HorizontalScrollView.java revision fdbf484be1eca388553d97a13a9500b98b18b474
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.content.Context; 20import android.content.res.TypedArray; 21import android.graphics.Rect; 22import android.util.AttributeSet; 23import android.view.FocusFinder; 24import android.view.KeyEvent; 25import android.view.MotionEvent; 26import android.view.VelocityTracker; 27import android.view.View; 28import android.view.ViewConfiguration; 29import android.view.ViewGroup; 30import android.view.ViewParent; 31import android.view.animation.AnimationUtils; 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 * 57 * @attr ref android.R.styleable#HorizontalScrollView_fillViewport 58 */ 59public class HorizontalScrollView extends FrameLayout { 60 private static final int ANIMATED_SCROLL_GAP = ScrollView.ANIMATED_SCROLL_GAP; 61 62 private static final float MAX_SCROLL_FACTOR = ScrollView.MAX_SCROLL_FACTOR; 63 64 65 private long mLastScroll; 66 67 private final Rect mTempRect = new Rect(); 68 private Scroller mScroller; 69 70 /** 71 * Flag to indicate that we are moving focus ourselves. This is so the 72 * code that watches for focus changes initiated outside this ScrollView 73 * knows that it does not have to do anything. 74 */ 75 private boolean mScrollViewMovedFocus; 76 77 /** 78 * Position of the last motion event. 79 */ 80 private float mLastMotionX; 81 82 /** 83 * True when the layout has changed but the traversal has not come through yet. 84 * Ideally the view hierarchy would keep track of this for us. 85 */ 86 private boolean mIsLayoutDirty = true; 87 88 /** 89 * The child to give focus to in the event that a child has requested focus while the 90 * layout is dirty. This prevents the scroll from being wrong if the child has not been 91 * laid out before requesting focus. 92 */ 93 private View mChildToScrollTo = null; 94 95 /** 96 * True if the user is currently dragging this ScrollView around. This is 97 * not the same as 'is being flinged', which can be checked by 98 * mScroller.isFinished() (flinging begins when the user lifts his finger). 99 */ 100 private boolean mIsBeingDragged = false; 101 102 /** 103 * Determines speed during touch scrolling 104 */ 105 private VelocityTracker mVelocityTracker; 106 107 /** 108 * When set to true, the scroll view measure its child to make it fill the currently 109 * visible area. 110 */ 111 private boolean mFillViewport; 112 113 /** 114 * Whether arrow scrolling is animated. 115 */ 116 private boolean mSmoothScrollingEnabled = true; 117 118 private int mTouchSlop; 119 private int mMinimumVelocity; 120 private int mMaximumVelocity; 121 122 /** 123 * ID of the active pointer. This is used to retain consistency during 124 * drags/flings if multiple pointers are used. 125 */ 126 private int mActivePointerId = INVALID_POINTER; 127 128 /** 129 * Sentinel value for no current active pointer. 130 * Used by {@link #mActivePointerId}. 131 */ 132 private static final int INVALID_POINTER = -1; 133 134 public HorizontalScrollView(Context context) { 135 this(context, null); 136 } 137 138 public HorizontalScrollView(Context context, AttributeSet attrs) { 139 this(context, attrs, com.android.internal.R.attr.horizontalScrollViewStyle); 140 } 141 142 public HorizontalScrollView(Context context, AttributeSet attrs, int defStyle) { 143 super(context, attrs, defStyle); 144 initScrollView(); 145 146 TypedArray a = context.obtainStyledAttributes(attrs, 147 android.R.styleable.HorizontalScrollView, defStyle, 0); 148 149 setFillViewport(a.getBoolean(android.R.styleable.HorizontalScrollView_fillViewport, false)); 150 151 a.recycle(); 152 } 153 154 @Override 155 protected float getLeftFadingEdgeStrength() { 156 if (getChildCount() == 0) { 157 return 0.0f; 158 } 159 160 final int length = getHorizontalFadingEdgeLength(); 161 if (mScrollX < length) { 162 return mScrollX / (float) length; 163 } 164 165 return 1.0f; 166 } 167 168 @Override 169 protected float getRightFadingEdgeStrength() { 170 if (getChildCount() == 0) { 171 return 0.0f; 172 } 173 174 final int length = getHorizontalFadingEdgeLength(); 175 final int rightEdge = getWidth() - mPaddingRight; 176 final int span = getChildAt(0).getRight() - mScrollX - rightEdge; 177 if (span < length) { 178 return span / (float) length; 179 } 180 181 return 1.0f; 182 } 183 184 /** 185 * @return The maximum amount this scroll view will scroll in response to 186 * an arrow event. 