HorizontalScrollView.java revision 9d0335b1e3a2c70506db2413ac8d8a0f88ba6bec
1/* 2 * Copyright (C) 2009 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 android.util.AttributeSet; 20import android.graphics.Rect; 21import android.view.View; 22import android.view.VelocityTracker; 23import android.view.ViewConfiguration; 24import android.view.ViewGroup; 25import android.view.KeyEvent; 26import android.view.FocusFinder; 27import android.view.MotionEvent; 28import android.view.ViewParent; 29import android.view.animation.AnimationUtils; 30import android.content.Context; 31import android.content.res.TypedArray; 32 33import java.util.List; 34 35/** 36 * Layout container for a view hierarchy that can be scrolled by the user, 37 * allowing it to be larger than the physical display. A HorizontalScrollView 38 * is a {@link FrameLayout}, meaning you should place one child in it 39 * containing the entire contents to scroll; this child may itself be a layout 40 * manager with a complex hierarchy of objects. A child that is often used 41 * is a {@link LinearLayout} in a horizontal orientation, presenting a horizontal 42 * array of top-level items that the user can scroll through. 43 * 44 * <p>You should never use a HorizontalScrollView with a {@link ListView}, since 45 * ListView takes care of its own scrolling. Most importantly, doing this 46 * defeats all of the important optimizations in ListView for dealing with 47 * large lists, since it effectively forces the ListView to display its entire 48 * list of items to fill up the infinite container supplied by HorizontalScrollView. 49 * 50 * <p>The {@link TextView} class also 51 * takes care of its own scrolling, so does not require a ScrollView, but 52 * using the two together is possible to achieve the effect of a text view 53 * within a larger container. 54 * 55 * <p>HorizontalScrollView only supports horizontal scrolling. 56 */ 57public class HorizontalScrollView extends FrameLayout { 58 private static final int ANIMATED_SCROLL_GAP = ScrollView.ANIMATED_SCROLL_GAP; 59 60 private static final float MAX_SCROLL_FACTOR = ScrollView.MAX_SCROLL_FACTOR; 61 62 63 private long mLastScroll; 64 65 private final Rect mTempRect = new Rect(); 66 private OverScroller mScroller; 67 68 /** 69 * Flag to indicate that we are moving focus ourselves. This is so the 70 * code that watches for focus changes initiated outside this ScrollView 71 * knows that it does not have to do anything. 72 */ 73 private boolean mScrollViewMovedFocus; 74 75 /** 76 * Position of the last motion event. 77 */ 78 private float mLastMotionX; 79 80 /** 81 * True when the layout has changed but the traversal has not come through yet. 82 * Ideally the view hierarchy would keep track of this for us. 83 */ 84 private boolean mIsLayoutDirty = true; 85 86 /** 87 * The child to give focus to in the event that a child has requested focus while the 88 * layout is dirty. This prevents the scroll from being wrong if the child has not been 89 * laid out before requesting focus. 90 */ 91 private View mChildToScrollTo = null; 92 93 /** 94 * True if the user is currently dragging this ScrollView around. This is 95 * not the same as 'is being flinged', which can be checked by 96 * mScroller.isFinished() (flinging begins when the user lifts his finger). 97 */ 98 private boolean mIsBeingDragged = false; 99 100 /** 101 * Determines speed during touch scrolling 102 */ 103 private VelocityTracker mVelocityTracker; 104 105 /** 106 * When set to true, the scroll view measure its child to make it fill the currently 107 * visible area. 108 */ 109 private boolean mFillViewport; 110 111 /** 112 * Whether arrow scrolling is animated. 113 */ 114 private boolean mSmoothScrollingEnabled = true; 115 116 private int mTouchSlop; 117 private int mMinimumVelocity; 118 private int mMaximumVelocity; 119 120 /** 121 * ID of the active pointer. This is used to retain consistency during 122 * drags/flings if multiple pointers are used. 123 */ 124 private int mActivePointerId = INVALID_POINTER; 125 126 /** 127 * Sentinel value for no current active pointer. 128 * Used by {@link #mActivePointerId}. 129 */ 130 private static final int INVALID_POINTER = -1; 131 132 public HorizontalScrollView(Context context) { 133 this(context, null); 134 } 135 136 public HorizontalScrollView(Context context, AttributeSet attrs) { 137 this(context, attrs, com.android.internal.R.attr.horizontalScrollViewStyle); 138 } 139 140 public HorizontalScrollView(Context context, AttributeSet attrs, int defStyle) { 141 super(context, attrs, defStyle); 142 initScrollView(); 143 144 TypedArray a = context.obtainStyledAttributes(attrs, 145 android.R.styleable.HorizontalScrollView, defStyle, 0); 146 147 setFillViewport(a.getBoolean(android.R.styleable.HorizontalScrollView_fillViewport, false)); 148 149 a.recycle(); 150 } 151 152 @Override 153 protected float getLeftFadingEdgeStrength() { 154 if (getChildCount() == 0) { 155 return 0.0f; 156 } 157 158 final int length = getHorizontalFadingEdgeLength(); 159 if (mScrollX < length) { 160 return mScrollX / (float) length; 161 } 162 163 return 1.0f; 164 } 165 166 @Override 167 protected float getRightFadingEdgeStrength() { 168 if (getChildCount() == 0) { 169 return 0.0f; 170 } 171 172 final int length = getHorizontalFadingEdgeLength(); 173 final int rightEdge = getWidth() - mPaddingRight; 174 final int span = getChildAt(0).getRight() - mScrollX - rightEdge; 175 if (span < length) { 176 return span / (float) length; 177 } 178 179 return 1.0f; 180 } 181 182 /** 183 * @return The maximum amount this scroll view will scroll in response to 184 * an arrow event. 