1/*
2 * Copyright (C) 2011 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
19import android.view.VelocityTracker;
20
21/**
22 * Helper for accessing features in {@link VelocityTracker}
23 * introduced after API level 4 in a backwards compatible fashion.
24 */
25public final class VelocityTrackerCompat {
26    /**
27     * Interface for the full API.
28     */
29    interface VelocityTrackerVersionImpl {
30        public float getXVelocity(VelocityTracker tracker, int pointerId);
31        public float getYVelocity(VelocityTracker tracker, int pointerId);
32    }
33
34    /**
35     * Interface implementation that doesn't use anything about v4 APIs.
36     */
37    static class BaseVelocityTrackerVersionImpl implements VelocityTrackerVersionImpl {
38        @Override
39        public float getXVelocity(VelocityTracker tracker, int pointerId) {
40            return tracker.getXVelocity();
41        }
42        @Override
43        public float getYVelocity(VelocityTracker tracker, int pointerId) {
44            return tracker.getYVelocity();
45        }
46    }
47
48    /**
49     * Interface implementation for devices with at least v11 APIs.
50     */
51    static class HoneycombVelocityTrackerVersionImpl implements VelocityTrackerVersionImpl {
52        @Override
53        public float getXVelocity(VelocityTracker tracker, int pointerId) {
54            return VelocityTrackerCompatHoneycomb.getXVelocity(tracker, pointerId);
55        }
56        @Override
57        public float getYVelocity(VelocityTracker tracker, int pointerId) {
58            return VelocityTrackerCompatHoneycomb.getYVelocity(tracker, pointerId);
59        }
60    }
61
62    /**
63     * Select the correct implementation to use for the current platform.
64     */
65    static final VelocityTrackerVersionImpl IMPL;
66    static {
67        if (android.os.Build.VERSION.SDK_INT >= 11) {
68            IMPL = new HoneycombVelocityTrackerVersionImpl();
69        } else {
70            IMPL = new BaseVelocityTrackerVersionImpl();
71        }
72    }
73
74    // -------------------------------------------------------------------
75
76    /**
77     * Call {@link VelocityTracker#getXVelocity(int)}.
78     * If running on a pre-{@link android.os.Build.VERSION_CODES#HONEYCOMB} device,
79     * returns {@link VelocityTracker#getXVelocity()}.
80     */
81    public static float getXVelocity(VelocityTracker tracker, int pointerId) {
82        return IMPL.getXVelocity(tracker, pointerId);
83    }
84
85    /**
86     * Call {@link VelocityTracker#getYVelocity(int)}.
87     * If running on a pre-{@link android.os.Build.VERSION_CODES#HONEYCOMB} device,
88     * returns {@link VelocityTracker#getYVelocity()}.
89     */
90    public static float getYVelocity(VelocityTracker tracker, int pointerId) {
91        return IMPL.getYVelocity(tracker, pointerId);
92    }
93
94    private VelocityTrackerCompat() {}
95}
96