187 */ 188 public int getMaxScrollAmount() { 189 return (int) (MAX_SCROLL_FACTOR * (mRight - mLeft)); 190 } 191 192 193 private void initScrollView() { 194 mScroller = new Scroller(getContext()); 195 setFocusable(true); 196 setDescendantFocusability(FOCUS_AFTER_DESCENDANTS); 197 setWillNotDraw(false); 198 final ViewConfiguration configuration = ViewConfiguration.get(mContext); 199 mTouchSlop = configuration.getScaledTouchSlop(); 200 mMinimumVelocity = configuration.getScaledMinimumFlingVelocity(); 201 mMaximumVelocity = configuration.getScaledMaximumFlingVelocity(); 202 } 203 204 @Override 205 public void addView(View child) { 206 if (getChildCount() > 0) { 207 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 208 } 209 210 super.addView(child); 211 } 212 213 @Override 214 public void addView(View child, int index) { 215 if (getChildCount() > 0) { 216 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 217 } 218 219 super.addView(child, index); 220 } 221 222 @Override 223 public void addView(View child, ViewGroup.LayoutParams params) { 224 if (getChildCount() > 0) { 225 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 226 } 227 228 super.addView(child, params); 229 } 230 231 @Override 232 public void addView(View child, int index, ViewGroup.LayoutParams params) { 233 if (getChildCount() > 0) { 234 throw new IllegalStateException("HorizontalScrollView can host only one direct child"); 235 } 236 237 super.addView(child, index, params); 238 } 239 240 /** 241 * @return Returns true this HorizontalScrollView can be scrolled 242 */ 243 private boolean canScroll() { 244 View child = getChildAt(0); 245 if (child != null) { 246 int childWidth = child.getWidth(); 247 return getWidth() < childWidth + mPaddingLeft + mPaddingRight ; 248 } 249 return false; 250 } 251 252 /** 253 * Indicates whether this HorizontalScrollView's content is stretched to 254 * fill the viewport. 255 * 256 * @return True if the content fills the viewport, false otherwise. 257 * 258 * @attr ref android.R.styleable#HorizontalScrollView_fillViewport 259 */ 260 public boolean isFillViewport() { 261 return mFillViewport; 262 } 263 264 /** 265 * Indicates this HorizontalScrollView whether it should stretch its content width 266 * to fill the viewport or not. 267 * 268 * @param fillViewport True to stretch the content's width to the viewport's 269 * boundaries, false otherwise. 270 * 271 * @attr ref android.R.styleable#HorizontalScrollView_fillViewport 272 */ 273 public void setFillViewport(boolean fillViewport) { 274 if (fillViewport != mFillViewport) { 275 mFillViewport = fillViewport; 276 requestLayout(); 277 } 278 } 279 280 /** 281 * @return Whether arrow scrolling will animate its transition. 282 */ 283 public boolean isSmoothScrollingEnabled() { 284 return mSmoothScrollingEnabled; 285 } 286 287 /** 288 * Set whether arrow scrolling will animate its transition. 289 * @param smoothScrollingEnabled whether arrow scrolling will animate its transition 290 */ 291 public void setSmoothScrollingEnabled(boolean smoothScrollingEnabled) { 292 mSmoothScrollingEnabled = smoothScrollingEnabled; 293 } 294 295 @Override 296 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 297 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 298 299 if (!mFillViewport) { 300 return; 301 } 302 303 final int widthMode = MeasureSpec.getMode(widthMeasureSpec); 304 if (widthMode == MeasureSpec.UNSPECIFIED) { 305 return; 306 } 307 308 if (getChildCount() > 0) { 309 final View child = getChildAt(0); 310 int width = getMeasuredWidth(); 311 if (child.getMeasuredWidth() < width) { 312 final FrameLayout.LayoutParams lp = (LayoutParams) child.getLayoutParams(); 313 314 int childHeightMeasureSpec = getChildMeasureSpec(heightMeasureSpec, mPaddingTop 315 + mPaddingBottom, lp.height); 316 width -= mPaddingLeft; 317 width -= mPaddingRight; 318 int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY); 319 320 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 321 } 322 } 323 } 324 325 @Override 326 public boolean dispatchKeyEvent(KeyEvent event) { 327 // Let the focused view and/or our descendants get the key first 328 return super.dispatchKeyEvent(event) || executeKeyEvent(event); 329 } 330 331 /** 332 * You can call this function yourself to have the scroll view perform 333 * scrolling from a key event, just as if the event had been dispatched to 334 * it by the view hierarchy. 335 * 336 * @param event The key event to execute. 337 * @return Return true if the event was handled, else false. 338 */ 339 public boolean executeKeyEvent(KeyEvent event) { 340 mTempRect.setEmpty(); 341 342 if (!canScroll()) { 343 if (isFocused()) { 344 View currentFocused = findFocus(); 345 if (currentFocused == this) currentFocused = null; 346 View nextFocused = FocusFinder.getInstance().findNextFocus(this, 347 currentFocused, View.FOCUS_RIGHT); 348 return nextFocused != null && nextFocused != this && 349 nextFocused.requestFocus(View.FOCUS_RIGHT); 350 } 351 return false; 352 } 353 354 boolean handled = false; 355 if (event.getAction() == KeyEvent.ACTION_DOWN) { 356 switch (event.getKeyCode()) { 357 case KeyEvent.KEYCODE_DPAD_LEFT: 358 if (!event.isAltPressed()) { 359 handled = arrowScroll(View.FOCUS_LEFT); 360 } else { 361 handled = fullScroll(View.FOCUS_LEFT); 362 } 363 break; 364 case KeyEvent.KEYCODE_DPAD_RIGHT: 365 if (!event.isAltPressed()) { 366 handled = arrowScroll(View.FOCUS_RIGHT); 367 } else { 368 handled = fullScroll(View.FOCUS_RIGHT); 369 } 370 break; 371 case KeyEvent.KEYCODE_SPACE: 372 pageScroll(event.isShiftPressed() ? View.FOCUS_LEFT : View.FOCUS_RIGHT); 373 break; 374 } 375 } 376 377 return handled; 378 } 379 380 private boolean inChild(int x, int y) { 381 if (getChildCount() > 0) { 382 final int scrollX = mScrollX; 383 final View child = getChildAt(0); 384 return !