185 */ 186 public int getMaxScrollAmount() { 187 return (int) (MAX_SCROLL_FACTOR * (mRight - mLeft)); 188 } 189 190 191 private void initScrollView() { 192 mScroller = new OverScroller(getContext()); 193 setFocusable(true); 194 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 195 setWillNotDraw(false); 196 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 197 mTouchSlop = configuration.getScaledTouchSlop(); 198 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 199 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 200 } 201 202 @Override 203 public void addView(View child) { 204 if (getChildCount() > 0) { 205 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 206 } 207 208 super.addView(child); 209 } 210 211 @Override 212 public void addView(View child, int index) { 213 if (getChildCount() > 0) { 214 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 215 } 216 217 super.addView(child, index); 218 } 219 220 @Override 221 public void addView(View child, ViewGroup.LayoutParams params) { 222 if (getChildCount() > 0) { 223 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 224 } 225 226 super.addView(child, params); 227 } 228 229 @Override 230 public void addView(View child, int index, ViewGroup.LayoutParams params) { 231 if (getChildCount() > 0) { 232 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 233 } 234 235 super.addView(child, index, params); 236 } 237 238 /** 239 * @return Returns true this HorizontalScrollView can be scrolled 240 */ 241 private boolean canScroll() { 242 View child = getChildAt(0); 243 if (child != null) { 244 int childWidth = child.getWidth(); 245 return getWidth() < childWidth + mPaddingLeft + mPaddingRight ; 246 } 247 return false; 248 } 249 250 /** 251 * Indicates whether this ScrollView's content is stretched to fill the viewport. 252 * 253 * @return True if the content fills the viewport, false otherwise. 254 */ 255 public boolean isFillViewport() { 256 return mFillViewport; 257 } 258 259 /** 260 * Indicates this ScrollView whether it should stretch its content width to fill 261 * the viewport or not. 262 * 263 * @param fillViewport True to stretch the content's width to the viewport's 264 * boundaries, false otherwise. 265 */ 266 public void setFillViewport(boolean fillViewport) { 267 if (fillViewport != mFillViewport) { 268 mFillViewport = fillViewport; 269 requestLayout(); 270 } 271 } 272 273 /** 274 * @return Whether arrow scrolling will animate its transition. 275 */ 276 public boolean isSmoothScrollingEnabled() { 277 return mSmoothScrollingEnabled; 278 } 279 280 /** 281 * Set whether arrow scrolling will animate its transition. 282 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 283 */ 284 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 285 mSmoothScrollingEnabled = smoothScrollingEnabled; 286 } 287 288 @Override 289 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 290 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 291 292 if (!mFillViewport) { 293 return; 294 } 295 296 final int widthMode = MeasureSpec.getMode(widthMeasureSpec); 297 if (widthMode == MeasureSpec.UNSPECIFIED) { 298 return; 299 } 300 301 if (getChildCount() > 0) { 302 final View child = getChildAt(0); 303 int width = getMeasuredWidth(); 304 if (child.getMeasuredWidth() < width) { 305 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 306 307 int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec, mPaddingTop 308 + mPaddingBottom, lp.height); 309 width -= mPaddingLeft; 310 width -= mPaddingRight; 311 int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY); 312 313 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 314 } 315 } 316 } 317 318 @Override 319 public boolean dispatchKeyEvent(KeyEvent event) { 320 // Let the focused view and/or our descendants get the key first 321 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 322 } 323 324 /** 325 * You can call this function yourself to have the scroll view perform 326 * scrolling from a key event, just as if the event had been dispatched to 327 * it by the view hierarchy. 328 * 329 * @param event The key event to execute. 330 * @return Return true if the event was handled, else false. 