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 17 package android.widget; 18 19 import android.content.Context; 20 import android.content.res.TypedArray; 21 import android.graphics.Rect; 22 import android.util.AttributeSet; 23 import android.view.FocusFinder; 24 import android.view.KeyEvent; 25 import android.view.MotionEvent; 26 import android.view.VelocityTracker; 27 import android.view.View; 28 import android.view.ViewConfiguration; 29 import android.view.ViewGroup; 30 import android.view.ViewParent; 31 import android.view.animation.AnimationUtils; 32 33 import com.android.internal.R; 34 35 import java.util.List; 36 37 /** 38 * Layout container for a view hierarchy that can be scrolled by the user, 39 * allowing it to be larger than the physical display. A ScrollView 40 * is a {@link FrameLayout}, meaning you should place one child in it 41 * containing the entire contents to scroll; this child may itself be a layout 42 * manager with a complex hierarchy of objects. A child that is often used 43 * is a {@link LinearLayout} in a vertical orientation, presenting a vertical 44 * array of top-level items that the user can scroll through. 45 * 46 * <p>The {@link TextView} class also 47 * takes care of its own scrolling, so does not require a ScrollView, but 48 * using the two together is possible to achieve the effect of a text view 49 * within a larger container. 50 * 51 * <p>ScrollView only supports vertical scrolling. 52 */ 53 public class ScrollView extends FrameLayout { 54 static final String TAG = "ScrollView"; 55 56 static final int ANIMATED_SCROLL_GAP = 250; 57 58 static final float MAX_SCROLL_FACTOR = 0.5f; 59 60 61 private long mLastScroll; 62 63 private final Rect mTempRect = new Rect(); 64 private Scroller mScroller; 65 66 /** 67 * Flag to indicate that we are moving focus ourselves. This is so the 68 * code that watches for focus changes initiated outside this ScrollView 69 * knows that it does not have to do anything. 70 */ 71 private boolean mScrollViewMovedFocus; 72 73 /** 74 * Position of the last motion event. 75 */ 76 private float mLastMotionY; 77 78 /** 79 * True when the layout has changed but the traversal has not come through yet. 80 * Ideally the view hierarchy would keep track of this for us. 81 */ 82 private boolean mIsLayoutDirty = true; 83 84 /** 85 * The child to give focus to in the event that a child has requested focus while the 86 * layout is dirty. This prevents the scroll from being wrong if the child has not been 87 * laid out before requesting focus. 88 */ 89 private View mChildToScrollTo = null; 90 91 /** 92 * True if the user is currently dragging this ScrollView around. This is 93 * not the same as 'is being flinged', which can be checked by 94 * mScroller.isFinished() (flinging begins when the user lifts his finger). 95 */ 96 private boolean mIsBeingDragged = false; 97 98 /** 99 * Determines speed during touch scrolling 100 */ 101 private VelocityTracker mVelocityTracker; 102 103 /** 104 * When set to true, the scroll view measure its child to make it fill the currently 105 * visible area. 106 */ 107 private boolean mFillViewport; 108 109 /** 110 * Whether arrow scrolling is animated. 111 */ 112 private boolean mSmoothScrollingEnabled = true; 113 114 private int mTouchSlop; 115 private int mMinimumVelocity; 116 private int mMaximumVelocity; 117 ScrollView(Context context)118 public ScrollView(Context context) { 119 this(context, null); 120 } 121 ScrollView(Context context, AttributeSet attrs)122 public ScrollView(Context context, AttributeSet attrs) { 123 this(context, attrs, com.android.internal.R.attr.scrollViewStyle); 124 } 125 ScrollView(Context context, AttributeSet attrs, int defStyle)126 public ScrollView(Context context, AttributeSet attrs, int defStyle) { 127 super(context, attrs, defStyle); 128 initScrollView(); 129 130 TypedArray a = 131 context.obtainStyledAttributes(attrs, com.android.internal.R.styleable.ScrollView, defStyle, 0); 132 133 setFillViewport(a.getBoolean(R.styleable.ScrollView_fillViewport, false)); 134 135 a.recycle(); 136 } 137 138 @Override getTopFadingEdgeStrength()139 protected float getTopFadingEdgeStrength() { 140 if (getChildCount() == 0) { 141 return 0.0f; 142 } 143 144 final int length = getVerticalFadingEdgeLength(); 145 if (mScrollY < length) { 146 return mScrollY / (float) length; 147 } 148 149 return 1.0f; 150 } 151 152 @Override getBottomFadingEdgeStrength()153 protected float getBottomFadingEdgeStrength() { 154 if (getChildCount() == 0) { 155 return 0.0f; 156 } 157 158 final int length = getVerticalFadingEdgeLength(); 159 final int bottomEdge = getHeight() - mPaddingBottom; 160 final int span = getChildAt(0).getBottom() - mScrollY - bottomEdge; 161 if (span < length) { 162 return span / (float) length; 163 } 164 165 return 1.0f; 166 } 167 168 /** 169 * @return The maximum amount this scroll view will scroll in response to 170 * an arrow event. 