(y < child.getTop() 385 || y >= child.getBottom() 386 || x < child.getLeft() - scrollX 387 || x >= child.getRight() - scrollX); 388 } 389 return false; 390 } 391 392 @Override 393 public boolean onInterceptTouchEvent(MotionEvent ev) { 394 /* 395 * This method JUST determines whether we want to intercept the motion. 396 * If we return true, onMotionEvent will be called and we do the actual 397 * scrolling there. 398 */ 399 400 /* 401 * Shortcut the most recurring case: the user is in the dragging 402 * state and he is moving his finger. We want to intercept this 403 * motion. 404 */ 405 final int action = ev.getAction(); 406 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 407 return true; 408 } 409 410 switch (action & MotionEvent.ACTION_MASK) { 411 case MotionEvent.ACTION_MOVE: { 412 /* 413 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 414 * whether the user has moved far enough from his original down touch. 415 */ 416 417 /* 418 * Locally do absolute value. mLastMotionX is set to the x value 419 * of the down event. 420 */ 421 final int activePointerId = mActivePointerId; 422 if (activePointerId == INVALID_POINTER) { 423 // If we don't have a valid id, the touch down wasn't on content. 424 break; 425 } 426 427 final int pointerIndex = ev.findPointerIndex(activePointerId); 428 final float x = ev.getX(pointerIndex); 429 final int xDiff = (int) Math.abs(x - mLastMotionX); 430 if (xDiff > mTouchSlop) { 431 mIsBeingDragged = true; 432 mLastMotionX = x; 433 if (mParent != null) mParent.requestDisallowInterceptTouchEvent(true); 434 } 435 break; 436 } 437 438 case MotionEvent.ACTION_DOWN: { 439 final float x = ev.getX(); 440 if (!inChild((int) x, (int) ev.getY())) { 441 mIsBeingDragged = false; 442 break; 443 } 444 445 /* 446 * Remember location of down touch. 447 * ACTION_DOWN always refers to pointer index 0. 448 */ 449 mLastMotionX = x; 450 mActivePointerId = ev.getPointerId(0); 451 452 /* 453 * If being flinged and user touches the screen, initiate drag; 454 * otherwise don't. mScroller.isFinished should be false when 455 * being flinged. 456 */ 457 mIsBeingDragged = !mScroller.isFinished(); 458 break; 459 } 460 461 case MotionEvent.ACTION_CANCEL: 462 case MotionEvent.ACTION_UP: 463 /* Release the drag */ 464 mIsBeingDragged = false; 465 mActivePointerId = INVALID_POINTER; 466 break; 467 case MotionEvent.ACTION_POINTER_UP: 468 onSecondaryPointerUp(ev); 469 break; 470 } 471 472 /* 473 * The only time we want to intercept motion events is if we are in the 474 * drag mode. 475 */ 476 return mIsBeingDragged; 477 } 478 479 @Override 480 public boolean onTouchEvent(MotionEvent ev) { 481 482 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 483 // Don't handle edge touches immediately -- they may actually belong to one of our 484 // descendants. 485 return false; 486 } 487 488 if (mVelocityTracker == null) { 489 mVelocityTracker = VelocityTracker.obtain(); 490 } 491 mVelocityTracker.addMovement(ev); 492 493 final int action = ev.getAction(); 494 495 switch (action & MotionEvent.ACTION_MASK) { 496 case MotionEvent.ACTION_DOWN: { 497 final float x = ev.getX(); 498 if (!(mIsBeingDragged = inChild((int) x, (int) ev.getY()))) { 499 return false; 500 } 501 502 /* 503 * If being flinged and user touches, stop the fling. isFinished 504 * will be false if being flinged. 505 */ 506 if (!mScroller.isFinished()) { 507 mScroller.abortAnimation(); 508 } 509 510 // Remember where the motion event started 511 mLastMotionX = x; 512 mActivePointerId = ev.getPointerId(0); 513 break; 514 } 515 case MotionEvent.ACTION_MOVE: 516 if (mIsBeingDragged) { 517 // Scroll to follow the motion event 518 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 519 final float x = ev.getX(activePointerIndex); 520 final int deltaX = (int) (mLastMotionX - x); 521 mLastMotionX = x; 522 523 scrollBy(deltaX, 0); 524 } 525 break; 526 case MotionEvent.ACTION_UP: 527 if (mIsBeingDragged) { 528 final VelocityTracker velocityTracker = mVelocityTracker; 529 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 530 int initialVelocity = (int) velocityTracker.getXVelocity(mActivePointerId); 531 532 if (getChildCount() > 0 && Math.abs(initialVelocity) > mMinimumVelocity) { 533 fling(-initialVelocity); 534 } 535 536 mActivePointerId = INVALID_POINTER; 537 mIsBeingDragged = false; 538 539 if (mVelocityTracker != null) { 540 mVelocityTracker.recycle(); 541 mVelocityTracker = null; 542 } 543 } 544 break; 545 case MotionEvent.ACTION_CANCEL: 546 if (mIsBeingDragged && getChildCount() > 0) { 547 mActivePointerId = INVALID_POINTER; 548 mIsBeingDragged = false; 549 if (mVelocityTracker != null) { 550 mVelocityTracker.recycle(); 551 mVelocityTracker = null; 552 } 553 } 554 break; 555 case MotionEvent.ACTION_POINTER_UP: 556 onSecondaryPointerUp(ev); 557 break; 558 } 559 return true; 560 } 561 562 private void onSecondaryPointerUp(MotionEvent ev) { 563 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 564 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 565 final int pointerId = ev.getPointerId(pointerIndex); 566 if (pointerId == mActivePointerId) { 567 // This was our active pointer going up. Choose a new 568 // active pointer and adjust accordingly. 