HorizontalScrollView.java revision a0d645cb6980113a624e6e70a7fa9ae5e91bbac8
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 */ 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 Scroller 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 Scroller(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 int scrollX = mScrollX; 376 final View child = getChildAt(0); 377 return !(y < child.getTop() 378 || y >= child.getBottom() 379 || x < child.getLeft() - scrollX 380 || x >= child.getRight() - scrollX); 381 } 382 return false; 383 } 384 385 @Override 386 public boolean onInterceptTouchEvent(MotionEvent ev) { 387 /* 388 * This method JUST determines whether we want to intercept the motion. 389 * If we return true, onMotionEvent will be called and we do the actual 390 * scrolling there. 391 */ 392 393 /* 394 * Shortcut the most recurring case: the user is in the dragging 395 * state and he is moving his finger. We want to intercept this 396 * motion. 397 */ 398 final int action = ev.getAction(); 399 if ((action == MotionEvent.ACTION_MOVE) && (mIsBeingDragged)) { 400 return true; 401 } 402 403 switch (action & MotionEvent.ACTION_MASK) { 404 case MotionEvent.ACTION_MOVE: { 405 /* 406 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check 407 * whether the user has moved far enough from his original down touch. 408 */ 409 410 /* 411 * Locally do absolute value. mLastMotionX is set to the x value 412 * of the down event. 413 */ 414 final int activePointerId = mActivePointerId; 415 if (activePointerId == INVALID_POINTER) { 416 // If we don't have a valid id, the touch down wasn't on content. 417 break; 418 } 419 420 final int pointerIndex = ev.findPointerIndex(activePointerId); 421 final float x = ev.getX(pointerIndex); 422 final int xDiff = (int) Math.abs(x - mLastMotionX); 423 if (xDiff > mTouchSlop) { 424 mIsBeingDragged = true; 425 mLastMotionX = x; 426 if (mParent != null) mParent.requestDisallowInterceptTouchEvent(true); 427 } 428 break; 429 } 430 431 case MotionEvent.ACTION_DOWN: { 432 final float x = ev.getX(); 433 if (!inChild((int) x, (int) ev.getY())) { 434 mIsBeingDragged = false; 435 break; 436 } 437 438 /* 439 * Remember location of down touch. 440 * ACTION_DOWN always refers to pointer index 0. 441 */ 442 mLastMotionX = x; 443 mActivePointerId = ev.getPointerId(0); 444 445 /* 446 * If being flinged and user touches the screen, initiate drag; 447 * otherwise don't. mScroller.isFinished should be false when 448 * being flinged. 449 */ 450 mIsBeingDragged = !mScroller.isFinished(); 451 break; 452 } 453 454 case MotionEvent.ACTION_CANCEL: 455 case MotionEvent.ACTION_UP: 456 /* Release the drag */ 457 mIsBeingDragged = false; 458 mActivePointerId = INVALID_POINTER; 459 break; 460 case MotionEvent.ACTION_POINTER_UP: 461 onSecondaryPointerUp(ev); 462 break; 463 } 464 465 /* 466 * The only time we want to intercept motion events is if we are in the 467 * drag mode. 468 */ 469 return mIsBeingDragged; 470 } 471 472 @Override 473 public boolean onTouchEvent(MotionEvent ev) { 474 475 if (ev.getAction() == MotionEvent.ACTION_DOWN && ev.getEdgeFlags() != 0) { 476 // Don't handle edge touches immediately -- they may actually belong to one of our 477 // descendants. 478 return false; 479 } 480 481 if (mVelocityTracker == null) { 482 mVelocityTracker = VelocityTracker.obtain(); 483 } 484 mVelocityTracker.addMovement(ev); 485 486 final int action = ev.getAction(); 487 488 switch (action & MotionEvent.ACTION_MASK) { 489 case MotionEvent.ACTION_DOWN: { 490 final float x = ev.getX(); 491 if (!(mIsBeingDragged = inChild((int) x, (int) ev.getY()))) { 492 return false; 493 } 494 495 /* 496 * If being flinged and user touches, stop the fling. isFinished 497 * will be false if being flinged. 