331 */ 332 public boolean executeKeyEvent(KeyEvent event) { 333 mTempRect.setEmpty(); 334 335 if (!canScroll()) { 336 if (isFocused()) { 337 View currentFocused = findFocus(); 338 if (currentFocused == this) currentFocused = null; 339 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 340 currentFocused, View.FOCUS_RIGHT); 341 return nextFocused != null && nextFocused != this && 342 nextFocused.requestFocus(View.FOCUS_RIGHT); 343 } 344 return false; 345 } 346 347 boolean handled = false; 348 if (event.getAction() == KeyEvent.ACTION_DOWN) { 349 switch (event.getKeyCode()) { 350 case KeyEvent.KEYCODE_DPAD_LEFT: 351 if (!event.isAltPressed()) { 352 handled = arrowScroll(View.FOCUS_LEFT); 353 } else { 354 handled = fullScroll(View.FOCUS_LEFT); 355 } 356 break; 357 case KeyEvent.KEYCODE_DPAD_RIGHT: 358 if (!event.isAltPressed()) { 359 handled = arrowScroll(View.FOCUS_RIGHT); 360 } else { 361 handled = fullScroll(View.FOCUS_RIGHT); 362 } 363 break; 364 case KeyEvent.KEYCODE_SPACE: 365 pageScroll(event.isShiftPressed() ? View.FOCUS_LEFT : View.FOCUS_RIGHT); 366 break; 367 } 368 } 369 370 return handled; 371 } 372 373 private boolean inChild(int x, int y) { 374 if (getChildCount() > 0) { 375 final View child = getChildAt(0); 376 return !(y < child.getTop() 377 || y >= child.getBottom() 378 || x < child.getLeft() 379 || x >= child.getRight()); 380 } 381 return false; 382 } 383 384 @Override 385 public boolean onInterceptTouchEvent(MotionEvent ev) { 386 /* 387 * This method JUST determines whether we want to intercept the motion. 388 * If we return true, onMotionEvent will be called and we do the actual 389 * scrolling there. 390 */ 391 392 /* 393 * Shortcut the most recurring case: the user is in the dragging 394 * state and he is moving his finger. We want to intercept this 395 * motion. 396 */ 397 final int action = ev.getAction(); 398 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 399 return true; 400 } 401 402 switch (action & MotionEvent.ACTION_MASK) { 403 case MotionEvent.ACTION_MOVE: { 404 /* 405 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 406 * whether the user has moved far enough from his original down touch. 407 */ 408 409 /* 410 * Locally do absolute value. mLastMotionX is set to the x value 411 * of the down event. 412 */ 413 final int activePointerId = mActivePointerId; 414 if (activePointerId == INVALID_POINTER) { 415 // If we don't have a valid id, the touch down wasn't on content. 416 break; 417 } 418 419 final int pointerIndex = ev.findPointerIndex(activePointerId); 420 final float x = ev.getX(pointerIndex); 421 final int xDiff = (int) Math.abs(x - mLastMotionX); 422 if (xDiff > mTouchSlop) { 423 mIsBeingDragged = true; 424 mLastMotionX = x; 425 if (mParent != null) mParent.requestDisallowInterceptTouchEvent(true); 426 } 427 break; 428 } 429 430 case MotionEvent.ACTION_DOWN: { 431 final float x = ev.getX(); 432 if (!inChild((int) x, (int) ev.getY())) { 433 mIsBeingDragged = false; 434 break; 435 } 436 437 /* 438 * Remember location of down touch. 439 * ACTION_DOWN always refers to pointer index 0. 440 */ 441 mLastMotionX = x; 442 mActivePointerId = ev.getPointerId(0); 443 444 /* 445 * If being flinged and user touches the screen, initiate drag; 446 * otherwise don't. mScroller.isFinished should be false when 447 * being flinged. 448 */ 449 mIsBeingDragged = !mScroller.isFinished(); 450 break; 451 } 452 453 case MotionEvent.ACTION_CANCEL: 454 case MotionEvent.ACTION_UP: 455 /* Release the drag */ 456 mIsBeingDragged = false; 457 mActivePointerId = INVALID_POINTER; 458 break; 459 case MotionEvent.ACTION_POINTER_UP: 460 onSecondaryPointerUp(ev); 461 break; 462 } 463 464 /* 465 * The only time we want to intercept motion events is if we are in the 466 * drag mode. 467 */ 468 return mIsBeingDragged; 469 } 470 471 @Override 472 public boolean onTouchEvent(MotionEvent ev) { 473 474 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 475 // Don't handle edge touches immediately -- they may actually belong to one of our 476 // descendants. 477 return false; 478 } 479 480 if (mVelocityTracker == null) { 481 mVelocityTracker = VelocityTracker.obtain(); 482 } 483 mVelocityTracker.addMovement(ev); 484 485 final int action = ev.getAction(); 486 487 switch (action & MotionEvent.ACTION_MASK) { 488 case MotionEvent.ACTION_DOWN: { 489 /* 490 * If being flinged and user touches, stop the fling. isFinished 491 * will be false if being flinged. 492 */ 493 if (!mScroller.isFinished()) { 494 mScroller.abortAnimation(); 495 } 496 497 final float x = ev.getX(); 498 if (!(mIsBeingDragged = inChild((int) x, (int) ev.getY()))) { 499 return false; 500 } 501 502 // Remember where the motion event started 503 mLastMotionX = x; 504 break; 505 } 506 case MotionEvent.ACTION_MOVE: 507 if (mIsBeingDragged) { 508 // Scroll to follow the motion event 509 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 510 final float x = ev.getX(activePointerIndex); 511 final int deltaX = (int) (mLastMotionX - x); 512 mLastMotionX = x; 513 514 final int oldX = mScrollX; 515 final int oldY = mScrollY; 516 overscrollBy(deltaX, 0, mScrollX, 0, getScrollRange(), 0, 517 getOverscrollMax(), 0, true); 518 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 519 } 520 break; 521 case MotionEvent.ACTION_UP: 522 if (mIsBeingDragged) { 523 final VelocityTracker velocityTracker = mVelocityTracker; 524 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 525 int initialVelocity = (int) velocityTracker.getXVelocity(mActivePointerId); 526 527 if (getChildCount() > 0) { 528 if ((Math.abs(initialVelocity) > mMinimumVelocity)) { 529 