569 // TODO: Make this decision more intelligent. 570 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 571 mLastMotionX = ev.getX(newPointerIndex); 572 mActivePointerId = ev.getPointerId(newPointerIndex); 573 if (mVelocityTracker != null) { 574 mVelocityTracker.clear(); 575 } 576 } 577 } 578 579 private int getScrollRange() { 580 int scrollRange = 0; 581 if (getChildCount() > 0) { 582 View child = getChildAt(0); 583 scrollRange = Math.max(0, 584 child.getWidth() - getWidth() - mPaddingLeft - mPaddingRight); 585 } 586 return scrollRange; 587 } 588 589 /** 590 * <p> 591 * Finds the next focusable component that fits in this View's bounds 592 * (excluding fading edges) pretending that this View's left is located at 593 * the parameter left. 594 * </p> 595 * 596 * @param leftFocus look for a candidate is the one at the left of the bounds 597 * if leftFocus is true, or at the right of the bounds if leftFocus 598 * is false 599 * @param left the left offset of the bounds in which a focusable must be 600 * found (the fading edge is assumed to start at this position) 601 * @param preferredFocusable the View that has highest priority and will be 602 * returned if it is within my bounds (null is valid) 603 * @return the next focusable component in the bounds or null if none can be found 604 */ 605 private View findFocusableViewInMyBounds(final boolean leftFocus, 606 final int left, View preferredFocusable) { 607 /* 608 * The fading edge's transparent side should be considered for focus 609 * since it's mostly visible, so we divide the actual fading edge length 610 * by 2. 611 */ 612 final int fadingEdgeLength = getHorizontalFadingEdgeLength() / 2; 613 final int leftWithoutFadingEdge = left + fadingEdgeLength; 614 final int rightWithoutFadingEdge = left + getWidth() - fadingEdgeLength; 615 616 if ((preferredFocusable != null) 617 && (preferredFocusable.getLeft() < rightWithoutFadingEdge) 618 && (preferredFocusable.getRight() > leftWithoutFadingEdge)) { 619 return preferredFocusable; 620 } 621 622 return findFocusableViewInBounds(leftFocus, leftWithoutFadingEdge, 623 rightWithoutFadingEdge); 624 } 625 626 /** 627 * <p> 628 * Finds the next focusable component that fits in the specified bounds. 629 * </p> 630 * 631 * @param leftFocus look for a candidate is the one at the left of the bounds 632 * if leftFocus is true, or at the right of the bounds if 633 * leftFocus is false 634 * @param left the left offset of the bounds in which a focusable must be 635 * found 636 * @param right the right offset of the bounds in which a focusable must 637 * be found 638 * @return the next focusable component in the bounds or null if none can 639 * be found 640 */ 641 private View findFocusableViewInBounds(boolean leftFocus, int left, int right) { 642 643 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 644 View focusCandidate = null; 645 646 /* 647 * A fully contained focusable is one where its left is below the bound's 648 * left, and its right is above the bound's right. A partially 649 * contained focusable is one where some part of it is within the 650 * bounds, but it also has some part that is not within bounds. A fully contained 651 * focusable is preferred to a partially contained focusable. 652 */ 653 boolean foundFullyContainedFocusable = false; 654 655 int count = focusables.size(); 656 for (int i = 0; i < count; i++) { 657 View view = focusables.get(i); 658 int viewLeft = view.getLeft(); 659 int viewRight = view.getRight(); 660 661 if (left < viewRight && viewLeft < right) { 662 /* 663 * the focusable is in the target area, it is a candidate for 664 * focusing 665 */ 666 667 final boolean viewIsFullyContained = (left < viewLeft) && 668 (viewRight < right); 669 670 if (focusCandidate == null) { 671 /* No candidate, take this one */ 672 focusCandidate = view; 673 foundFullyContainedFocusable = viewIsFullyContained; 674 } else { 675 final boolean viewIsCloserToBoundary = 676 (leftFocus && viewLeft < focusCandidate.getLeft()) || 677 (!leftFocus && viewRight > focusCandidate.getRight()); 678 679 if (foundFullyContainedFocusable) { 680 if (viewIsFullyContained && viewIsCloserToBoundary) { 681 /* 682 * We're