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