fling(-initialVelocity); 530 } else { 531 final int right = getScrollRange(); 532 if (mScroller.springback(mScrollX, mScrollY, 0, right, 0, 0)) { 533 invalidate(); 534 } 535 } 536 } 537 538 mActivePointerId = INVALID_POINTER; 539 mIsBeingDragged = false; 540 541 if (mVelocityTracker != null) { 542 mVelocityTracker.recycle(); 543 mVelocityTracker = null; 544 } 545 } 546 break; 547 case MotionEvent.ACTION_POINTER_UP: 548 onSecondaryPointerUp(ev); 549 break; 550 } 551 return true; 552 } 553 554 private void onSecondaryPointerUp(MotionEvent ev) { 555 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 556 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 557 final int pointerId = ev.getPointerId(pointerIndex); 558 if (pointerId == mActivePointerId) { 559 // This was our active pointer going up. Choose a new 560 // active pointer and adjust accordingly. 561 // TODO: Make this decision more intelligent. 562 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 563 mLastMotionX = ev.getX(newPointerIndex); 564 mActivePointerId = ev.getPointerId(newPointerIndex); 565 if (mVelocityTracker != null) { 566 mVelocityTracker.clear(); 567 } 568 } 569 } 570 571 @Override 572 protected void onOverscrolled(int scrollX, int scrollY, 573 boolean clampedX, boolean clampedY) { 574 // Treat animating scrolls differently; see #computeScroll() for why. 575 if (!mScroller.isFinished()) { 576 mScrollX = scrollX; 577 mScrollY = scrollY; 578 if (clampedX) { 579 mScroller.springback(mScrollX, mScrollY, 0, getScrollRange(), 0, 0); 580 } 581 } else { 582 super.scrollTo(scrollX, scrollY); 583 } 584 } 585 586 private int getOverscrollMax() { 587 int childCount = getChildCount(); 588 int containerOverscroll = (getWidth() - mPaddingLeft - mPaddingRight) / 3; 589 if (childCount > 0) { 590 return Math.min(containerOverscroll, getChildAt(0).getWidth() / 3); 591 } else { 592 return containerOverscroll; 593 } 594 } 595 596 private int getScrollRange() { 597 int scrollRange = 0; 598 if (getChildCount() > 0) { 599 View child = getChildAt(0); 600 scrollRange = Math.max(0, 601 child.getWidth() - getWidth() - mPaddingLeft - mPaddingRight); 602 } 603 return scrollRange; 604 } 605 606 /** 607 * <p> 608 * Finds the next focusable component that fits in this View's bounds 609 * (excluding fading edges) pretending that this View's left is located at 610 * the parameter left. 611 * </p> 612 * 613 * @param leftFocus look for a candidate is the one at the left of the bounds 614 * if leftFocus is true, or at the right of the bounds if leftFocus 615 * is false 616 * @param left the left offset of the bounds in which a focusable must be 617 * found (the fading edge is assumed to start at this position) 618 * @param preferredFocusable the View that has highest priority and will be 619 * returned if it is within my bounds (null is valid) 620 * @return the next focusable component in the bounds or null if none can be found 621 */ 622 private View findFocusableViewInMyBounds(final boolean leftFocus, 623 final int left, View preferredFocusable) { 624 /* 625 * The fading edge's transparent side should be considered for focus 626 * since it's mostly visible, so we divide the actual fading edge length 627 * by 2. 628 */ 629 final int fadingEdgeLength = getHorizontalFadingEdgeLength() / 2; 630 final int leftWithoutFadingEdge = left + fadingEdgeLength; 631 final int rightWithoutFadingEdge = left + getWidth() - fadingEdgeLength; 632 633 if ((preferredFocusable != null) 634 && (preferredFocusable.getLeft() < rightWithoutFadingEdge) 635 && (preferredFocusable.getRight() > leftWithoutFadingEdge)) { 636 return preferredFocusable; 637 } 638 639 return findFocusableViewInBounds(leftFocus, leftWithoutFadingEdge, 640 rightWithoutFadingEdge); 641 } 642 643 /** 644 * <p> 645 * Finds the next focusable component that fits in the specified bounds. 646 * </p> 647 * 648 * @param leftFocus look for a candidate is the one at the left of the bounds 649 * if leftFocus is true, or at the right of the bounds if 650 * leftFocus is false 651 * @param left the left offset of the bounds in which a focusable must be 652 * found 653 * @param right the right offset of the bounds in which a focusable must 654 * be found 655 * @return the next focusable component in the bounds or null if none can 656 * be found 657 */ 658 private View findFocusableViewInBounds(boolean leftFocus, int left, int right) { 659 660 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 661 View focusCandidate = null; 662 663 /* 664 * A fully contained focusable is one where its left is below the bound's 665 * left, and its right is above the bound's right. A partially 666 * contained focusable is one where some part of it is within the 667 * bounds, but it also has some part that is not within bounds. A fully contained 668 * focusable is preferred to a partially contained focusable. 