今天突然发现使用Messenger不止可以实现进程间通信,它实际上是一种标准的通信模式,同一进程一样可以通信
1.Activity向Service发送信息
1) 首先在Service中定义一个Service专用的Handler,并重写onBind()方法将Handler包装之后返回
public class MessengerService extends Service {
Handler serviceHandler = new Handler(){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
}
};
@Nullable
@Override
public IBinder onBind(Intent intent) {
Messenger messenger = new Messenger(serviceHandler);
return messenger.getBinder(); //Activity在bindService时就会获得这个IBinder对象
}
}
2)通过bindService()在Activity中获取可以向Service发送消息的Messenger对象
Messenger serviceMessenger; //在Activity中定义一个成员变量serviceMessenger,这个对象专门用来向Service发送信息
ServiceConnection conn = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
serviceMessenger = new Messenger(service); //这样在使用bindService()方法之后,serviceMessenger就可以向Service发送信息了
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
发送信息
private void sendMessage() { //实际上这个message是发送到了Service的Handler中去
Message message = Message.obtain();
try {
serviceMessenger.send(message); //因为Messenger可用于远程通信,所以要try-catch
} catch (RemoteException e) {
e.printStackTrace();
}
}
2.Service向Activity发送信息
1) 先在Activity中定义一个Handler用来接受Service发送的信息
Handler activityHandler = new Handler(Looper.getMainLooper()){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
}
};
2) 既然已经有了向Service发送信息的能力了,那就直接把Handler包装在Messenger中发送给Service
Messenger activityMessenger = new Messenger(activityHandler); //包装Activity的handler
Message message = Message.obtain();
message.what = MessengerService.GET_ACTIVITY_MESSENGER;
message.replyTo = activityMessenger;
try {
serviceMessenger.send(message); //实际上是将message发送给Service的Handler处理
} catch (RemoteException e) {
e.printStackTrace();
}
3) Service获取Messenger
public static final int GET_ACTIVITY_MESSENGER = -2;
Messenger activityMessenger = null;
Handler serviceHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what){
case GET_ACTIVITY_MESSENGER: //标识
activityMessenger = msg.replyTo; //获取了Activity的Messenger
break;
}
}
};
4) Service向Activity发送信息
private void sendSomethingToActivity(){
Message message = Message.obtain();
//这里添加message需要携带的信息
try {
activityMessenger.send(message); //实际上是将message发送给了Activity的Handler来处理
} catch (RemoteException e) {
e.printStackTrace();
}
}
3. 互相发送信息
到这也应该明白了,要向对方发送信息,直接调用Messenger的send()方法就可以把携带信息的message发送给对方了
//Activity发送给Service
private void sendSomethingToService(){
Message message = Message.obtain();
//添加发送的信息到message中
try {
serviceMessenger.send(message);
} catch (RemoteException e) {
e.printStackTrace();
}
}
//Service发送给Activity
private void sendSomethingToActivity(){
Message message = Message.obtain();
//添加发送的信息到message中
try {
activityMessenger.send(message);
} catch (RemoteException e) {
e.printStackTrace();
}
}
看起来写得麻烦,实际上降低了两个类的依赖,对以后的扩展很有帮助
因为这个是个固定的写法,甚至可以直接写进BaseActivity中或者BaseService中