171 */ getMaxScrollAmount()172 public int getMaxScrollAmount() { 173 return (int) (MAX_SCROLL_FACTOR * (mBottom - mTop)); 174 } 175 176 initScrollView()177 private void initScrollView() { 178 mScroller = new Scroller(getContext()); 179 setFocusable(true); 180 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 181 setWillNotDraw(false); 182 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 183 mTouchSlop = configuration.getScaledTouchSlop(); 184 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 185 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 186 } 187 188 @Override addView(View child)189 public void addView(View child) { 190 if (getChildCount() > 0) { 191 throw new IllegalStateException("ScrollView can host only one direct child"); 192 } 193 194 super.addView(child); 195 } 196 197 @Override addView(View child, int index)198 public void addView(View child, int index) { 199 if (getChildCount() > 0) { 200 throw new IllegalStateException("ScrollView can host only one direct child"); 201 } 202 203 super.addView(child, index); 204 } 205 206 @Override addView(View child, ViewGroup.LayoutParams params)207 public void addView(View child, ViewGroup.LayoutParams params) { 208 if (getChildCount() > 0) { 209 throw new IllegalStateException("ScrollView can host only one direct child"); 210 } 211 212 super.addView(child, params); 213 } 214 215 @Override addView(View child, int index, ViewGroup.LayoutParams params)216 public void addView(View child, int index, ViewGroup.LayoutParams params) { 217 if (getChildCount() > 0) { 218 throw new IllegalStateException("ScrollView can host only one direct child"); 219 } 220 221 super.addView(child, index, params); 222 } 223 224 /** 225 * @return Returns true this ScrollView can be scrolled 226 */ canScroll()227 private boolean canScroll() { 228 View child = getChildAt(0); 229 if (child != null) { 230 int childHeight = child.getHeight(); 231 return getHeight() < childHeight + mPaddingTop + mPaddingBottom; 232 } 233 return false; 234 } 235 236 /** 237 * Indicates whether this ScrollView's content is stretched to fill the viewport. 238 * 239 * @return True if the content fills the viewport, false otherwise. 240 */ isFillViewport()241 public boolean isFillViewport() { 242 return mFillViewport; 243 } 244 245 /** 246 * Indicates this ScrollView whether it should stretch its content height to fill 247 * the viewport or not. 248 * 249 * @param fillViewport True to stretch the content's height to the viewport's 250 * boundaries, false otherwise. 251 */ setFillViewport(boolean fillViewport)252 public void setFillViewport(boolean fillViewport) { 253 if (fillViewport != mFillViewport) { 254 mFillViewport = fillViewport; 255 requestLayout(); 256 } 257 } 258 259 /** 260 * @return Whether arrow scrolling will animate its transition. 261 */ isSmoothScrollingEnabled()262 public boolean isSmoothScrollingEnabled() { 263 return mSmoothScrollingEnabled; 264 } 265 266 /** 267 * Set whether arrow scrolling will animate its transition. 268 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 269 */ setSmoothScrollingEnabled(boolean smoothScrollingEnabled)270 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 271 mSmoothScrollingEnabled = smoothScrollingEnabled; 272 } 273 274 @Override onMeasure(int widthMeasureSpec, int heightMeasureSpec)275 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 276 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 277 278 if (!mFillViewport) { 279 return; 280 } 281 282 final int heightMode = MeasureSpec.getMode(heightMeasureSpec); 283 if (heightMode == MeasureSpec.UNSPECIFIED) { 284 return; 285 } 286 287 if (getChildCount() > 0) { 288 final View child = getChildAt(0); 289 int height = getMeasuredHeight(); 290 if (child.getMeasuredHeight() < height) { 291 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 292 293 int childWidthMeasureSpec = getChildMeasureSpec(widthMeasureSpec, mPaddingLeft 294 + mPaddingRight, lp.width); 295 height -= mPaddingTop; 296 height -= mPaddingBottom; 297 int childHeightMeasureSpec = 298 MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY); 299 300 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 301 } 302 } 303 } 304 305 @Override dispatchKeyEvent(KeyEvent event)306 public boolean dispatchKeyEvent(KeyEvent event) { 307 // Let the focused view and/or our descendants get the key first 308 boolean handled = super.dispatchKeyEvent(event); 309 if (handled) { 310 return true; 311 } 312 return executeKeyEvent(event); 313 } 314 315 /** 316 * You can call this function yourself to have the scroll view perform 317 * scrolling from a key event, just as if the event had been dispatched to 318 * it by the view hierarchy. 319 * 320 * @param event The key event to execute. 321 * @return Return true if the event was handled, else false. 