1 /*
2  * Copyright (C) 2008 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.launcher2;
18 
19 import android.content.Context;
20 import android.graphics.PointF;
21 import android.graphics.Rect;
22 import android.util.Log;
23 
24 /**
25  * Interface defining an object that can receive a drag.
26  *
27  */
28 public interface DropTarget {
29 
30     public static final String TAG = "DropTarget";
31 
32     class DragObject {
33         public int x = -1;
34         public int y = -1;
35 
36         /** X offset from the upper-left corner of the cell to where we touched.  */
37         public int xOffset = -1;
38 
39         /** Y offset from the upper-left corner of the cell to where we touched.  */
40         public int yOffset = -1;
41 
42         /** This indicates whether a drag is in final stages, either drop or cancel. It
43          * differentiates onDragExit, since this is called when the drag is ending, above
44          * the current drag target, or when the drag moves off the current drag object.
45          */
46         public boolean dragComplete = false;
47 
48         /** The view that moves around while you drag.  */
49         public DragView dragView = null;
50 
51         /** The data associated with the object being dragged */
52         public Object dragInfo = null;
53 
54         /** Where the drag originated */
55         public DragSource dragSource = null;
56 
57         /** Post drag animation runnable */
58         public Runnable postAnimationRunnable = null;
59 
60         /** Indicates that the drag operation was cancelled */
61         public boolean cancelled = false;
62 
63         /** Defers removing the DragView from the DragLayer until after the drop animation. */
64         public boolean deferDragViewCleanupPostAnimation = true;
65 
DragObject()66         public DragObject() {
67         }
68     }
69 
70     public static class DragEnforcer implements DragController.DragListener {
71         int dragParity = 0;
72 
DragEnforcer(Context context)73         public DragEnforcer(Context context) {
74             Launcher launcher = (Launcher) context;
75             launcher.getDragController().addDragListener(this);
76         }
77 
onDragEnter()78         void onDragEnter() {
79             dragParity++;
80             if (dragParity != 1) {
81                 Log.e(TAG, "onDragEnter: Drag contract violated: " + dragParity);
82             }
83         }
84 
onDragExit()85         void onDragExit() {
86             dragParity--;
87             if (dragParity != 0) {
88                 Log.e(TAG, "onDragExit: Drag contract violated: " + dragParity);
89             }
90         }
91 
92         @Override
onDragStart(DragSource source, Object info, int dragAction)93         public void onDragStart(DragSource source, Object info, int dragAction) {
94             if (dragParity != 0) {
95                 Log.e(TAG, "onDragEnter: Drag contract violated: " + dragParity);
96             }
97         }
98 
99         @Override
onDragEnd()100         public void onDragEnd() {
101             if (dragParity != 0) {
102                 Log.e(TAG, "onDragExit: Drag contract violated: " + dragParity);
103             }
104         }
105     }
106 
107     /**
108      * Used to temporarily disable certain drop targets
109      *
110      * @return boolean specifying whether this drop target is currently enabled
111      */
isDropEnabled()112     boolean isDropEnabled();
113 
114     /**
115      * Handle an object being dropped on the DropTarget
116      *
117      * @param source DragSource where the drag started
118      * @param x X coordinate of the drop location
119      * @param y Y coordinate of the drop location
120      * @param xOffset Horizontal offset with the object being dragged where the original
121      *          touch happened
122      * @param yOffset Vertical offset with the object being dragged where the original
123      *          touch happened
124      * @param dragView The DragView that's being dragged around on screen.
125      * @param dragInfo Data associated with the object being dragged
126      *
127      */
onDrop(DragObject dragObject)128     void onDrop(DragObject dragObject);
129 
onDragEnter(DragObject dragObject)130     void onDragEnter(DragObject dragObject);
131 
onDragOver(DragObject dragObject)132     void onDragOver(DragObject dragObject);
133 
onDragExit(DragObject dragObject)134     void onDragExit(DragObject dragObject);
135 
136     /**
137      * Handle an object being dropped as a result of flinging to delete and will be called in place
138      * of onDrop().  (This is only called on objects that are set as the DragController's
139      * fling-to-delete target.
140      */
onFlingToDelete(DragObject dragObject, int x, int y, PointF vec)141     void onFlingToDelete(DragObject dragObject, int x, int y, PointF vec);
142 
143     /**
144      * Allows a DropTarget to delegate drag and drop events to another object.
145      *
146      * Most subclasses will should just return null from this method.
147      *
148      * @param source DragSource where the drag started
149      * @param x X coordinate of the drop location
150      * @param y Y coordinate of the drop location
151      * @param xOffset Horizontal offset with the object being dragged where the original
152      *          touch happened
153      * @param yOffset Vertical offset with the object being dragged where the original
154      *          touch happened
155      * @param dragView The DragView that's being dragged around on screen.
156      * @param dragInfo Data associated with the object being dragged
157      *
158      * @return The DropTarget to delegate to, or null to not delegate to another object.
159      */
getDropTargetDelegate(DragObject dragObject)160     DropTarget getDropTargetDelegate(DragObject dragObject);
161 
162     /**
163      * Check if a drop action can occur at, or near, the requested location.
164      * This will be called just before onDrop.
165      *
166      * @param source DragSource where the drag started
167      * @param x X coordinate of the drop location
168      * @param y Y coordinate of the drop location
169      * @param xOffset Horizontal offset with the object being dragged where the
170      *            original touch happened
171      * @param yOffset Vertical offset with the object being dragged where the
172      *            original touch happened
173      * @param dragView The DragView that's being dragged around on screen.
174      * @param dragInfo Data associated with the object being dragged
175      * @return True if the drop will be accepted, false otherwise.
176      */
acceptDrop(DragObject dragObject)177     boolean acceptDrop(DragObject dragObject);
178 
179     // These methods are implemented in Views
getHitRect(Rect outRect)180     void getHitRect(Rect outRect);
getLocationInDragLayer(int[] loc)181     void getLocationInDragLayer(int[] loc);
getLeft()182     int getLeft();
getTop()183     int getTop();
184 }
185