1/* 2 * Copyright (C) 2013 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 18package android.support.v4.widget; 19 20import android.content.Context; 21import android.support.v4.view.MotionEventCompat; 22import android.support.v4.view.VelocityTrackerCompat; 23import android.support.v4.view.ViewCompat; 24import android.util.Log; 25import android.view.MotionEvent; 26import android.view.VelocityTracker; 27import android.view.View; 28import android.view.ViewConfiguration; 29import android.view.ViewGroup; 30import android.view.animation.Interpolator; 31 32import java.util.Arrays; 33 34/** 35 * ViewDragHelper is a utility class for writing custom ViewGroups. It offers a number 36 * of useful operations and state tracking for allowing a user to drag and reposition 37 * views within their parent ViewGroup. 38 */ 39public class ViewDragHelper { 40 private static final String TAG = "ViewDragHelper"; 41 42 /** 43 * A null/invalid pointer ID. 44 */ 45 public static final int INVALID_POINTER = -1; 46 47 /** 48 * A view is not currently being dragged or animating as a result of a fling/snap. 49 */ 50 public static final int STATE_IDLE = 0; 51 52 /** 53 * A view is currently being dragged. The position is currently changing as a result 54 * of user input or simulated user input. 55 */ 56 public static final int STATE_DRAGGING = 1; 57 58 /** 59 * A view is currently settling into place as a result of a fling or 60 * predefined non-interactive motion. 61 */ 62 public static final int STATE_SETTLING = 2; 63 64 /** 65 * Edge flag indicating that the left edge should be affected. 66 */ 67 public static final int EDGE_LEFT = 1 << 0; 68 69 /** 70 * Edge flag indicating that the right edge should be affected. 71 */ 72 public static final int EDGE_RIGHT = 1 << 1; 73 74 /** 75 * Edge flag indicating that the top edge should be affected. 76 */ 77 public static final int EDGE_TOP = 1 << 2; 78 79 /** 80 * Edge flag indicating that the bottom edge should be affected. 81 */ 82 public static final int EDGE_BOTTOM = 1 << 3; 83 84 /** 85 * Edge flag set indicating all edges should be affected. 86 */ 87 public static final int EDGE_ALL = EDGE_LEFT | EDGE_TOP | EDGE_RIGHT | EDGE_BOTTOM; 88 89 /** 90 * Indicates that a check should occur along the horizontal axis 91 */ 92 public static final int DIRECTION_HORIZONTAL = 1 << 0; 93 94 /** 95 * Indicates that a check should occur along the vertical axis 96 */ 97 public static final int DIRECTION_VERTICAL = 1 << 1; 98 99 /** 100 * Indicates that a check should occur along all axes 101 */ 102 public static final int DIRECTION_ALL = DIRECTION_HORIZONTAL | DIRECTION_VERTICAL; 103 104 private static final int EDGE_SIZE = 20; // dp 105 106 private static final int BASE_SETTLE_DURATION = 256; // ms 107 private static final int MAX_SETTLE_DURATION = 600; // ms 108 109 // Current drag state; idle, dragging or settling 110 private int mDragState; 111 112 // Distance to travel before a drag may begin 113 private int mTouchSlop; 114 115 // Last known position/pointer tracking 116 private int mActivePointerId = INVALID_POINTER; 117 private float[] mInitialMotionX; 118 private float[] mInitialMotionY; 119 private float[] mLastMotionX; 120 private float[] mLastMotionY; 121 private int[] mInitialEdgesTouched; 122 private int[] mEdgeDragsInProgress; 123 private int[] mEdgeDragsLocked; 124 private int mPointersDown; 125 126 private VelocityTracker mVelocityTracker; 127 private float mMaxVelocity; 128 private float mMinVelocity; 129 130 private int mEdgeSize; 131 private int mTrackingEdges; 132 133 private ScrollerCompat mScroller; 134 135 private final Callback mCallback; 136 137 private View mCapturedView; 138 private boolean mReleaseInProgress; 139 140 private final ViewGroup mParentView; 141 142 /** 143 * A Callback is used as a communication channel with the ViewDragHelper back to the 144 * parent view using it. <code>on*</code>methods are invoked on siginficant events and several 145 * accessor methods are expected to provide the ViewDragHelper with more information 146 * about the state of the parent view upon request. The callback also makes decisions 147 * governing the range and draggability of child views. 148 */ 149 public abstract static class Callback { 150 /** 151 * Called when the drag state changes. See the <code>STATE_*</code> constants 152 * for more information. 153 * 154 * @param state The new drag state 155 * 156 * @see #STATE_IDLE 157 * @see #STATE_DRAGGING 158 * @see #STATE_SETTLING 159 */ 160 public void onViewDragStateChanged(int state) {} 161 162 /** 163 * Called when the captured view's position changes as the result of a drag or settle. 164 * 165 * @param changedView View whose position changed 166 * @param left New X coordinate of the left edge of the view 167 * @param top New Y coordinate of the top edge of the view 168 * @param dx Change in X position from the last call 169 * @param dy Change in Y position from the last call 170 */ 171 public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {} 172 173 /** 174 * Called when a child view is captured for dragging or settling. The ID of the pointer 175 * currently dragging the captured view is supplied. If activePointerId is 176 * identified as {@link #INVALID_POINTER} the capture is programmatic instead of 177 * pointer-initiated. 178 * 179 * @param capturedChild Child view that was captured 180 * @param activePointerId Pointer id tracking the child capture 181 */ 182 public void onViewCaptured(View capturedChild, int activePointerId) {} 183 184 /** 185 * Called when the child view is no longer being actively dragged. 186 * The fling velocity is also supplied, if relevant. The velocity values may 187 * be clamped to system minimums or maximums. 188 * 189 * <p>Calling code may decide to fling or otherwise release the view to let it 190 * settle into place. It should do so using {@link #settleCapturedViewAt(int, int)} 191 * or {@link #flingCapturedView(int, int, int, int)}. If the Callback invokes 192 * one of these methods, the ViewDragHelper will enter {@link #STATE_SETTLING} 193 * and the view capture will not fully end until it comes to a complete stop. 194 * If neither of these methods is invoked before <code>onViewReleased</code> returns, 195 * the view will stop in place and the ViewDragHelper will return to 196 * {@link #STATE_IDLE}.</p> 197 * 198 * @param releasedChild The captured child view now being released 199 * @param xvel X velocity of the pointer as it left the screen in pixels per second. 200 * @param yvel Y velocity of the pointer as it left the screen in pixels per second. 201 */ 202 public void onViewReleased(View releasedChild, float xvel, float yvel) {} 203 204 /** 205 * Called when one of the subscribed edges in the parent view has been touched 206 * by the user while no child view is currently captured. 