498 */ 499 if (!mScroller.isFinished()) { 500 mScroller.abortAnimation(); 501 } 502 503 // Remember where the motion event started 504 mLastMotionX = x; 505 mActivePointerId = ev.getPointerId(0); 506 break; 507 } 508 case MotionEvent.ACTION_MOVE: 509 if (mIsBeingDragged) { 510 // Scroll to follow the motion event 511 final int activePointerIndex = ev.findPointerIndex(mActivePointerId); 512 final float x = ev.getX(activePointerIndex); 513 final int deltaX = (int) (mLastMotionX - x); 514 mLastMotionX = x; 515 516 scrollBy(deltaX, 0); 517 } 518 break; 519 case MotionEvent.ACTION_UP: 520 if (mIsBeingDragged) { 521 final VelocityTracker velocityTracker = mVelocityTracker; 522 velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity); 523 int initialVelocity = (int) velocityTracker.getXVelocity(mActivePointerId); 524 525 if (getChildCount() > 0 && Math.abs(initialVelocity) > mMinimumVelocity) { 526 fling(-initialVelocity); 527 } 528 529 mActivePointerId = INVALID_POINTER; 530 mIsBeingDragged = false; 531 532 if (mVelocityTracker != null) { 533 mVelocityTracker.recycle(); 534 mVelocityTracker = null; 535 } 536 } 537 break; 538 case MotionEvent.ACTION_CANCEL: 539 if (mIsBeingDragged && getChildCount() > 0) { 540 mActivePointerId = INVALID_POINTER; 541 mIsBeingDragged = false; 542 if (mVelocityTracker != null) { 543 mVelocityTracker.recycle(); 544 mVelocityTracker = null; 545 } 546 } 547 break; 548 case MotionEvent.ACTION_POINTER_UP: 549 onSecondaryPointerUp(ev); 550 break; 551 } 552 return true; 553 } 554 555 private void onSecondaryPointerUp(MotionEvent ev) { 556 final int pointerIndex = (ev.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK) >> 557 MotionEvent.ACTION_POINTER_INDEX_SHIFT; 558 final int pointerId = ev.getPointerId(pointerIndex); 559 if (pointerId == mActivePointerId) { 560 // This was our active pointer going up. Choose a new 561 // active pointer and adjust accordingly. 562 // TODO: Make this decision more intelligent. 563 final int newPointerIndex = pointerIndex == 0 ? 1 : 0; 564 mLastMotionX = ev.getX(newPointerIndex); 565 mActivePointerId = ev.getPointerId(newPointerIndex); 566 if (mVelocityTracker != null) { 567 mVelocityTracker.clear(); 568 } 569 } 570 } 571 572 private int getScrollRange() { 573 int scrollRange = 0; 574 if (getChildCount() > 0) { 575 View child = getChildAt(0); 576 scrollRange = Math.max(0, 577 child.getWidth() - getWidth() - mPaddingLeft - mPaddingRight); 578 } 579 return scrollRange; 580 } 581 582 /** 583 * <p> 584 * Finds the next focusable component that fits in this View's bounds 585 * (excluding fading edges) pretending that this View's left is located at 586 * the parameter left. 587 * </p> 588 * 589 * @param leftFocus look for a candidate is the one at the left of the bounds 590 * if leftFocus is true, or at the right of the bounds if leftFocus 591 * is false 592 * @param left the left offset of the bounds in which a focusable must be 593 * found (the fading edge is assumed to start at this position) 594 * @param preferredFocusable the View that has highest priority and will be 595 * returned if it is within my bounds (null is valid) 596 * @return the next focusable component in the bounds or null if none can be found 597 */ 598 private View findFocusableViewInMyBounds(final boolean leftFocus, 599 final int left, View preferredFocusable) { 600 /* 601 * The fading edge's transparent side should be considered for focus 602 * since it's mostly visible, so we divide the actual fading edge length 603 * by 2. 