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.ViewCompat; 22 import android.util.Log; 23 import android.view.MotionEvent; 24 import android.view.VelocityTracker; 25 import android.view.View; 26 import android.view.ViewConfiguration; 27 import android.view.ViewGroup; 28 import android.view.animation.Interpolator; 29 import android.widget.OverScroller; 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 OverScroller 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 abstract static 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 @Override 328 public float getInterpolation(float t) { 329 t -= 1.0f; 330 return t * t * t * t * t + 1.0f; 331 } 332 }; 333 334 private final Runnable mSetIdleRunnable = new Runnable() { 335 @Override 336 public void run() { 337 setDragState(STATE_IDLE); 338 } 339 }; 340 341 /** 342 * Factory method to create a new ViewDragHelper. 343 * 344 * @param forParent Parent view to monitor 345 * @param cb Callback to provide information and receive events 346 * @return a new ViewDragHelper instance 347 */ create(ViewGroup forParent, Callback cb)348 public static ViewDragHelper create(ViewGroup forParent, Callback cb) { 349 return new ViewDragHelper(forParent.getContext(), forParent, cb); 350 } 351 352 /** 353 * Factory method to create a new ViewDragHelper. 354 * 355 * @param forParent Parent view to monitor 356 * @param sensitivity Multiplier for how sensitive the helper should be about detecting 357 * the start of a drag. Larger values are more sensitive. 1.0f is normal. 358 * @param cb Callback to provide information and receive events 359 * @return a new ViewDragHelper instance 360 */ create(ViewGroup forParent, float sensitivity, Callback cb)361 public static ViewDragHelper create(ViewGroup forParent, float sensitivity, Callback cb) { 362 final ViewDragHelper helper = create(forParent, cb); 363 helper.mTouchSlop = (int) (helper.mTouchSlop * (1 / sensitivity)); 364 return helper; 365 } 366 367 /** 368 * Apps should use ViewDragHelper.create() to get a new instance. 369 * This will allow VDH to use internal compatibility implementations for different 370 * platform versions. 371 * 372 * @param context Context to initialize config-dependent params from 373 * @param forParent Parent view to monitor 374 */ ViewDragHelper(Context context, ViewGroup forParent, Callback cb)375 private ViewDragHelper(Context context, ViewGroup forParent, Callback cb) { 376 if (forParent == null) { 377 throw new IllegalArgumentException("Parent view may not be null"); 378 } 379 if (cb == null) { 380 throw new IllegalArgumentException("Callback may not be null"); 381 } 382 383 mParentView = forParent; 384 mCallback = cb; 385 386 final ViewConfiguration vc = ViewConfiguration.get(context); 387 final float density = context.getResources().getDisplayMetrics().density; 388 mEdgeSize = (int) (EDGE_SIZE * density + 0.5f); 389 390 mTouchSlop = vc.getScaledTouchSlop(); 391 mMaxVelocity = vc.getScaledMaximumFlingVelocity(); 392 mMinVelocity = vc.getScaledMinimumFlingVelocity(); 393 mScroller = new OverScroller(context, sInterpolator); 394 } 395 396 /** 397 * Set the minimum velocity that will be detected as having a magnitude greater than zero 398 * in pixels per second. Callback methods accepting a velocity will be clamped appropriately. 399 * 400 * @param minVel Minimum velocity to detect 401 */ setMinVelocity(float minVel)402 public void setMinVelocity(float minVel) { 403 mMinVelocity = minVel; 404 } 405 406 /** 407 * Return the currently configured minimum velocity. Any flings with a magnitude less 408 * than this value in pixels per second. Callback methods accepting a velocity will receive 409 * zero as a velocity value if the real detected velocity was below this threshold. 410 * 411 * @return the minimum velocity that will be detected 412 */ getMinVelocity()413 public float getMinVelocity() { 414 return mMinVelocity; 415 } 416 417 /** 418 * Retrieve the current drag state of this helper. This will return one of 419 * {@link #STATE_IDLE}, {@link #STATE_DRAGGING} or {@link #STATE_SETTLING}. 420 * @return The current drag state 421 */ getViewDragState()422 public int getViewDragState() { 423 return mDragState; 424 } 425 426 /** 427 * Enable edge tracking for the selected edges of the parent view. 428 * The callback's {@link Callback#onEdgeTouched(int, int)} and 429 * {@link Callback#onEdgeDragStarted(int, int)} methods will only be invoked 430 * for edges for which edge tracking has been enabled. 431 * 432 * @param edgeFlags Combination of edge flags describing the edges to watch 433 * @see #EDGE_LEFT 434 * @see #EDGE_TOP 435 * @see #EDGE_RIGHT 436 * @see #EDGE_BOTTOM 437 */ setEdgeTrackingEnabled(int edgeFlags)438 public void setEdgeTrackingEnabled(int edgeFlags) { 439 mTrackingEdges = edgeFlags; 440 } 441 442 /** 443 * Return the size of an edge. This is the range in pixels along the edges of this view 444 * that will actively detect edge touches or drags if edge tracking is enabled. 445 * 446 * @return The size of an edge in pixels 447 * @see #setEdgeTrackingEnabled(int) 448 */ getEdgeSize()449 public int getEdgeSize() { 450 return mEdgeSize; 451 } 452 453 /** 454 * Capture a specific child view for dragging within the parent. The callback will be notified 455 * but {@link Callback#tryCaptureView(android.view.View, int)} will not be asked permission to 456 * capture this view. 457 * 458 * @param childView Child view to capture 459 * @param activePointerId ID of the pointer that is dragging the captured child view 460 */ captureChildView(View childView, int activePointerId)461 public void captureChildView(View childView, int activePointerId) { 462 if (childView.getParent() != mParentView) { 463 throw new IllegalArgumentException("captureChildView: parameter must be a descendant " 464 + "of the ViewDragHelper's tracked parent view (" + mParentView + ")"); 465 } 466 467 mCapturedView = childView; 468 mActivePointerId = activePointerId; 469 mCallback.onViewCaptured(childView, activePointerId); 470 setDragState(STATE_DRAGGING); 471 } 472 473 /** 474 * @return The currently captured view, or null if no view has been captured. 