207 * 208 * @param edgeFlags A combination of edge flags describing the edge(s) currently touched 209 * @param pointerId ID of the pointer touching the described edge(s) 210 * @see #EDGE_LEFT 211 * @see #EDGE_TOP 212 * @see #EDGE_RIGHT 213 * @see #EDGE_BOTTOM 214 */ 215 public void onEdgeTouched(int edgeFlags, int pointerId) {} 216 217 /** 218 * Called when the given edge may become locked. This can happen if an edge drag 219 * was preliminarily rejected before beginning, but after {@link #onEdgeTouched(int, int)} 220 * was called. This method should return true to lock this edge or false to leave it 221 * unlocked. The default behavior is to leave edges unlocked. 222 * 223 * @param edgeFlags A combination of edge flags describing the edge(s) locked 224 * @return true to lock the edge, false to leave it unlocked 225 */ 226 public boolean onEdgeLock(int edgeFlags) { 227 return false; 228 } 229 230 /** 231 * Called when the user has started a deliberate drag away from one 232 * of the subscribed edges in the parent view while no child view is currently captured. 233 * 234 * @param edgeFlags A combination of edge flags describing the edge(s) dragged 235 * @param pointerId ID of the pointer touching the described edge(s) 236 * @see #EDGE_LEFT 237 * @see #EDGE_TOP 238 * @see #EDGE_RIGHT 239 * @see #EDGE_BOTTOM 240 */ 241 public void onEdgeDragStarted(int edgeFlags, int pointerId) {} 242 243 /** 244 * Called to determine the Z-order of child views. 245 * 246 * @param index the ordered position to query for 247 * @return index of the view that should be ordered at position <code>index</code> 248 */ 249 public int getOrderedChildIndex(int index) { 250 return index; 251 } 252 253 /** 254 * Return the magnitude of a draggable child view's horizontal range of motion in pixels. 255 * This method should return 0 for views that cannot move horizontally. 256 * 257 * @param child Child view to check 258 * @return range of horizontal motion in pixels 259 */ 260 public int getViewHorizontalDragRange(View child) { 261 return 0; 262 } 263 264 /** 265 * Return the magnitude of a draggable child view's vertical range of motion in pixels. 266 * This method should return 0 for views that cannot move vertically. 267 * 268 * @param child Child view to check 269 * @return range of vertical motion in pixels 270 */ 271 public int getViewVerticalDragRange(View child) { 272 return 0; 273 } 274 275 /** 276 * Called when the user's input indicates that they want to capture the given child view 277 * with the pointer indicated by pointerId. The callback should return true if the user 278 * is permitted to drag the given view with the indicated pointer. 279 * 280 * <p>ViewDragHelper may call this method multiple times for the same view even if 281 * the view is already captured; this indicates that a new pointer is trying to take 282 * control of the view.</p> 283 * 284 * <p>If this method returns true, a call to {@link #onViewCaptured(android.view.View, int)} 285 * will follow if the capture is successful.</p> 286 * 287 * @param child Child the user is attempting to capture 288 * @param pointerId ID of the pointer attempting the capture 289 * @return true if capture should be allowed, false otherwise 290 */ 291 public abstract boolean tryCaptureView(View child, int pointerId); 292 293 /** 294 * Restrict the motion of the dragged child view along the horizontal axis. 295 * The default implementation does not allow horizontal motion; the extending 296 * class must override this method and provide the desired clamping. 297 * 298 * 299 * @param child Child view being dragged 300 * @param left Attempted motion along the X axis 301 * @param dx Proposed change in position for left 302 * @return The new clamped position for left 303 */ 304 public int clampViewPositionHorizontal(View child, int left, int dx) { 305 return 0; 306 } 307 308 /** 309 * Restrict the motion of the dragged child view along the vertical axis. 310 * The default implementation does not allow vertical motion; the extending 311 * class must override this method and provide the desired clamping. 312 * 313 * 314 * @param child Child view being dragged 315 * @param top Attempted motion along the Y axis 316 * @param dy Proposed change in position for top 317 * @return The new clamped position for top 318 */ 319 public int clampViewPositionVertical(View child, int top, int dy) { 320 return 0; 321 } 322 } 323 324 /** 325 * Interpolator defining the animation curve for mScroller 326 */ 327 private static final Interpolator sInterpolator = new Interpolator() { 328 @Override 329 public float getInterpolation(float t) { 330 t -= 1.0f; 331 return t * t * t * t * t + 1.0f; 332 } 333 }; 334 335 private final Runnable mSetIdleRunnable = new Runnable() { 336 @Override 337 public void run() { 338 setDragState(STATE_IDLE); 339 } 340 }; 341 342 /** 343 * Factory method to create a new ViewDragHelper. 344 * 345 * @param forParent Parent view to monitor 346 * @param cb Callback to provide information and receive events 347 * @return a new ViewDragHelper instance 348 */ 349 public static ViewDragHelper create(ViewGroup forParent, Callback cb) { 350 return new ViewDragHelper(forParent.getContext(), forParent, cb); 351 } 352 353 /** 354 * Factory method to create a new ViewDragHelper. 355 * 356 * @param forParent Parent view to monitor 357 * @param sensitivity Multiplier for how sensitive the helper should be about detecting 358 * the start of a drag. Larger values are more sensitive. 1.0f is normal. 359 * @param cb Callback to provide information and receive events 360 * @return a new ViewDragHelper instance 361 */ 362 public static ViewDragHelper create(ViewGroup forParent, float sensitivity, Callback cb) { 363 final ViewDragHelper helper = create(forParent, cb); 364 helper.mTouchSlop = (int) (helper.mTouchSlop * (1 / sensitivity)); 365 return helper; 366 } 367 368 /** 369 * Apps should use ViewDragHelper.create() to get a new instance. 370 * This will allow VDH to use internal compatibility implementations for different 371 * platform versions. 372 * 373 * @param context Context to initialize config-dependent params from 374 * @param forParent Parent view to monitor 375 */ 376 private ViewDragHelper(Context context, ViewGroup forParent, Callback cb) { 377 if (forParent == null) { 378 throw new IllegalArgumentException("Parent view may not be null"); 379 } 380 if (cb == null) { 381 throw new IllegalArgumentException("Callback may not be null"); 382 } 383 384 mParentView = forParent; 385 mCallback = cb; 386 387 final ViewConfiguration vc = ViewConfiguration.get(context); 388 final float density = context.getResources().getDisplayMetrics().density; 389 mEdgeSize = (int) (EDGE_SIZE * density + 0.5f); 390 391 mTouchSlop = vc.getScaledTouchSlop(); 392 mMaxVelocity = vc.getScaledMaximumFlingVelocity(); 393 mMinVelocity = vc.getScaledMinimumFlingVelocity(); 394 mScroller = ScrollerCompat.create(context, sInterpolator); 395 } 396 397 /** 398 * Set the minimum velocity that will be detected as having a magnitude greater than zero 399 * in pixels per second. Callback methods accepting a velocity will be clamped appropriately. 