604 */ 605 final int fadingEdgeLength = getHorizontalFadingEdgeLength() / 2; 606 final int leftWithoutFadingEdge = left + fadingEdgeLength; 607 final int rightWithoutFadingEdge = left + getWidth() - fadingEdgeLength; 608 609 if ((preferredFocusable != null) 610 && (preferredFocusable.getLeft() < rightWithoutFadingEdge) 611 && (preferredFocusable.getRight() > leftWithoutFadingEdge)) { 612 return preferredFocusable; 613 } 614 615 return findFocusableViewInBounds(leftFocus, leftWithoutFadingEdge, 616 rightWithoutFadingEdge); 617 } 618 619 /** 620 * <p> 621 * Finds the next focusable component that fits in the specified bounds. 622 * </p> 623 * 624 * @param leftFocus look for a candidate is the one at the left of the bounds 625 * if leftFocus is true, or at the right of the bounds if 626 * leftFocus is false 627 * @param left the left offset of the bounds in which a focusable must be 628 * found 629 * @param right the right offset of the bounds in which a focusable must 630 * be found 631 * @return the next focusable component in the bounds or null if none can 632 * be found 633 */ 634 private View findFocusableViewInBounds(boolean leftFocus, int left, int right) { 635 636 List<View> focusables = getFocusables(View.FOCUS_FORWARD); 637 View focusCandidate = null; 638 639 /* 640 * A fully contained focusable is one where its left is below the bound's 641 * left, and its right is above the bound's right. A partially 642 * contained focusable is one where some part of it is within the 643 * bounds, but it also has some part that is not within bounds. A fully contained 644 * focusable is preferred to a partially contained focusable. 645 */ 646 boolean foundFullyContainedFocusable = false; 647 648 int count = focusables.size(); 649 for (int i = 0; i < count; i++) { 650 View view = focusables.get(i); 651 int viewLeft = view.getLeft(); 652 int viewRight = view.getRight(); 653 654 if (left < viewRight && viewLeft < right) { 655 /* 656 * the focusable is in the target area, it is a candidate for 657 * focusing 658 */ 659 660 final boolean viewIsFullyContained = (left < viewLeft) && 661 (viewRight < right); 662 663 if (focusCandidate == null) { 664 /* No candidate, take this one */ 665 focusCandidate = view; 666 foundFullyContainedFocusable = viewIsFullyContained; 667 } else { 668 final boolean viewIsCloserToBoundary = 669 (leftFocus && viewLeft < focusCandidate.getLeft()) || 670 (!leftFocus && viewRight > focusCandidate.getRight()); 671 672 if (foundFullyContainedFocusable) { 673 if (viewIsFullyContained && viewIsCloserToBoundary) { 674 /* 675 * We're dealing with only fully contained views, so 676 * it has to be closer to the boundary to beat our 677 * candidate 678 */ 679 focusCandidate = view; 680 } 681 } else { 682 if (viewIsFullyContained) { 683 /* Any fully contained view beats a partially contained view */ 684 focusCandidate = view; 685 foundFullyContainedFocusable = true; 686 } else if (viewIsCloserToBoundary) { 687 /* 688 * Partially contained view beats another partially 689 * contained view if it's closer 690 */ 691 focusCandidate = view; 692 } 693 } 694 } 695 } 696 } 697 698 return focusCandidate; 699 } 700 701 /** 702 * <p>Handles scrolling in response to a "page up/down" shortcut press. This 703 * method will scroll the view by one page left or right and give the focus 704 * to the leftmost/rightmost component in the new visible area. If no 705 * component is a good candidate for focus, this scrollview reclaims the 706 * focus.