322 */ executeKeyEvent(KeyEvent event)323 public boolean executeKeyEvent(KeyEvent event) { 324 mTempRect.setEmpty(); 325 326 if (!canScroll()) { 327 if (isFocused()) { 328 View currentFocused = findFocus(); 329 if (currentFocused == this) currentFocused = null; 330 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 331 currentFocused, View.FOCUS_DOWN); 332 return nextFocused != null 333 && nextFocused != this 334 && nextFocused.requestFocus(View.FOCUS_DOWN); 335 } 336 return false; 337 } 338 339 boolean handled = false; 340 if (event.getAction() == KeyEvent.ACTION_DOWN) { 341 switch (event.getKeyCode()) { 342 case KeyEvent.KEYCODE_DPAD_UP: 343 if (!event.isAltPressed()) { 344 handled = arrowScroll(View.FOCUS_UP); 345 } else { 346 handled = fullScroll(View.FOCUS_UP); 347 } 348 break; 349 case KeyEvent.KEYCODE_DPAD_DOWN: 350 if (!event.isAltPressed()) { 351 handled = arrowScroll(View.FOCUS_DOWN); 352 } else { 353 handled = fullScroll(View.FOCUS_DOWN); 354 } 355 break; 356 case KeyEvent.KEYCODE_SPACE: 357 pageScroll(event.isShiftPressed() ? View.FOCUS_UP : View.FOCUS_DOWN); 358 break; 359 } 360 } 361 362 return handled; 363 } 364 365 @Override onInterceptTouchEvent(MotionEvent ev)366 public boolean onInterceptTouchEvent(MotionEvent ev) { 367 /* 368 * This method JUST determines whether we want to intercept the motion. 369 * If we return true, onMotionEvent will be called and we do the actual 370 * scrolling there. 371 */ 372 373 /* 374 * Shortcut the most recurring case: the user is in the dragging 375 * state and he is moving his finger. We want to intercept this 376 * motion. 377 */ 378 final int action = ev.getAction(); 379 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 380 return true; 381 } 382 383 if (!canScroll()) { 384 mIsBeingDragged = false; 385 return false; 386 } 387 388 final float y = ev.getY(); 389 390 switch (action) { 391 case MotionEvent.ACTION_MOVE: 392 /* 393 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 394 * whether the user has moved far enough from his original down touch. 395 */ 396 397 /* 398 * Locally do absolute value. mLastMotionY is set to the y value 399 * of the down event. 400 */ 401 final int yDiff = (int) Math.abs(y - mLastMotionY); 402 if (yDiff > mTouchSlop) { 403 mIsBeingDragged = true; 404 } 405 break; 406 407 case MotionEvent.ACTION_DOWN: 408 /* Remember location of down touch */ 409 mLastMotionY = y; 410 411 /* 412 * If being flinged and user touches the screen, initiate drag; 413 * otherwise don't. mScroller.isFinished should be false when 414 * being flinged. 415 */ 416 mIsBeingDragged = !mScroller.isFinished(); 417 break; 418 419 case MotionEvent.ACTION_CANCEL: 420 case MotionEvent.ACTION_UP: 421 /* Release the drag */ 422 mIsBeingDragged = false; 423 break; 424 } 425 426 /* 427 * The only time we want to intercept motion events is if we are in the 428 * drag mode. 429 */ 430 return mIsBeingDragged; 431 } 432 433 @Override onTouchEvent(MotionEvent ev)434 public boolean onTouchEvent(MotionEvent ev) { 435 436 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 437 // Don't handle edge touches immediately -- they may actually belong to one of our 438 // descendants. 439 return false; 440 } 441 442 if (!canScroll()) { 443 return false; 444 } 445 446 if (mVelocityTracker == null) { 447 mVelocityTracker = VelocityTracker.obtain(); 448 } 449 mVelocityTracker.addMovement(ev); 450 451 final int action = ev.getAction(); 452 final float y = ev.getY(); 453 454 switch (action) { 455 case MotionEvent.ACTION_DOWN: 456 /* 457 * If being flinged and user touches, stop the fling. isFinished 458 * will be false if being flinged. 459 */ 460 if (!mScroller.isFinished()) { 461 mScroller.abortAnimation(); 462 } 463 464 // Remember where the motion event started 465 mLastMotionY = y; 466 break; 467 case MotionEvent.ACTION_MOVE: 468 // Scroll to follow the motion event 469 final int deltaY = (int) (mLastMotionY - y); 470 mLastMotionY = y; 471 472 if (deltaY < 0) { 473 if (mScrollY > 0) { 474 scrollBy(0, deltaY); 475 } 476 } else if (deltaY > 0) { 477 final int bottomEdge = getHeight() - mPaddingBottom; 478 final int availableToScroll = getChildAt(0).getBottom() - mScrollY - bottomEdge; 479 if (availableToScroll > 0) { 480 scrollBy(0, Math.min(availableToScroll, deltaY)); 481 } 482 } 483 break; 484 case MotionEvent.ACTION_UP: 485 final VelocityTracker velocityTracker = mVelocityTracker; 486 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 487 int initialVelocity = (int) velocityTracker.getYVelocity(); 488 489 if ((Math.abs(initialVelocity) > mMinimumVelocity) && getChildCount() > 0) { 490 fling(-initialVelocity); 491 } 492 493 if (mVelocityTracker != null) { 494 mVelocityTracker.recycle(); 495 mVelocityTracker = null; 496 } 497 } 498 return true; 499 } 500 501 /** 502 * <p> 503 * Finds the next focusable component that fits in this View's bounds 504 * (excluding fading edges) pretending that this View's top is located at 505 * the parameter