DropTarget.java revision cb3382b1bfe1a534b1b44f5c4def9b2db605ac90 
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
17package com.android.launcher2;
18
19import android.graphics.Rect;
20
21/**
22 * Interface defining an object that can receive a drag.
23 *
24 */
25public interface DropTarget {
26
27    class DragObject {
28        public int x = -1;
29        public int y = -1;
30
31        /** X offset from the upper-left corner of the cell to where we touched.  */
32        public int xOffset = -1;
33
34        /** Y offset from the upper-left corner of the cell to where we touched.  */
35        public int yOffset = -1;
36
37        /** The view that moves around while you drag.  */
38        public DragView dragView = null;
39
40        /** The data associated with the object being dragged */
41        public Object dragInfo = null;
42
43        /** Where the drag originated */
44        public DragSource dragSource = null;
45
46        public DragObject() {
47        }
48    }
49
50    /**
51     * Used to temporarily disable certain drop targets
52     *
53     * @return boolean specifying whether this drop target is currently enabled
54     */
55    boolean isDropEnabled();
56
57    /**
58     * Handle an object being dropped on the DropTarget
59     *
60     * @param source DragSource where the drag started
61     * @param x X coordinate of the drop location
62     * @param y Y coordinate of the drop location
63     * @param xOffset Horizontal offset with the object being dragged where the original
64     *          touch happened
65     * @param yOffset Vertical offset with the object being dragged where the original
66     *          touch happened
67     * @param dragView The DragView that's being dragged around on screen.
68     * @param dragInfo Data associated with the object being dragged
69     *
70     */
71    void onDrop(DragObject dragObject);
72
73    void onDragEnter(DragObject dragObject);
74
75    void onDragOver(DragObject dragObject);
76
77    void onDragExit(DragObject dragObject);
78
79    /**
80     * Allows a DropTarget to delegate drag and drop events to another object.
81     *
82     * Most subclasses will should just return null from this method.
83     *
84     * @param source DragSource where the drag started
85     * @param x X coordinate of the drop location
86     * @param y Y coordinate of the drop location
87     * @param xOffset Horizontal offset with the object being dragged where the original
88     *          touch happened
89     * @param yOffset Vertical offset with the object being dragged where the original
90     *          touch happened
91     * @param dragView The DragView that's being dragged around on screen.
92     * @param dragInfo Data associated with the object being dragged
93     *
94     * @return The DropTarget to delegate to, or null to not delegate to another object.
95     */
96    DropTarget getDropTargetDelegate(DragObject dragObject);
97
98    /**
99     * Check if a drop action can occur at, or near, the requested location.
100     * This will be called just before onDrop.
101     *
102     * @param source DragSource where the drag started
103     * @param x X coordinate of the drop location
104     * @param y Y coordinate of the drop location
105     * @param xOffset Horizontal offset with the object being dragged where the
106     *            original touch happened
107     * @param yOffset Vertical offset with the object being dragged where the
108     *            original touch happened
109     * @param dragView The DragView that's being dragged around on screen.
110     * @param dragInfo Data associated with the object being dragged
111     * @return True if the drop will be accepted, false otherwise.
112     */
113    boolean acceptDrop(DragObject dragObject);
114
115    // These methods are implemented in Views
116    void getHitRect(Rect outRect);
117    void getLocationOnScreen(int[] loc);
118    int getLeft();
119    int getTop();
120}
121