Display Alert Dialog in Android

An alert dialog is a popup window that is displayed in front of the current content. It asks the user to make a decision or enter additional details. An alert dialog can consist of title, content and a list of action buttons.

In the layout XML file, we added the Button which is used to display the alert dialog.

app/src/main/res/layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/myButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="Open" />

</RelativeLayout>

An alert dialog can be constructed using the AlertDialog.Builder. A title and message can be set using the setTitle() and setMessage() methods.

An alert dialog can have three different action buttons.

An alert dialog can be displayed by using show() method.

app/src/main/java/com/example/app/MainActivity.kt

package com.example.app

import android.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity()
{
    override fun onCreate(savedInstanceState: Bundle?)
    {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        myButton.setOnClickListener { showAlertDialog() }
    }

    private fun showAlertDialog()
    {
        val dialog = AlertDialog.Builder(this)
        dialog.setTitle("Update")
        dialog.setMessage("Are you sure want to update settings?")

        dialog.setPositiveButton("Yes") { _, _ ->
            Log.d("MY_APP", "Yes")
        }
        dialog.setNegativeButton("No") { _, _ ->
            Log.d("MY_APP", "No")
        }
        dialog.setNeutralButton("Remind me later") { _, _ ->
            Log.d("MY_APP", "Remind me later")
        }

        dialog.show()
    }
}