</p> 707 * 708 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 709 * to go one page left or {@link android.view.View#FOCUS_RIGHT} 710 * to go one page right 711 * @return true if the key event is consumed by this method, false otherwise 712 */ 713 public boolean pageScroll(int direction) { 714 boolean right = direction == View.FOCUS_RIGHT; 715 int width = getWidth(); 716 717 if (right) { 718 mTempRect.left = getScrollX() + width; 719 int count = getChildCount(); 720 if (count > 0) { 721 View view = getChildAt(0); 722 if (mTempRect.left + width > view.getRight()) { 723 mTempRect.left = view.getRight() - width; 724 } 725 } 726 } else { 727 mTempRect.left = getScrollX() - width; 728 if (mTempRect.left < 0) { 729 mTempRect.left = 0; 730 } 731 } 732 mTempRect.right = mTempRect.left + width; 733 734 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 735 } 736 737 /** 738 * <p>Handles scrolling in response to a "home/end" shortcut press. This 739 * method will scroll the view to the left or right and give the focus 740 * to the leftmost/rightmost component in the new visible area. If no 741 * component is a good candidate for focus, this scrollview reclaims the 742 * focus.</p> 743 * 744 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 745 * to go the left of the view or {@link android.view.View#FOCUS_RIGHT} 746 * to go the right 747 * @return true if the key event is consumed by this method, false otherwise 748 */ 749 public boolean fullScroll(int direction) { 750 boolean right = direction == View.FOCUS_RIGHT; 751 int width = getWidth(); 752 753 mTempRect.left = 0; 754 mTempRect.right = width; 755 756 if (right) { 757 int count = getChildCount(); 758 if (count > 0) { 759 View view = getChildAt(0); 760 mTempRect.right = view.getRight(); 761 mTempRect.left = mTempRect.right - width; 762 } 763 } 764 765 return scrollAndFocus(direction, mTempRect.left, mTempRect.right); 766 } 767 768 /** 769 * <p>Scrolls the view to make the area defined by <code>left</code> and 770 * <code>right</code> visible. This method attempts to give the focus 771 * to a component visible in this area. If no component can be focused in 772 * the new visible area, the focus is reclaimed by this scrollview.</p> 773 * 774 * @param direction the scroll direction: {@link android.view.View#FOCUS_LEFT} 775 * to go left {@link android.view.View#FOCUS_RIGHT} to right 776 * @param left the left offset of the new area to be made visible 777 * @param right the right offset of the new area to be made visible 778 * @return true if the key event is consumed by this method, false otherwise 779 */ 780 private boolean scrollAndFocus(int direction, int left, int right) { 781 boolean handled = true; 782 783 int width = getWidth(); 784 int containerLeft = getScrollX(); 785 int containerRight = containerLeft + width; 786 boolean goLeft = direction == View.FOCUS_LEFT; 787 788 View newFocused = findFocusableViewInBounds(goLeft, left, right); 789 if (newFocused == null) { 790 newFocused = this; 791 } 792 793 if (left >= containerLeft && right <= containerRight) { 794 handled = false; 795 } else { 796 int delta = goLeft ? (left - containerLeft) : (right - containerRight); 797 doScrollX(delta); 798 } 799 800 if (newFocused != findFocus() && newFocused.requestFocus(direction)) { 801 mScrollViewMovedFocus = true; 802 mScrollViewMovedFocus = false; 803 } 804 805 return handled; 806 } 807 808 /** 809 * Handle scrolling in response to a left or right arrow click. 810 * 811 * @param direction The direction corresponding to the arrow key that was 812 * pressed 813 * @return True if we consumed the event, false otherwise 814 */ 815 public boolean arrowScroll(int direction) { 816 817 View currentFocused = findFocus(); 818 if (currentFocused == this) currentFocused = null; 819 820 View nextFocused = FocusFinder.getInstance().findNextFocus(this, currentFocused, direction); 821 822 final int maxJump = getMaxScrollAmount(); 823 824 if (nextFocused != null && isWithinDeltaOfScreen(nextFocused, maxJump)) { 825 nextFocused.getDrawingRect(mTempRect); 826 offsetDescendantRectToMyCoords(nextFocused, mTempRect); 827 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 828 doScrollX(scrollDelta); 829 nextFocused.requestFocus(direction); 830 } else { 831 // no new focus 832 int scrollDelta = maxJump; 833 834 if (direction == View.FOCUS_LEFT && getScrollX() < scrollDelta) { 835 scrollDelta = getScrollX(); 836 } else if (direction == View.FOCUS_RIGHT && getChildCount() > 0) { 837 838 int daRight = getChildAt(0).getRight(); 839 840 int screenRight = getScrollX() + getWidth(); 841 842 if (daRight - screenRight < maxJump) { 843 scrollDelta = daRight - screenRight; 844 } 845 } 846 if (scrollDelta == 0) { 847 return false; 848 } 849 doScrollX(direction == View.FOCUS_RIGHT ? scrollDelta : -scrollDelta); 850 } 851 852 if (currentFocused != null && currentFocused.isFocused() 853 && isOffScreen(currentFocused)) { 854 // previously focused item still has focus and is off screen, give 855 // it up (take it back to ourselves) 856 // (also, need to temporarily force FOCUS_BEFORE_DESCENDANTS so we are 857 // sure to 858 // get it) 859 final int descendantFocusability = getDescendantFocusability(); // save 860 setDescendantFocusability(ViewGroup.FOCUS_BEFORE_DESCENDANTS); 861 requestFocus(); 862 setDescendantFocusability(descendantFocusability); // restore 863 } 864 return true; 865 } 866 867 /** 868 * @return whether the descendant of this scroll view is scrolled off 869 * screen. 870 */ 871 private boolean isOffScreen(View descendant) { 872 return !isWithinDeltaOfScreen(descendant, 0); 873 } 874 875 /** 876 * @return whether the descendant of this scroll view is within delta 877 * pixels of being on the screen. 878 */ 879 private boolean isWithinDeltaOfScreen(View descendant, int delta) { 880 descendant.getDrawingRect(mTempRect); 881 offsetDescendantRectToMyCoords(descendant, mTempRect); 882 883 return (mTempRect.right + delta) >= getScrollX() 884 && (mTempRect.left - delta) <= (getScrollX() + getWidth()); 885 } 886 887 /** 888 * Smooth scroll by a X delta 889 * 890 * @param delta the number of pixels to scroll by on the X axis 891 */ 892 private void doScrollX(int delta) { 893 if (delta != 0) { 894 if (mSmoothScrollingEnabled) { 895 smoothScrollBy(delta, 0); 896 } else { 897 scrollBy(delta, 0); 898 } 899 } 900 } 901 902 /** 903 * Like {@link View#scrollBy}, but scroll smoothly instead of immediately. 904 * 905 * @param dx the number of pixels to scroll by on the X axis 906 * @param dy the number of pixels to scroll by on the Y axis 907 */ 908 public final void smoothScrollBy(int dx, int dy) { 909 if (getChildCount() == 0) { 910 // Nothing to do. 911 return; 912 } 913 long duration = AnimationUtils.currentAnimationTimeMillis() - mLastScroll; 914 if (duration > ANIMATED_SCROLL_GAP) { 915 final int width = getWidth() - mPaddingRight - mPaddingLeft; 916 final int right = getChildAt(0).getWidth(); 917 final int maxX = Math.max(0, right - width); 918 final int scrollX = mScrollX; 919 dx = Math.max(0, Math.min(scrollX + dx, maxX)) - scrollX; 920 921 mScroller.startScroll(scrollX, mScrollY, dx, 0); 922 invalidate(); 923 } else { 924 if (!mScroller.isFinished()) { 925 mScroller.abortAnimation(); 926 } 927 scrollBy(dx, dy); 928 } 929 mLastScroll = AnimationUtils.currentAnimationTimeMillis(); 930 } 931 932 /** 933 * Like {@link #scrollTo}, but scroll smoothly instead of immediately. 934 * 935 * @param x the position where to scroll on the X axis 936 * @param y the position where to scroll on the Y axis 937 */ 938 public final void smoothScrollTo(int x, int y) { 939 smoothScrollBy(x - mScrollX, y - mScrollY); 940 } 941 942 /** 943 * <p>The scroll range of a scroll view is the overall width of all of its 944 * children.