400 * 401 * @param minVel Minimum velocity to detect 402 */ 403 public void setMinVelocity(float minVel) { 404 mMinVelocity = minVel; 405 } 406 407 /** 408 * Return the currently configured minimum velocity. Any flings with a magnitude less 409 * than this value in pixels per second. Callback methods accepting a velocity will receive 410 * zero as a velocity value if the real detected velocity was below this threshold. 411 * 412 * @return the minimum velocity that will be detected 413 */ 414 public float getMinVelocity() { 415 return mMinVelocity; 416 } 417 418 /** 419 * Retrieve the current drag state of this helper. This will return one of 420 * {@link #STATE_IDLE}, {@link #STATE_DRAGGING} or {@link #STATE_SETTLING}. 421 * @return The current drag state 422 */ 423 public int getViewDragState() { 424 return mDragState; 425 } 426 427 /** 428 * Enable edge tracking for the selected edges of the parent view. 429 * The callback's {@link Callback#onEdgeTouched(int, int)} and 430 * {@link Callback#onEdgeDragStarted(int, int)} methods will only be invoked 431 * for edges for which edge tracking has been enabled. 432 * 433 * @param edgeFlags Combination of edge flags describing the edges to watch 434 * @see #EDGE_LEFT 435 * @see #EDGE_TOP 436 * @see #EDGE_RIGHT 437 * @see #EDGE_BOTTOM 438 */ 439 public void setEdgeTrackingEnabled(int edgeFlags) { 440 mTrackingEdges = edgeFlags; 441 } 442 443 /** 444 * Return the size of an edge. This is the range in pixels along the edges of this view 445 * that will actively detect edge touches or drags if edge tracking is enabled. 446 * 447 * @return The size of an edge in pixels 448 * @see #setEdgeTrackingEnabled(int) 449 */ 450 public int getEdgeSize() { 451 return mEdgeSize; 452 } 453 454 /** 455 * Capture a specific child view for dragging within the parent. The callback will be notified 456 * but {@link Callback#tryCaptureView(android.view.View, int)} will not be asked permission to 457 * capture this view. 458 * 459 * @param childView Child view to capture 460 * @param activePointerId ID of the pointer that is dragging the captured child view 461 */ 462 public void captureChildView(View childView, int activePointerId) { 463 if (childView.getParent() != mParentView) { 464 throw new IllegalArgumentException("captureChildView: parameter must be a descendant " 465 + "of the ViewDragHelper's tracked parent view (" + mParentView + ")"); 466 } 467 468 mCapturedView = childView; 469 mActivePointerId = activePointerId; 470 mCallback.onViewCaptured(childView, activePointerId); 471 setDragState(STATE_DRAGGING); 472 } 473 474 /** 475 * @return The currently captured view, or null if no view has been captured. 476 */ 477 public View getCapturedView() { 478 return mCapturedView; 479 } 480 481 /** 482 * @return The ID of the pointer currently dragging the captured view, 483 * or {@link #INVALID_POINTER}. 484 */ 485 public int getActivePointerId() { 486 return mActivePointerId; 487 } 488 489 /** 490 * @return The minimum distance in pixels that the user must travel to initiate a drag 491 */ 492 public int getTouchSlop() { 493 return mTouchSlop; 494 } 495 496 /** 497 * The result of a call to this method is equivalent to 498 * {@link #processTouchEvent(android.view.MotionEvent)} receiving an ACTION_CANCEL event. 499 */ 500 public void cancel() { 501 mActivePointerId = INVALID_POINTER; 502 clearMotionHistory(); 503 504 if (mVelocityTracker != null) { 505 mVelocityTracker.recycle(); 506 mVelocityTracker = null; 507 } 508 } 509 510 /** 511 * {@link #cancel()}, but also abort all motion in progress and snap to the end of any 512 * animation. 513 */ 514 public void abort() { 515 cancel(); 516 if (mDragState == STATE_SETTLING) { 517 final int oldX = mScroller.getCurrX(); 518 final int oldY = mScroller.getCurrY(); 519 mScroller.abortAnimation(); 520 final int newX = mScroller.getCurrX(); 521 final int newY = mScroller.getCurrY(); 522 mCallback.onViewPositionChanged(mCapturedView, newX, newY, newX - oldX, newY - oldY); 523 } 524 setDragState(STATE_IDLE); 525 } 526 527 /** 528 * Animate the view <code>child</code> to the given (left, top) position. 529 * If this method returns true, the caller should invoke {@link #continueSettling(boolean)} 530 * on each subsequent frame to continue the motion until it returns false. If this method 531 * returns false there is no further work to do to complete the movement. 532 * 533 * <p>This operation does not count as a capture event, though {@link #getCapturedView()} 534 * will still report the sliding view while the slide is in progress.</p> 535 * 536 * @param child Child view to capture and animate 537 * @param finalLeft Final left position of child 538 * @param finalTop Final top position of child 539 * @return true if animation should continue through {@link #continueSettling(boolean)} calls 540 */ 541 public boolean smoothSlideViewTo(View child, int finalLeft, int finalTop) { 542 mCapturedView = child; 543 mActivePointerId = INVALID_POINTER; 544 545 boolean continueSliding = forceSettleCapturedViewAt(finalLeft, finalTop, 0, 0); 546 if (!continueSliding && mDragState == STATE_IDLE && mCapturedView != null) { 547 // If we're in an IDLE state to begin with and aren't moving anywhere, we 548 // end up having a non-null capturedView with an IDLE dragState 549 mCapturedView = null; 550 } 551 552 return continueSliding; 553 } 554 555 /** 556 * Settle the captured view at the given (left, top) position. 557 * The appropriate velocity from prior motion will be taken into account. 558 * If this method returns true, the caller should invoke {@link #continueSettling(boolean)} 559 * on each subsequent frame to continue the motion until it returns false. If this method 560 * returns false there is no further work to do to complete the movement. 561 * 562 * @param finalLeft Settled left edge position for the captured view 563 * @param finalTop Settled top edge position for the captured view 564 * @return true if animation should continue through {@link #continueSettling(boolean)} calls 565 */ 566 public boolean settleCapturedViewAt(int finalLeft, int finalTop) { 567 if (!mReleaseInProgress) { 568 throw new IllegalStateException("Cannot settleCapturedViewAt outside of a call to " 569 + "Callback#onViewReleased"); 570 } 571 572 return forceSettleCapturedViewAt(finalLeft, finalTop, 573 (int) VelocityTrackerCompat.getXVelocity(mVelocityTracker, mActivePointerId), 574 (int) VelocityTrackerCompat.getYVelocity(mVelocityTracker, mActivePointerId)); 575 } 576 577 /** 578 * Settle the captured view at the given (left, top) position. 