top. 506 * </p> 507 * 508 * @param topFocus look for a candidate is the one at the top of the bounds 509 * if topFocus is true, or at the bottom of the bounds if topFocus is 510 * false 511 * @param top the top offset of the bounds in which a focusable must be 512 * found (the fading edge is assumed to start at this position) 513 * @param preferredFocusable the View that has highest priority and will be 514 * returned if it is within my bounds (null is valid) 515 * @return the next focusable component in the bounds or null if none can be 516 * found 517 */ findFocusableViewInMyBounds(final boolean topFocus, final int top, View preferredFocusable)518 private View findFocusableViewInMyBounds(final boolean topFocus, 519 final int top, View preferredFocusable) { 520 /* 521 * The fading edge's transparent side should be considered for focus 522 * since it's mostly visible, so we divide the actual fading edge length 523 * by 2. 524 */ 525 final int fadingEdgeLength = getVerticalFadingEdgeLength() / 2; 526 final int topWithoutFadingEdge = top + fadingEdgeLength; 527 final int bottomWithoutFadingEdge = top + getHeight() - fadingEdgeLength; 528 529 if ((preferredFocusable != null) 530 && (preferredFocusable.getTop() < bottomWithoutFadingEdge) 531 && (preferredFocusable.getBottom() > topWithoutFadingEdge)) { 532 return preferredFocusable; 533 } 534 535 return findFocusableViewInBounds(topFocus, topWithoutFadingEdge, 536 bottomWithoutFadingEdge); 537 } 538 539 /** 540 * <p> 541 * Finds the next focusable component that fits in the specified bounds. 542 * </p> 543 * 544 * @param topFocus look for a candidate is the one at the top of the bounds 545 * if topFocus is true, or at the bottom of the bounds if topFocus is 546 * false 547 * @param top the top offset of the bounds in which a focusable must be 548 * found 549 * @param bottom the bottom offset of the bounds in which a focusable must 550 * be found 551 * @return the next focusable component in the bounds or null if none can 552 * be found 553 */ findFocusableViewInBounds(boolean topFocus, int top, int bottom)554 private View findFocusableViewInBounds(boolean topFocus, int top, int bottom) { 555 556 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 557 View focusCandidate = null; 558 559 /* 560 * A fully contained focusable is one where its top is below the bound's 561 * top, and its bottom is above the bound's bottom. A partially 562 * contained focusable is one where some part of it is within the 563 * bounds, but it also has some part that is not within bounds. A fully contained 564 * focusable is preferred to a partially contained focusable. 565 */ 566 boolean foundFullyContainedFocusable = false; 567 568 int count = focusables.size(); 569 for (int i = 0; i < count; i++) { 570 View view = focusables.get(i); 571 int viewTop = view.getTop(); 572 int viewBottom = view.getBottom(); 573 574 if (top < viewBottom && viewTop < bottom) { 575 /* 576 * the focusable is in the target area, it is a candidate for 577 * focusing 578 */ 579 580 final boolean viewIsFullyContained = (top < viewTop) && 581 (viewBottom < bottom); 582 583 if (focusCandidate == null) { 584 /* No candidate, take this one */ 585 focusCandidate = view; 586 foundFullyContainedFocusable = viewIsFullyContained; 587 } else { 588 final boolean viewIsCloserToBoundary = 589 (topFocus && viewTop < focusCandidate.getTop()) || 590 (!topFocus && viewBottom > focusCandidate 591 .getBottom()); 592 593 if (foundFullyContainedFocusable) { 594 if (viewIsFullyContained && viewIsCloserToBoundary) { 595 /* 596 * We're dealing with only fully contained views, so 597 * it has to be closer to the boundary to beat our 598 * candidate 599 */ 600 focusCandidate = view; 601 } 602 } else { 603 if (viewIsFullyContained) { 604 /* Any fully contained view beats a partially contained view */ 605 focusCandidate = view; 606 foundFullyContainedFocusable = true; 607 } else if (viewIsCloserToBoundary) { 608 /* 609 * Partially contained view beats another partially 610 * contained view if it's closer 611 */ 612 focusCandidate = view; 613 } 614 } 615 } 616 } 617 } 618 619 return focusCandidate; 620 } 621 622 /** 623 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 624 * method will scroll the view by one page up or down and give the focus 625 * to the topmost/bottommost component in the new visible area. If no 626 * component is a good candidate for focus, this scrollview reclaims the 627 * focus.