475 */ getCapturedView()476 public View getCapturedView() { 477 return mCapturedView; 478 } 479 480 /** 481 * @return The ID of the pointer currently dragging the captured view, 482 * or {@link #INVALID_POINTER}. 483 */ getActivePointerId()484 public int getActivePointerId() { 485 return mActivePointerId; 486 } 487 488 /** 489 * @return The minimum distance in pixels that the user must travel to initiate a drag 490 */ getTouchSlop()491 public int getTouchSlop() { 492 return mTouchSlop; 493 } 494 495 /** 496 * The result of a call to this method is equivalent to 497 * {@link #processTouchEvent(android.view.MotionEvent)} receiving an ACTION_CANCEL event. 498 */ cancel()499 public void cancel() { 500 mActivePointerId = INVALID_POINTER; 501 clearMotionHistory(); 502 503 if (mVelocityTracker != null) { 504 mVelocityTracker.recycle(); 505 mVelocityTracker = null; 506 } 507 } 508 509 /** 510 * {@link #cancel()}, but also abort all motion in progress and snap to the end of any 511 * animation. 512 */ abort()513 public void abort() { 514 cancel(); 515 if (mDragState == STATE_SETTLING) { 516 final int oldX = mScroller.getCurrX(); 517 final int oldY = mScroller.getCurrY(); 518 mScroller.abortAnimation(); 519 final int newX = mScroller.getCurrX(); 520 final int newY = mScroller.getCurrY(); 521 mCallback.onViewPositionChanged(mCapturedView, newX, newY, newX - oldX, newY - oldY); 522 } 523 setDragState(STATE_IDLE); 524 } 525 526 /** 527 * Animate the view <code>child</code> to the given (left, top) position. 528 * If this method returns true, the caller should invoke {@link #continueSettling(boolean)} 529 * on each subsequent frame to continue the motion until it returns false. If this method 530 * returns false there is no further work to do to complete the movement. 531 * 532 * <p>This operation does not count as a capture event, though {@link #getCapturedView()} 533 * will still report the sliding view while the slide is in progress.</p> 534 * 535 * @param child Child view to capture and animate 536 * @param finalLeft Final left position of child 537 * @param finalTop Final top position of child 538 * @return true if animation should continue through {@link #continueSettling(boolean)} calls 539 */ smoothSlideViewTo(View child, int finalLeft, int finalTop)540 public boolean smoothSlideViewTo(View child, int finalLeft, int finalTop) { 541 mCapturedView = child; 542 mActivePointerId = INVALID_POINTER; 543 544 boolean continueSliding = forceSettleCapturedViewAt(finalLeft, finalTop, 0, 0); 545 if (!continueSliding && mDragState == STATE_IDLE && mCapturedView != null) { 546 // If we're in an IDLE state to begin with and aren't moving anywhere, we 547 // end up having a non-null capturedView with an IDLE dragState 548 mCapturedView = null; 549 } 550 551 return continueSliding; 552 } 553 554 /** 555 * Settle the captured view at the given (left, top) position. 556 * The appropriate velocity from prior motion will be taken into account. 557 * If this method returns true, the caller should invoke {@link #continueSettling(boolean)} 558 * on each subsequent frame to continue the motion until it returns false. If this method 559 * returns false there is no further work to do to complete the movement. 560 * 561 * @param finalLeft Settled left edge position for the captured view 562 * @param finalTop Settled top edge position for the captured view 563 * @return true if animation should continue through {@link #continueSettling(boolean)} calls 564 */ settleCapturedViewAt(int finalLeft, int finalTop)565 public boolean settleCapturedViewAt(int finalLeft, int finalTop) { 566 if (!mReleaseInProgress) { 567 throw new IllegalStateException("Cannot settleCapturedViewAt outside of a call to " 568 + "Callback#onViewReleased"); 569 } 570 571 return forceSettleCapturedViewAt(finalLeft, finalTop, 572 (int) mVelocityTracker.getXVelocity(mActivePointerId), 573 (int) mVelocityTracker.getYVelocity(mActivePointerId)); 574 } 575 576 /** 577 * Settle the captured view at the given (left, top) position. 578 * 579 * @param finalLeft Target left position for the captured view 580 * @param finalTop Target top position for the captured view 581 * @param xvel Horizontal velocity 582 * @param yvel Vertical velocity 583 * @return true if animation should continue through {@link #continueSettling(boolean)} calls 584 */ forceSettleCapturedViewAt(int finalLeft, int finalTop, int xvel, int yvel)585 private boolean forceSettleCapturedViewAt(int finalLeft, int finalTop, int xvel, int yvel) { 586 final int startLeft = mCapturedView.getLeft(); 587 final int startTop = mCapturedView.getTop(); 588 final int dx = finalLeft - startLeft; 589 final int dy = finalTop - startTop; 590 591 if (dx == 0 && dy == 0) { 592 // Nothing to do. Send callbacks, be done. 593 mScroller.abortAnimation(); 594 setDragState(STATE_IDLE); 595 return false; 596 } 597 598 final int duration = computeSettleDuration(mCapturedView, dx, dy, xvel, yvel); 599 mScroller.startScroll(startLeft, startTop, dx, dy, duration); 600 601 setDragState(STATE_SETTLING); 602 return true; 603 } 604 computeSettleDuration(View child, int dx, int dy, int xvel, int yvel)605 private int computeSettleDuration(View child, int dx, int dy, int xvel, int yvel) { 606 xvel = clampMag(xvel, (int) mMinVelocity, (int) mMaxVelocity); 607 yvel = clampMag(yvel, (int) mMinVelocity, (int) mMaxVelocity); 