579 * 580 * @param finalLeft Target left position for the captured view 581 * @param finalTop Target top position for the captured view 582 * @param xvel Horizontal velocity 583 * @param yvel Vertical velocity 584 * @return true if animation should continue through {@link #continueSettling(boolean)} calls 585 */ 586 private boolean forceSettleCapturedViewAt(int finalLeft, int finalTop, int xvel, int yvel) { 587 final int startLeft = mCapturedView.getLeft(); 588 final int startTop = mCapturedView.getTop(); 589 final int dx = finalLeft - startLeft; 590 final int dy = finalTop - startTop; 591 592 if (dx == 0 && dy == 0) { 593 // Nothing to do. Send callbacks, be done. 594 mScroller.abortAnimation(); 595 setDragState(STATE_IDLE); 596 return false; 597 } 598 599 final int duration = computeSettleDuration(mCapturedView, dx, dy, xvel, yvel); 600 mScroller.startScroll(startLeft, startTop, dx, dy, duration); 601 602 setDragState(STATE_SETTLING); 603 return true; 604 } 605 606 private int computeSettleDuration(View child, int dx, int dy, int xvel, int yvel) { 607 xvel = clampMag(xvel, (int) mMinVelocity, (int) mMaxVelocity); 608 yvel = clampMag(yvel, (int) mMinVelocity, (int) mMaxVelocity); 609 final int absDx = Math.abs(dx); 610 final int absDy = Math.abs(dy); 611 final int absXVel = Math.abs(xvel); 612 final int absYVel = Math.abs(yvel); 613 final int addedVel = absXVel + absYVel; 614 final int addedDistance = absDx + absDy; 615 616 final float xweight = xvel != 0 ? (float) absXVel / addedVel : 617 (float) absDx / addedDistance; 618 final float yweight = yvel != 0 ? (float) absYVel / addedVel : 619 (float) absDy / addedDistance; 620 621 int xduration = computeAxisDuration(dx, xvel, mCallback.getViewHorizontalDragRange(child)); 622 int yduration = computeAxisDuration(dy, yvel, mCallback.getViewVerticalDragRange(child)); 623 624 return (int) (xduration * xweight + yduration * yweight); 625 } 626 627 private int computeAxisDuration(int delta, int velocity, int motionRange) { 628 if (delta == 0) { 629 return 0; 630 } 631 632 final int width = mParentView.getWidth(); 633 final int halfWidth = width / 2; 634 final float distanceRatio = Math.min(1f, (float) Math.abs(delta) / width); 635 final float distance = halfWidth + halfWidth 636 * distanceInfluenceForSnapDuration(distanceRatio); 637 638 int duration; 639 velocity = Math.abs(velocity); 640 if (velocity > 0) { 641 duration = 4 * Math.round(1000 * Math.abs(distance / velocity)); 642 } else { 643 final float range = (float) Math.abs(delta) / motionRange; 644 duration = (int) ((range + 1) * BASE_SETTLE_DURATION); 645 } 646 return Math.min(duration, MAX_SETTLE_DURATION); 647 } 648 649 /** 650 * Clamp the magnitude of value for absMin and absMax. 651 * If the value is below the minimum, it will be clamped to zero. 652 * If the value is above the maximum, it will be clamped to the maximum. 653 * 654 * @param value Value to clamp 655 * @param absMin Absolute value of the minimum significant value to return 656 * @param absMax Absolute value of the maximum value to return 657 * @return The clamped value with the same sign as <code>value</code> 658 */ 659 private int clampMag(int value, int absMin, int absMax) { 660 final int absValue = Math.abs(value); 661 if (absValue < absMin) return 0; 662 if (absValue > absMax) return value > 0 ? absMax : -absMax; 663 return value; 664 } 665 666 /** 667 * Clamp the magnitude of value for absMin and absMax. 668 * If the value is below the minimum, it will be clamped to zero. 669 * If the value is above the maximum, it will be clamped to the maximum. 670 * 671 * @param value Value to clamp 672 * @param absMin Absolute value of the minimum significant value to return 673 * @param absMax Absolute value of the maximum value to return 674 * @return The clamped value with the same sign as <code>value</code> 675 */ 676 private float clampMag(float value, float absMin, float absMax) { 677 final float absValue = Math.abs(value); 678 if (absValue < absMin) return 0; 679 if (absValue > absMax) return value > 0 ? absMax : -absMax; 680 return value; 681 } 682 683 private float distanceInfluenceForSnapDuration(float f) { 684 f -= 0.5f; // center the values about 0. 685 f *= 0.3f * Math.PI / 2.0f; 686 return (float) Math.sin(f); 687 } 688 689 /** 690 * Settle the captured view based on standard free-moving fling behavior. 691 * The caller should invoke {@link #continueSettling(boolean)} on each subsequent frame 692 * to continue the motion until it returns false. 693 * 694 * @param minLeft Minimum X position for the view's left edge 695 * @param minTop Minimum Y position for the view's top edge 696 * @param maxLeft Maximum X position for the view's left edge 697 * @param maxTop Maximum Y position for the view's top edge 698 */ 699 public void flingCapturedView(int minLeft, int minTop, int maxLeft, int maxTop) { 700 if (!mReleaseInProgress) { 701 throw new IllegalStateException("Cannot flingCapturedView outside of a call to " 702 + "Callback#onViewReleased"); 703 } 704 705 mScroller.fling(mCapturedView.getLeft(), mCapturedView.getTop(), 706 (int) VelocityTrackerCompat.getXVelocity(mVelocityTracker, mActivePointerId), 707 (int) VelocityTrackerCompat.getYVelocity(mVelocityTracker, mActivePointerId), 708 minLeft, maxLeft, minTop, maxTop); 709 710 setDragState(STATE_SETTLING); 711 } 712 713 /** 714 * Move the captured settling view by the appropriate amount for the current time. 715 * If <code>continueSettling</code> returns true, the caller should call it again 716 * on the next frame to continue. 717 * 718 * @param deferCallbacks true if state callbacks should be deferred via posted message. 719 * Set this to true if you are calling this method from 720 * {@link android.view.View#computeScroll()} or similar methods 721 * invoked as part of layout or drawing. 722 * @return true if settle is still in progress 723 */ 724 public boolean continueSettling(boolean deferCallbacks) { 725 if (mDragState == STATE_SETTLING) { 726 boolean keepGoing = mScroller.computeScrollOffset(); 727 final int x = mScroller.getCurrX(); 728 final int y = mScroller.getCurrY(); 729 final int dx = x - mCapturedView.getLeft(); 730 final int dy = y - mCapturedView.getTop(); 731 732 if (dx != 0) { 733 ViewCompat.offsetLeftAndRight(mCapturedView, dx); 734 } 735 if (dy != 0) { 736 ViewCompat.offsetTopAndBottom(mCapturedView, dy); 737 } 738 739 if (dx != 0 || dy != 0) { 740 mCallback.onViewPositionChanged(mCapturedView, x, y, dx, dy); 741 } 742 743 if (keepGoing && x == mScroller.getFinalX() && y == mScroller.getFinalY()) { 744 // Close enough. The interpolator/scroller might think we're still moving 745 // but the user sure doesn't. 746 mScroller.abortAnimation(); 747 keepGoing = false; 748 } 749 750 if (!keepGoing) { 751 if (deferCallbacks) { 752 mParentView.post(mSetIdleRunnable); 753 } else { 754 setDragState(STATE_IDLE); 755 } 756 } 757 } 758 759 return mDragState == STATE_SETTLING; 760 } 761 762 /** 763 * Like all callback events this must happen on the UI thread, but release 764 * involves some extra semantics. During a release (mReleaseInProgress) 765 * is the only time it is valid to call {@link #settleCapturedViewAt(int, int)} 766 * or {@link #flingCapturedView(int, int, int, int)}. 