dealing with only fully contained views, so 683 * it has to be closer to the boundary to beat our 684 * candidate 685 */ 686 focusCandidate = view; 687 } 688 } else { 689 if (viewIsFullyContained) { 690 /* Any fully contained view beats a partially contained view */ 691 focusCandidate = view; 692 foundFullyContainedFocusable = true; 693 } else if (viewIsCloserToBoundary) { 694 /* 695 * Partially contained view beats another partially 696 * contained view if it's closer 697 */ 698 focusCandidate = view; 699 } 700 } 701 } 702 } 703 } 704 705 return focusCandidate; 706 } 707 708 /** 709 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 710 * method will scroll the view by one page left or right and give the focus 711 * to the leftmost/rightmost component in the new visible area. If no 712 * component is a good candidate for focus, this scrollview reclaims the 713 * focus.</p> 714 * 715 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 716 * to go one page left or {@link android.view.View#FOCUS_RIGHT} 717 * to go one page right 718 * @return true if the key event is consumed by this method, false otherwise 719 */ 720 public boolean pageScroll(int direction) { 721 boolean right = direction == View.FOCUS_RIGHT; 722 int width = getWidth(); 723 724 if (right) { 725 mTempRect.left = getScrollX() + width; 726 int count = getChildCount(); 727 if (count > 0) { 728 View view = getChildAt(0); 729 if (mTempRect.left + width > view.getRight()) { 730 mTempRect.left = view.getRight() - width; 731 } 732 } 733 } else { 734 mTempRect.left = getScrollX() - width; 735 if (mTempRect.left < 0) { 736 mTempRect.left = 0; 737 } 738 } 739 mTempRect.right = mTempRect.left + width; 740 741 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 742 } 743 744 /** 745 * <p>Handles scrolling in response to a "home/end" shortcut press. This 746 * method will scroll the view to the left or right and give the focus 747 * to the leftmost/rightmost component in the new visible area. If no 748 * component is a good candidate for focus, this scrollview reclaims the 749 * focus.</p> 750 * 751 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 752 * to go the left of the view or {@link android.view.View#FOCUS_RIGHT} 753 * to go the right 754 * @return true if the key event is consumed by this method, false otherwise 755 */ 756 public boolean fullScroll(int direction) { 757 boolean right = direction == View.FOCUS_RIGHT; 758 int width = getWidth(); 759 760 mTempRect.left = 0; 761 mTempRect.right = width; 762 763 if (right) { 764 int count = getChildCount(); 765 if (count > 0) { 766 View view = getChildAt(0); 767 mTempRect.right = view.getRight(); 768 mTempRect.left = mTempRect.right - width; 769 } 770 } 771 772 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 773 } 774 775 /** 776 * <p>Scrolls the view to make the area defined by <code>left</code> and 777 * <code>right</code> visible. This method attempts to give the focus 778 * to a component visible in this area. If no component can be focused in 779 * the new visible area, the focus is reclaimed by this scrollview.</p> 780 * 781 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 782 * to go left {@link android.view.View#FOCUS_RIGHT} to right 783 * @param left the left offset of the new area to be made visible 784 * @param right the right offset of the new area to be made visible 785 * @return true if the key event is consumed by this method, false otherwise 786 */ 787 private boolean scrollAndFocus(int direction, int left, int right) { 788 boolean handled = true; 789 790 int width = getWidth(); 791 int containerLeft = getScrollX(); 792 int containerRight = containerLeft + width; 793 boolean goLeft = direction == View.FOCUS_LEFT; 794 795 View newFocused = findFocusableViewInBounds(goLeft, left, right); 796 if (newFocused == null) { 797 newFocused = this; 798 } 799 800 if (left >= containerLeft && right <= containerRight) { 801 handled = false; 802 } else { 803 int delta = goLeft ? (left - containerLeft) : (right - containerRight); 804 doScrollX(delta); 805 } 806 807 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 808 mScrollViewMovedFocus = true; 809 mScrollViewMovedFocus = false; 810 } 811 812 return handled; 813 } 814 815 /** 816 * Handle scrolling in response to a left or right arrow click. 