669 */ 670 boolean foundFullyContainedFocusable = false; 671 672 int count = focusables.size(); 673 for (int i = 0; i < count; i++) { 674 View view = focusables.get(i); 675 int viewLeft = view.getLeft(); 676 int viewRight = view.getRight(); 677 678 if (left < viewRight && viewLeft < right) { 679 /* 680 * the focusable is in the target area, it is a candidate for 681 * focusing 682 */ 683 684 final boolean viewIsFullyContained = (left < viewLeft) && 685 (viewRight < right); 686 687 if (focusCandidate == null) { 688 /* No candidate, take this one */ 689 focusCandidate = view; 690 foundFullyContainedFocusable = viewIsFullyContained; 691 } else { 692 final boolean viewIsCloserToBoundary = 693 (leftFocus && viewLeft < focusCandidate.getLeft()) || 694 (!leftFocus && viewRight > focusCandidate.getRight()); 695 696 if (foundFullyContainedFocusable) { 697 if (viewIsFullyContained && viewIsCloserToBoundary) { 698 /* 699 * We're dealing with only fully contained views, so 700 * it has to be closer to the boundary to beat our 701 * candidate 702 */ 703 focusCandidate = view; 704 } 705 } else { 706 if (viewIsFullyContained) { 707 /* Any fully contained view beats a partially contained view */ 708 focusCandidate = view; 709 foundFullyContainedFocusable = true; 710 } else if (viewIsCloserToBoundary) { 711 /* 712 * Partially contained view beats another partially 713 * contained view if it's closer 714 */ 715 focusCandidate = view; 716 } 717 } 718 } 719 } 720 } 721 722 return focusCandidate; 723 } 724 725 /** 726 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 727 * method will scroll the view by one page left or right and give the focus 728 * to the leftmost/rightmost component in the new visible area. If no 729 * component is a good candidate for focus, this scrollview reclaims the 730 * focus.</p> 731 * 732 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 733 * to go one page left or {@link android.view.View#FOCUS_RIGHT} 734 * to go one page right 735 * @return true if the key event is consumed by this method, false otherwise 736 */ 737 public boolean pageScroll(int direction) { 738 boolean right = direction == View.FOCUS_RIGHT; 739 int width = getWidth(); 740 741 if (right) { 742 mTempRect.left = getScrollX() + width; 743 int count = getChildCount(); 744 if (count > 0) { 745 View view = getChildAt(0); 746 if (mTempRect.left + width > view.getRight()) { 747 mTempRect.left = view.getRight() - width; 748 } 749 } 750 } else { 751 mTempRect.left = getScrollX() - width; 752 if (mTempRect.left < 0) { 753 mTempRect.left = 0; 754 } 755 } 756 mTempRect.right = mTempRect.left + width; 757 758 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 759 } 760 761 /** 762 * <p>Handles scrolling in response to a "home/end" shortcut press. This 763 * method will scroll the view to the left or right and give the focus 764 * to the leftmost/rightmost component in the new visible area. If no 765 * component is a good candidate for focus, this scrollview reclaims the 766 * focus.</p> 767 * 768 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 769 * to go the left of the view or {@link android.view.View#FOCUS_RIGHT} 770 * to go the right 771 * @return true if the key event is consumed by this method, false otherwise 772 */ 773 public boolean fullScroll(int direction) { 774 boolean right = direction == View.FOCUS_RIGHT; 775 int width = getWidth(); 776 777 mTempRect.left = 0; 778 mTempRect.right = width; 779 780 if (right) { 781 int count = getChildCount(); 782 if (count > 0) { 783 View view = getChildAt(0); 784 mTempRect.right = view.getRight(); 785 mTempRect.left = mTempRect.right - width; 786 } 787 } 788 789 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 790 } 791 792 /** 793 * <p>Scrolls the view to make the area defined by <code>left</code> and 794 * <code>right</code> visible. This method attempts to give the focus 795 * to a component visible in this area. If no component can be focused in 796 * the new visible area, the focus is reclaimed by this scrollview.</p> 797 * 798 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 799 * to go left {@link android.view.View#FOCUS_RIGHT} to right 800 * @param left the left offset of the new area to be made visible 801 * @param right the right offset of the new area to be made visible 802 * @return true if the key event is consumed by this method, false otherwise 803 */ 804 private boolean scrollAndFocus(int direction, int left, int right) { 805 boolean handled = true; 806 807 int width = getWidth(); 808 int containerLeft = getScrollX(); 809 int containerRight = containerLeft + width; 810 boolean goLeft = direction == View.FOCUS_LEFT; 811 812 View newFocused = findFocusableViewInBounds(goLeft, left, right); 813 if (newFocused == null) { 814 newFocused = this; 815 } 816 817 if (left >= containerLeft && right <= containerRight) { 818 handled = false; 819 } else { 820 int delta = goLeft ? (left - containerLeft) : (right - containerRight); 821 doScrollX(delta); 822 } 823 824 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 825 mScrollViewMovedFocus = true; 826 mScrollViewMovedFocus = false; 827 } 828 829 return handled; 830 } 831 832 /** 833 * Handle scrolling in response to a left or right arrow click. 