LocationManager requestLocationUpdates

Question

我编写了以下代码，以便在收到位置更新时（这是主线程）在线程上进行回调：

Handler handler; // this Handler is initialized in the following thread
Runnable r = new Runnable() {
    public void run() {
        Looper.prepare();
        handler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                Log.d("MSG", msg.toString());
            }
        };
        Looper.loop();
    }
};
Thread t = new Thread(r);
t.start();


LocationManager lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
lm.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, new LocationListener() {
    public void onLocationChanged(Location location) {
        Log.d("UPD", "onLocationChanged");
    }
    [...]
}, handler.getLooper());

我希望在收到更新时在日志中看到MSG。相反，当我看到UPD行时，我看不到MSG。

然后，当我传递一个looper时，requestLocationUpdates的正确行为是什么？