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/*
* Copyright (C) 2014 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.location;
import android.annotation.NonNull;
import android.content.Context;
import android.os.Handler;
import android.os.RemoteException;
import android.util.Log;
import com.android.internal.util.Preconditions;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
/**
* A base handler class to manage transport and local listeners.
*
* @hide
*/
abstract class LocalListenerHelper<TListener> {
private final HashMap<TListener, Handler> mListeners = new HashMap<>();
private final String mTag;
private final Context mContext;
protected LocalListenerHelper(Context context, String name) {
Preconditions.checkNotNull(name);
mContext = context;
mTag = name;
}
/**
* Adds a {@param listener} to the list of listeners on which callbacks will be executed. The
* execution will happen on the {@param handler} thread or alternatively in the callback thread
* if a {@code null} handler value is passed.
*/
public boolean add(@NonNull TListener listener, Handler handler) {
Preconditions.checkNotNull(listener);
synchronized (mListeners) {
// we need to register with the service first, because we need to find out if the
// service will actually support the request before we attempt anything
if (mListeners.isEmpty()) {
boolean registeredWithService;
try {
registeredWithService = registerWithServer();
} catch (RemoteException e) {
Log.e(mTag, "Error handling first listener.", e);
return false;
}
if (!registeredWithService) {
Log.e(mTag, "Unable to register listener transport.");
return false;
}
}
if (mListeners.containsKey(listener)) {
return true;
}
mListeners.put(listener, handler);
return true;
}
}
public void remove(@NonNull TListener listener) {
Preconditions.checkNotNull(listener);
synchronized (mListeners) {
boolean removed = mListeners.containsKey(listener);
mListeners.remove(listener);
boolean isLastRemoved = removed && mListeners.isEmpty();
if (isLastRemoved) {
try {
unregisterFromServer();
} catch (RemoteException e) {
Log.v(mTag, "Error handling last listener removal", e);
}
}
}
}
protected abstract boolean registerWithServer() throws RemoteException;
protected abstract void unregisterFromServer() throws RemoteException;
protected interface ListenerOperation<TListener> {
void execute(TListener listener) throws RemoteException;
}
protected Context getContext() {
return mContext;
}
private void executeOperation(ListenerOperation<TListener> operation, TListener listener) {
try {
operation.execute(listener);
} catch (RemoteException e) {
Log.e(mTag, "Error in monitored listener.", e);
// don't return, give a fair chance to all listeners to receive the event
}
}
protected void foreach(final ListenerOperation<TListener> operation) {
Collection<Map.Entry<TListener, Handler>> listeners;
synchronized (mListeners) {
listeners = new ArrayList<>(mListeners.entrySet());
}
for (final Map.Entry<TListener, Handler> listener : listeners) {
if (listener.getValue() == null) {
executeOperation(operation, listener.getKey());
} else {
listener.getValue().post(new Runnable() {
@Override
public void run() {
executeOperation(operation, listener.getKey());
}
});
}
}
}
}
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