608 final int absDx = Math.abs(dx); 609 final int absDy = Math.abs(dy); 610 final int absXVel = Math.abs(xvel); 611 final int absYVel = Math.abs(yvel); 612 final int addedVel = absXVel + absYVel; 613 final int addedDistance = absDx + absDy; 614 615 final float xweight = xvel != 0 ? (float) absXVel / addedVel : 616 (float) absDx / addedDistance; 617 final float yweight = yvel != 0 ? (float) absYVel / addedVel : 618 (float) absDy / addedDistance; 619 620 int xduration = computeAxisDuration(dx, xvel, mCallback.getViewHorizontalDragRange(child)); 621 int yduration = computeAxisDuration(dy, yvel, mCallback.getViewVerticalDragRange(child)); 622 623 return (int) (xduration * xweight + yduration * yweight); 624 } 625 computeAxisDuration(int delta, int velocity, int motionRange)626 private int computeAxisDuration(int delta, int velocity, int motionRange) { 627 if (delta == 0) { 628 return 0; 629 } 630 631 final int width = mParentView.getWidth(); 632 final int halfWidth = width / 2; 633 final float distanceRatio = Math.min(1f, (float) Math.abs(delta) / width); 634 final float distance = halfWidth + halfWidth 635 * distanceInfluenceForSnapDuration(distanceRatio); 636 637 int duration; 638 velocity = Math.abs(velocity); 639 if (velocity > 0) { 640 duration = 4 * Math.round(1000 * Math.abs(distance / velocity)); 641 } else { 642 final float range = (float) Math.abs(delta) / motionRange; 643 duration = (int) ((range + 1) * BASE_SETTLE_DURATION); 644 } 645 return Math.min(duration, MAX_SETTLE_DURATION); 646 } 647 648 /** 649 * Clamp the magnitude of value for absMin and absMax. 650 * If the value is below the minimum, it will be clamped to zero. 651 * If the value is above the maximum, it will be clamped to the maximum. 652 * 653 * @param value Value to clamp 654 * @param absMin Absolute value of the minimum significant value to return 655 * @param absMax Absolute value of the maximum value to return 656 * @return The clamped value with the same sign as <code>value</code> 657 */ clampMag(int value, int absMin, int absMax)658 private int clampMag(int value, int absMin, int absMax) { 659 final int absValue = Math.abs(value); 660 if (absValue < absMin) return 0; 661 if (absValue > absMax) return value > 0 ? absMax : -absMax; 662 return value; 663 } 664 665 /** 666 * Clamp the magnitude of value for absMin and absMax. 667 * If the value is below the minimum, it will be clamped to zero. 668 * If the value is above the maximum, it will be clamped to the maximum. 669 * 670 * @param value Value to clamp 671 * @param absMin Absolute value of the minimum significant value to return 672 * @param absMax Absolute value of the maximum value to return 673 * @return The clamped value with the same sign as <code>value</code> 674 */ clampMag(float value, float absMin, float absMax)675 private float clampMag(float value, float absMin, float absMax) { 676 final float absValue = Math.abs(value); 677 if (absValue < absMin) return 0; 678 if (absValue > absMax) return value > 0 ? absMax : -absMax; 679 return value; 680 } 681 distanceInfluenceForSnapDuration(float f)682 private float distanceInfluenceForSnapDuration(float f) { 683 f -= 0.5f; // center the values about 0. 684 f *= 0.3f * (float) Math.PI / 2.0f; 685 return (float) Math.sin(f); 686 } 687 688 /** 689 * Settle the captured view based on standard free-moving fling behavior. 690 * The caller should invoke {@link #continueSettling(boolean)} on each subsequent frame 691 * to continue the motion until it returns false. 692 * 693 * @param minLeft Minimum X position for the view's left edge 694 * @param minTop Minimum Y position for the view's top edge 695 * @param maxLeft Maximum X position for the view's left edge 696 * @param maxTop Maximum Y position for the view's top edge 697 */ flingCapturedView(int minLeft, int minTop, int maxLeft, int maxTop)698 public void flingCapturedView(int minLeft, int minTop, int maxLeft, int maxTop) { 699 if (!mReleaseInProgress) { 700 throw new IllegalStateException("Cannot flingCapturedView outside of a call to " 701 + "Callback#onViewReleased"); 702 } 703 704 mScroller.fling(mCapturedView.getLeft(), mCapturedView.getTop(), 705 (int) mVelocityTracker.getXVelocity(mActivePointerId), 706 (int) mVelocityTracker.getYVelocity(mActivePointerId), 707 minLeft, maxLeft, minTop, maxTop); 708 709 setDragState(STATE_SETTLING); 710 } 711 712 /** 713 * Move the captured settling view by the appropriate amount for the current time. 714 * If <code>continueSettling</code> returns true, the caller should call it again 715 * on the next frame to continue. 716 * 717 * @param deferCallbacks true if state callbacks should be deferred via posted message. 718 * Set this to true if you are calling this method from 719 * {@link android.view.View#computeScroll()} or similar methods 720 * invoked as part of layout or drawing. 721 * @return true if settle is still in progress 722 */ continueSettling(boolean deferCallbacks)723 public boolean continueSettling(boolean deferCallbacks) { 724 if (mDragState == STATE_SETTLING) { 725 boolean keepGoing = mScroller.computeScrollOffset(); 726 final int x = mScroller.getCurrX(); 727 final int y = mScroller.getCurrY(); 728 final int dx = x - mCapturedView.getLeft(); 729 final int dy = y - mCapturedView.getTop(); 730 731 if (dx != 0) { 732 ViewCompat.offsetLeftAndRight(mCapturedView, dx); 733 } 734 if (dy != 0) { 735 ViewCompat.offsetTopAndBottom(mCapturedView, dy); 736 } 737 738 if (dx != 0 || dy != 0) { 739 mCallback.onViewPositionChanged(mCapturedView, x, y, dx, dy); 740 } 741 742 if (keepGoing && x == mScroller.getFinalX() && y == mScroller.getFinalY()) { 743 // Close enough. The interpolator/scroller might think we're still moving 744 // but the user sure doesn't. 745 mScroller.abortAnimation(); 746 keepGoing = false; 747 } 748 749 if (!keepGoing) { 750 if (deferCallbacks) { 751 mParentView.post(mSetIdleRunnable); 752 } else { 753 setDragState(STATE_IDLE); 754 } 755 } 756 } 757 758 return mDragState == STATE_SETTLING; 759 } 760 761 /** 762 * Like all callback events this must happen on the UI thread, but release 763 * involves some extra semantics. During a release (mReleaseInProgress) 764 * is the only time it is valid to call {@link #settleCapturedViewAt(int, int)} 765 * or {@link #flingCapturedView(int, int, int, int)}. 