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 
LocalListenerHelper(Context context, String name)43     protected LocalListenerHelper(Context context, String name) {
44         Preconditions.checkNotNull(name);
45         mContext = context;
46         mTag = name;
47     }
48 
add(@onNull TListener listener, Handler handler)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 
remove(@onNull TListener listener)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 
registerWithServer()91     protected abstract boolean registerWithServer() throws RemoteException;
unregisterFromServer()92     protected abstract void unregisterFromServer() throws RemoteException;
93 
94     protected interface ListenerOperation<TListener> {
execute(TListener listener)95         void execute(TListener listener) throws RemoteException;
96     }
97 
getContext()98     protected Context getContext() {
99         return mContext;
100     }
101 
executeOperation(ListenerOperation<TListener> operation, TListener listener)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 
foreach(final ListenerOperation<TListener> operation)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