</p> 628 * 629 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 630 * to go one page up or 631 * {@link android.view.View#FOCUS_DOWN} to go one page down 632 * @return true if the key event is consumed by this method, false otherwise 633 */ pageScroll(int direction)634 public boolean pageScroll(int direction) { 635 boolean down = direction == View.FOCUS_DOWN; 636 int height = getHeight(); 637 638 if (down) { 639 mTempRect.top = getScrollY() + height; 640 int count = getChildCount(); 641 if (count > 0) { 642 View view = getChildAt(count - 1); 643 if (mTempRect.top + height > view.getBottom()) { 644 mTempRect.top = view.getBottom() - height; 645 } 646 } 647 } else { 648 mTempRect.top = getScrollY() - height; 649 if (mTempRect.top < 0) { 650 mTempRect.top = 0; 651 } 652 } 653 mTempRect.bottom = mTempRect.top + height; 654 655 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 656 } 657 658 /** 659 * <p>Handles scrolling in response to a "home/end" shortcut press. This 660 * method will scroll the view to the top or bottom and give the focus 661 * to the topmost/bottommost component in the new visible area. If no 662 * component is a good candidate for focus, this scrollview reclaims the 663 * focus.</p> 664 * 665 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 666 * to go the top of the view or 667 * {@link android.view.View#FOCUS_DOWN} to go the bottom 668 * @return true if the key event is consumed by this method, false otherwise 669 */ fullScroll(int direction)670 public boolean fullScroll(int direction) { 671 boolean down = direction == View.FOCUS_DOWN; 672 int height = getHeight(); 673 674 mTempRect.top = 0; 675 mTempRect.bottom = height; 676 677 if (down) { 678 int count = getChildCount(); 679 if (count > 0) { 680 View view = getChildAt(count - 1); 681 mTempRect.bottom = view.getBottom(); 682 mTempRect.top = mTempRect.bottom - height; 683 } 684 } 685 686 return scrollAndFocus(direction, mTempRect.top, mTempRect.bottom); 687 } 688 689 /** 690 * <p>Scrolls the view to make the area defined by <code>top</code> and 691 * <code>bottom</code> visible. This method attempts to give the focus 692 * to a component visible in this area. If no component can be focused in 693 * the new visible area, the focus is reclaimed by this scrollview.</p> 694 * 695 * @param direction the scroll direction: {@link android.view.View#FOCUS_UP} 696 * to go upward 697 * {@link android.view.View#FOCUS_DOWN} to downward 698 * @param top the top offset of the new area to be made visible 699 * @param bottom the bottom offset of the new area to be made visible 700 * @return true if the key event is consumed by this method, false otherwise 701 */ scrollAndFocus(int direction, int top, int bottom)702 private boolean scrollAndFocus(int direction, int top, int bottom) { 703 boolean handled = true; 704 705 int height = getHeight(); 706 int containerTop = getScrollY(); 707 int containerBottom = containerTop + height; 708 boolean up = direction == View.FOCUS_UP; 709 710 View newFocused = findFocusableViewInBounds(up, top, bottom); 711 if (newFocused == null) { 712 newFocused = this; 713 } 714 715 if (top >= containerTop && bottom <= containerBottom) { 716 handled = false; 717 } else { 718 int delta = up ? (top - containerTop) : (bottom - containerBottom); 719 doScrollY(delta); 720 } 721 722 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 723 mScrollViewMovedFocus = true; 724 mScrollViewMovedFocus = false; 725 } 726 727 return handled; 728 } 729 730 /** 731 * Handle scrolling in response to an up or down arrow click. 732 * 733 * @param direction The direction corresponding to the arrow key that was 734 * pressed 735 * @return True if we consumed the event, false otherwise 736 */ arrowScroll(int direction)737 public boolean arrowScroll(int direction) { 738 739 View currentFocused = findFocus(); 740 if (currentFocused == this) currentFocused = null; 741 742 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 743 744 final int maxJump = getMaxScrollAmount(); 745 746 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump, getHeight())) { 747 nextFocused.getDrawingRect(mTempRect); 748 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 749 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 750 doScrollY(scrollDelta); 751 nextFocused.requestFocus(direction); 752 } else { 753 // no new focus 754 int scrollDelta = maxJump; 755 756 if (direction == View.FOCUS_UP && getScrollY() < scrollDelta) { 757 scrollDelta = getScrollY(); 758 } else if (direction == View.FOCUS_DOWN) { 759 if (getChildCount() > 0) { 760 int daBottom = getChildAt(0).getBottom(); 761 762 int screenBottom = getScrollY() + getHeight(); 763 764 if (daBottom - screenBottom < maxJump) { 765 scrollDelta = daBottom - screenBottom; 766 } 767 } 768 } 769 if (scrollDelta == 0) { 770 return false; 771 } 772 doScrollY(direction == View.FOCUS_DOWN ? scrollDelta : -scrollDelta); 773 } 774 775 if (currentFocused != null && currentFocused.isFocused() 776 && isOffScreen(currentFocused)) { 777 // previously focused item still has focus and is off screen, give 778 // it up (take it back to ourselves) 779 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 780 // sure to 781 // get it) 782 final int descendantFocusability = getDescendantFocusability(); // save 783 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 784 requestFocus(); 785 setDescendantFocusability(descendantFocusability); // restore 786 } 787 return true; 788 } 789 790 /** 791 * @return whether the descendant of this scroll view is scrolled off 792 * screen. 