Confirm dialog before exit android studio

Hi guys I have an exit button on my main activity XML however I need it so when the user clicks it, it opens a dialogue to confirm the exit, if yes then exit. if no take them back.

here's my code so far, don't have any of that part however as I don't know where to start.

package com.tradingsoftwarelimited.labelprinter10;



import android.app.Activity;

import android.app.AlertDialog;

import android.content.DialogInterface;

import android.support.v7.app.ActionBarActivity;

import android.os.Bundle;

import android.view.Menu;

import android.view.View;

import android.widget.Button;

import android.widget.Toast;





public class MainActivity extends ActionBarActivity {



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);









    //Sets Edit and Data Button to hidden

    Button hiddenButton = (Button) findViewById(R.id.editButton);

    hiddenButton.setVisibility(View.INVISIBLE);

    Button hiddenButton1 = (Button) findViewById(R.id.dataButton);

    hiddenButton1.setVisibility(View.INVISIBLE);



    //Acknolages settings button

    Button showButton = (Button) findViewById(R.id.settingsButton);



    //if clicked

    showButton.setOnClickListener(new View.OnClickListener() {

        @Override

        public void onClick(View v) {

            //If clicked show Edit and data Button

            Button showButton = (Button) (findViewById(R.id.editButton));

            showButton.setVisibility(View.VISIBLE);

            Button showButton1 = (Button) (findViewById(R.id.dataButton));

            showButton1.setVisibility(View.VISIBLE);





        }

    });



}









    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getSupportActionBar().hide();

        return true;

        }

    };





;