834 * 835 * @param direction The direction corresponding to the arrow key that was 836 * pressed 837 * @return True if we consumed the event, false otherwise 838 */ 839 public boolean arrowScroll(int direction) { 840 841 View currentFocused = findFocus(); 842 if (currentFocused == this) currentFocused = null; 843 844 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 845 846 final int maxJump = getMaxScrollAmount(); 847 848 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 849 nextFocused.getDrawingRect(mTempRect); 850 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 851 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 852 doScrollX(scrollDelta); 853 nextFocused.requestFocus(direction); 854 } else { 855 // no new focus 856 int scrollDelta = maxJump; 857 858 if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) { 859 scrollDelta = getScrollX(); 860 } else if (direction == View.FOCUS_RIGHT && getChildCount() > 0) { 861 862 int daRight = getChildAt(0).getRight(); 863 864 int screenRight = getScrollX() + getWidth(); 865 866 if (daRight - screenRight < maxJump) { 867 scrollDelta = daRight - screenRight; 868 } 869 } 870 if (scrollDelta == 0) { 871 return false; 872 } 873 doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta); 874 } 875 876 if (currentFocused != null && currentFocused.isFocused() 877 && isOffScreen(currentFocused)) { 878 // previously focused item still has focus and is off screen, give 879 // it up (take it back to ourselves) 880 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 881 // sure to 882 // get it) 883 final int descendantFocusability = getDescendantFocusability(); // save 884 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 885 requestFocus(); 886 setDescendantFocusability(descendantFocusability); // restore 887 } 888 return true; 889 } 890 891 /** 892 * @return whether the descendant of this scroll view is scrolled off 893 * screen. 894 */ 895 private boolean isOffScreen(View descendant) { 896 return !isWithinDeltaOfScreen(descendant, 0); 897 } 898 899 /** 900 * @return whether the descendant of this scroll view is within delta 901 * pixels of being on the screen. 902 */ 903 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 904 descendant.getDrawingRect(mTempRect); 905 offsetDescendantRectToMyCoords(descendant, mTempRect); 906 907 return (mTempRect.right + delta) >= getScrollX() 908 && (mTempRect.left - delta) <= (getScrollX() + getWidth()); 909 } 910 911 /** 912 * Smooth scroll by a X delta 913 * 914 * @param delta the number of pixels to scroll by on the X axis 915 */ 916 private void doScrollX(int delta) { 917 if (delta != 0) { 918 if (mSmoothScrollingEnabled) { 919 smoothScrollBy(delta, 0); 920 } else { 921 scrollBy(delta, 0); 922 } 923 } 924 } 925 926 /** 927 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 928 * 929 * @param dx the number of pixels to scroll by on the X axis 930 * @param dy the number of pixels to scroll by on the Y axis 931 */ 932 public final void smoothScrollBy(int dx, int dy) { 933 if (getChildCount() == 0) { 934 // Nothing to do. 935 return; 936 } 937 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 938 if (duration > ANIMATED_SCROLL_GAP) { 939 final int width = getWidth() - mPaddingRight - mPaddingLeft; 940 final int right = getChildAt(0).getWidth(); 941 final int maxX = Math.max(0, right - width); 942 final int scrollX = mScrollX; 943 dx = Math.max(0, Math.min(scrollX + dx, maxX)) - scrollX; 944 945 mScroller.startScroll(scrollX, mScrollY, dx, 0); 946 awakenScrollBars(mScroller.getDuration()); 947 invalidate(); 948 } else { 949 if (!mScroller.isFinished()) { 950 mScroller.abortAnimation(); 951 } 952 scrollBy(dx, dy); 953 } 954 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 955 } 956 957 /** 958 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 959 * 960 * @param x the position where to scroll on the X axis 961 * @param y the position where to scroll on the Y axis 962 */ 963 public final void smoothScrollTo(int x, int y) { 964 smoothScrollBy(x - mScrollX, y - mScrollY); 965 } 966 967 /** 968 * <p>The scroll range of a scroll view is the overall width of all of its 969 * children.</p> 970 */ 971 @Override 972 protected int computeHorizontalScrollRange() { 973 final int count = getChildCount(); 974 final int contentWidth = getWidth() - mPaddingLeft - mPaddingRight; 975 if (count == 0) { 976 return contentWidth; 977 } 978 979 int scrollRange = getChildAt(0).getRight(); 980 final int scrollX = mScrollX; 981 final int overscrollRight = Math.max(0, scrollRange - contentWidth); 982 if (scrollX < 0) { 983 scrollRange -= scrollX; 984 } else if (scrollX > overscrollRight) { 985 scrollRange += scrollX - overscrollRight; 986 } 987 988 return scrollRange; 989 } 990 991 @Override 992 protected int computeHorizontalScrollOffset() { 993 return Math.max(0, super.computeHorizontalScrollOffset()); 994 } 995 996 @Override 997 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 998 ViewGroup.LayoutParams lp = child.getLayoutParams(); 999 1000 int childWidthMeasureSpec; 1001 int childHeightMeasureSpec; 1002 1003 childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop 1004 + mPaddingBottom, lp.height); 1005 1006 childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 1007 1008 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1009 } 