</p> 945 */ 946 @Override 947 protected int computeHorizontalScrollRange() { 948 final int count = getChildCount(); 949 final int contentWidth = getWidth() - mPaddingLeft - mPaddingRight; 950 if (count == 0) { 951 return contentWidth; 952 } 953 954 return getChildAt(0).getRight(); 955 } 956 957 @Override 958 protected int computeHorizontalScrollOffset() { 959 return Math.max(0, super.computeHorizontalScrollOffset()); 960 } 961 962 @Override 963 protected void measureChild(View child, int parentWidthMeasureSpec, int parentHeightMeasureSpec) { 964 ViewGroup.LayoutParams lp = child.getLayoutParams(); 965 966 int childWidthMeasureSpec; 967 int childHeightMeasureSpec; 968 969 childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, mPaddingTop 970 + mPaddingBottom, lp.height); 971 972 childWidthMeasureSpec = MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED); 973 974 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 975 } 976 977 @Override 978 protected void measureChildWithMargins(View child, int parentWidthMeasureSpec, int widthUsed, 979 int parentHeightMeasureSpec, int heightUsed) { 980 final MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams(); 981 982 final int childHeightMeasureSpec = getChildMeasureSpec(parentHeightMeasureSpec, 983 mPaddingTop + mPaddingBottom + lp.topMargin + lp.bottomMargin 984 + heightUsed, lp.height); 985 final int childWidthMeasureSpec = MeasureSpec.makeMeasureSpec( 986 lp.leftMargin + lp.rightMargin, MeasureSpec.UNSPECIFIED); 987 988 child.measure(childWidthMeasureSpec, childHeightMeasureSpec); 989 } 990 991 @Override 992 public void computeScroll() { 993 if (mScroller.computeScrollOffset()) { 994 // This is called at drawing time by ViewGroup. We don't want to 995 // re-show the scrollbars at this point, which scrollTo will do, 996 // so we replicate most of scrollTo here. 997 // 998 // It's a little odd to call onScrollChanged from inside the drawing. 999 // 1000 // It is, except when you remember that computeScroll() is used to 1001 // animate scrolling. So unless we want to defer the onScrollChanged() 1002 // until the end of the animated scrolling, we don't really have a 1003 // choice here. 1004 // 1005 // I agree. The alternative, which I think would be worse, is to post 1006 // something and tell the subclasses later. This is bad because there 1007 // will be a window where mScrollX/Y is different from what the app 1008 // thinks it is. 1009 // 1010 int oldX = mScrollX; 1011 int oldY = mScrollY; 1012 int x = mScroller.getCurrX(); 1013 int y = mScroller.getCurrY(); 1014 1015 if (getChildCount() > 0) { 1016 View child = getChildAt(0); 1017 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1018 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1019 if (x != oldX || y != oldY) { 1020 mScrollX = x; 1021 mScrollY = y; 1022 onScrollChanged(x, y, oldX, oldY); 1023 } 1024 } 1025 awakenScrollBars(); 1026 1027 // Keep on drawing until the animation has finished. 1028 postInvalidate(); 1029 } 1030 } 1031 1032 /** 1033 * Scrolls the view to the given child. 1034 * 1035 * @param child the View to scroll to 1036 */ 1037 private void scrollToChild(View child) { 1038 child.getDrawingRect(mTempRect); 1039 1040 /* Offset from child's local coordinates to ScrollView coordinates */ 1041 offsetDescendantRectToMyCoords(child, mTempRect); 1042 1043 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1044 1045 if (scrollDelta != 0) { 1046 scrollBy(scrollDelta, 0); 1047 } 1048 } 1049 1050 /** 1051 * If rect is off screen, scroll just enough to get it (or at least the 1052 * first screen size chunk of it) on screen. 1053 * 1054 * @param rect The rectangle. 1055 * @param immediate True to scroll immediately without animation 1056 * @return true if scrolling was performed 1057 */ 1058 private boolean scrollToChildRect(Rect rect, boolean immediate) { 1059 final int delta = computeScrollDeltaToGetChildRectOnScreen(rect); 1060 final boolean scroll = delta != 0; 1061 if (scroll) { 1062 if (immediate) { 1063 scrollBy(delta, 0); 1064 } else { 1065 smoothScrollBy(delta, 0); 1066 } 1067 } 1068 return scroll; 1069 } 1070 1071 /** 1072 * Compute the amount to scroll in the X direction in order to get 1073 * a rectangle completely on the screen (or, if taller than the screen, 1074 * at least the first screen size chunk of it). 