使用布尔变量exit 来控制（变量在run方法内部）

public class MainActivity extends AppCompatActivity {
    private Button searchGoBtn;
    public volatile boolean exit = false;

    public void go(View view){
        exit=true;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        searchGoBtn = (Button) findViewById(R.id.search_go_btn);

        new Thread(){

            @Override
            public void run() {
                while (!exit){
                    try {
                        Thread.sleep(200);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("FileDemo.run");

                }


            }
        }.start();
    }
}

    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

        android:id="@+id/search_go_btn"
      android:onClick="go"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"/>

比较正宗的写法（线程是内部类的形式）

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {


    MyThread myThread;
    public void go(View view){
        myThread.exit=true;
    }
    class MyThread extends Thread{
        public volatile boolean exit = false;
        @Override
        public void run() {
            while (!exit){
                try {
                    Thread.sleep(200);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("FileDemo.run");

            }
        }
    }
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        myThread = new MyThread();
        myThread.start();

    }




}