817 * 818 * @param direction The direction corresponding to the arrow key that was 819 * pressed 820 * @return True if we consumed the event, false otherwise 821 */ 822 public boolean arrowScroll(int direction) { 823 824 View currentFocused = findFocus(); 825 if (currentFocused == this) currentFocused = null; 826 827 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 828 829 final int maxJump = getMaxScrollAmount(); 830 831 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 832 nextFocused.getDrawingRect(mTempRect); 833 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 834 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 835 doScrollX(scrollDelta); 836 nextFocused.requestFocus(direction); 837 } else { 838 // no new focus 839 int scrollDelta = maxJump; 840 841 if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) { 842 scrollDelta = getScrollX(); 843 } else if (direction == View.FOCUS_RIGHT && getChildCount() > 0) { 844 845 int daRight = getChildAt(0).getRight(); 846 847 int screenRight = getScrollX() + getWidth(); 848 849 if (daRight - screenRight < maxJump) { 850 scrollDelta = daRight - screenRight; 851 } 852 } 853 if (scrollDelta == 0) { 854 return false; 855 } 856 doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta); 857 } 858 859 if (currentFocused != null && currentFocused.isFocused() 860 && isOffScreen(currentFocused)) { 861 // previously focused item still has focus and is off screen, give 862 // it up (take it back to ourselves) 863 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 864 // sure to 865 // get it) 866 final int descendantFocusability = getDescendantFocusability(); // save 867 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 868 requestFocus(); 869 setDescendantFocusability(descendantFocusability); // restore 870 } 871 return true; 872 } 873 874 /** 875 * @return whether the descendant of this scroll view is scrolled off 876 * screen. 877 */ 878 private boolean isOffScreen(View descendant) { 879 return !isWithinDeltaOfScreen(descendant, 0); 880 } 881 882 /** 883 * @return whether the descendant of this scroll view is within delta 884 * pixels of being on the screen. 885 */ 886 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 887 descendant.getDrawingRect(mTempRect); 888 offsetDescendantRectToMyCoords(descendant, mTempRect); 889 890 return (mTempRect.right + delta) >= getScrollX() 891 && (mTempRect.left - delta) <= (getScrollX() + getWidth()); 892 } 893 894 /** 895 * Smooth scroll by a X delta 896 * 897 * @param delta the number of pixels to scroll by on the X axis 898 */ 899 private void doScrollX(int delta) { 900 if (delta != 0) { 901 if (mSmoothScrollingEnabled) { 902 smoothScrollBy(delta, 0); 903 } else { 904 scrollBy(delta, 0); 905 } 906 } 907 } 908 909 /** 910 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 911 * 912 * @param dx the number of pixels to scroll by on the X axis 913 * @param dy the number of pixels to scroll by on the Y axis 914 */ 915 public final void smoothScrollBy(int dx, int dy) { 916 if (getChildCount() == 0) { 917 // Nothing to do. 918 return; 919 } 920 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 921 if (duration > ANIMATED_SCROLL_GAP) { 922 final int width = getWidth() - mPaddingRight - mPaddingLeft; 923 final int right = getChildAt(0).getWidth(); 924 final int maxX = Math.max(0, right - width); 925 final int scrollX = mScrollX; 926 dx = Math.max(0, Math.min(scrollX + dx, maxX)) - scrollX; 927 928 mScroller.startScroll(scrollX, mScrollY, dx, 0); 929 invalidate(); 930 } else { 931 if (!mScroller.isFinished()) { 932 mScroller.abortAnimation(); 933 } 934 scrollBy(dx, dy); 935 } 936 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 937 } 938 939 /** 940 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 941 * 942 * @param x the position where to scroll on the X axis 943 * @param y the position where to scroll on the Y axis 944 */ 945 public final void smoothScrollTo(int x, int y) { 946 smoothScrollBy(x - mScrollX, y - mScrollY); 947 } 948 949 /** 950 * <p>The scroll range of a scroll view is the overall width of all of its 951 * children.</p> 952 */ 953 @Override 954 protected int computeHorizontalScrollRange() { 955 final int count = getChildCount(); 956 final int contentWidth = getWidth() - mPaddingLeft - mPaddingRight; 957 if (count == 0) { 958 return contentWidth; 959 } 960 961 return getChildAt(0).getRight(); 962 } 963 964 @Override 965 protected int computeHorizontalScrollOffset() { 966 return Math.max(0, super.computeHorizontalScrollOffset()); 967 } 968 969 @Override 970 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 971 ViewGroup.LayoutParams lp = child.getLayoutParams(); 972 973 int childWidthMeasureSpec; 974 int childHeightMeasureSpec; 975 976 childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop 977 + mPaddingBottom, lp.height); 978 979 childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 980 981 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 982 } 983 984 @Override 985 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 986 int parentHeightMeasureSpec, int heightUsed) { 987 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 988 989 final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, 990 mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin 991 + heightUsed, lp.height); 992 final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( 993 lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); 994 995 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 996 } 997 998 @Override 999 public void computeScroll() { 1000 if (mScroller.computeScrollOffset()) { 1001 // This is called at drawing time by ViewGroup. We don't want to 1002 // re-show the scrollbars at this point, which scrollTo will do, 1003 // so we replicate most of scrollTo here. 1004 // 1005 // It's a little odd to call onScrollChanged from inside the drawing. 