<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:orientation="vertical"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity">

   <Button

       android:id="@+id/change"

       android:layout_width="match_parent"

       android:layout_height="wrap_content"

       android:text="改变内容"/>

   <TextView

       android:id="@+id/text"

       android:layout_width="match_parent"

       android:layout_height="wrap_content"

       android:layout_centerInParent="true"

       android:text="你好，世界！"

       android:textSize="20sp"/>

</RelativeLayout>

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 implements View.OnClickListener{

    private TextView text;

    public static final int UPDATE_TEXT=;

    private Handler handler=new Handler(){

        public void handleMessage(Message msg){

            switch (msg.what){

                case UPDATE_TEXT:

                    text.setText("遇见你真好");

                    break;

                    default:

                        break;

            }

        }

    };

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        text=(TextView)findViewById(R.id.text);

        Button ChangeText=(Button)findViewById(R.id.change);

        ChangeText.setOnClickListener(this);

    }

    public void onClick(View v)

    {

        switch (v.getId())

        {

            case R.id.change:

                new Thread(new Runnable() {

                    @Override

                    public void run() {

                        Message message=new Message();

                        message.what=UPDATE_TEXT;

                        handler.sendMessage(message);

                    }

                }).start();

                break;

                default:

                    break;

        }

    }

}