ConfigurationHelper.java revision 552766fa685c63ad760c92239faaba12e6ad51f1 
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
17package android.support.v4.content.res;
18
19import android.content.res.Resources;
20import android.os.Build;
21import android.support.annotation.NonNull;
22
23/**
24 * Helper class which allows access to properties of {@link android.content.res.Configuration} in
25 * a backward compatible fashion.
26 */
27public final class ConfigurationHelper {
28
29    private static final ConfigurationHelperImpl IMPL;
30
31    static {
32        final int sdk = Build.VERSION.SDK_INT;
33        if (sdk >= 17) {
34            IMPL = new JellybeanMr1Impl();
35        } else if (sdk >= 13) {
36            IMPL = new HoneycombMr2Impl();
37        } else {
38            IMPL = new GingerbreadImpl();
39        }
40    }
41
42    private ConfigurationHelper() {}
43
44    private interface ConfigurationHelperImpl {
45        int getScreenHeightDp(@NonNull Resources resources);
46        int getScreenWidthDp(@NonNull Resources resources);
47        int getSmallestScreenWidthDp(@NonNull Resources resources);
48        int getDensityDpi(@NonNull Resources resources);
49    }
50
51    private static class GingerbreadImpl implements ConfigurationHelperImpl {
52        GingerbreadImpl() {
53        }
54
55        @Override
56        public int getScreenHeightDp(@NonNull Resources resources) {
57            return ConfigurationHelperGingerbread.getScreenHeightDp(resources);
58        }
59
60        @Override
61        public int getScreenWidthDp(@NonNull Resources resources) {
62            return ConfigurationHelperGingerbread.getScreenWidthDp(resources);
63        }
64
65        @Override
66        public int getSmallestScreenWidthDp(@NonNull Resources resources) {
67            return ConfigurationHelperGingerbread.getSmallestScreenWidthDp(resources);
68        }
69
70        @Override
71        public int getDensityDpi(@NonNull Resources resources) {
72            return ConfigurationHelperGingerbread.getDensityDpi(resources);
73        }
74    }
75
76    private static class HoneycombMr2Impl extends GingerbreadImpl {
77        HoneycombMr2Impl() {
78        }
79
80        @Override
81        public int getScreenHeightDp(@NonNull Resources resources) {
82            return ConfigurationHelperHoneycombMr2.getScreenHeightDp(resources);
83        }
84
85        @Override
86        public int getScreenWidthDp(@NonNull Resources resources) {
87            return ConfigurationHelperHoneycombMr2.getScreenWidthDp(resources);
88        }
89
90        @Override
91        public int getSmallestScreenWidthDp(@NonNull Resources resources) {
92            return ConfigurationHelperHoneycombMr2.getSmallestScreenWidthDp(resources);
93        }
94    }
95
96    private static class JellybeanMr1Impl extends HoneycombMr2Impl {
97        JellybeanMr1Impl() {
98        }
99
100        @Override
101        public int getDensityDpi(@NonNull Resources resources) {
102            return ConfigurationHelperJellybeanMr1.getDensityDpi(resources);
103        }
104    }
105
106    /**
107     * Returns the current height of the available screen space, in dp units.
108     *
109     * <p>Uses {@code Configuration.screenHeightDp} when available, otherwise an approximation
110     * is computed and returned.</p>
111     */
112    public static int getScreenHeightDp(@NonNull Resources resources) {
113        return IMPL.getScreenHeightDp(resources);
114    }
115
116    /**
117     * Returns the current width of the available screen space, in dp units.
118     *
119     * <p>Uses {@code Configuration.screenWidthDp} when available, otherwise an approximation
120     * is computed and returned.</p>
121     */
122    public static int getScreenWidthDp(@NonNull Resources resources) {
123        return IMPL.getScreenWidthDp(resources);
124    }
125
126    /**
127     * Returns The smallest screen size an application will see in normal operation, in dp units.
128     *
129     * <p>Uses {@code Configuration.smallestScreenWidthDp} when available, otherwise an
130     * approximation is computed and returned.</p>
131     */
132    public static int getSmallestScreenWidthDp(@NonNull Resources resources) {
133        return IMPL.getSmallestScreenWidthDp(resources);
134    }
135
136    /**
137     * Returns the target screen density being rendered to.
138     *
139     * <p>Uses {@code Configuration.densityDpi} when available, otherwise an approximation
140     * is computed and returned.</p>
141     */
142    public static int getDensityDpi(@NonNull Resources resources) {
143        return IMPL.getDensityDpi(resources);
144    }
145}
146