1006 // 1007 // It is, except when you remember that computeScroll() is used to 1008 // animate scrolling. So unless we want to defer the onScrollChanged() 1009 // until the end of the animated scrolling, we don't really have a 1010 // choice here. 1011 // 1012 // I agree. The alternative, which I think would be worse, is to post 1013 // something and tell the subclasses later. This is bad because there 1014 // will be a window where mScrollX/Y is different from what the app 1015 // thinks it is. 1016 // 1017 int oldX = mScrollX; 1018 int oldY = mScrollY; 1019 int x = mScroller.getCurrX(); 1020 int y = mScroller.getCurrY(); 1021 1022 if (getChildCount() > 0) { 1023 View child = getChildAt(0); 1024 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1025 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1026 if (x != oldX || y != oldY) { 1027 mScrollX = x; 1028 mScrollY = y; 1029 onScrollChanged(x, y, oldX, oldY); 1030 } 1031 } 1032 awakenScrollBars(); 1033 1034 // Keep on drawing until the animation has finished. 1035 postInvalidate(); 1036 } 1037 } 1038 1039 /** 1040 * Scrolls the view to the given child. 1041 * 1042 * @param child the View to scroll to 1043 */ 1044 private void scrollToChild(View child) { 1045 child.getDrawingRect(mTempRect); 1046 1047 /* Offset from child's local coordinates to ScrollView coordinates */ 1048 offsetDescendantRectToMyCoords(child, mTempRect); 1049 1050 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1051 1052 if (scrollDelta != 0) { 1053 scrollBy(scrollDelta, 0); 1054 } 1055 } 1056 1057 /** 1058 * If rect is off screen, scroll just enough to get it (or at least the 1059 * first screen size chunk of it) on screen. 1060 * 1061 * @param rect The rectangle. 1062 * @param immediate True to scroll immediately without animation 1063 * @return true if scrolling was performed 1064 */ 1065 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1066 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1067 final boolean scroll = delta != 0; 1068 if (scroll) { 1069 if (immediate) { 1070 scrollBy(delta, 0); 1071 } else { 1072 smoothScrollBy(delta, 0); 1073 } 1074 } 1075 return scroll; 1076 } 1077 1078 /** 1079 * Compute the amount to scroll in the X direction in order to get 1080 * a rectangle completely on the screen (or, if taller than the screen, 1081 * at least the first screen size chunk of it). 1082 * 1083 * @param rect The rect. 1084 * @return The scroll delta. 1085 */ 1086 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1087 if (getChildCount() == 0) return 0; 1088 1089 int width = getWidth(); 1090 int screenLeft = getScrollX(); 1091 int screenRight = screenLeft + width; 1092 1093 int fadingEdge = getHorizontalFadingEdgeLength(); 1094 1095 // leave room for left fading edge as long as rect isn't at very left 1096 if (rect.left > 0) { 1097 screenLeft += fadingEdge; 1098 } 1099 1100 // leave room for right fading edge as long as rect isn't at very right 1101 if (rect.right < getChildAt(0).getWidth()) { 1102 screenRight -= fadingEdge; 1103 } 1104 1105 int scrollXDelta = 0; 1106 1107 if (rect.right > screenRight && rect.left > screenLeft) { 1108 // need to move right to get it in view: move right just enough so 1109 // that the entire rectangle is in view (or at least the first 1110 // screen size chunk). 1111 1112 if (rect.width() > width) { 1113 // just enough to get screen size chunk on 1114 scrollXDelta += (rect.left - screenLeft); 1115 } else { 1116 // get entire rect at right of screen 1117 scrollXDelta += (rect.right - screenRight); 1118 } 1119 1120 // make sure we aren't scrolling beyond the end of our content 1121 int right = getChildAt(0).getRight(); 1122 int distanceToRight = right - screenRight; 1123 scrollXDelta = Math.min(scrollXDelta, distanceToRight); 1124 1125 } else if (rect.left < screenLeft && rect.right < screenRight) { 1126 // need to move right to get it in view: move right just enough so that 1127 // entire rectangle is in view (or at least the first screen 1128 // size chunk of it). 1129 1130 if (rect.width() > width) { 1131 // screen size chunk 1132 scrollXDelta -= (screenRight - rect.right); 1133 } else { 1134 // entire rect at left 1135 scrollXDelta -= (screenLeft - rect.left); 1136 } 1137 1138 // make sure we aren't scrolling any further than the left our content 1139 scrollXDelta = Math.max(scrollXDelta, -getScrollX()); 1140 } 1141 return scrollXDelta; 1142 } 1143 1144 @Override 1145 public void requestChildFocus(View child, View focused) { 1146 if (!mScrollViewMovedFocus) { 1147 if (!mIsLayoutDirty) { 1148 scrollToChild(focused); 1149 } else { 1150 // The child may not be laid out yet, we can't compute the scroll yet 1151 mChildToScrollTo = focused; 1152 } 1153 } 1154 super.requestChildFocus(child, focused); 1155 } 1156 1157 1158 /** 1159 * When looking for focus in children of a scroll view, need to be a little 1160 * more careful not to give focus to something that is scrolled off screen. 