Android - Thread Communication

package johnson.test;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Looper;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class HelloAndroidActivity extends Activity {

	private static final String TAG = "MainThread";
	private Handler mMainHandler, mChildHandler;
	private TextView info;
	private Button msgBtn;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);

		info = (TextView) findViewById(R.id.info);
		msgBtn = (Button) findViewById(R.id.msgBtn);

		mMainHandler = new Handler() {

			@Override
			public void handleMessage(Message msg) {
				Log.i("lgh", "Got an incoming message from the child thread - "
						+ (String) msg.obj);
				// 接收子线程的消息
				info.setText((String) msg.obj);
			}

		};

		new ChildThread().start();

		msgBtn.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {

				if (mChildHandler != null) {

					// 发送消息给子线程
					Message childMsg = mChildHandler.obtainMessage();
					childMsg.obj = mMainHandler.getLooper().getThread()
							.getName()
							+ " says Hello";
					mChildHandler.sendMessage(childMsg);

					Log.i("lgh", "Send a message to the child thread - "
							+ (String) childMsg.obj);

				}
			}
		});

	}

	public void onDestroy() {
		super.onDestroy();
		Log.i("lgh", "Stop looping the child thread's message queue");

		mChildHandler.getLooper().quit();
	}

	class ChildThread extends Thread {

		private static final String CHILD_TAG = "ChildThread";

		public void run() {
			this.setName("ChildThread");

			// 初始化消息循环队列，需要在Handler创建之前
			Looper.prepare();

			mChildHandler = new Handler() {
				@Override
				public void handleMessage(Message msg) {
					Log.i("lgh",
							"Got an incoming message from the main thread - "
									+ (String) msg.obj);

					try {

						// 在子线程中可以做一些耗时的工作
						sleep(100);

						Message toMain = mMainHandler.obtainMessage();
						toMain.obj = "This is "
								+ this.getLooper().getThread().getName()
								+ ".  Did you send me \"" + (String) msg.obj
								+ "\"?";

						mMainHandler.sendMessage(toMain);

						Log.i("lgh", "Send a message to the main thread - "
								+ (String) toMain.obj);

					} catch (InterruptedException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}

			};

			Log.i("lgh", "Child handler is bound to - "
					+ mChildHandler.getLooper().getThread().getName());

			// 启动子线程消息循环队列
			Looper.loop();
		}
	}
}