在子线程中更新UI，只能使用Handler

package com.pingyijinren.test;

import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity{
public static final int UPDATE_TEXT=1;
private TextView textView;
private Button button;

private Handler handler=new Handler(){
public void handleMessage(Message msg){
switch(msg.what){
case UPDATE_TEXT:
textView.setText("HelloWorld");
break;
default:
break;
}
}
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

textView=(TextView)findViewById(R.id.textView);
button=(Button)findViewById(R.id.button);

button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new Thread(new Runnable(){
@Override
public void run(){
Message message=new Message();
message.what=UPDATE_TEXT;
handler.sendMessage(message);
}
}).start();
}
});
}
}