How to Show Alert Dialog in Android

Creating alert dialog is very easy. In this tutorial i will be discussing about creating alert dialogues.
A dialog is a small window that prompts the user to make a decision or enter additional information. A dialog does not fill the screen and is normally used for modal events that require users to take an action before they can proceed.

1.activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Click on Show Alert Dialog to show the Alert Dialog"
        />
    <Button
        android:id="@+id/button_show_alert_dialog"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="Show Alert Dialog" />

</LinearLayout>

2.MainActivity.java

package com.example.semwal.alertdialog;

import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    /* Called when the activity is first created. */

    // this context will use when we work with Alert Dialog
    final Context context = this;

    // just for test, when we click this button, we will see the alert dialog.
    private Button button;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.button_show_alert_dialog);

        //Create onclick listener class
        button.setOnClickListener(new View.OnClickListener() {
            //When you click the button, Alert dialog will be showed
            public void onClick(View v) {
       /* Alert Dialog Code Start*/
                AlertDialog.Builder alert = new AlertDialog.Builder(context);
                alert.setTitle("Alert Dialog With EditText"); //Set Alert dialog title here
                alert.setMessage("Enter Your Name Here"); //Message here

                // Set an EditText view to get user input
                final EditText input = new EditText(context);
                alert.setView(input);

                alert.setPositiveButton("OK", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int whichButton) {
                        //You will get as string input data in this variable.
                        // here we convert the input to a string and show in a toast.
                        String srt = input.getEditableText().toString();
                        Toast.makeText(context,srt,Toast.LENGTH_LONG).show();
                    } // End of onClick(DialogInterface dialog, int whichButton)
                }); //End of alert.setPositiveButton
                alert.setNegativeButton("CANCEL", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int whichButton) {
                        // Canceled.
                        dialog.cancel();
                    }
                }); //End of alert.setNegativeButton
                AlertDialog alertDialog = alert.create();
                alertDialog.show();
       /* Alert Dialog Code End*/
            }// End of onClick(View v)
        }); //button.setOnClickListener
    }//End of onCreate
}//class AlertDialogExample extends Activity