LocalListenerHelper.java revision 6568d709e78d6ccaf256b7d0e4a19cdfb26deafb 
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
17package android.location;
18
19import com.android.internal.util.Preconditions;
20
21import android.annotation.NonNull;
22import android.content.Context;
23import android.os.RemoteException;
24import android.util.Log;
25
26import java.util.ArrayList;
27import java.util.Collection;
28import java.util.HashSet;
29
30/**
31 * A base handler class to manage transport and local listeners.
32 *
33 * @hide
34 */
35abstract class LocalListenerHelper<TListener> {
36    private final HashSet<TListener> mListeners = new HashSet<>();
37
38    private final String mTag;
39    private final Context mContext;
40
41    protected LocalListenerHelper(Context context, String name) {
42        Preconditions.checkNotNull(name);
43        mContext = context;
44        mTag = name;
45    }
46
47    public boolean add(@NonNull TListener listener) {
48        Preconditions.checkNotNull(listener);
49        synchronized (mListeners) {
50            // we need to register with the service first, because we need to find out if the
51            // service will actually support the request before we attempt anything
52            if (mListeners.isEmpty()) {
53                boolean registeredWithService;
54                try {
55                    registeredWithService = registerWithServer();
56                } catch (RemoteException e) {
57                    Log.e(mTag, "Error handling first listener.", e);
58                    return false;
59                }
60                if (!registeredWithService) {
61                    Log.e(mTag, "Unable to register listener transport.");
62                    return false;
63                }
64            }
65            if (mListeners.contains(listener)) {
66                return true;
67            }
68            return mListeners.add(listener);
69        }
70    }
71
72    public void remove(@NonNull TListener listener) {
73        Preconditions.checkNotNull(listener);
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                    Log.v(mTag, "Error handling last listener removal", e);
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 Context getContext() {
95        return mContext;
96    }
97
98    protected void foreach(ListenerOperation<TListener> operation) {
99        Collection<TListener> listeners;
100        synchronized (mListeners) {
101            listeners = new ArrayList<>(mListeners);
102        }
103        for (TListener listener : listeners) {
104            try {
105                operation.execute(listener);
106            } catch (RemoteException e) {
107                Log.e(mTag, "Error in monitored listener.", e);
108                // don't return, give a fair chance to all listeners to receive the event
109            }
110        }
111    }
112}
113