In this tutorial we will learn How to use Alert Dialog in Android Using Android Studio.
An AlertDialog shows a floating screen and waits for the user to click on a button to be dismissed.
The AlertDialog is an almost modal screen that
(1) presents a brief message to the user typically shown as a small floating window that partially obscures the underlying view, and
(2) collects a simple answer (usually by clicking an option button) .

So lets create a project.

Step 1  – Create new Android project.
Step 2 –  Add a button to the main activity as shown in the picture below.

src/main/AndroidManifest.xml

<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"
    android:id="@+id/abc">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Alert"
        android:id="@+id/button"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
</RelativeLayout>

 

layout/activity_main.xml

package com.example.programmingknowledge.thefirstapp;

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.MenuItem;
import android.view.View;
import android.widget.Button;

public class MainActivity extends ActionBarActivity {
      private  static Button button_sbm;
      @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
          onButtonClickListener();
    }

    public void onButtonClickListener() {
        button_sbm = (Button)findViewById(R.id.button);
        button_sbm.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        AlertDialog.Builder a_builder = new AlertDialog.Builder(MainActivity.this);
                        a_builder.setMessage("Do you want to Close this App !!!")
                                .setCancelable(false)
                                .setPositiveButton("Yes",new DialogInterface.OnClickListener() {
                                    @Override
                                    public void onClick(DialogInterface dialog, int which) {
                                        finish();
                                    }
                                })
                                .setNegativeButton("No",new DialogInterface.OnClickListener() {
                                    @Override
                                    public void onClick(DialogInterface dialog, int which) {
                                        dialog.cancel();
                                    }
                                }) ;
                        AlertDialog alert = a_builder.create();
                        alert.setTitle("Alert !!!");
                        alert.show();
                    }
                }
        );
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

Now run your app

OUTPUT