767 */ 768 private void dispatchViewReleased(float xvel, float yvel) { 769 mReleaseInProgress = true; 770 mCallback.onViewReleased(mCapturedView, xvel, yvel); 771 mReleaseInProgress = false; 772 773 if (mDragState == STATE_DRAGGING) { 774 // onViewReleased didn't call a method that would have changed this. Go idle. 775 setDragState(STATE_IDLE); 776 } 777 } 778 779 private void clearMotionHistory() { 780 if (mInitialMotionX == null) { 781 return; 782 } 783 Arrays.fill(mInitialMotionX, 0); 784 Arrays.fill(mInitialMotionY, 0); 785 Arrays.fill(mLastMotionX, 0); 786 Arrays.fill(mLastMotionY, 0); 787 Arrays.fill(mInitialEdgesTouched, 0); 788 Arrays.fill(mEdgeDragsInProgress, 0); 789 Arrays.fill(mEdgeDragsLocked, 0); 790 mPointersDown = 0; 791 } 792 793 private void clearMotionHistory(int pointerId) { 794 if (mInitialMotionX == null || !isPointerDown(pointerId)) { 795 return; 796 } 797 mInitialMotionX[pointerId] = 0; 798 mInitialMotionY[pointerId] = 0; 799 mLastMotionX[pointerId] = 0; 800 mLastMotionY[pointerId] = 0; 801 mInitialEdgesTouched[pointerId] = 0; 802 mEdgeDragsInProgress[pointerId] = 0; 803 mEdgeDragsLocked[pointerId] = 0; 804 mPointersDown &= ~(1 << pointerId); 805 } 806 807 private void ensureMotionHistorySizeForId(int pointerId) { 808 if (mInitialMotionX == null || mInitialMotionX.length <= pointerId) { 809 float[] imx = new float[pointerId + 1]; 810 float[] imy = new float[pointerId + 1]; 811 float[] lmx = new float[pointerId + 1]; 812 float[] lmy = new float[pointerId + 1]; 813 int[] iit = new int[pointerId + 1]; 814 int[] edip = new int[pointerId + 1]; 815 int[] edl = new int[pointerId + 1]; 816 817 if (mInitialMotionX != null) { 818 System.arraycopy(mInitialMotionX, 0, imx, 0, mInitialMotionX.length); 819 System.arraycopy(mInitialMotionY, 0, imy, 0, mInitialMotionY.length); 820 System.arraycopy(mLastMotionX, 0, lmx, 0, mLastMotionX.length); 821 System.arraycopy(mLastMotionY, 0, lmy, 0, mLastMotionY.length); 822 System.arraycopy(mInitialEdgesTouched, 0, iit, 0, mInitialEdgesTouched.length); 823 System.arraycopy(mEdgeDragsInProgress, 0, edip, 0, mEdgeDragsInProgress.length); 824 System.arraycopy(mEdgeDragsLocked, 0, edl, 0, mEdgeDragsLocked.length); 825 } 826 827 mInitialMotionX = imx; 828 mInitialMotionY = imy; 829 mLastMotionX = lmx; 830 mLastMotionY = lmy; 831 mInitialEdgesTouched = iit; 832 mEdgeDragsInProgress = edip; 833 mEdgeDragsLocked = edl; 834 } 835 } 836 837 private void saveInitialMotion(float x, float y, int pointerId) { 838 ensureMotionHistorySizeForId(pointerId); 839 mInitialMotionX[pointerId] = mLastMotionX[pointerId] = x; 840 mInitialMotionY[pointerId] = mLastMotionY[pointerId] = y; 841 mInitialEdgesTouched[pointerId] = getEdgesTouched((int) x, (int) y); 842 mPointersDown |= 1 << pointerId; 843 } 844 845 private void saveLastMotion(MotionEvent ev) { 846 final int pointerCount = ev.getPointerCount(); 847 for (int i = 0; i < pointerCount; i++) { 848 final int pointerId = ev.getPointerId(i); 849 // If pointer is invalid then skip saving on ACTION_MOVE. 850 if (!isValidPointerForActionMove(pointerId)) { 851 continue; 852 } 853 final float x = ev.getX(i); 854 final float y = ev.getY(i); 855 mLastMotionX[pointerId] = x; 856 mLastMotionY[pointerId] = y; 857 } 858 } 859 860 /** 861 * Check if the given pointer ID represents a pointer that is currently down (to the best 862 * of the ViewDragHelper's knowledge). 863 * 864 * <p>The state used to report this information is populated by the methods 865 * {@link #shouldInterceptTouchEvent(android.view.MotionEvent)} or 866 * {@link #processTouchEvent(android.view.MotionEvent)}. If one of these methods has not 867 * been called for all relevant MotionEvents to track, the information reported 868 * by this method may be stale or incorrect.</p> 869 * 870 * @param pointerId pointer ID to check; corresponds to IDs provided by MotionEvent 871 * @return true if the pointer with the given ID is still down 872 */ 873 public boolean isPointerDown(int pointerId) { 874 return (mPointersDown & 1 << pointerId) != 0; 875 } 876 877 void setDragState(int state) { 878 mParentView.removeCallbacks(mSetIdleRunnable); 879 if (mDragState != state) { 880 mDragState = state; 881 mCallback.onViewDragStateChanged(state); 882 if (mDragState == STATE_IDLE) { 883 mCapturedView = null; 884 } 885 } 886 } 887 888 /** 889 * Attempt to capture the view with the given pointer ID. The callback will be involved. 890 * This will put us into the "dragging" state. If we've already captured this view with 891 * this pointer this method will immediately return true without consulting the callback. 892 * 893 * @param toCapture View to capture 894 * @param pointerId Pointer to capture with 895 * @return true if capture was successful 896 */ 897 boolean tryCaptureViewForDrag(View toCapture, int pointerId) { 898 if (toCapture == mCapturedView && mActivePointerId == pointerId) { 899 // Already done! 900 return true; 901 } 902 if (toCapture != null && mCallback.tryCaptureView(toCapture, pointerId)) { 903 mActivePointerId = pointerId; 904 captureChildView(toCapture, pointerId); 905 return true; 906 } 907 return false; 908 } 909 910 /** 911 * Tests scrollability within child views of v given a delta of dx. 912 * 913 * @param v View to test for horizontal scrollability 914 * @param checkV Whether the view v passed should itself be checked for scrollability (true), 915 * or just its children (false). 916 * @param dx Delta scrolled in pixels along the X axis 917 * @param dy Delta scrolled in pixels along the Y axis 918 * @param x X coordinate of the active touch point 919 * @param y Y coordinate of the active touch point 920 * @return true if child views of v can be scrolled by delta of dx. 921 */ 922 protected boolean canScroll(View v, boolean checkV, int dx, int dy, int x, int y) { 923 if (v instanceof ViewGroup) { 924 final ViewGroup group = (ViewGroup) v; 925 final int scrollX = v.getScrollX(); 926 final int scrollY = v.getScrollY(); 927 final int count = group.getChildCount(); 928 // Count backwards - let topmost views consume scroll distance first. 929 for (int i = count - 1; i >= 0; i--) { 930 // TODO: Add versioned support here for transformed views. 931 // This will not work for transformed views in Honeycomb+ 932 final View child = group.getChildAt(i); 933 if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() 934 && y + scrollY >= child.getTop() && y + scrollY < child.getBottom() 935 && canScroll(child, true, dx, dy, x + scrollX - child.getLeft(), 936 y + scrollY - child.getTop())) { 937 return true; 938 } 939 } 940 } 941 942 return checkV && (ViewCompat.canScrollHorizontally(v, -dx) 943 || ViewCompat.canScrollVertically(v, -dy)); 944 } 945 946 /** 947 * Check if this event as provided to the parent view's onInterceptTouchEvent should 948 * cause the parent to intercept the touch event stream. 