766 */ dispatchViewReleased(float xvel, float yvel)767 private void dispatchViewReleased(float xvel, float yvel) { 768 mReleaseInProgress = true; 769 mCallback.onViewReleased(mCapturedView, xvel, yvel); 770 mReleaseInProgress = false; 771 772 if (mDragState == STATE_DRAGGING) { 773 // onViewReleased didn't call a method that would have changed this. Go idle. 774 setDragState(STATE_IDLE); 775 } 776 } 777 clearMotionHistory()778 private void clearMotionHistory() { 779 if (mInitialMotionX == null) { 780 return; 781 } 782 Arrays.fill(mInitialMotionX, 0); 783 Arrays.fill(mInitialMotionY, 0); 784 Arrays.fill(mLastMotionX, 0); 785 Arrays.fill(mLastMotionY, 0); 786 Arrays.fill(mInitialEdgesTouched, 0); 787 Arrays.fill(mEdgeDragsInProgress, 0); 788 Arrays.fill(mEdgeDragsLocked, 0); 789 mPointersDown = 0; 790 } 791 clearMotionHistory(int pointerId)792 private void clearMotionHistory(int pointerId) { 793 if (mInitialMotionX == null || !isPointerDown(pointerId)) { 794 return; 795 } 796 mInitialMotionX[pointerId] = 0; 797 mInitialMotionY[pointerId] = 0; 798 mLastMotionX[pointerId] = 0; 799 mLastMotionY[pointerId] = 0; 800 mInitialEdgesTouched[pointerId] = 0; 801 mEdgeDragsInProgress[pointerId] = 0; 802 mEdgeDragsLocked[pointerId] = 0; 803 mPointersDown &= ~(1 << pointerId); 804 } 805 ensureMotionHistorySizeForId(int pointerId)806 private void ensureMotionHistorySizeForId(int pointerId) { 807 if (mInitialMotionX == null || mInitialMotionX.length <= pointerId) { 808 float[] imx = new float[pointerId + 1]; 809 float[] imy = new float[pointerId + 1]; 810 float[] lmx = new float[pointerId + 1]; 811 float[] lmy = new float[pointerId + 1]; 812 int[] iit = new int[pointerId + 1]; 813 int[] edip = new int[pointerId + 1]; 814 int[] edl = new int[pointerId + 1]; 815 816 if (mInitialMotionX != null) { 817 System.arraycopy(mInitialMotionX, 0, imx, 0, mInitialMotionX.length); 818 System.arraycopy(mInitialMotionY, 0, imy, 0, mInitialMotionY.length); 819 System.arraycopy(mLastMotionX, 0, lmx, 0, mLastMotionX.length); 820 System.arraycopy(mLastMotionY, 0, lmy, 0, mLastMotionY.length); 821 System.arraycopy(mInitialEdgesTouched, 0, iit, 0, mInitialEdgesTouched.length); 822 System.arraycopy(mEdgeDragsInProgress, 0, edip, 0, mEdgeDragsInProgress.length); 823 System.arraycopy(mEdgeDragsLocked, 0, edl, 0, mEdgeDragsLocked.length); 824 } 825 826 mInitialMotionX = imx; 827 mInitialMotionY = imy; 828 mLastMotionX = lmx; 829 mLastMotionY = lmy; 830 mInitialEdgesTouched = iit; 831 mEdgeDragsInProgress = edip; 832 mEdgeDragsLocked = edl; 833 } 834 } 835 saveInitialMotion(float x, float y, int pointerId)836 private void saveInitialMotion(float x, float y, int pointerId) { 837 ensureMotionHistorySizeForId(pointerId); 838 mInitialMotionX[pointerId] = mLastMotionX[pointerId] = x; 839 mInitialMotionY[pointerId] = mLastMotionY[pointerId] = y; 840 mInitialEdgesTouched[pointerId] = getEdgesTouched((int) x, (int) y); 841 mPointersDown |= 1 << pointerId; 842 } 843 saveLastMotion(MotionEvent ev)844 private void saveLastMotion(MotionEvent ev) { 845 final int pointerCount = ev.getPointerCount(); 846 for (int i = 0; i < pointerCount; i++) { 847 final int pointerId = ev.getPointerId(i); 848 // If pointer is invalid then skip saving on ACTION_MOVE. 849 if (!isValidPointerForActionMove(pointerId)) { 850 continue; 851 } 852 final float x = ev.getX(i); 853 final float y = ev.getY(i); 854 mLastMotionX[pointerId] = x; 855 mLastMotionY[pointerId] = y; 856 } 857 } 858 859 /** 860 * Check if the given pointer ID represents a pointer that is currently down (to the best 861 * of the ViewDragHelper's knowledge). 862 * 863 * <p>The state used to report this information is populated by the methods 864 * {@link #shouldInterceptTouchEvent(android.view.MotionEvent)} or 865 * {@link #processTouchEvent(android.view.MotionEvent)}. If one of these methods has not 866 * been called for all relevant MotionEvents to track, the information reported 867 * by this method may be stale or incorrect.</p> 868 * 869 * @param pointerId pointer ID to check; corresponds to IDs provided by MotionEvent 870 * @return true if the pointer with the given ID is still down 871 */ isPointerDown(int pointerId)872 public boolean isPointerDown(int pointerId) { 873 return (mPointersDown & 1 << pointerId) != 0; 874 } 875 setDragState(int state)876 void setDragState(int state) { 877 mParentView.removeCallbacks(mSetIdleRunnable); 878 if (mDragState != state) { 879 mDragState = state; 880 mCallback.onViewDragStateChanged(state); 881 if (mDragState == STATE_IDLE) { 882 mCapturedView = null; 883 } 884 } 885 } 886 887 /** 888 * Attempt to capture the view with the given pointer ID. The callback will be involved. 889 * This will put us into the "dragging" state. If we've already captured this view with 890 * this pointer this method will immediately return true without consulting the callback. 