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.documentsui;
18 
19 import static com.android.documentsui.base.Shared.DEBUG;
20 
21 import android.util.Log;
22 
23 import com.android.documentsui.base.DocumentInfo;
24 
25 import java.util.List;
26 
27 /**
28  * A helper class for drag and drop operations
29  */
30 public final class DragAndDropHelper {
31 
32     private static final String TAG = "DragAndDropHelper";
33 
DragAndDropHelper()34     private DragAndDropHelper() {}
35 
36     /**
37      * Helper method to see whether an item can be dropped/copied into a particular destination.
38      * Don't copy from the cwd into a provided list of prohibited directories. (ie. into cwd, into a
39      * selected directory). Note: this currently doesn't work for multi-window drag, because
40      * localState isn't carried over from one process to another.
41      */
canCopyTo(Object dragLocalState, DocumentInfo dst)42     public static boolean canCopyTo(Object dragLocalState, DocumentInfo dst) {
43         if (dst == null) {
44             if (DEBUG) Log.d(TAG, "Invalid destination. Ignoring.");
45             return false;
46         }
47 
48         if (dragLocalState == null || !(dragLocalState instanceof List<?>)) {
49             if (DEBUG) Log.d(TAG, "Invalid local state object. Will allow copy.");
50             return true;
51         }
52 
53         List<?> src = (List<?>) dragLocalState;
54         if (src.contains(dst)) {
55             if (DEBUG) Log.d(TAG, "Drop target same as source. Ignoring.");
56             return false;
57         }
58         return true;
59     }
60 }
61