src.android.util.KeyValueSettingObserver Maven / Gradle / Ivy
/*
* 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.
*
* 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()}.
*
*
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);
}
}
}