| /* |
| * Copyright (C) 2017 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.net.util; |
| |
| import android.content.BroadcastReceiver; |
| import android.content.Context; |
| import android.content.Intent; |
| import android.content.IntentFilter; |
| import android.os.Handler; |
| import android.util.Log; |
| |
| import java.util.concurrent.atomic.AtomicInteger; |
| import java.util.function.Consumer; |
| |
| |
| /** |
| * A utility class that runs the provided callback on the provided handler when |
| * intents matching the provided filter arrive. Intents received by a stale |
| * receiver are safely ignored. |
| * |
| * Calls to startListening() and stopListening() must happen on the same thread. |
| * |
| * @hide |
| */ |
| public class VersionedBroadcastListener { |
| private static final boolean DBG = false; |
| |
| private final String mTag; |
| private final Context mContext; |
| private final Handler mHandler; |
| private final IntentFilter mFilter; |
| private final Consumer<Intent> mCallback; |
| private final AtomicInteger mGenerationNumber; |
| private BroadcastReceiver mReceiver; |
| |
| public VersionedBroadcastListener(String tag, Context ctx, Handler handler, |
| IntentFilter filter, Consumer<Intent> callback) { |
| mTag = tag; |
| mContext = ctx; |
| mHandler = handler; |
| mFilter = filter; |
| mCallback = callback; |
| mGenerationNumber = new AtomicInteger(0); |
| } |
| |
| /** Start listening to intent broadcast. */ |
| public void startListening() { |
| if (DBG) Log.d(mTag, "startListening"); |
| if (mReceiver != null) return; |
| |
| mReceiver = new Receiver(mTag, mGenerationNumber, mCallback); |
| mContext.registerReceiver(mReceiver, mFilter, null, mHandler); |
| } |
| |
| /** Stop listening to intent broadcast. */ |
| public void stopListening() { |
| if (DBG) Log.d(mTag, "stopListening"); |
| if (mReceiver == null) return; |
| |
| mGenerationNumber.incrementAndGet(); |
| mContext.unregisterReceiver(mReceiver); |
| mReceiver = null; |
| } |
| |
| private static class Receiver extends BroadcastReceiver { |
| public final String tag; |
| public final AtomicInteger atomicGenerationNumber; |
| public final Consumer<Intent> callback; |
| // Used to verify this receiver is still current. |
| public final int generationNumber; |
| |
| Receiver(String tag, AtomicInteger atomicGenerationNumber, Consumer<Intent> callback) { |
| this.tag = tag; |
| this.atomicGenerationNumber = atomicGenerationNumber; |
| this.callback = callback; |
| generationNumber = atomicGenerationNumber.incrementAndGet(); |
| } |
| |
| @Override |
| public void onReceive(Context context, Intent intent) { |
| final int currentGenerationNumber = atomicGenerationNumber.get(); |
| |
| if (DBG) { |
| Log.d(tag, "receiver generationNumber=" + generationNumber |
| + ", current generationNumber=" + currentGenerationNumber); |
| } |
| if (generationNumber != currentGenerationNumber) return; |
| |
| callback.accept(intent); |
| } |
| } |
| } |