891 * 892 * @param toCapture View to capture 893 * @param pointerId Pointer to capture with 894 * @return true if capture was successful 895 */ tryCaptureViewForDrag(View toCapture, int pointerId)896 boolean tryCaptureViewForDrag(View toCapture, int pointerId) { 897 if (toCapture == mCapturedView && mActivePointerId == pointerId) { 898 // Already done! 899 return true; 900 } 901 if (toCapture != null && mCallback.tryCaptureView(toCapture, pointerId)) { 902 mActivePointerId = pointerId; 903 captureChildView(toCapture, pointerId); 904 return true; 905 } 906 return false; 907 } 908 909 /** 910 * Tests scrollability within child views of v given a delta of dx. 911 * 912 * @param v View to test for horizontal scrollability 913 * @param checkV Whether the view v passed should itself be checked for scrollability (true), 914 * or just its children (false). 915 * @param dx Delta scrolled in pixels along the X axis 916 * @param dy Delta scrolled in pixels along the Y axis 917 * @param x X coordinate of the active touch point 918 * @param y Y coordinate of the active touch point 919 * @return true if child views of v can be scrolled by delta of dx. 920 */ canScroll(View v, boolean checkV, int dx, int dy, int x, int y)921 protected boolean canScroll(View v, boolean checkV, int dx, int dy, int x, int y) { 922 if (v instanceof ViewGroup) { 923 final ViewGroup group = (ViewGroup) v; 924 final int scrollX = v.getScrollX(); 925 final int scrollY = v.getScrollY(); 926 final int count = group.getChildCount(); 927 // Count backwards - let topmost views consume scroll distance first. 928 for (int i = count - 1; i >= 0; i--) { 929 // TODO: Add versioned support here for transformed views. 930 // This will not work for transformed views in Honeycomb+ 931 final View child = group.getChildAt(i); 932 if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() 933 && y + scrollY >= child.getTop() && y + scrollY < child.getBottom() 934 && canScroll(child, true, dx, dy, x + scrollX - child.getLeft(), 935 y + scrollY - child.getTop())) { 936 return true; 937 } 938 } 939 } 940 941 return checkV && (v.canScrollHorizontally(-dx) || v.canScrollVertically(-dy)); 942 } 943 944 /** 945 * Check if this event as provided to the parent view's onInterceptTouchEvent should 946 * cause the parent to intercept the touch event stream. 947 * 948 * @param ev MotionEvent provided to onInterceptTouchEvent 949 * @return true if the parent view should return true from onInterceptTouchEvent 950 */ shouldInterceptTouchEvent(MotionEvent ev)951 public boolean shouldInterceptTouchEvent(MotionEvent ev) { 952 final int action = ev.getActionMasked(); 953 final int actionIndex = ev.getActionIndex(); 954 955 if (action == MotionEvent.ACTION_DOWN) { 956 // Reset things for a new event stream, just in case we didn't get 957 // the whole previous stream. 958 cancel(); 959 } 960 961 if (mVelocityTracker == null) { 962 mVelocityTracker = VelocityTracker.obtain(); 963 } 964 mVelocityTracker.addMovement(ev); 965 966 switch (action) { 967 case MotionEvent.ACTION_DOWN: { 968 final float x = ev.getX(); 969 final float y = ev.getY(); 970 final int pointerId = ev.getPointerId(0); 971 saveInitialMotion(x, y, pointerId); 972 973 final View toCapture = findTopChildUnder((int) x, (int) y); 974 975 // Catch a settling view if possible. 976 if (toCapture == mCapturedView && mDragState == STATE_SETTLING) { 977 tryCaptureViewForDrag(toCapture, pointerId); 978 } 979 980 final int edgesTouched = mInitialEdgesTouched[pointerId]; 981 if ((edgesTouched & mTrackingEdges) != 0) { 982 mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId); 983 } 984 break; 985 } 986 987 case MotionEvent.ACTION_POINTER_DOWN: { 988 final int pointerId = ev.getPointerId(actionIndex); 989 final float x = ev.getX(actionIndex); 990 final float y = ev.getY(actionIndex); 991 992 saveInitialMotion(x, y, pointerId); 993 994 // A ViewDragHelper can only manipulate one view at a time. 995 if (mDragState == STATE_IDLE) { 996 final int edgesTouched = mInitialEdgesTouched[pointerId]; 997 if ((edgesTouched & mTrackingEdges) != 0) { 998 mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId); 999 } 1000 } else if (mDragState == STATE_SETTLING) { 1001 // Catch a settling view if possible. 1002 final View toCapture = findTopChildUnder((int) x, (int) y); 1003 if (toCapture == mCapturedView) { 1004 tryCaptureViewForDrag(toCapture, pointerId); 1005 } 1006 } 1007 break; 1008 } 1009 1010 case MotionEvent.ACTION_MOVE: { 1011 if (mInitialMotionX == null || mInitialMotionY == null) break; 1012 1013 // First to cross a touch slop over a draggable view wins. Also report edge drags. 1014 final int pointerCount = ev.getPointerCount(); 1015 for (int i = 0; i < pointerCount; i++) { 1016 final int pointerId = ev.getPointerId(i); 1017 1018 // If pointer is invalid then skip the ACTION_MOVE. 1019 if (!isValidPointerForActionMove(pointerId)) continue; 1020 1021 final float x = ev.getX(i); 1022 final float y = ev.getY(i); 1023 final float dx = x - mInitialMotionX[pointerId]; 1024 final float dy = y - mInitialMotionY[pointerId]; 1025 1026 final View toCapture = findTopChildUnder((int) x, (int) y); 1027 final boolean pastSlop = toCapture != null && checkTouchSlop(toCapture, dx, dy); 1028 if (pastSlop) { 1029 // check the callback's 1030 // getView[Horizontal|Vertical]DragRange methods to know 1031 // if you can move at all along an axis, then see if it 1032 // would clamp to the same value. If you can't move at 1033 // all in every dimension with a nonzero range, bail. 1034 final int oldLeft = toCapture.getLeft(); 1035 final int targetLeft = oldLeft + (int) dx; 1036 final int newLeft = mCallback.clampViewPositionHorizontal(toCapture, 1037 targetLeft, (int) dx); 1038 final int oldTop = toCapture.getTop(); 1039 final int targetTop = oldTop + (int) dy; 1040 final int newTop = mCallback.clampViewPositionVertical(toCapture, targetTop, 1041 (int) dy); 1042 final int hDragRange = mCallback.getViewHorizontalDragRange(toCapture); 1043 final int vDragRange = mCallback.getViewVerticalDragRange(toCapture); 