1010 1011 @Override 1012 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 1013 int parentHeightMeasureSpec, int heightUsed) { 1014 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 1015 1016 final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, 1017 mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin 1018 + heightUsed, lp.height); 1019 final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( 1020 lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); 1021 1022 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 1023 } 1024 1025 @Override 1026 public void computeScroll() { 1027 if (mScroller.computeScrollOffset()) { 1028 // This is called at drawing time by ViewGroup. We don't want to 1029 // re-show the scrollbars at this point, which scrollTo will do, 1030 // so we replicate most of scrollTo here. 1031 // 1032 // It's a little odd to call onScrollChanged from inside the drawing. 1033 // 1034 // It is, except when you remember that computeScroll() is used to 1035 // animate scrolling. So unless we want to defer the onScrollChanged() 1036 // until the end of the animated scrolling, we don't really have a 1037 // choice here. 1038 // 1039 // I agree. The alternative, which I think would be worse, is to post 1040 // something and tell the subclasses later. This is bad because there 1041 // will be a window where mScrollX/Y is different from what the app 1042 // thinks it is. 1043 // 1044 int oldX = mScrollX; 1045 int oldY = mScrollY; 1046 int x = mScroller.getCurrX(); 1047 int y = mScroller.getCurrY(); 1048 1049 if (oldX != x || oldY != y) { 1050 overscrollBy(x - oldX, y - oldY, oldX, oldY, getScrollRange(), 0, 1051 getOverscrollMax(), 0, false); 1052 onScrollChanged(mScrollX, mScrollY, oldX, oldY); 1053 } 1054 1055 // Keep on drawing until the animation has finished. 1056 postInvalidate(); 1057 } 1058 } 1059 1060 /** 1061 * Scrolls the view to the given child. 1062 * 1063 * @param child the View to scroll to 1064 */ 1065 private void scrollToChild(View child) { 1066 child.getDrawingRect(mTempRect); 1067 1068 /* Offset from child's local coordinates to ScrollView coordinates */ 1069 offsetDescendantRectToMyCoords(child, mTempRect); 1070 1071 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1072 1073 if (scrollDelta != 0) { 1074 scrollBy(scrollDelta, 0); 1075 } 1076 } 1077 1078 /** 1079 * If rect is off screen, scroll just enough to get it (or at least the 1080 * first screen size chunk of it) on screen. 1081 * 1082 * @param rect The rectangle. 1083 * @param immediate True to scroll immediately without animation 1084 * @return true if scrolling was performed 1085 */ 1086 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1087 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1088 final boolean scroll = delta != 0; 1089 if (scroll) { 1090 if (immediate) { 1091 scrollBy(delta, 0); 1092 } else { 1093 smoothScrollBy(delta, 0); 1094 } 1095 } 1096 return scroll; 1097 } 1098 1099 /** 1100 * Compute the amount to scroll in the X direction in order to get 1101 * a rectangle completely on the screen (or, if taller than the screen, 1102 * at least the first screen size chunk of it). 1103 * 1104 * @param rect The rect. 1105 * @return The scroll delta. 1106 */ 1107 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1108 if (getChildCount() == 0) return 0; 1109 1110 int width = getWidth(); 1111 int screenLeft = getScrollX(); 1112 int screenRight = screenLeft + width; 1113 1114 int fadingEdge = getHorizontalFadingEdgeLength(); 1115 1116 // leave room for left fading edge as long as rect isn't at very left 1117 if (rect.left > 0) { 1118 screenLeft += fadingEdge; 1119 } 1120 1121 // leave room for right fading edge as long as rect isn't at very right 1122 if (rect.right < getChildAt(0).getWidth()) { 1123 screenRight -= fadingEdge; 1124 } 1125 1126 int scrollXDelta = 0; 1127 1128 if (rect.right > screenRight && rect.left > screenLeft) { 1129 // need to move right to get it in view: move right just enough so 1130 // that the entire rectangle is in view (or at least the first 1131 // screen size chunk). 1132 1133 if (rect.width() > width) { 1134 // just enough to get screen size chunk on 1135 scrollXDelta += (rect.left - screenLeft); 1136 } else { 1137 // get entire rect at right of screen 1138 scrollXDelta += (rect.right - screenRight); 1139 } 1140 1141 // make sure we aren't scrolling beyond the end of our content 1142 int right = getChildAt(0).getRight(); 1143 int distanceToRight = right - screenRight; 1144 scrollXDelta = Math.min(scrollXDelta, distanceToRight); 1145 1146 } else if (rect.left < screenLeft && rect.right < screenRight) { 1147 // need to move right to get it in view: move right just enough so that 1148 // entire rectangle is in view (or at least the first screen 1149 // size chunk of it). 