949 * 950 * @param ev MotionEvent provided to onInterceptTouchEvent 951 * @return true if the parent view should return true from onInterceptTouchEvent 952 */ 953 public boolean shouldInterceptTouchEvent(MotionEvent ev) { 954 final int action = MotionEventCompat.getActionMasked(ev); 955 final int actionIndex = MotionEventCompat.getActionIndex(ev); 956 957 if (action == MotionEvent.ACTION_DOWN) { 958 // Reset things for a new event stream, just in case we didn't get 959 // the whole previous stream. 960 cancel(); 961 } 962 963 if (mVelocityTracker == null) { 964 mVelocityTracker = VelocityTracker.obtain(); 965 } 966 mVelocityTracker.addMovement(ev); 967 968 switch (action) { 969 case MotionEvent.ACTION_DOWN: { 970 final float x = ev.getX(); 971 final float y = ev.getY(); 972 final int pointerId = ev.getPointerId(0); 973 saveInitialMotion(x, y, pointerId); 974 975 final View toCapture = findTopChildUnder((int) x, (int) y); 976 977 // Catch a settling view if possible. 978 if (toCapture == mCapturedView && mDragState == STATE_SETTLING) { 979 tryCaptureViewForDrag(toCapture, pointerId); 980 } 981 982 final int edgesTouched = mInitialEdgesTouched[pointerId]; 983 if ((edgesTouched & mTrackingEdges) != 0) { 984 mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId); 985 } 986 break; 987 } 988 989 case MotionEventCompat.ACTION_POINTER_DOWN: { 990 final int pointerId = ev.getPointerId(actionIndex); 991 final float x = ev.getX(actionIndex); 992 final float y = ev.getY(actionIndex); 993 994 saveInitialMotion(x, y, pointerId); 995 996 // A ViewDragHelper can only manipulate one view at a time. 997 if (mDragState == STATE_IDLE) { 998 final int edgesTouched = mInitialEdgesTouched[pointerId]; 999 if ((edgesTouched & mTrackingEdges) != 0) { 1000 mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId); 1001 } 1002 } else if (mDragState == STATE_SETTLING) { 1003 // Catch a settling view if possible. 1004 final View toCapture = findTopChildUnder((int) x, (int) y); 1005 if (toCapture == mCapturedView) { 1006 tryCaptureViewForDrag(toCapture, pointerId); 1007 } 1008 } 1009 break; 1010 } 1011 1012 case MotionEvent.ACTION_MOVE: { 1013 if (mInitialMotionX == null || mInitialMotionY == null) break; 1014 1015 // First to cross a touch slop over a draggable view wins. Also report edge drags. 1016 final int pointerCount = ev.getPointerCount(); 1017 for (int i = 0; i < pointerCount; i++) { 1018 final int pointerId = ev.getPointerId(i); 1019 1020 // If pointer is invalid then skip the ACTION_MOVE. 1021 if (!isValidPointerForActionMove(pointerId)) continue; 1022 1023 final float x = ev.getX(i); 1024 final float y = ev.getY(i); 1025 final float dx = x - mInitialMotionX[pointerId]; 1026 final float dy = y - mInitialMotionY[pointerId]; 1027 1028 final View toCapture = findTopChildUnder((int) x, (int) y); 1029 final boolean pastSlop = toCapture != null && checkTouchSlop(toCapture, dx, dy); 1030 if (pastSlop) { 1031 // check the callback's 1032 // getView[Horizontal|Vertical]DragRange methods to know 1033 // if you can move at all along an axis, then see if it 1034 // would clamp to the same value. If you can't move at 1035 // all in every dimension with a nonzero range, bail. 1036 final int oldLeft = toCapture.getLeft(); 1037 final int targetLeft = oldLeft + (int) dx; 1038 final int newLeft = mCallback.clampViewPositionHorizontal(toCapture, 1039 targetLeft, (int) dx); 1040 final int oldTop = toCapture.getTop(); 1041 final int targetTop = oldTop + (int) dy; 1042 final int newTop = mCallback.clampViewPositionVertical(toCapture, targetTop, 1043 (int) dy); 1044 final int horizontalDragRange = mCallback.getViewHorizontalDragRange( 1045 toCapture); 1046 final int verticalDragRange = mCallback.getViewVerticalDragRange(toCapture); 1047 if ((horizontalDragRange == 0 || horizontalDragRange > 0 1048 && newLeft == oldLeft) && (verticalDragRange == 0 1049 || verticalDragRange > 0 && newTop == oldTop)) { 1050 break; 1051 } 1052 } 1053 reportNewEdgeDrags(dx, dy, pointerId); 1054 if (mDragState == STATE_DRAGGING) { 1055 // Callback might have started an edge drag 1056 break; 1057 } 1058 1059 if (pastSlop && tryCaptureViewForDrag(toCapture, pointerId)) { 1060 break; 1061 } 1062 } 1063 saveLastMotion(ev); 1064 break; 1065 } 1066 1067 case MotionEventCompat.ACTION_POINTER_UP: { 1068 final int pointerId = ev.getPointerId(actionIndex); 1069 clearMotionHistory(pointerId); 1070 break; 1071 } 1072 1073 case MotionEvent.ACTION_UP: 1074 case MotionEvent.ACTION_CANCEL: { 1075 cancel(); 1076 break; 1077 } 1078 } 1079 1080 return mDragState == STATE_DRAGGING; 1081 } 1082 1083 /** 1084 * Process a touch event received by the parent view. This method will dispatch callback events 1085 * as needed before returning. The parent view's onTouchEvent implementation should call this. 1086 * 1087 * @param ev The touch event received by the parent view 1088 */ 1089 public void processTouchEvent(MotionEvent ev) { 1090 final int action = MotionEventCompat.getActionMasked(ev); 1091 final int actionIndex = MotionEventCompat.getActionIndex(ev); 1092 1093 if (action == MotionEvent.ACTION_DOWN) { 1094 // Reset things for a new event stream, just in case we didn't get 1095 // the whole previous stream. 1096 cancel(); 1097 } 1098 1099 if (mVelocityTracker == null) { 1100 mVelocityTracker = VelocityTracker.obtain(); 1101 } 1102 mVelocityTracker.addMovement(ev); 1103 1104 switch (action) { 1105 case MotionEvent.ACTION_DOWN: { 1106 final float x = ev.getX(); 1107 final float y = ev.getY(); 1108 final int pointerId = ev.getPointerId(0); 1109 final View toCapture = findTopChildUnder((int) x, (int) y); 1110 1111 saveInitialMotion(x, y, pointerId); 1112 1113 // Since the parent is already directly processing this touch event, 1114 // there is no reason to delay for a slop before dragging. 1115 // Start immediately if possible. 1116 tryCaptureViewForDrag(toCapture, pointerId); 1117 1118 final int edgesTouched = mInitialEdgesTouched[pointerId]; 1119 if ((edgesTouched & mTrackingEdges) != 0) { 1120 mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId); 1121 } 1122 break; 1123 } 1124 1125 case MotionEventCompat.ACTION_POINTER_DOWN: { 1126 final int pointerId = ev.getPointerId(actionIndex); 1127 final float x = ev.getX(actionIndex); 1128 final float y = ev.getY(actionIndex); 1129 1130 saveInitialMotion(x, y, pointerId); 1131 1132 // A ViewDragHelper can only manipulate one view at a time. 1133 if (mDragState == STATE_IDLE) { 1134 // If we're idle we can do anything! Treat it like a normal down event. 