1075 * 1076 * @param rect The rect. 1077 * @return The scroll delta. 1078 */ 1079 protected int computeScrollDeltaToGetChildRectOnScreen(Rect rect) { 1080 if (getChildCount() == 0) return 0; 1081 1082 int width = getWidth(); 1083 int screenLeft = getScrollX(); 1084 int screenRight = screenLeft + width; 1085 1086 int fadingEdge = getHorizontalFadingEdgeLength(); 1087 1088 // leave room for left fading edge as long as rect isn't at very left 1089 if (rect.left > 0) { 1090 screenLeft += fadingEdge; 1091 } 1092 1093 // leave room for right fading edge as long as rect isn't at very right 1094 if (rect.right < getChildAt(0).getWidth()) { 1095 screenRight -= fadingEdge; 1096 } 1097 1098 int scrollXDelta = 0; 1099 1100 if (rect.right > screenRight && rect.left > screenLeft) { 1101 // need to move right to get it in view: move right just enough so 1102 // that the entire rectangle is in view (or at least the first 1103 // screen size chunk). 1104 1105 if (rect.width() > width) { 1106 // just enough to get screen size chunk on 1107 scrollXDelta += (rect.left - screenLeft); 1108 } else { 1109 // get entire rect at right of screen 1110 scrollXDelta += (rect.right - screenRight); 1111 } 1112 1113 // make sure we aren't scrolling beyond the end of our content 1114 int right = getChildAt(0).getRight(); 1115 int distanceToRight = right - screenRight; 1116 scrollXDelta = Math.min(scrollXDelta, distanceToRight); 1117 1118 } else if (rect.left < screenLeft && rect.right < screenRight) { 1119 // need to move right to get it in view: move right just enough so that 1120 // entire rectangle is in view (or at least the first screen 1121 // size chunk of it). 1122 1123 if (rect.width() > width) { 1124 // screen size chunk 1125 scrollXDelta -= (screenRight - rect.right); 1126 } else { 1127 // entire rect at left 1128 scrollXDelta -= (screenLeft - rect.left); 1129 } 1130 1131 // make sure we aren't scrolling any further than the left our content 1132 scrollXDelta = Math.max(scrollXDelta, -getScrollX()); 1133 } 1134 return scrollXDelta; 1135 } 1136 1137 @Override 1138 public void requestChildFocus(View child, View focused) { 1139 if (!mScrollViewMovedFocus) { 1140 if (!mIsLayoutDirty) { 1141 scrollToChild(focused); 1142 } else { 1143 // The child may not be laid out yet, we can't compute the scroll yet 1144 mChildToScrollTo = focused; 1145 } 1146 } 1147 super.requestChildFocus(child, focused); 1148 } 1149 1150 1151 /** 1152 * When looking for focus in children of a scroll view, need to be a little 1153 * more careful not to give focus to something that is scrolled off screen. 1154 * 1155 * This is more expensive than the default {@link android.view.ViewGroup} 1156 * implementation, otherwise this behavior might have been made the default. 1157 */ 1158 @Override 1159 protected boolean onRequestFocusInDescendants(int direction, 1160 Rect previouslyFocusedRect) { 1161 1162 // convert from forward / backward notation to up / down / left / right 1163 // (ugh). 1164 if (direction == View.FOCUS_FORWARD) { 1165 direction = View.FOCUS_RIGHT; 1166 } else if (direction == View.FOCUS_BACKWARD) { 1167 direction = View.FOCUS_LEFT; 1168 } 1169 1170 final View nextFocus = previouslyFocusedRect == null ? 