Android程序的主线程（UI线程）无法跑有时间耗费的代码，所以一个好习惯是将各种与UI无关的操作，比如网络通信（包括http、ftp、mail、socket）、文件操作、数值计算等放在子线程中。为了方便操作UI线程(Activity主类)中的各种方法和变量，将子线程写成Activity主类中的内部类是个较省事的方式。

实例代码：

Archer_runnable()可直接使用主类中的Message和bundle来向主类发送消息，也可使用主类中定义的其它方法。

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.widget.Toast;
public class MainActivity extends Activity {private Thread Archer_Thread;// ------------------------------------private Message msg;private Bundle bundle;private StringBuilder sb_contact;// ------------------------------------public MainActivity() {}protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);Button bn_Ballista = (Button) this.findViewById(R.id.button_Ballista);bn_Ballista.setOnClickListener(new BallistaListener());Archer_Thread = new Thread(Archer_runnable);Archer_Thread.start();}public boolean onCreateOptionsMenu(Menu menu) {getMenuInflater().inflate(R.menu.main, menu);return true;}public Handler mHandler = new Handler() {String str_tmp;public void handleMessage(Message msg) {switch (msg.what) {case 0x12: {str_tmp = msg.getData().getString("result");Toast.makeText(MainActivity.this, "...", Toast.LENGTH_SHORT).show();break;}default:break;}}};Runnable Archer_runnable = new Runnable() {public void run() {sb_contact = new StringBuilder("contact: ");msg = new Message();bundle = new Bundle();// /-----------------------------------------msg.what = 0x12;bundle.putString("result", sb_contact.toString());msg.setData(bundle);mHandler.sendMessage(msg);}};
}