793 */ isOffScreen(View descendant)794 private boolean isOffScreen(View descendant) { 795 return !isWithinDeltaOfScreen(descendant, 0, getHeight()); 796 } 797 798 /** 799 * @return whether the descendant of this scroll view is within delta 800 * pixels of being on the screen. 801 */ isWithinDeltaOfScreen(View descendant, int delta, int height)802 private boolean isWithinDeltaOfScreen(View descendant, int delta, int height) { 803 descendant.getDrawingRect(mTempRect); 804 offsetDescendantRectToMyCoords(descendant, mTempRect); 805 806 return (mTempRect.bottom + delta) >= getScrollY() 807 && (mTempRect.top - delta) <= (getScrollY() + height); 808 } 809 810 /** 811 * Smooth scroll by a Y delta 812 * 813 * @param delta the number of pixels to scroll by on the Y axis 814 */ doScrollY(int delta)815 private void doScrollY(int delta) { 816 if (delta != 0) { 817 if (mSmoothScrollingEnabled) { 818 smoothScrollBy(0, delta); 819 } else { 820 scrollBy(0, delta); 821 } 822 } 823 } 824 825 /** 826 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 827 * 828 * @param dx the number of pixels to scroll by on the X axis 829 * @param dy the number of pixels to scroll by on the Y axis 830 */ smoothScrollBy(int dx, int dy)831 public final void smoothScrollBy(int dx, int dy) { 832 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 833 if (duration > ANIMATED_SCROLL_GAP) { 834 mScroller.startScroll(mScrollX, mScrollY, dx, dy); 835 awakenScrollBars(mScroller.getDuration()); 836 invalidate(); 837 } else { 838 if (!mScroller.isFinished()) { 839 mScroller.abortAnimation(); 840 } 841 scrollBy(dx, dy); 842 } 843 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 844 } 845 846 /** 847 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 848 * 849 * @param x the position where to scroll on the X axis 850 * @param y the position where to scroll on the Y axis 851 */ smoothScrollTo(int x, int y)852 public final void smoothScrollTo(int x, int y) { 853 smoothScrollBy(x - mScrollX, y - mScrollY); 854 } 855 856 /** 857 * <p>The scroll range of a scroll view is the overall height of all of its 858 * children.</p> 859 */ 860 @Override computeVerticalScrollRange()861 protected int computeVerticalScrollRange() { 862 int count = getChildCount(); 863 return count == 0 ? getHeight() : (getChildAt(0)).getBottom(); 864 } 865 866 867 @Override measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec)868 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 869 ViewGroup.LayoutParams lp = child.getLayoutParams(); 870 871 int childWidthMeasureSpec; 872 int childHeightMeasureSpec; 873 874 childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, mPaddingLeft 875 + mPaddingRight, lp.width); 876 877 childHeightMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 878 879 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 880 } 881 882 @Override measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, int parentHeightMeasureSpec, int heightUsed)883 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 884 int parentHeightMeasureSpec, int heightUsed) { 885 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 886 887 final int childWidthMeasureSpec = getChildMeasureSpec(parentWidthMeasureSpec, 888 mPaddingLeft + mPaddingRight + lp.leftMargin + lp.rightMargin 889 + widthUsed, lp.width); 890 final int childHeightMeasureSpec = MeasureSpec.makeMeasureSpec( 891 lp.topMargin + lp.bottomMargin, MeasureSpec.UNSPECIFIED); 892 893 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 894 } 895 896 @Override computeScroll()897 public void computeScroll() { 898 if (mScroller.computeScrollOffset()) { 899 // This is called at drawing time by ViewGroup. We don't want to 900 // re-show the scrollbars at this point, which scrollTo will do, 901 // so we replicate most of scrollTo here. 902 // 903 // It's a little odd to call onScrollChanged from inside the drawing. 904 // 905 // It is, except when you remember that computeScroll() is used to 906 // animate scrolling. So unless we want to defer the onScrollChanged() 907 // until the end of the animated scrolling, we don't really have a 908 // choice here. 909 // 910 // I agree. The alternative, which I think would be worse, is to post 911 // something and tell the subclasses later. This is bad because there 912 // will be a window where mScrollX/Y is different from what the app 913 // thinks it is. 914 // 915 int oldX = mScrollX; 916 int oldY = mScrollY; 917 int x = mScroller.getCurrX(); 918 int y = mScroller.getCurrY(); 919 if (getChildCount() > 0) { 920 View child = getChildAt(0); 921 mScrollX = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 922 mScrollY = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 923 } else { 924 mScrollX = x; 925 mScrollY = y; 926 } 927 if (oldX != mScrollX || oldY != mScrollY) { 928 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 929 } 930 931 // Keep on drawing until the animation has finished. 