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.view;
18
19/**
20 * Helper for accessing features in <code>ScaleGestureDetector</code> introduced
21 * after API level 19 (KitKat) in a backwards compatible fashion.
22 */
23public final class ScaleGestureDetectorCompat {
24    static final ScaleGestureDetectorImpl IMPL;
25
26    interface ScaleGestureDetectorImpl {
27
28        public void setQuickScaleEnabled(Object o, boolean enabled);
29
30        public boolean isQuickScaleEnabled(Object o);
31    }
32
33    private static class BaseScaleGestureDetectorImpl implements ScaleGestureDetectorImpl {
34        BaseScaleGestureDetectorImpl() {
35        }
36
37        @Override
38        public void setQuickScaleEnabled(Object o, boolean enabled) {
39            // Intentionally blank
40        }
41
42        @Override
43        public boolean isQuickScaleEnabled(Object o) {
44            return false;
45        }
46    }
47
48    private static class ScaleGestureDetectorCompatKitKatImpl implements ScaleGestureDetectorImpl {
49        ScaleGestureDetectorCompatKitKatImpl() {
50        }
51
52        @Override
53        public void setQuickScaleEnabled(Object o, boolean enabled) {
54            ScaleGestureDetectorCompatKitKat.setQuickScaleEnabled(o, enabled);
55        }
56
57        @Override
58        public boolean isQuickScaleEnabled(Object o) {
59            return ScaleGestureDetectorCompatKitKat.isQuickScaleEnabled(o);
60        }
61    }
62
63    static {
64        final int version = android.os.Build.VERSION.SDK_INT;
65        if (version >= 19) { // KitKat
66            IMPL = new ScaleGestureDetectorCompatKitKatImpl();
67        } else {
68            IMPL = new BaseScaleGestureDetectorImpl();
69        }
70    }
71
72    private ScaleGestureDetectorCompat() {}
73
74    /**
75     * Set whether the associated <code>OnScaleGestureListener</code> should receive onScale
76     * callbacks when the user performs a doubleTap followed by a swipe. Note that this is enabled
77     * by default if the app targets API 19 and newer.
78     * @param enabled true to enable quick scaling, false to disable
79     */
80    public static void setQuickScaleEnabled(Object scaleGestureDetector, boolean enabled) {
81        IMPL.setQuickScaleEnabled(scaleGestureDetector, enabled);
82    }
83
84    /**
85     * Return whether the quick scale gesture, in which the user performs a double tap followed by a
86     * swipe, should perform scaling. See <code>setQuickScaleEnabled(Object, boolean)<code>.
87     */
88    public static boolean isQuickScaleEnabled(Object scaleGestureDetector) {
89        return IMPL.isQuickScaleEnabled(scaleGestureDetector); // KitKat
90    }
91}
92