1150 1151 if (rect.width() > width) { 1152 // screen size chunk 1153 scrollXDelta -= (screenRight - rect.right); 1154 } else { 1155 // entire rect at left 1156 scrollXDelta -= (screenLeft - rect.left); 1157 } 1158 1159 // make sure we aren't scrolling any further than the left our content 1160 scrollXDelta = Math.max(scrollXDelta, -getScrollX()); 1161 } 1162 return scrollXDelta; 1163 } 1164 1165 @Override 1166 public void requestChildFocus(View child, View focused) { 1167 if (!mScrollViewMovedFocus) { 1168 if (!mIsLayoutDirty) { 1169 scrollToChild(focused); 1170 } else { 1171 // The child may not be laid out yet, we can't compute the scroll yet 1172 mChildToScrollTo = focused; 1173 } 1174 } 1175 super.requestChildFocus(child, focused); 1176 } 1177 1178 1179 /** 1180 * When looking for focus in children of a scroll view, need to be a little 1181 * more careful not to give focus to something that is scrolled off screen. 1182 * 1183 * This is more expensive than the default {@link android.view.ViewGroup} 1184 * implementation, otherwise this behavior might have been made the default. 1185 */ 1186 @Override 1187 protected boolean onRequestFocusInDescendants(int direction, 1188 Rect previouslyFocusedRect) { 1189 1190 // convert from forward / backward notation to up / down / left / right 1191 // (ugh). 1192 if (direction == View.FOCUS_FORWARD) { 1193 direction = View.FOCUS_RIGHT; 1194 } else if (direction == View.FOCUS_BACKWARD) { 1195 direction = View.FOCUS_LEFT; 1196 } 1197 1198 final View nextFocus = previouslyFocusedRect == null ? 1199 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1200 FocusFinder.getInstance().findNextFocusFromRect(this, 1201 previouslyFocusedRect, direction); 1202 1203 if (nextFocus == null) { 1204 return false; 1205 } 1206 1207 if (isOffScreen(nextFocus)) { 1208 return false; 1209 } 1210 1211 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1212 } 1213 1214 @Override 1215 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1216 boolean immediate) { 1217 // offset into coordinate space of this scroll view 1218 rectangle.offset(child.getLeft() - child.getScrollX(), 1219 child.getTop() - child.getScrollY()); 1220 1221 return scrollToChildRect(rectangle, immediate); 1222 } 1223 1224 @Override 1225 public void requestLayout() { 1226 mIsLayoutDirty = true; 1227 super.requestLayout(); 1228 } 1229 1230 @Override 1231 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1232 super.onLayout(changed, l, t, r, b); 1233 mIsLayoutDirty = false; 1234 // Give a child focus if it needs it 1235 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1236 scrollToChild(mChildToScrollTo); 1237 } 1238 mChildToScrollTo = null; 1239 1240 // Calling this with the present values causes it to re-clam them 1241 scrollTo(mScrollX, mScrollY); 1242 } 1243 1244 @Override 1245 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1246 super.onSizeChanged(w, h, oldw, oldh); 1247 1248 View currentFocused = findFocus(); 1249 if (null == currentFocused || this == currentFocused) 1250 return; 1251 1252 final int maxJump = mRight - mLeft; 1253 1254 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1255 currentFocused.getDrawingRect(mTempRect); 1256 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1257 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1258 doScrollX(scrollDelta); 1259 } 1260 } 1261 1262 /** 1263 * Return true if child is an descendant of parent, (or equal to the parent). 1264 */ 1265 private boolean isViewDescendantOf(View child, View parent) { 1266 if (child == parent) { 1267 return true; 1268 } 1269 1270 final ViewParent theParent = child.getParent(); 1271 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1272 } 1273 1274 /** 1275 * Fling the scroll view 1276 * 1277 * @param velocityX The initial velocity in the X direction. Positive 1278 * numbers mean that the finger/curor is moving down the screen, 1279 * which means we want to scroll towards the left. 1280 */ 1281 public void fling(int velocityX) { 1282 if (getChildCount() > 0) { 1283 int width = getWidth() - mPaddingRight - mPaddingLeft; 1284 int right = getChildAt(0).getWidth(); 1285 1286 mScroller.fling(mScrollX, mScrollY, velocityX, 0, 0, 1287 Math.max(0, right - width), 0, 0, width/2, 0); 1288 1289 final boolean movingRight = velocityX > 0; 1290 1291 View newFocused = findFocusableViewInMyBounds(movingRight, 1292 mScroller.getFinalX(), findFocus()); 1293 1294 if (newFocused == null) { 1295 newFocused = this; 1296 } 1297 1298 if (newFocused != findFocus() 1299 && newFocused.requestFocus(movingRight ? View.FOCUS_RIGHT : View.FOCUS_LEFT)) { 1300 mScrollViewMovedFocus = true; 1301 mScrollViewMovedFocus = false; 1302 } 1303 1304 awakenScrollBars(mScroller.getDuration()); 1305 invalidate(); 1306 } 1307 } 1308 1309 /** 1310 * {@inheritDoc} 1311 * 1312 * <p>This version also clamps the scrolling to the bounds of our child. 1313 */ 1314 public void scrollTo(int x, int y) { 1315 // we rely on the fact the View.scrollBy calls scrollTo. 1316 if (getChildCount() > 0) { 1317 View child = getChildAt(0); 1318 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1319 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1320 if (x != mScrollX || y != mScrollY) { 1321 super.scrollTo(x, y); 1322 } 1323 } 1324 } 1325 1326 private int clamp(int n, int my, int child) { 1327 if (my >= child || n < 0) { 1328 return 0; 1329 } 1330 if ((my + n) > child) { 1331 return child - my; 1332 } 1333 return n; 1334 } 1335} 1336