import androidx.appcompat.app.AppCompatActivity;

import android.app.AlertDialog;

import android.content.DialogInterface;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

public class MainActivity extends AppCompatActivity {

            Button exitButton;

            @Override

            protected void onCreate(Bundle savedInstanceState) {

                super.onCreate(savedInstanceState);

                setContentView(R.layout.activity_main);

                exitButton = (Button)findViewById(R.id.exit);

                exitButton.setOnClickListener(new View.OnClickListener() {

                    @Override

                    public void onClick(View view) {

                        AlertDialog alertDialog = new AlertDialog.Builder(MainActivity.this)

                                .setTitle("退出程序")

                                .setMessage("是否退出程序")

                                .setPositiveButton("确定", new DialogInterface.OnClickListener() {

                                    @Override

                                    public void onClick(DialogInterface dialogInterface, int i) {

                                        finish();

                                    }

                                })

                                .setNegativeButton("取消", new DialogInterface.OnClickListener() {

                                    @Override

                                    public void onClick(DialogInterface dialogInterface, int i) {

                                        return;

                                    }

                                }).create();

                        alertDialog.show();

                    }

                });

            }

        }

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

<androidx.constraintlayout.widget.ConstraintLayout 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:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity">

    <Button

        android:id="@+id/exit"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="退出"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintLeft_toLeftOf="parent"

        app:layout_constraintRight_toRightOf="parent"

        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>