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      1 /*
      2  * Copyright (C) 2016 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 package com.android.launcher3.dragndrop;
     18 
     19 import android.graphics.PointF;
     20 import android.os.SystemClock;
     21 import android.view.DragEvent;
     22 import android.view.MotionEvent;
     23 import android.view.VelocityTracker;
     24 import android.view.ViewConfiguration;
     25 
     26 import com.android.launcher3.ButtonDropTarget;
     27 import com.android.launcher3.DropTarget;
     28 import com.android.launcher3.Launcher;
     29 import com.android.launcher3.R;
     30 import com.android.launcher3.util.FlingAnimation;
     31 
     32 /**
     33  * Utility class to manage fling to delete action during drag and drop.
     34  */
     35 public class FlingToDeleteHelper {
     36 
     37     private static final float MAX_FLING_DEGREES = 35f;
     38 
     39     private final Launcher mLauncher;
     40     private final int mFlingToDeleteThresholdVelocity;
     41 
     42     private ButtonDropTarget mDropTarget;
     43     private VelocityTracker mVelocityTracker;
     44 
     45     public FlingToDeleteHelper(Launcher launcher) {
     46         mLauncher = launcher;
     47         mFlingToDeleteThresholdVelocity = launcher.getResources()
     48                 .getDimensionPixelSize(R.dimen.drag_flingToDeleteMinVelocity);
     49     }
     50 
     51     public void recordMotionEvent(MotionEvent ev) {
     52         if (mVelocityTracker == null) {
     53             mVelocityTracker = VelocityTracker.obtain();
     54         }
     55         mVelocityTracker.addMovement(ev);
     56     }
     57 
     58     /**
     59      * Same as {@link #recordMotionEvent}. It creates a temporary {@link MotionEvent} object
     60      * using {@param event} for tracking velocity.
     61      */
     62     public void recordDragEvent(long dragStartTime, DragEvent event) {
     63         final int motionAction;
     64         switch (event.getAction()) {
     65             case DragEvent.ACTION_DRAG_STARTED:
     66                 motionAction = MotionEvent.ACTION_DOWN;
     67                 break;
     68             case DragEvent.ACTION_DRAG_LOCATION:
     69                 motionAction = MotionEvent.ACTION_MOVE;
     70                 break;
     71             case DragEvent.ACTION_DRAG_ENDED:
     72                 motionAction = MotionEvent.ACTION_UP;
     73                 break;
     74             default:
     75                 return;
     76         }
     77         MotionEvent emulatedEvent = MotionEvent.obtain(dragStartTime, SystemClock.uptimeMillis(),
     78                 motionAction, event.getX(), event.getY(), 0);
     79         recordMotionEvent(emulatedEvent);
     80         emulatedEvent.recycle();
     81     }
     82 
     83     public void releaseVelocityTracker() {
     84         if (mVelocityTracker != null) {
     85             mVelocityTracker.recycle();
     86             mVelocityTracker = null;
     87         }
     88     }
     89 
     90     public DropTarget getDropTarget() {
     91         return mDropTarget;
     92     }
     93 
     94     public Runnable getFlingAnimation(DropTarget.DragObject dragObject) {
     95         PointF vel = isFlingingToDelete();
     96         if (vel == null) {
     97             return null;
     98         }
     99         return new FlingAnimation(dragObject, vel, mDropTarget, mLauncher);
    100     }
    101 
    102     /**
    103      * Determines whether the user flung the current item to delete it.
    104      *
    105      * @return the vector at which the item was flung, or null if no fling was detected.
    106      */
    107     private PointF isFlingingToDelete() {
    108         if (mDropTarget == null) {
    109             mDropTarget = (ButtonDropTarget) mLauncher.findViewById(R.id.delete_target_text);
    110         }
    111         if (mDropTarget == null || !mDropTarget.isDropEnabled()) return null;
    112         ViewConfiguration config = ViewConfiguration.get(mLauncher);
    113         mVelocityTracker.computeCurrentVelocity(1000, config.getScaledMaximumFlingVelocity());
    114         PointF vel = new PointF(mVelocityTracker.getXVelocity(), mVelocityTracker.getYVelocity());
    115         float theta = MAX_FLING_DEGREES + 1;
    116         if (mVelocityTracker.getYVelocity() < mFlingToDeleteThresholdVelocity) {
    117             // Do a quick dot product test to ensure that we are flinging upwards
    118             PointF upVec = new PointF(0f, -1f);
    119             theta = getAngleBetweenVectors(vel, upVec);
    120         } else if (mLauncher.getDeviceProfile().isVerticalBarLayout() &&
    121                 mVelocityTracker.getXVelocity() < mFlingToDeleteThresholdVelocity) {
    122             // Remove icon is on left side instead of top, so check if we are flinging to the left.
    123             PointF leftVec = new PointF(-1f, 0f);
    124             theta = getAngleBetweenVectors(vel, leftVec);
    125         }
    126         if (theta <= Math.toRadians(MAX_FLING_DEGREES)) {
    127             return vel;
    128         }
    129         return null;
    130     }
    131 
    132     private float getAngleBetweenVectors(PointF vec1, PointF vec2) {
    133         return (float) Math.acos(((vec1.x * vec2.x) + (vec1.y * vec2.y)) /
    134                 (vec1.length() * vec2.length()));
    135     }
    136 }
    137