1161 * 1162 * This is more expensive than the default {@link android.view.ViewGroup} 1163 * implementation, otherwise this behavior might have been made the default. 1164 */ 1165 @Override 1166 protected boolean onRequestFocusInDescendants(int direction, 1167 Rect previouslyFocusedRect) { 1168 1169 // convert from forward / backward notation to up / down / left / right 1170 // (ugh). 1171 if (direction == View.FOCUS_FORWARD) { 1172 direction = View.FOCUS_RIGHT; 1173 } else if (direction == View.FOCUS_BACKWARD) { 1174 direction = View.FOCUS_LEFT; 1175 } 1176 1177 final View nextFocus = previouslyFocusedRect == null ? 1178 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1179 FocusFinder.getInstance().findNextFocusFromRect(this, 1180 previouslyFocusedRect, direction); 1181 1182 if (nextFocus == null) { 1183 return false; 1184 } 1185 1186 if (isOffScreen(nextFocus)) { 1187 return false; 1188 } 1189 1190 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1191 } 1192 1193 @Override 1194 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1195 boolean immediate) { 1196 // offset into coordinate space of this scroll view 1197 rectangle.offset(child.getLeft() - child.getScrollX(), 1198 child.getTop() - child.getScrollY()); 1199 1200 return scrollToChildRect(rectangle, immediate); 1201 } 1202 1203 @Override 1204 public void requestLayout() { 1205 mIsLayoutDirty = true; 1206 super.requestLayout(); 1207 } 1208 1209 @Override 1210 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1211 super.onLayout(changed, l, t, r, b); 1212 mIsLayoutDirty = false; 1213 // Give a child focus if it needs it 1214 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1215 scrollToChild(mChildToScrollTo); 1216 } 1217 mChildToScrollTo = null; 1218 1219 // Calling this with the present values causes it to re-clam them 1220 scrollTo(mScrollX, mScrollY); 1221 } 1222 1223 @Override 1224 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1225 super.onSizeChanged(w, h, oldw, oldh); 1226 1227 View currentFocused = findFocus(); 1228 if (null == currentFocused || this == currentFocused) 1229 return; 1230 1231 final int maxJump = mRight - mLeft; 1232 1233 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1234 currentFocused.getDrawingRect(mTempRect); 1235 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1236 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1237 doScrollX(scrollDelta); 1238 } 1239 } 1240 1241 /** 1242 * Return true if child is an descendant of parent, (or equal to the parent). 1243 */ 1244 private boolean isViewDescendantOf(View child, View parent) { 1245 if (child == parent) { 1246 return true; 1247 } 1248 1249 final ViewParent theParent = child.getParent(); 1250 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1251 } 1252 1253 /** 1254 * Fling the scroll view 1255 * 1256 * @param velocityX The initial velocity in the X direction. Positive 1257 * numbers mean that the finger/curor is moving down the screen, 1258 * which means we want to scroll towards the left. 1259 */ 1260 public void fling(int velocityX) { 1261 if (getChildCount() > 0) { 1262 int width = getWidth() - mPaddingRight - mPaddingLeft; 1263 int right = getChildAt(0).getWidth(); 1264 1265 mScroller.fling(mScrollX, mScrollY, velocityX, 0, 0, 1266 Math.max(0, right - width), 0, 0); 1267 1268 final boolean movingRight = velocityX > 0; 1269 1270 View newFocused = findFocusableViewInMyBounds(movingRight, 1271 mScroller.getFinalX(), findFocus()); 1272 1273 if (newFocused == null) { 1274 newFocused = this; 1275 } 1276 1277 if (newFocused != findFocus() 1278 && newFocused.requestFocus(movingRight ? View.FOCUS_RIGHT : View.FOCUS_LEFT)) { 1279 mScrollViewMovedFocus = true; 1280 mScrollViewMovedFocus = false; 1281 } 1282 1283 invalidate(); 1284 } 1285 } 1286 1287 /** 1288 * {@inheritDoc} 1289 * 1290 * <p>This version also clamps the scrolling to the bounds of our child. 1291 */ 1292 public void scrollTo(int x, int y) { 1293 // we rely on the fact the View.scrollBy calls scrollTo. 1294 if (getChildCount() > 0) { 1295 View child = getChildAt(0); 1296 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1297 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1298 if (x != mScrollX || y != mScrollY) { 1299 super.scrollTo(x, y); 1300 } 1301 } 1302 } 1303 1304 private int clamp(int n, int my, int child) { 1305 if (my >= child || n < 0) { 1306 return 0; 1307 } 1308 if ((my + n) > child) { 1309 return child - my; 1310 } 1311 return n; 1312 } 1313} 1314