Annie Meng | 48b2eca | 2018-03-08 20:38:43 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2018 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 android.util; |
| 18 | |
| 19 | import android.content.ContentResolver; |
| 20 | import android.database.ContentObserver; |
| 21 | import android.net.Uri; |
| 22 | import android.os.Handler; |
| 23 | |
| 24 | /** |
| 25 | * Abstract class for observing changes to a specified setting stored as a comma-separated key value |
| 26 | * list of parameters. Registers and unregisters a {@link ContentObserver} and handles updates when |
| 27 | * the setting changes. |
| 28 | * |
| 29 | * <p>Subclasses should pass in the relevant setting's {@link Uri} in the constructor and implement |
| 30 | * {@link #update(KeyValueListParser)} to receive updates when the value changes. |
| 31 | * Calls to {@link #update(KeyValueListParser)} only trigger after calling {@link |
| 32 | * #start()}. |
| 33 | * |
| 34 | * <p>To get the most up-to-date parameter values, first call {@link #start()} before accessing the |
| 35 | * values to start observing changes, and then call {@link #stop()} once finished. |
| 36 | * |
| 37 | * @hide |
| 38 | */ |
| 39 | public abstract class KeyValueSettingObserver { |
| 40 | private static final String TAG = "KeyValueSettingObserver"; |
| 41 | |
| 42 | private final KeyValueListParser mParser = new KeyValueListParser(','); |
| 43 | |
| 44 | private final ContentObserver mObserver; |
| 45 | private final ContentResolver mResolver; |
| 46 | private final Uri mSettingUri; |
| 47 | |
| 48 | public KeyValueSettingObserver(Handler handler, ContentResolver resolver, |
| 49 | Uri uri) { |
| 50 | mObserver = new SettingObserver(handler); |
| 51 | mResolver = resolver; |
| 52 | mSettingUri = uri; |
| 53 | } |
| 54 | |
| 55 | /** Starts observing changes for the setting. Pair with {@link #stop()}. */ |
| 56 | public void start() { |
| 57 | mResolver.registerContentObserver(mSettingUri, false, mObserver); |
| 58 | setParserValue(); |
| 59 | update(mParser); |
| 60 | } |
| 61 | |
| 62 | /** Stops observing changes for the setting. */ |
| 63 | public void stop() { |
| 64 | mResolver.unregisterContentObserver(mObserver); |
| 65 | } |
| 66 | |
| 67 | /** |
| 68 | * Returns the {@link String} representation of the setting. Subclasses should implement this |
| 69 | * for their setting. |
| 70 | */ |
| 71 | public abstract String getSettingValue(ContentResolver resolver); |
| 72 | |
| 73 | /** Updates the parser with the current setting value. */ |
| 74 | private void setParserValue() { |
| 75 | String setting = getSettingValue(mResolver); |
| 76 | try { |
| 77 | mParser.setString(setting); |
| 78 | } catch (IllegalArgumentException e) { |
| 79 | Slog.e(TAG, "Malformed setting: " + setting); |
| 80 | } |
| 81 | } |
| 82 | |
| 83 | /** Subclasses should implement this to update references to their parameters. */ |
| 84 | public abstract void update(KeyValueListParser parser); |
| 85 | |
| 86 | private class SettingObserver extends ContentObserver { |
| 87 | private SettingObserver(Handler handler) { |
| 88 | super(handler); |
| 89 | } |
| 90 | |
| 91 | @Override |
| 92 | public void onChange(boolean selfChange) { |
| 93 | setParserValue(); |
| 94 | update(mParser); |
| 95 | } |
| 96 | } |
| 97 | } |