ListPopupWindowCompat.java revision 379312ec6d3e517f8bb8fcf2e9876b42f9495df3 
1/*
2 * Copyright (C) 2013 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 android.support.v4.widget;
18
19import android.view.View;
20import android.view.View.OnTouchListener;
21
22/**
23 * Helper for accessing features in ListPopupWindow introduced after API level 4
24 * in a backwards compatible fashion.
25 */
26public class ListPopupWindowCompat {
27    /**
28     * Interface for the full API.
29     */
30    interface ListPopupWindowImpl {
31        public OnTouchListener createDragToOpenListener(Object listPopupWindow, View src);
32    }
33
34    /**
35     * Interface implementation that doesn't use anything above v4 APIs.
36     */
37    static class BaseListPopupWindowImpl implements ListPopupWindowImpl {
38        @Override
39        public OnTouchListener createDragToOpenListener(Object listPopupWindow, View src) {
40            return null;
41        }
42    }
43
44    /**
45     * Interface implementation for devices with at least KitKat APIs.
46     */
47    static class KitKatListPopupWindowImpl extends BaseListPopupWindowImpl {
48        @Override
49        public OnTouchListener createDragToOpenListener(Object listPopupWindow, View src) {
50            return ListPopupWindowCompatKitKat.createDragToOpenListener(listPopupWindow, src);
51        }
52    }
53
54    /**
55     * Select the correct implementation to use for the current platform.
56     */
57    static final ListPopupWindowImpl IMPL;
58    static {
59        final int version = android.os.Build.VERSION.SDK_INT;
60        if (version >= 19) {
61            IMPL = new KitKatListPopupWindowImpl();
62        } else {
63            IMPL = new BaseListPopupWindowImpl();
64        }
65    }
66
67    private ListPopupWindowCompat() {
68        // This class is not publicly instantiable.
69    }
70
71    /**
72     * On API {@link android.os.Build.VERSION_CODES#KITKAT} and higher, returns
73     * an {@link OnTouchListener} that can be added to the source view to
74     * implement drag-to-open behavior. Generally, the source view should be the
75     * same view that was passed to ListPopupWindow.setAnchorView(View).
76     * <p>
77     * When the listener is set on a view, touching that view and dragging
78     * outside of its bounds will open the popup window. Lifting will select the
79     * currently touched list item.
80     * <p>
81     * Example usage:
82     *
83     * <pre>
84     * ListPopupWindow myPopup = new ListPopupWindow(context);
85     * myPopup.setAnchor(myAnchor);
86     * OnTouchListener dragListener = myPopup.createDragToOpenListener(myAnchor);
87     * myAnchor.setOnTouchListener(dragListener);
88     * </pre>
89     *
90     * @param listPopupWindow the ListPopupWindow against which to invoke the
91     *            method
92     * @param src the view on which the resulting listener will be set
93     * @return a touch listener that controls drag-to-open behavior, or null on
94     *         unsupported APIs
95     */
96    public static OnTouchListener createDragToOpenListener(Object listPopupWindow, View src) {
97        return IMPL.createDragToOpenListener(listPopupWindow, src);
98    }
99}
100