932 postInvalidate(); 933 } 934 } 935 936 /** 937 * Scrolls the view to the given child. 938 * 939 * @param child the View to scroll to 940 */ scrollToChild(View child)941 private void scrollToChild(View child) { 942 child.getDrawingRect(mTempRect); 943 944 /* Offset from child's local coordinates to ScrollView coordinates */ 945 offsetDescendantRectToMyCoords(child, mTempRect); 946 947 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 948 949 if (scrollDelta != 0) { 950 scrollBy(0, scrollDelta); 951 } 952 } 953 954 /** 955 * If rect is off screen, scroll just enough to get it (or at least the 956 * first screen size chunk of it) on screen. 957 * 958 * @param rect The rectangle. 959 * @param immediate True to scroll immediately without animation 960 * @return true if scrolling was performed 961 */ scrollToChildRect(Rect rect, boolean immediate)962 private boolean scrollToChildRect(Rect rect, boolean immediate) { 963 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 964 final boolean scroll = delta != 0; 965 if (scroll) { 966 if (immediate) { 967 scrollBy(0, delta); 968 } else { 969 smoothScrollBy(0, delta); 970 } 971 } 972 return scroll; 973 } 974 975 /** 976 * Compute the amount to scroll in the Y direction in order to get 977 * a rectangle completely on the screen (or, if taller than the screen, 978 * at least the first screen size chunk of it). 979 * 980 * @param rect The rect. 981 * @return The scroll delta. 982 */ computeScrollDeltaToGetChildRectOnScreen(Rect rect)983 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 984 if (getChildCount() == 0) return 0; 985 986 int height = getHeight(); 987 int screenTop = getScrollY(); 988 int screenBottom = screenTop + height; 989 990 int fadingEdge = getVerticalFadingEdgeLength(); 991 992 // leave room for top fading edge as long as rect isn't at very top 993 if (rect.top > 0) { 994 screenTop += fadingEdge; 995 } 996 997 // leave room for bottom fading edge as long as rect isn't at very bottom 998 if (rect.bottom < getChildAt(0).getHeight()) { 999 screenBottom -= fadingEdge; 1000 } 1001 1002 int scrollYDelta = 0; 1003 1004 if (rect.bottom > screenBottom && rect.top > screenTop) { 1005 // need to move down to get it in view: move down just enough so 1006 // that the entire rectangle is in view (or at least the first 1007 // screen size chunk). 1008 1009 if (rect.height() > height) { 1010 // just enough to get screen size chunk on 1011 scrollYDelta += (rect.top - screenTop); 1012 } else { 1013 // get entire rect at bottom of screen 1014 scrollYDelta += (rect.bottom - screenBottom); 1015 } 1016 1017 // make sure we aren't scrolling beyond the end of our content 1018 int bottom = getChildAt(0).getBottom(); 1019 int distanceToBottom = bottom - screenBottom; 1020 scrollYDelta = Math.min(scrollYDelta, distanceToBottom); 1021 1022 } else if (rect.top < screenTop && rect.bottom < screenBottom) { 1023 // need to move up to get it in view: move up just enough so that 1024 // entire rectangle is in view (or at least the first screen 1025 // size chunk of it). 1026 1027 if (rect.height() > height) { 1028 // screen size chunk 1029 scrollYDelta -= (screenBottom - rect.bottom); 1030 } else { 1031 // entire rect at top 1032 scrollYDelta -= (screenTop - rect.top); 1033 } 1034 1035 // make sure we aren't scrolling any further than the top our content 1036 scrollYDelta = Math.max(scrollYDelta, -getScrollY()); 1037 } 1038 return scrollYDelta; 1039 } 1040 1041 @Override requestChildFocus(View child, View focused)1042 public void requestChildFocus(View child, View focused) { 1043 if (!mScrollViewMovedFocus) { 1044 if (!mIsLayoutDirty) { 1045 scrollToChild(focused); 1046 } else { 1047 // The child may not be laid out yet, we can't compute the scroll yet 1048 mChildToScrollTo = focused; 1049 } 1050 } 1051 super.requestChildFocus(child, focused); 1052 } 1053 1054 1055 /** 1056 * When looking for focus in children of a scroll view, need to be a little 1057 * more careful not to give focus to something that is scrolled off screen. 1058 * 1059 * This is more expensive than the default {@link android.view.ViewGroup} 1060 * implementation, otherwise this behavior might have been made the default. 1061 */ 1062 @Override onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect)1063 protected boolean onRequestFocusInDescendants(int direction, 1064 Rect previouslyFocusedRect) { 1065 1066 // convert from forward / backward notation to up / down / left / right 1067 // (ugh). 1068 if (direction == View.FOCUS_FORWARD) { 1069 direction = View.FOCUS_DOWN; 1070 } else if (direction == View.FOCUS_BACKWARD) { 1071 direction = View.FOCUS_UP; 1072 } 1073 1074 final View nextFocus = previouslyFocusedRect == null ? 