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      1 /*
      2  * Copyright (C) 2014 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.location;
     18 
     19 import com.android.internal.util.Preconditions;
     20 
     21 import android.annotation.NonNull;
     22 import android.os.RemoteException;
     23 import android.util.Log;
     24 
     25 import java.util.ArrayList;
     26 import java.util.Collection;
     27 import java.util.HashSet;
     28 
     29 /**
     30  * A base handler class to manage transport and local listeners.
     31  *
     32  * @hide
     33  */
     34 abstract class LocalListenerHelper<TListener> {
     35     private final HashSet<TListener> mListeners = new HashSet<TListener>();
     36     private final String mTag;
     37 
     38     protected LocalListenerHelper(String name) {
     39         Preconditions.checkNotNull(name);
     40         mTag = name;
     41     }
     42 
     43     public boolean add(@NonNull TListener listener) {
     44         Preconditions.checkNotNull(listener);
     45 
     46         synchronized (mListeners) {
     47             // we need to register with the service first, because we need to find out if the
     48             // service will actually support the request before we attempt anything
     49             if (mListeners.isEmpty()) {
     50                 boolean registeredWithService;
     51                 try {
     52                     registeredWithService = registerWithServer();
     53                 } catch (RemoteException e) {
     54                     Log.e(mTag, "Error handling first listener.", e);
     55                     return false;
     56                 }
     57                 if (!registeredWithService) {
     58                     Log.e(mTag, "Unable to register listener transport.");
     59                     return false;
     60                 }
     61             }
     62 
     63             if (mListeners.contains(listener)) {
     64                 return true;
     65             }
     66             mListeners.add(listener);
     67         }
     68         return true;
     69     }
     70 
     71     public void remove(@NonNull TListener listener) {
     72         Preconditions.checkNotNull(listener);
     73 
     74         synchronized (mListeners) {
     75             boolean removed = mListeners.remove(listener);
     76             boolean isLastRemoved = removed && mListeners.isEmpty();
     77             if (isLastRemoved) {
     78                 try {
     79                     unregisterFromServer();
     80                 } catch (RemoteException e) {
     81 
     82                 }
     83             }
     84         }
     85     }
     86 
     87     protected abstract boolean registerWithServer() throws RemoteException;
     88     protected abstract void unregisterFromServer() throws RemoteException;
     89 
     90     protected interface ListenerOperation<TListener> {
     91         void execute(TListener listener) throws RemoteException;
     92     }
     93 
     94     protected void foreach(ListenerOperation operation) {
     95         Collection<TListener> listeners;
     96         synchronized (mListeners) {
     97             listeners = new ArrayList<TListener>(mListeners);
     98         }
     99 
    100         for (TListener listener : listeners) {
    101             try {
    102                 operation.execute(listener);
    103             } catch (RemoteException e) {
    104                 Log.e(mTag, "Error in monitored listener.", e);
    105                 // don't return, give a fair chance to all listeners to receive the event
    106             }
    107         }
    108     }
    109 }
    110