public class LooperDemoActivity extends Activity {
private WorkerThread mWorkerThread;
private TextView mStatusLine;
private Handler mMainHandler;

@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.looper_demo_activity);
mMainHandler = new Handler() {
@Override
public void handleMessage(Message msg) {
String text = (String) msg.obj;
if (TextUtils.isEmpty(text)) {
return;
}
mStatusLine.setText(text);
}
};

mWorkerThread = new WorkerThread();
final Button action = (Button) findViewById(R.id.looper_demo_action);
action.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
mWorkerThread.executeTask("please do me a favor");
}
});
final Button end = (Button) findViewById(R.id.looper_demo_quit);
end.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
mWorkerThread.exit();
}
});
mStatusLine = (TextView) findViewById(R.id.looper_demo_displayer);
mStatusLine.setText("Press 'do me a favor' to execute a task, press 'end of service' to stop looper thread");
}

@Override
public void onDestroy() {
super.onDestroy();
mWorkerThread.exit();
mWorkerThread = null;
}

private class WorkerThread extends Thread {
protected static final String TAG = "WorkerThread";
private Handler mHandler;
private Looper mLooper;

public WorkerThread() {
start();
}

public void run() {
// Attention: if you obtain looper before Looper#prepare(), you can still use the looper
// to process message even after you call Looper#quit(), which means the looper does not
//really quit.
Looper.prepare();
// So we should call Looper#myLooper() after Looper#prepare(). Anyway, we should put all stuff between Looper#prepare()
// and Looper#loop().
// In this case, you will receive "Handler{4051e4a0} sending message to a Handler on a dead thread
// 05-09 08:37:52.118: W/MessageQueue(436): java.lang.RuntimeException: Handler{4051e4a0} sending message
// to a Handler on a dead thread", when try to send a message to a looper which Looper#quit() had called,
// because the thread attaching the Looper and Handler dies once Looper#quit() gets called.
mLooper = Looper.myLooper();
// either new Handler() and new Handler(mLooper) will work
mHandler = new Handler(mLooper) {
@Override
public void handleMessage(Message msg) {
/*
* Attention: object Message is not reusable, you must obtain a new one for each time you want to use it.
* Otherwise you got "android.util.AndroidRuntimeException: { what=1000 when=-15ms obj=it is my please
* to serve you, please be patient to wait!........ } This message is already in use."
*/
// Message newMsg = Message.obtain();
StringBuilder sb = new StringBuilder();
sb.append("it is my please to serve you, please be patient to wait!\n");
Log.e(TAG, "workerthread, it is my please to serve you, please be patient to wait!");
for (int i = 1; i < 100; i++) {
sb.append(".");
Message newMsg = Message.obtain();
newMsg.obj = sb.toString();
mMainHandler.sendMessage(newMsg);
Log.e(TAG, "workthread, working" + sb.toString());
SystemClock.sleep(100);
}
Log.e(TAG, "workerthread, your work is done.");
sb.append("\nyour work is done");
Message newMsg = Message.obtain();
newMsg.obj = sb.toString();
mMainHandler.sendMessage(newMsg);
}
};
Looper.loop();
}

public void exit() {
if (mLooper != null) {
mLooper.quit();
mLooper = null;
}
}

// This method returns immediately, it just push an Message into Thread's MessageQueue.
// You can also call this method continuously, the task will be executed one by one in the
// order of which they are pushed into MessageQueue(they are called).
public void executeTask(String text) {
if (mLooper == null || mHandler == null) {
Message msg = Message.obtain();
msg.obj = "Sorry man, it is out of service";
mMainHandler.sendMessage(msg);
return;
}
Message msg = Message.obtain();
msg.obj = text;
mHandler.sendMessage(msg);
}
}
}