I'm having a bit of trouble understanding how to use the Looper
prepare()
/loop()
/quit()
logic.
I have three threads: one is the UI thread, one is a game logic thread and the last is a network communication thread (a background thread, lives only while being used).
The game thread has many dependencies on the results of the network calls, so I wanted to spin the network thread off of the game thread and have a Handler
post the result back.
Of course, since the UI thread is not involved I need to call Looper.prepare()
... somewhere. I thought it should be called in the game thread, but I can't do that because loop()
takes it over.
How do I go about posting back to the game thread from network thread with my handler?
What's going on is that once you call Looper.prepare() followed by Looper.loop() on a Thread, all that Thread will ever do is service its MessageQueue until someone calls quit() on its Looper.
The other thing to realize is that, by default, when a Handler is instantiated, it's code will always execute on the Thread it was created on
What you should do is create a new Thread and in run() call Looper.prepare(), setup any Handlers, and then call Looper.loop().
Bearing these things in mind here is the basic pattern I use a lot of places. Also, there's a good chance you should just be using AsyncTask instead.
public class NetworkThread extends Thread {
private Handler mHandler;
private Handler mCallback;
private int QUIT = 0;
private int DOWNLOAD_FILE = 1;
public NetworkThread(Handler onDownloaded) {
mCallback = onDownloaded;
}
public void run() {
Looper.prepare();
mHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
// things that this thread should do
case QUIT:
Looper.myLooper().quit();
break;
case DOWNLOAD_FILE:
// download the file
mCallback.sendMessage(/*result is ready*/);
}
}
}
Looper.loop();
}
public void stopWorking() {
// construct message to send to mHandler that causes it to call
// Looper.myLooper().quit
}
public void downloadFile(String url) {
// construct a message to send to mHandler that will cause it to
// download the file
}
}