1135 1136 final View toCapture = findTopChildUnder((int) x, (int) y); 1137 tryCaptureViewForDrag(toCapture, pointerId); 1138 1139 final int edgesTouched = mInitialEdgesTouched[pointerId]; 1140 if ((edgesTouched & mTrackingEdges) != 0) { 1141 mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId); 1142 } 1143 } else if (isCapturedViewUnder((int) x, (int) y)) { 1144 // We're still tracking a captured view. If the same view is under this 1145 // point, we'll swap to controlling it with this pointer instead. 1146 // (This will still work if we're "catching" a settling view.) 1147 1148 tryCaptureViewForDrag(mCapturedView, pointerId); 1149 } 1150 break; 1151 } 1152 1153 case MotionEvent.ACTION_MOVE: { 1154 if (mDragState == STATE_DRAGGING) { 1155 // If pointer is invalid then skip the ACTION_MOVE. 1156 if (!isValidPointerForActionMove(mActivePointerId)) break; 1157 1158 final int index = ev.findPointerIndex(mActivePointerId); 1159 final float x = ev.getX(index); 1160 final float y = ev.getY(index); 1161 final int idx = (int) (x - mLastMotionX[mActivePointerId]); 1162 final int idy = (int) (y - mLastMotionY[mActivePointerId]); 1163 1164 dragTo(mCapturedView.getLeft() + idx, mCapturedView.getTop() + idy, idx, idy); 1165 1166 saveLastMotion(ev); 1167 } else { 1168 // Check to see if any pointer is now over a draggable view. 1169 final int pointerCount = ev.getPointerCount(); 1170 for (int i = 0; i < pointerCount; i++) { 1171 final int pointerId = ev.getPointerId(i); 1172 1173 // If pointer is invalid then skip the ACTION_MOVE. 1174 if (!isValidPointerForActionMove(pointerId)) continue; 1175 1176 final float x = ev.getX(i); 1177 final float y = ev.getY(i); 1178 final float dx = x - mInitialMotionX[pointerId]; 1179 final float dy = y - mInitialMotionY[pointerId]; 1180 1181 reportNewEdgeDrags(dx, dy, pointerId); 1182 if (mDragState == STATE_DRAGGING) { 1183 // Callback might have started an edge drag. 1184 break; 1185 } 1186 1187 final View toCapture = findTopChildUnder((int) x, (int) y); 1188 if (checkTouchSlop(toCapture, dx, dy) 1189 && tryCaptureViewForDrag(toCapture, pointerId)) { 1190 break; 1191 } 1192 } 1193 saveLastMotion(ev); 1194 } 1195 break; 1196 } 1197 1198 case MotionEventCompat.ACTION_POINTER_UP: { 1199 final int pointerId = ev.getPointerId(actionIndex); 1200 if (mDragState == STATE_DRAGGING && pointerId == mActivePointerId) { 1201 // Try to find another pointer that's still holding on to the captured view. 1202 int newActivePointer = INVALID_POINTER; 1203 final int pointerCount = ev.getPointerCount(); 1204 for (int i = 0; i < pointerCount; i++) { 1205 final int id = ev.getPointerId(i); 1206 if (id == mActivePointerId) { 1207 // This one's going away, skip. 1208 continue; 1209 } 1210 1211 final float x = ev.getX(i); 1212 final float y = ev.getY(i); 1213 if (findTopChildUnder((int) x, (int) y) == mCapturedView 1214 && tryCaptureViewForDrag(mCapturedView, id)) { 1215 newActivePointer = mActivePointerId; 1216 break; 1217 } 1218 } 1219 1220 if (newActivePointer == INVALID_POINTER) { 1221 // We didn't find another pointer still touching the view, release it. 1222 releaseViewForPointerUp(); 1223 } 1224 } 1225 clearMotionHistory(pointerId); 1226 break; 1227 } 1228 1229 case MotionEvent.ACTION_UP: { 1230 if (mDragState == STATE_DRAGGING) { 1231 releaseViewForPointerUp(); 1232 } 1233 cancel(); 1234 break; 1235 } 1236 1237 case MotionEvent.ACTION_CANCEL: { 1238 if (mDragState == STATE_DRAGGING) { 1239 dispatchViewReleased(0, 0); 1240 } 1241 cancel(); 1242 break; 1243 } 1244 } 1245 } 1246 1247 private void reportNewEdgeDrags(float dx, float dy, int pointerId) { 1248 int dragsStarted = 0; 1249 if (checkNewEdgeDrag(dx, dy, pointerId, EDGE_LEFT)) { 1250 dragsStarted |= EDGE_LEFT; 1251 } 1252 if (checkNewEdgeDrag(dy, dx, pointerId, EDGE_TOP)) { 1253 dragsStarted |= EDGE_TOP; 1254 } 1255 if (checkNewEdgeDrag(dx, dy, pointerId, EDGE_RIGHT)) { 1256 dragsStarted |= EDGE_RIGHT; 1257 } 1258 if (checkNewEdgeDrag(dy, dx, pointerId, EDGE_BOTTOM)) { 1259 dragsStarted |= EDGE_BOTTOM; 1260 } 1261 1262 if (dragsStarted != 0) { 1263 mEdgeDragsInProgress[pointerId] |= dragsStarted; 1264 mCallback.onEdgeDragStarted(dragsStarted, pointerId); 1265 } 1266 } 1267 1268 private boolean checkNewEdgeDrag(float delta, float odelta, int pointerId, int edge) { 1269 final float absDelta = Math.abs(delta); 1270 final float absODelta = Math.abs(odelta); 1271 1272 if ((mInitialEdgesTouched[pointerId] & edge) != edge || (mTrackingEdges & edge) == 0 1273 || (mEdgeDragsLocked[pointerId] & edge) == edge 1274 || (mEdgeDragsInProgress[pointerId] & edge) == edge 1275 || (absDelta <= mTouchSlop && absODelta <= mTouchSlop)) { 1276 return false; 1277 } 1278 if (absDelta < absODelta * 0.5f && mCallback.onEdgeLock(edge)) { 1279 mEdgeDragsLocked[pointerId] |= edge; 1280 return false; 1281 } 1282 return (mEdgeDragsInProgress[pointerId] & edge) == 0 && absDelta > mTouchSlop; 1283 } 1284 1285 /** 1286 * Check if we've crossed a reasonable touch slop for the given child view. 1287 * If the child cannot be dragged along the horizontal or vertical axis, motion 1288 * along that axis will not count toward the slop check. 1289 * 1290 * @param child Child to check 1291 * @param dx Motion since initial position along X axis 1292 * @param dy Motion since initial position along Y axis 1293 * @return true if the touch slop has been crossed 1294 */ 1295 private boolean checkTouchSlop(View child, float dx, float dy) { 1296 if (child == null) { 1297 return false; 1298 } 1299 final boolean checkHorizontal = mCallback.getViewHorizontalDragRange(child) > 0; 1300 final boolean checkVertical = mCallback.getViewVerticalDragRange(child) > 0; 1301 1302 if (checkHorizontal && checkVertical) { 1303 return dx * dx + dy * dy > mTouchSlop * mTouchSlop; 1304 } else if (checkHorizontal) { 1305 return Math.abs(dx) > mTouchSlop; 1306 } else if (checkVertical) { 1307 return Math.abs(dy) > mTouchSlop; 1308 } 1309 return false; 1310 } 1311 1312 /** 1313 * Check if any pointer tracked in the current gesture has crossed 1314 * the required slop threshold. 1315 * 1316 * <p>This depends on internal state populated by 1317 * {@link #shouldInterceptTouchEvent(android.view.MotionEvent)} or 1318 * {@link #processTouchEvent(android.view.MotionEvent)}. You should only rely on 1319 * the results of this method after all currently available touch data 1320 * has been provided to one of these two methods.</p> 1321 * 1322 * @param directions Combination of direction flags, see {@link #DIRECTION_HORIZONTAL}, 1323 * {@link #DIRECTION_VERTICAL}, {@link #DIRECTION_ALL} 1324 * @return true if the slop threshold has been crossed, false otherwise 1325 */ 1326 public boolean checkTouchSlop(int directions) { 1327 final int count = mInitialMotionX.length; 1328 for (int i = 0; i < count; i++) { 1329 if (checkTouchSlop(directions, i)) { 1330 return true; 1331 } 1332 } 1333 return false; 1334 } 1335 1336 /** 1337 * Check if the specified pointer tracked in the current gesture has crossed 1338 * the required slop threshold. 