随机二选一

1-Main2Activity.java

package com.example.lenovo.textapp4;

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

import java.io.Reader;
import java.util.Random;

public class Main2Activity extends AppCompatActivity {

    Button bt_1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        bt_1=(Button)findViewById(R.id.bt_1);

    }
            Random r=new Random();

            public void bt_on(View v) {

                for (int i=0;i<10;i++)
                {
                    new Thread(){
                        @Override
                        public void run() {
                            try{
                                Thread.sleep(r.nextInt(3000));
                            }catch (Exception e){

                            }
                            runOnUiThread(new Runnable() {
                                @Override
                                public void run() {
                                    bt_1.setText("北京");
                                }
                            });
                            return;
                        }
                    }.start();

                    new Thread() {
                        @Override
                        public void run() {
                            try {
                                Thread.sleep(r.nextInt(3000));
                            }catch (Exception e){

                            }
                            runOnUiThread(new Runnable() {
                                @Override
                                public void run() {

                                    bt_1.setText("上海");
                                }
                            });
                            return;
                        }
                    }.start();
                }

            }
        }

2-activity_main2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.lenovo.textapp4.Main2Activity">

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/bt_1"
        android:text="城市"
        android:onClick="bt_on"/>

</LinearLayout>