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 
FlingToDeleteHelper(Launcher launcher)45     public FlingToDeleteHelper(Launcher launcher) {
46         mLauncher = launcher;
47         mFlingToDeleteThresholdVelocity = launcher.getResources()
48                 .getDimensionPixelSize(R.dimen.drag_flingToDeleteMinVelocity);
49     }
50 
recordMotionEvent(MotionEvent ev)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      */
recordDragEvent(long dragStartTime, DragEvent event)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 
releaseVelocityTracker()83     public void releaseVelocityTracker() {
84         if (mVelocityTracker != null) {
85             mVelocityTracker.recycle();
86             mVelocityTracker = null;
87         }
88     }
89 
getDropTarget()90     public DropTarget getDropTarget() {
91         return mDropTarget;
92     }
93 
getFlingAnimation(DropTarget.DragObject dragObject, DragOptions options)94     public Runnable getFlingAnimation(DropTarget.DragObject dragObject, DragOptions options) {
95         PointF vel = isFlingingToDelete();
96         options.isFlingToDelete = vel != null;
97         if (!options.isFlingToDelete) {
98             return null;
99         }
100         return new FlingAnimation(dragObject, vel, mDropTarget, mLauncher, options);
101     }
102 
103     /**
104      * Determines whether the user flung the current item to delete it.
105      *
106      * @return the vector at which the item was flung, or null if no fling was detected.
107      */
isFlingingToDelete()108     private PointF isFlingingToDelete() {
109         if (mVelocityTracker == null) return null;
110         if (mDropTarget == null) {
111             mDropTarget = (ButtonDropTarget) mLauncher.findViewById(R.id.delete_target_text);
112         }
113         if (mDropTarget == null || !mDropTarget.isDropEnabled()) return null;
114         ViewConfiguration config = ViewConfiguration.get(mLauncher);
115         mVelocityTracker.computeCurrentVelocity(1000, config.getScaledMaximumFlingVelocity());
116         PointF vel = new PointF(mVelocityTracker.getXVelocity(), mVelocityTracker.getYVelocity());
117         float theta = MAX_FLING_DEGREES + 1;
118         if (mVelocityTracker.getYVelocity() < mFlingToDeleteThresholdVelocity) {
119             // Do a quick dot product test to ensure that we are flinging upwards
120             PointF upVec = new PointF(0f, -1f);
121             theta = getAngleBetweenVectors(vel, upVec);
122         } else if (mLauncher.getDeviceProfile().isVerticalBarLayout() &&
123                 mVelocityTracker.getXVelocity() < mFlingToDeleteThresholdVelocity) {
124             // Remove icon is on left side instead of top, so check if we are flinging to the left.
125             PointF leftVec = new PointF(-1f, 0f);
126             theta = getAngleBetweenVectors(vel, leftVec);
127         }
128         if (theta <= Math.toRadians(MAX_FLING_DEGREES)) {
129             return vel;
130         }
131         return null;
132     }
133 
getAngleBetweenVectors(PointF vec1, PointF vec2)134     private float getAngleBetweenVectors(PointF vec1, PointF vec2) {
135         return (float) Math.acos(((vec1.x * vec2.x) + (vec1.y * vec2.y)) /
136                 (vec1.length() * vec2.length()));
137     }
138 }
139