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