocused == null) { 1267 newFocused = this; 1268 } 1269 1270 if (newFocused != findFocus() 1271 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1272 mScrollViewMovedFocus = true; 1273 mScrollViewMovedFocus = false; 1274 } 1275 1276 invalidate(); 1277 } 1278 } 1279 1280 /** 1281 * {@inheritDoc} 1282 * 1283 * <p>This version also clamps the scrolling to the bounds of our child. 1284 */ 1285 @Override 1286 public void scrollTo(int x, int y) { 1287 // we rely on the fact the View.scrollBy calls scrollTo. 1288 if (getChildCount() > 0) { 1289 View child = getChildAt(0); 1290 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1291 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1292 if (x != mScrollX || y != mScrollY) { 1293 super.scrollTo(x, y); 1294 } 1295 } 1296 } 1297 1298 private int clamp(int n, int my, int child) { 1299 if (my >= child || n < 0) { 1300 /* my >= child is this case: 1301 * |--------------- me ---------------| 1302 * |------ child ------| 1303 * or 1304 * |--------------- me ---------------| 1305 * |------ child ------| 1306 * or 1307 * |--------------- me ---------------| 1308 * |------ child ------| 1309 * 1310 * n < 0 is this case: 1311 * |------ me ------| 1312 * |-------- child --------| 1313 * |-- mScrollX --| 1314 */ 1315 return 0; 1316 } 1317 if ((my+n) > child) { 1318 /* this case: 1319 * |------ me ------| 1320 * |------ child ------| 1321 * |-- mScrollX --| 1322 */ 1323 return child-my; 1324 } 1325 return n; 1326 } 1327} 1328