1044 if ((hDragRange == 0 || (hDragRange > 0 && newLeft == oldLeft)) 1045 && (vDragRange == 0 || (vDragRange > 0 && newTop == oldTop))) { 1046 break; 1047 } 1048 } 1049 reportNewEdgeDrags(dx, dy, pointerId); 1050 if (mDragState == STATE_DRAGGING) { 1051 // Callback might have started an edge drag 1052 break; 1053 } 1054 1055 if (pastSlop && tryCaptureViewForDrag(toCapture, pointerId)) { 1056 break; 1057 } 1058 } 1059 saveLastMotion(ev); 1060 break; 1061 } 1062 1063 case MotionEvent.ACTION_POINTER_UP: { 1064 final int pointerId = ev.getPointerId(actionIndex); 1065 clearMotionHistory(pointerId); 1066 break; 1067 } 1068 1069 case MotionEvent.ACTION_UP: 1070 case MotionEvent.ACTION_CANCEL: { 1071 cancel(); 1072 break; 1073 } 1074 } 1075 1076 return mDragState == STATE_DRAGGING; 1077 } 1078 1079 /** 1080 * Process a touch event received by the parent view. This method will dispatch callback events 1081 * as needed before returning. The parent view's onTouchEvent implementation should call this. 1082 * 1083 * @param ev The touch event received by the parent view 1084 */ processTouchEvent(MotionEvent ev)1085 public void processTouchEvent(MotionEvent ev) { 1086 final int action = ev.getActionMasked(); 1087 final int actionIndex = ev.getActionIndex(); 1088 1089 if (action == MotionEvent.ACTION_DOWN) { 1090 // Reset things for a new event stream, just in case we didn't get 1091 // the whole previous stream. 1092 cancel(); 1093 } 1094 1095 if (mVelocityTracker == null) { 1096 mVelocityTracker = VelocityTracker.obtain(); 1097 } 1098 mVelocityTracker.addMovement(ev); 1099 1100 switch (action) { 1101 case MotionEvent.ACTION_DOWN: { 1102 final float x = ev.getX(); 1103 final float y = ev.getY(); 1104 final int pointerId = ev.getPointerId(0); 1105 final View toCapture = findTopChildUnder((int) x, (int) y); 1106 1107 saveInitialMotion(x, y, pointerId); 1108 1109 // Since the parent is already directly processing this touch event, 1110 // there is no reason to delay for a slop before dragging. 1111 // Start immediately if possible. 1112 tryCaptureViewForDrag(toCapture, pointerId); 1113 1114 final int edgesTouched = mInitialEdgesTouched[pointerId]; 1115 if ((edgesTouched & mTrackingEdges) != 0) { 1116 mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId); 1117 } 1118 break; 1119 } 1120 1121 case MotionEvent.ACTION_POINTER_DOWN: { 1122 final int pointerId = ev.getPointerId(actionIndex); 1123 final float x = ev.getX(actionIndex); 1124 final float y = ev.getY(actionIndex); 1125 1126 saveInitialMotion(x, y, pointerId); 1127 1128 // A ViewDragHelper can only manipulate one view at a time. 1129 if (mDragState == STATE_IDLE) { 1130 // If we're idle we can do anything! Treat it like a normal down event. 1131 1132 final View toCapture = findTopChildUnder((int) x, (int) y); 1133 tryCaptureViewForDrag(toCapture, pointerId); 1134 1135 final int edgesTouched = mInitialEdgesTouched[pointerId]; 1136 if ((edgesTouched & mTrackingEdges) != 0) { 1137 mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId); 1138 } 1139 } else if (isCapturedViewUnder((int) x, (int) y)) { 1140 // We're still tracking a captured view. If the same view is under this 1141 // point, we'll swap to controlling it with this pointer instead. 1142 // (This will still work if we're "catching" a settling view.) 1143 1144 tryCaptureViewForDrag(mCapturedView, pointerId); 1145 } 1146 break; 1147 } 1148 1149 case MotionEvent.ACTION_MOVE: { 1150 if (mDragState == STATE_DRAGGING) { 1151 // If pointer is invalid then skip the ACTION_MOVE. 1152 if (!isValidPointerForActionMove(mActivePointerId)) break; 1153 1154 final int index = ev.findPointerIndex(mActivePointerId); 1155 final float x = ev.getX(index); 1156 final float y = ev.getY(index); 1157 final int idx = (int) (x - mLastMotionX[mActivePointerId]); 1158 final int idy = (int) (y - mLastMotionY[mActivePointerId]); 1159 1160 dragTo(mCapturedView.getLeft() + idx, mCapturedView.getTop() + idy, idx, idy); 1161 1162 saveLastMotion(ev); 1163 } else { 1164 // Check to see if any pointer is now over a draggable view. 1165 final int pointerCount = ev.getPointerCount(); 1166 for (int i = 0; i < pointerCount; i++) { 1167 final int pointerId = ev.getPointerId(i); 1168 1169 // If pointer is invalid then skip the ACTION_MOVE. 1170 if (!isValidPointerForActionMove(pointerId)) continue; 1171 1172 final float x = ev.getX(i); 1173 final float y = ev.getY(i); 1174 final float dx = x - mInitialMotionX[pointerId]; 1175 final float dy = y - mInitialMotionY[pointerId]; 1176 1177 reportNewEdgeDrags(dx, dy, pointerId); 1178 if (mDragState == STATE_DRAGGING) { 1179 // Callback might have started an edge drag. 1180 break; 1181 } 1182 1183 final View toCapture = findTopChildUnder((int) x, (int) y); 1184 if (checkTouchSlop(toCapture, dx, dy) 1185 && tryCaptureViewForDrag(toCapture, pointerId)) { 1186 break; 1187 } 1188 } 1189 saveLastMotion(ev); 1190 } 1191 break; 1192 } 1193 1194 case MotionEvent.ACTION_POINTER_UP: { 1195 final int pointerId = ev.getPointerId(actionIndex); 1196 if (mDragState == STATE_DRAGGING && pointerId == mActivePointerId) { 1197 // Try to find another pointer that's still holding on to the captured view. 1198 int newActivePointer = INVALID_POINTER; 1199 final int pointerCount = ev.getPointerCount(); 1200 for (int i = 0; i < pointerCount; i++) { 1201 final int id = ev.getPointerId(i); 1202 if (id == mActivePointerId) { 1203 // This one's going away, skip. 1204 continue; 1205 } 1206 1207 final float x = ev.getX(i); 1208 final float y = ev.getY(i); 1209 if (findTopChildUnder((int) x, (int) y) == mCapturedView 1210 && tryCaptureViewForDrag(mCapturedView, id)) { 1211 newActivePointer = mActivePointerId; 1212 break; 1213 } 1214 } 1215 1216 if (newActivePointer == INVALID_POINTER) { 1217 // We didn't find another pointer still touching the view, release it. 1218 releaseViewForPointerUp(); 1219 } 1220 } 1221 clearMotionHistory(pointerId); 1222 break; 1223 } 1224 1225 case MotionEvent.ACTION_UP: { 1226 if (mDragState == STATE_DRAGGING) { 1227 releaseViewForPointerUp(); 1228 } 1229 cancel(); 1230 break; 1231 } 1232 1233 case MotionEvent.ACTION_CANCEL: { 1234 if (mDragState == STATE_DRAGGING) { 1235 dispatchViewReleased(0, 0); 1236 } 1237 cancel(); 1238 break; 1239 } 1240 } 1241 } 1242 reportNewEdgeDrags(float dx, float dy, int pointerId)1243 private void reportNewEdgeDrags(float dx, float dy, int pointerId) { 1244 int dragsStarted = 0; 1245 if (checkNewEdgeDrag(dx, dy, pointerId, EDGE_LEFT)) { 1246 dragsStarted |= EDGE_LEFT; 1247 } 1248 if (checkNewEdgeDrag(dy, dx, pointerId, EDGE_TOP)) { 1249 dragsStarted |= EDGE_TOP; 1250 } 1251 if (checkNewEdgeDrag(dx, dy, pointerId, EDGE_RIGHT)) { 1252 dragsStarted |= EDGE_RIGHT; 1253 } 1254 if (checkNewEdgeDrag(dy, dx, pointerId, EDGE_BOTTOM)) { 1255 dragsStarted |= EDGE_BOTTOM; 1256 } 1257 1258 if (dragsStarted != 0) { 1259 mEdgeDragsInProgress[pointerId] |= dragsStarted; 1260 mCallback.onEdgeDragStarted(dragsStarted, pointerId); 1261 } 1262 } 1263 checkNewEdgeDrag(float delta, float odelta, int pointerId, int edge)1264 private boolean checkNewEdgeDrag(float delta, float odelta, int pointerId, int edge) { 1265 final float absDelta = Math.abs(delta); 1266 final float absODelta = Math.abs(odelta); 1267 1268 if ((mInitialEdgesTouched[pointerId] & edge) != edge || (mTrackingEdges & edge) == 0 1269 || (mEdgeDragsLocked[pointerId] & edge) == edge 1270 || (mEdgeDragsInProgress[pointerId] & edge) == edge 1271 || (absDelta <= mTouchSlop && absODelta <= mTouchSlop)) { 1272 return false; 1273 } 1274 if (absDelta < absODelta * 0.5f && mCallback.onEdgeLock(edge)) { 1275 mEdgeDragsLocked[pointerId] |= edge; 1276 return false; 1277 } 1278 return (mEdgeDragsInProgress[pointerId] & edge) == 0 && absDelta > mTouchSlop; 1279 } 1280 1281 /** 1282 * Check if we've crossed a reasonable touch slop for the given child view. 1283 * If the child cannot be dragged along the horizontal or vertical axis, motion 1284 * along that axis will not count toward the slop check. 1285 * 1286 * @param child Child to check 1287 * @param dx Motion since initial position along X axis 1288 * @param dy Motion since initial position along Y axis 1289 * @return true if the touch slop has been crossed 1290 */ checkTouchSlop(View child, float dx, float dy)1291 private boolean checkTouchSlop(View child, float dx, float dy) { 1292 if (child == null) { 1293 return false; 1294 } 1295 final boolean checkHorizontal = mCallback.getViewHorizontalDragRange(child) > 0; 1296 final boolean checkVertical = mCallback.getViewVerticalDragRange(child) > 0; 1297 1298 if (checkHorizontal && checkVertical) { 1299 return dx * dx + dy * dy > mTouchSlop * mTouchSlop; 1300 } else if (checkHorizontal) { 1301 return Math.abs(dx) > mTouchSlop; 1302 } else if (checkVertical) { 1303 return Math.abs(dy) > mTouchSlop; 1304 } 1305 return false; 1306 } 1307 1308 /** 1309 * Check if any pointer tracked in the current gesture has crossed 1310 * the required slop threshold. 1311 * 1312 * <p>This depends on internal state populated by 1313 * {@link #shouldInterceptTouchEvent(android.view.MotionEvent)} or 1314 * {@link #processTouchEvent(android.view.MotionEvent)}. You should only rely on 1315 * the results of this method after all currently available touch data 1316 * has been provided to one of these two methods.</p> 1317 * 1318 * @param directions Combination of direction flags, see {@link #DIRECTION_HORIZONTAL}, 1319 * {@link #DIRECTION_VERTICAL}, {@link #DIRECTION_ALL} 1320 * @return true if the slop threshold has been crossed, false otherwise 1321 */ checkTouchSlop(int directions)1322 public boolean checkTouchSlop(int directions) { 1323 final int count = mInitialMotionX.length; 1324 for (int i = 0; i < count; i++) { 1325 if (checkTouchSlop(directions, i)) { 1326 return true; 1327 } 1328 } 1329 return false; 1330 } 1331 1332 /** 1333 * Check if the specified pointer tracked in the current gesture has crossed 1334 * the required slop threshold. 1335 * 1336 * <p>This depends on internal state populated by 1337 * {@link #shouldInterceptTouchEvent(android.view.MotionEvent)} or 1338 * {@link #processTouchEvent(android.view.MotionEvent)}. You should only rely on 1339 * the results of this method after all currently available touch data 1340 * has been provided to one of these two methods.</p> 1341 * 1342 * @param directions Combination of direction flags, see {@link #DIRECTION_HORIZONTAL}, 1343 * {@link #DIRECTION_VERTICAL}, {@link #DIRECTION_ALL} 1344 * @param pointerId ID of the pointer to slop check as specified by MotionEvent 1345 * @return true if the slop threshold has been crossed, false otherwise 1346 */ checkTouchSlop(int directions, int pointerId)1347 public boolean checkTouchSlop(int directions, int pointerId) { 1348 if (!isPointerDown(pointerId)) { 1349 return false; 1350 } 1351 1352 final boolean checkHorizontal = (directions & DIRECTION_HORIZONTAL) == DIRECTION_HORIZONTAL; 1353 final boolean checkVertical = (directions & DIRECTION_VERTICAL) == DIRECTION_VERTICAL; 1354 1355 final float dx = mLastMotionX[pointerId] - mInitialMotionX[pointerId]; 1356 final float dy = mLastMotionY[pointerId] - mInitialMotionY[pointerId]; 1357 1358 if (checkHorizontal && checkVertical) { 1359 return dx * dx + dy * dy > mTouchSlop * mTouchSlop; 1360 } else if (checkHorizontal) { 1361 return Math.abs(dx) > mTouchSlop; 1362 } else if (checkVertical) { 1363 return Math.abs(dy) > mTouchSlop; 1364 } 1365 return false; 1366 } 1367 1368 /** 1369 * Check if any of the edges specified were initially touched in the currently active gesture. 