Android 连接网络时显示进度条

public class HelloXML extends Activity {
private static final int MESSAGETYPE_01 = 0x0001;
private ProgressDialog progressDialog = null;

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

progressDialog = ProgressDialog.show(HelloXML.this, "下载", "正在下载,请稍候！");

new Thread() {
public void run() {
try {

// 连接网络获取数据

} catch (Exception e) {
// 在GUI显示错误提示
// tv.setText("Error: " + e.getMessage());

}

Message msg_listData = new Message();
msg_listData.what = MESSAGETYPE_01;
handler.sendMessage(msg_listData);
}
}.start();
}

private Handler handler = new Handler() {

public void handleMessage(Message message) {
switch (message.what) {
case MESSAGETYPE_01:
//刷新UI，显示数据，并关闭进度条
progressDialog.dismiss(); //关闭进度条
break;
}
}
};
}