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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.content.Context;
     23 import android.os.Handler;
     24 import android.os.RemoteException;
     25 import android.util.Log;
     26 
     27 import java.util.ArrayList;
     28 import java.util.Collection;
     29 import java.util.HashMap;
     30 import java.util.Map;
     31 
     32 /**
     33  * A base handler class to manage transport and local listeners.
     34  *
     35  * @hide
     36  */
     37 abstract class LocalListenerHelper<TListener> {
     38     private final HashMap<TListener, Handler> mListeners = new HashMap<>();
     39 
     40     private final String mTag;
     41     private final Context mContext;
     42 
     43     protected LocalListenerHelper(Context context, String name) {
     44         Preconditions.checkNotNull(name);
     45         mContext = context;
     46         mTag = name;
     47     }
     48 
     49     public boolean add(@NonNull TListener listener, Handler handler) {
     50         Preconditions.checkNotNull(listener);
     51         synchronized (mListeners) {
     52             // we need to register with the service first, because we need to find out if the
     53             // service will actually support the request before we attempt anything
     54             if (mListeners.isEmpty()) {
     55                 boolean registeredWithService;
     56                 try {
     57                     registeredWithService = registerWithServer();
     58                 } catch (RemoteException e) {
     59                     Log.e(mTag, "Error handling first listener.", e);
     60                     return false;
     61                 }
     62                 if (!registeredWithService) {
     63                     Log.e(mTag, "Unable to register listener transport.");
     64                     return false;
     65                 }
     66             }
     67             if (mListeners.containsKey(listener)) {
     68                 return true;
     69             }
     70             mListeners.put(listener, handler);
     71             return true;
     72         }
     73     }
     74 
     75     public void remove(@NonNull TListener listener) {
     76         Preconditions.checkNotNull(listener);
     77         synchronized (mListeners) {
     78             boolean removed = mListeners.containsKey(listener);
     79             mListeners.remove(listener);
     80             boolean isLastRemoved = removed && mListeners.isEmpty();
     81             if (isLastRemoved) {
     82                 try {
     83                     unregisterFromServer();
     84                 } catch (RemoteException e) {
     85                     Log.v(mTag, "Error handling last listener removal", e);
     86                 }
     87             }
     88         }
     89     }
     90 
     91     protected abstract boolean registerWithServer() throws RemoteException;
     92     protected abstract void unregisterFromServer() throws RemoteException;
     93 
     94     protected interface ListenerOperation<TListener> {
     95         void execute(TListener listener) throws RemoteException;
     96     }
     97 
     98     protected Context getContext() {
     99         return mContext;
    100     }
    101 
    102     private void executeOperation(ListenerOperation<TListener> operation, TListener listener) {
    103         try {
    104             operation.execute(listener);
    105         } catch (RemoteException e) {
    106             Log.e(mTag, "Error in monitored listener.", e);
    107             // don't return, give a fair chance to all listeners to receive the event
    108         }
    109     }
    110 
    111     protected void foreach(final ListenerOperation<TListener> operation) {
    112         Collection<Map.Entry<TListener, Handler>> listeners;
    113         synchronized (mListeners) {
    114             listeners = new ArrayList<>(mListeners.entrySet());
    115         }
    116         for (final Map.Entry<TListener, Handler> listener : listeners) {
    117             if (listener.getValue() == null) {
    118                 executeOperation(operation, listener.getKey());
    119             } else {
    120                 listener.getValue().post(new Runnable() {
    121                     @Override
    122                     public void run() {
    123                         executeOperation(operation, listener.getKey());
    124                     }
    125                 });
    126             }
    127         }
    128     }
    129 }
    130