1370 * If there is no currently active gesture this method will return false. 1371 * 1372 * @param edges Edges to check for an initial edge touch. See {@link #EDGE_LEFT}, 1373 * {@link #EDGE_TOP}, {@link #EDGE_RIGHT}, {@link #EDGE_BOTTOM} and 1374 * {@link #EDGE_ALL} 1375 * @return true if any of the edges specified were initially touched in the current gesture 1376 */ isEdgeTouched(int edges)1377 public boolean isEdgeTouched(int edges) { 1378 final int count = mInitialEdgesTouched.length; 1379 for (int i = 0; i < count; i++) { 1380 if (isEdgeTouched(edges, i)) { 1381 return true; 1382 } 1383 } 1384 return false; 1385 } 1386 1387 /** 1388 * Check if any of the edges specified were initially touched by the pointer with 1389 * the specified ID. If there is no currently active gesture or if there is no pointer with 1390 * the given ID currently down this method will return false. 1391 * 1392 * @param edges Edges to check for an initial edge touch. See {@link #EDGE_LEFT}, 1393 * {@link #EDGE_TOP}, {@link #EDGE_RIGHT}, {@link #EDGE_BOTTOM} and 1394 * {@link #EDGE_ALL} 1395 * @return true if any of the edges specified were initially touched in the current gesture 1396 */ isEdgeTouched(int edges, int pointerId)1397 public boolean isEdgeTouched(int edges, int pointerId) { 1398 return isPointerDown(pointerId) && (mInitialEdgesTouched[pointerId] & edges) != 0; 1399 } 1400 releaseViewForPointerUp()1401 private void releaseViewForPointerUp() { 1402 mVelocityTracker.computeCurrentVelocity(1000, mMaxVelocity); 1403 final float xvel = clampMag( 1404 mVelocityTracker.getXVelocity(mActivePointerId), 1405 mMinVelocity, mMaxVelocity); 1406 final float yvel = clampMag( 1407 mVelocityTracker.getYVelocity(mActivePointerId), 1408 mMinVelocity, mMaxVelocity); 1409 dispatchViewReleased(xvel, yvel); 1410 } 1411 dragTo(int left, int top, int dx, int dy)1412 private void dragTo(int left, int top, int dx, int dy) { 1413 int clampedX = left; 1414 int clampedY = top; 1415 final int oldLeft = mCapturedView.getLeft(); 1416 final int oldTop = mCapturedView.getTop(); 1417 if (dx != 0) { 1418 clampedX = mCallback.clampViewPositionHorizontal(mCapturedView, left, dx); 1419 ViewCompat.offsetLeftAndRight(mCapturedView, clampedX - oldLeft); 1420 } 1421 if (dy != 0) { 1422 clampedY = mCallback.clampViewPositionVertical(mCapturedView, top, dy); 1423 ViewCompat.offsetTopAndBottom(mCapturedView, clampedY - oldTop); 1424 } 1425 1426 if (dx != 0 || dy != 0) { 1427 final int clampedDx = clampedX - oldLeft; 1428 final int clampedDy = clampedY - oldTop; 1429 mCallback.onViewPositionChanged(mCapturedView, clampedX, clampedY, 1430 clampedDx, clampedDy); 1431 } 1432 } 1433 1434 /** 1435 * Determine if the currently captured view is under the given point in the 1436 * parent view's coordinate system. If there is no captured view this method 1437 * will return false. 1438 * 1439 * @param x X position to test in the parent's coordinate system 1440 * @param y Y position to test in the parent's coordinate system 1441 * @return true if the captured view is under the given point, false otherwise 1442 */ isCapturedViewUnder(int x, int y)1443 public boolean isCapturedViewUnder(int x, int y) { 1444 return isViewUnder(mCapturedView, x, y); 1445 } 1446 1447 /** 1448 * Determine if the supplied view is under the given point in the 1449 * parent view's coordinate system. 1450 * 1451 * @param view Child view of the parent to hit test 1452 * @param x X position to test in the parent's coordinate system 1453 * @param y Y position to test in the parent's coordinate system 1454 * @return true if the supplied view is under the given point, false otherwise 1455 */ isViewUnder(View view, int x, int y)1456 public boolean isViewUnder(View view, int x, int y) { 1457 if (view == null) { 1458 return false; 1459 } 1460 return x >= view.getLeft() 1461 && x < view.getRight() 1462 && y >= view.getTop() 1463 && y < view.getBottom(); 1464 } 1465 1466 /** 1467 * Find the topmost child under the given point within the parent view's coordinate system. 1468 * The child order is determined using {@link Callback#getOrderedChildIndex(int)}. 1469 * 1470 * @param x X position to test in the parent's coordinate system 1471 * @param y Y position to test in the parent's coordinate system 1472 * @return The topmost child view under (x, y) or null if none found. 1473 */ findTopChildUnder(int x, int y)1474 public View findTopChildUnder(int x, int y) { 1475 final int childCount = mParentView.getChildCount(); 1476 for (int i = childCount - 1; i >= 0; i--) { 1477 final View child = mParentView.getChildAt(mCallback.getOrderedChildIndex(i)); 1478 if (x >= child.getLeft() && x < child.getRight() 1479 && y >= child.getTop() && y < child.getBottom()) { 1480 return child; 1481 } 1482 } 1483 return null; 1484 } 1485 getEdgesTouched(int x, int y)1486 private int getEdgesTouched(int x, int y) { 1487 int result = 0; 1488 1489 if (x < mParentView.getLeft() + mEdgeSize) result |= EDGE_LEFT; 1490 if (y < mParentView.getTop() + mEdgeSize) result |= EDGE_TOP; 1491 if (x > mParentView.getRight() - mEdgeSize) result |= EDGE_RIGHT; 1492 if (y > mParentView.getBottom() - mEdgeSize) result |= EDGE_BOTTOM; 1493 1494 return result; 1495 } 1496 isValidPointerForActionMove(int pointerId)1497 private boolean isValidPointerForActionMove(int pointerId) { 1498 if (!isPointerDown(pointerId)) { 1499 Log.e(TAG, "Ignoring pointerId=" + pointerId + " because ACTION_DOWN was not received " 1500 + "for this pointer before ACTION_MOVE. It likely happened because " 1501 + " ViewDragHelper did not receive all the events in the event stream."); 1502 return false; 1503 } 1504 return true; 1505 } 1506 } 1507