1339 * 1340 * <p>This depends on internal state populated by 1341 * {@link #shouldInterceptTouchEvent(android.view.MotionEvent)} or 1342 * {@link #processTouchEvent(android.view.MotionEvent)}. You should only rely on 1343 * the results of this method after all currently available touch data 1344 * has been provided to one of these two methods.</p> 1345 * 1346 * @param directions Combination of direction flags, see {@link #DIRECTION_HORIZONTAL}, 1347 * {@link #DIRECTION_VERTICAL}, {@link #DIRECTION_ALL} 1348 * @param pointerId ID of the pointer to slop check as specified by MotionEvent 1349 * @return true if the slop threshold has been crossed, false otherwise 1350 */ 1351 public boolean checkTouchSlop(int directions, int pointerId) { 1352 if (!isPointerDown(pointerId)) { 1353 return false; 1354 } 1355 1356 final boolean checkHorizontal = (directions & DIRECTION_HORIZONTAL) == DIRECTION_HORIZONTAL; 1357 final boolean checkVertical = (directions & DIRECTION_VERTICAL) == DIRECTION_VERTICAL; 1358 1359 final float dx = mLastMotionX[pointerId] - mInitialMotionX[pointerId]; 1360 final float dy = mLastMotionY[pointerId] - mInitialMotionY[pointerId]; 1361 1362 if (checkHorizontal && checkVertical) { 1363 return dx * dx + dy * dy > mTouchSlop * mTouchSlop; 1364 } else if (checkHorizontal) { 1365 return Math.abs(dx) > mTouchSlop; 1366 } else if (checkVertical) { 1367 return Math.abs(dy) > mTouchSlop; 1368 } 1369 return false; 1370 } 1371 1372 /** 1373 * Check if any of the edges specified were initially touched in the currently active gesture. 1374 * If there is no currently active gesture this method will return false. 1375 * 1376 * @param edges Edges to check for an initial edge touch. See {@link #EDGE_LEFT}, 1377 * {@link #EDGE_TOP}, {@link #EDGE_RIGHT}, {@link #EDGE_BOTTOM} and 1378 * {@link #EDGE_ALL} 1379 * @return true if any of the edges specified were initially touched in the current gesture 1380 */ 1381 public boolean isEdgeTouched(int edges) { 1382 final int count = mInitialEdgesTouched.length; 1383 for (int i = 0; i < count; i++) { 1384 if (isEdgeTouched(edges, i)) { 1385 return true; 1386 } 1387 } 1388 return false; 1389 } 1390 1391 /** 1392 * Check if any of the edges specified were initially touched by the pointer with 1393 * the specified ID. If there is no currently active gesture or if there is no pointer with 1394 * the given ID currently down this method will return false. 1395 * 1396 * @param edges Edges to check for an initial edge touch. See {@link #EDGE_LEFT}, 1397 * {@link #EDGE_TOP}, {@link #EDGE_RIGHT}, {@link #EDGE_BOTTOM} and 1398 * {@link #EDGE_ALL} 1399 * @return true if any of the edges specified were initially touched in the current gesture 1400 */ 1401 public boolean isEdgeTouched(int edges, int pointerId) { 1402 return isPointerDown(pointerId) && (mInitialEdgesTouched[pointerId] & edges) != 0; 1403 } 1404 1405 private void releaseViewForPointerUp() { 1406 mVelocityTracker.computeCurrentVelocity(1000, mMaxVelocity); 1407 final float xvel = clampMag( 1408 VelocityTrackerCompat.getXVelocity(mVelocityTracker, mActivePointerId), 1409 mMinVelocity, mMaxVelocity); 1410 final float yvel = clampMag( 1411 VelocityTrackerCompat.getYVelocity(mVelocityTracker, mActivePointerId), 1412 mMinVelocity, mMaxVelocity); 1413 dispatchViewReleased(xvel, yvel); 1414 } 1415 1416 private void dragTo(int left, int top, int dx, int dy) { 1417 int clampedX = left; 1418 int clampedY = top; 1419 final int oldLeft = mCapturedView.getLeft(); 1420 final int oldTop = mCapturedView.getTop(); 1421 if (dx != 0) { 1422 clampedX = mCallback.clampViewPositionHorizontal(mCapturedView, left, dx); 1423 ViewCompat.offsetLeftAndRight(mCapturedView, clampedX - oldLeft); 1424 } 1425 if (dy != 0) { 1426 clampedY = mCallback.clampViewPositionVertical(mCapturedView, top, dy); 1427 ViewCompat.offsetTopAndBottom(mCapturedView, clampedY - oldTop); 1428 } 1429 1430 if (dx != 0 || dy != 0) { 1431 final int clampedDx = clampedX - oldLeft; 1432 final int clampedDy = clampedY - oldTop; 1433 mCallback.onViewPositionChanged(mCapturedView, clampedX, clampedY, 1434 clampedDx, clampedDy); 1435 } 1436 } 1437 1438 /** 1439 * Determine if the currently captured view is under the given point in the 1440 * parent view's coordinate system. If there is no captured view this method 1441 * will return false. 1442 * 1443 * @param x X position to test in the parent's coordinate system 1444 * @param y Y position to test in the parent's coordinate system 1445 * @return true if the captured view is under the given point, false otherwise 1446 */ 1447 public boolean isCapturedViewUnder(int x, int y) { 1448 return isViewUnder(mCapturedView, x, y); 1449 } 1450 1451 /** 1452 * Determine if the supplied view is under the given point in the 1453 * parent view's coordinate system. 1454 * 1455 * @param view Child view of the parent to hit test 1456 * @param x X position to test in the parent's coordinate system 1457 * @param y Y position to test in the parent's coordinate system 1458 * @return true if the supplied view is under the given point, false otherwise 1459 */ 1460 public boolean isViewUnder(View view, int x, int y) { 1461 if (view == null) { 1462 return false; 1463 } 1464 return x >= view.getLeft() 1465 && x < view.getRight() 1466 && y >= view.getTop() 1467 && y < view.getBottom(); 1468 } 1469 1470 /** 1471 * Find the topmost child under the given point within the parent view's coordinate system. 1472 * The child order is determined using {@link Callback#getOrderedChildIndex(int)}. 1473 * 1474 * @param x X position to test in the parent's coordinate system 1475 * @param y Y position to test in the parent's coordinate system 1476 * @return The topmost child view under (x, y) or null if none found. 1477 */ 1478 public View findTopChildUnder(int x, int y) { 1479 final int childCount = mParentView.getChildCount(); 1480 for (int i = childCount - 1; i >= 0; i--) { 1481 final View child = mParentView.getChildAt(mCallback.getOrderedChildIndex(i)); 1482 if (x >= child.getLeft() && x < child.getRight() 1483 && y >= child.getTop() && y < child.getBottom()) { 1484 return child; 1485 } 1486 } 1487 return null; 1488 } 1489 1490 private int getEdgesTouched(int x, int y) { 1491 int result = 0; 1492 1493 if (x < mParentView.getLeft() + mEdgeSize) result |= EDGE_LEFT; 1494 if (y < mParentView.getTop() + mEdgeSize) result |= EDGE_TOP; 1495 if (x > mParentView.getRight() - mEdgeSize) result |= EDGE_RIGHT; 1496 if (y > mParentView.getBottom() - mEdgeSize) result |= EDGE_BOTTOM; 1497 1498 return result; 1499 } 1500 1501 private boolean isValidPointerForActionMove(int pointerId) { 1502 if (!isPointerDown(pointerId)) { 1503 Log.e(TAG, "Ignoring pointerId=" + pointerId + " because ACTION_DOWN was not received " 1504 + "for this pointer before ACTION_MOVE. It likely happened because " 1505 + " ViewDragHelper did not receive all the events in the event stream."); 1506 return false; 1507 } 1508 return true; 1509 } 1510} 1511