1075 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1076 FocusFinder.getInstance().findNextFocusFromRect(this, 1077 previouslyFocusedRect, direction); 1078 1079 if (nextFocus == null) { 1080 return false; 1081 } 1082 1083 if (isOffScreen(nextFocus)) { 1084 return false; 1085 } 1086 1087 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1088 } 1089 1090 @Override requestChildRectangleOnScreen(View child, Rect rectangle, boolean immediate)1091 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1092 boolean immediate) { 1093 // offset into coordinate space of this scroll view 1094 rectangle.offset(child.getLeft() - child.getScrollX(), 1095 child.getTop() - child.getScrollY()); 1096 1097 return scrollToChildRect(rectangle, immediate); 1098 } 1099 1100 @Override requestLayout()1101 public void requestLayout() { 1102 mIsLayoutDirty = true; 1103 super.requestLayout(); 1104 } 1105 1106 @Override onLayout(boolean changed, int l, int t, int r, int b)1107 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1108 super.onLayout(changed, l, t, r, b); 1109 mIsLayoutDirty = false; 1110 // Give a child focus if it needs it 1111 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1112 scrollToChild(mChildToScrollTo); 1113 } 1114 mChildToScrollTo = null; 1115 1116 // Calling this with the present values causes it to re-clam them 1117 scrollTo(mScrollX, mScrollY); 1118 } 1119 1120 @Override onSizeChanged(int w, int h, int oldw, int oldh)1121 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1122 super.onSizeChanged(w, h, oldw, oldh); 1123 1124 View currentFocused = findFocus(); 1125 if (null == currentFocused || this == currentFocused) 1126 return; 1127 1128 // If the currently-focused view was visible on the screen when the 1129 // screen was at the old height, then scroll the screen to make that 1130 // view visible with the new screen height. 1131 if (isWithinDeltaOfScreen(currentFocused, 0, oldh)) { 1132 currentFocused.getDrawingRect(mTempRect); 1133 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1134 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1135 doScrollY(scrollDelta); 1136 } 1137 } 1138 1139 /** 1140 * Return true if child is an descendant of parent, (or equal to the parent). 1141 */ isViewDescendantOf(View child, View parent)1142 private boolean isViewDescendantOf(View child, View parent) { 1143 if (child == parent) { 1144 return true; 1145 } 1146 1147 final ViewParent theParent = child.getParent(); 1148 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1149 } 1150 1151 /** 1152 * Fling the scroll view 1153 * 1154 * @param velocityY The initial velocity in the Y direction. Positive 1155 * numbers mean that the finger/curor is moving down the screen, 1156 * which means we want to scroll towards the top. 1157 */ fling(int velocityY)1158 public void fling(int velocityY) { 1159 if (getChildCount() > 0) { 1160 int height = getHeight() - mPaddingBottom - mPaddingTop; 1161 int bottom = getChildAt(0).getHeight(); 1162 1163 mScroller.fling(mScrollX, mScrollY, 0, velocityY, 0, 0, 0, bottom - height); 1164 1165 final boolean movingDown = velocityY > 0; 1166 1167 View newFocused = 1168 findFocusableViewInMyBounds(movingDown, mScroller.getFinalY(), findFocus()); 1169 if (newFocused == null) { 1170 newFocused = this; 1171 } 1172 1173 if (newFocused != findFocus() 1174 && newFocused.requestFocus(movingDown ? View.FOCUS_DOWN : View.FOCUS_UP)) { 1175 mScrollViewMovedFocus = true; 1176 mScrollViewMovedFocus = false; 1177 } 1178 1179 awakenScrollBars(mScroller.getDuration()); 1180 invalidate(); 1181 } 1182 } 1183 1184 /** 1185 * {@inheritDoc} 1186 * 1187 * <p>This version also clamps the scrolling to the bounds of our child. 1188 */ scrollTo(int x, int y)1189 public void scrollTo(int x, int y) { 1190 // we rely on the fact the View.scrollBy calls scrollTo. 1191 if (getChildCount() > 0) { 1192 View child = getChildAt(0); 1193 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1194 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1195 if (x != mScrollX || y != mScrollY) { 1196 super.scrollTo(x, y); 1197 } 1198 } 1199 } 1200 clamp(int n, int my, int child)1201 private int clamp(int n, int my, int child) { 1202 if (my >= child || n < 0) { 1203 /* my >= child is this case: 1204 * |--------------- me ---------------| 1205 * |------ child ------| 1206 * or 1207 * |--------------- me ---------------| 1208 * |------ child ------| 1209 * or 1210 * |--------------- me ---------------| 1211 * |------ child ------| 1212 * 1213 * n < 0 is this case: 1214 * |------ me ------| 1215 * |-------- child --------| 1216 * |-- mScrollX --| 1217 */ 1218 return 0; 1219 } 1220 if ((my+n) > child) { 1221 /* this case: 1222 * |------ me ------| 1223 * |------ child ------| 1224 * |-- mScrollX --| 1225 */ 1226 return child-my; 1227 } 1228 return n; 1229 } 1230 } 1231