1171 FocusFinder.getInstance().findNextFocus(this, null, direction) : 1172 FocusFinder.getInstance().findNextFocusFromRect(this, 1173 previouslyFocusedRect, direction); 1174 1175 if (nextFocus == null) { 1176 return false; 1177 } 1178 1179 if (isOffScreen(nextFocus)) { 1180 return false; 1181 } 1182 1183 return nextFocus.requestFocus(direction, previouslyFocusedRect); 1184 } 1185 1186 @Override 1187 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 1188 boolean immediate) { 1189 // offset into coordinate space of this scroll view 1190 rectangle.offset(child.getLeft() - child.getScrollX(), 1191 child.getTop() - child.getScrollY()); 1192 1193 return scrollToChildRect(rectangle, immediate); 1194 } 1195 1196 @Override 1197 public void requestLayout() { 1198 mIsLayoutDirty = true; 1199 super.requestLayout(); 1200 } 1201 1202 @Override 1203 protected void onLayout(boolean changed, int l, int t, int r, int b) { 1204 super.onLayout(changed, l, t, r, b); 1205 mIsLayoutDirty = false; 1206 // Give a child focus if it needs it 1207 if (mChildToScrollTo != null && isViewDescendantOf(mChildToScrollTo, this)) { 1208 scrollToChild(mChildToScrollTo); 1209 } 1210 mChildToScrollTo = null; 1211 1212 // Calling this with the present values causes it to re-clam them 1213 scrollTo(mScrollX, mScrollY); 1214 } 1215 1216 @Override 1217 protected void onSizeChanged(int w, int h, int oldw, int oldh) { 1218 super.onSizeChanged(w, h, oldw, oldh); 1219 1220 View currentFocused = findFocus(); 1221 if (null == currentFocused || this == currentFocused) 1222 return; 1223 1224 final int maxJump = mRight - mLeft; 1225 1226 if (isWithinDeltaOfScreen(currentFocused, maxJump)) { 1227 currentFocused.getDrawingRect(mTempRect); 1228 offsetDescendantRectToMyCoords(currentFocused, mTempRect); 1229 int scrollDelta = computeScrollDeltaToGetChildRectOnScreen(mTempRect); 1230 doScrollX(scrollDelta); 1231 } 1232 } 1233 1234 /** 1235 * Return true if child is an descendant of parent, (or equal to the parent). 1236 */ 1237 private boolean isViewDescendantOf(View child, View parent) { 1238 if (child == parent) { 1239 return true; 1240 } 1241 1242 final ViewParent theParent = child.getParent(); 1243 return (theParent instanceof ViewGroup) && isViewDescendantOf((View) theParent, parent); 1244 } 1245 1246 /** 1247 * Fling the scroll view 1248 * 1249 * @param velocityX The initial velocity in the X direction. Positive 1250 * numbers mean that the finger/curor is moving down the screen, 1251 * which means we want to scroll towards the left. 1252 */ 1253 public void fling(int velocityX) { 1254 if (getChildCount() > 0) { 1255 int width = getWidth() - mPaddingRight - mPaddingLeft; 1256 int right = getChildAt(0).getWidth(); 1257 1258 mScroller.fling(mScrollX, mScrollY, velocityX, 0, 0, 1259 Math.max(0, right - width), 0, 0); 1260 1261 final boolean movingRight = velocityX > 0; 1262 1263 View newFocused = findFocusableViewInMyBounds(movingRight, 1264 mScroller.getFinalX(), findFocus()); 1265 1266 if (newFocused == null) { 1267 newFocused = this; 1268 } 1269 1270 if (newFocused != findFocus() 1271 && newFocused.requestFocus(movingRight ? View.FOCUS_RIGHT : View.FOCUS_LEFT)) { 1272 mScrollViewMovedFocus = true; 1273 mScrollViewMovedFocus = false; 1274 } 1275 1276 invalidate(); 1277 } 1278 } 1279 1280 /** 1281 * {@inheritDoc} 1282 * 1283 * <p>This version also clamps the scrolling to the bounds of our child. 1284 */ 1285 public void scrollTo(int x, int y) { 1286 // we rely on the fact the View.scrollBy calls scrollTo. 1287 if (getChildCount() > 0) { 1288 View child = getChildAt(0); 1289 x = clamp(x, getWidth() - mPaddingRight - mPaddingLeft, child.getWidth()); 1290 y = clamp(y, getHeight() - mPaddingBottom - mPaddingTop, child.getHeight()); 1291 if (x != mScrollX || y != mScrollY) { 1292 super.scrollTo(x, y); 1293 } 1294 } 1295 } 1296 1297 private int clamp(int n, int my, int child) { 1298 if (my >= child || n < 0) { 1299 return 0; 1300 } 1301 if ((my + n) > child) { 1302 return child - my; 1303 } 1304 return n; 1305 } 1306} 1307