| /* |
| * Copyright (C) 2018 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package android.util; |
| |
| import android.content.ContentResolver; |
| import android.database.ContentObserver; |
| import android.net.Uri; |
| import android.os.Handler; |
| |
| /** |
| * Abstract class for observing changes to a specified setting stored as a comma-separated key value |
| * list of parameters. Registers and unregisters a {@link ContentObserver} and handles updates when |
| * the setting changes. |
| * |
| * <p>Subclasses should pass in the relevant setting's {@link Uri} in the constructor and implement |
| * {@link #update(KeyValueListParser)} to receive updates when the value changes. |
| * Calls to {@link #update(KeyValueListParser)} only trigger after calling {@link |
| * #start()}. |
| * |
| * <p>To get the most up-to-date parameter values, first call {@link #start()} before accessing the |
| * values to start observing changes, and then call {@link #stop()} once finished. |
| * |
| * @hide |
| */ |
| public abstract class KeyValueSettingObserver { |
| private static final String TAG = "KeyValueSettingObserver"; |
| |
| private final KeyValueListParser mParser = new KeyValueListParser(','); |
| |
| private final ContentObserver mObserver; |
| private final ContentResolver mResolver; |
| private final Uri mSettingUri; |
| |
| public KeyValueSettingObserver(Handler handler, ContentResolver resolver, |
| Uri uri) { |
| mObserver = new SettingObserver(handler); |
| mResolver = resolver; |
| mSettingUri = uri; |
| } |
| |
| /** Starts observing changes for the setting. Pair with {@link #stop()}. */ |
| public void start() { |
| mResolver.registerContentObserver(mSettingUri, false, mObserver); |
| setParserValue(); |
| update(mParser); |
| } |
| |
| /** Stops observing changes for the setting. */ |
| public void stop() { |
| mResolver.unregisterContentObserver(mObserver); |
| } |
| |
| /** |
| * Returns the {@link String} representation of the setting. Subclasses should implement this |
| * for their setting. |
| */ |
| public abstract String getSettingValue(ContentResolver resolver); |
| |
| /** Updates the parser with the current setting value. */ |
| private void setParserValue() { |
| String setting = getSettingValue(mResolver); |
| try { |
| mParser.setString(setting); |
| } catch (IllegalArgumentException e) { |
| Slog.e(TAG, "Malformed setting: " + setting); |
| } |
| } |
| |
| /** Subclasses should implement this to update references to their parameters. */ |
| public abstract void update(KeyValueListParser parser); |
| |
| private class SettingObserver extends ContentObserver { |
| private SettingObserver(Handler handler) { |
| super(handler); |
| } |
| |
| @Override |
| public void onChange(boolean selfChange) { |
| setParserValue(); |
| update(mParser); |
| } |
| } |
| } |