原因：android中相关的view和控件不是线程安全的，我们必须单独做处理。这里借此引出Handler的使用。
Handler的官方描述：
A Handler allows you to send and process
Message
and Runnable objects associated with a thread's MessageQueue.
Each Handler instance is associated with a single thread and that thread's message queue. When you create a new Handler, it is bound to the thread / message queue of the thread that is creating it -- from that point on, it will deliver messages and runnables
to that message queue and execute them as they come out of the message queue
Handler的使用场合：
1、
to schedule messages and runnables to be executed as some point in the future;
安排messages和runnables在将来的某个时间点执行。
2、 to enqueue an action to be performed on a different thread than your own.
将action入队以备在一个不同的线程中执行。即可以实现线程间通信。比如当你创建子线程时，你可以再你的子线程中拿到父线程中创建的Handler对象，就可以通过该对象向父线程的消息队列发送消息了。由于Android要求在UI线程中更新界面，因此，可以通过该方法在其它线程中更新界面。
通过Handler更新UI实例：
步骤：
1、创建Handler对象（此处创建于主线程中便于更新UI）。
2、构建Runnable对象，在Runnable中更新界面。
3、在子线程的run方法中向UI线程post，runnable对象来更新UI。
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;
import java.net.UnknownHostException;
import android.os.Bundle;
import android.os.Handler;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.widget.TextView;
public class SimpleClientActivity extends Activity {
private static final String TAG = "SimpleClientActivity";
private TextView show;
private Handler handler = null;
private String line;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_simple_client);
show = (TextView)findViewById(R.id.show);
handler = new Handler();
new Thread(commRunnable).start();
}
Runnable commRunnable = new Runnable() {
@Override
public void run() {
try {
Socket socket = new Socket("192.168.1.188", 30000);
Log.i(TAG, socket.toString());
BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
line = br.readLine();
handler.post(updateRunnable);
br.close();
socket.close();
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
Runnable updateRunnable = new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
show.setText("来自服务器的数据:"+ line);
}
};
}