Show Alert Dialog on Button Click in Android - RRutors

Last updated Dec 14, 2021

In this android example tutorial, we will see how to show an Alert Dialog by using Kotlin in android studio.

What is Alert Dialog?
Android AlertDialog is a subclass of Dialog class. It's used to force a user to make a decision in a small dialogue box before continuing with the same activity without switching screens. A dialog shows the title, message, up to three buttons or a custom layout. Through alert dialog, we create positive (yes), negative (no) and neutral (cancel) decision buttons.

Implementation:

To begin, Create a new project in android studio and enter the name, select the project location and language to Kotlin. Then press the Finish button.
Open the activity_alert_dialog.xml file and add the LinearLayout with orientation (Vertical or horizontal).

</LinearLayout>

In activity_alert_dialog.xml file, insert an Button inside a LinearLayout.

Add id of Button by using id atribute and text using text attribute

android:id="@+id/btn"
android:text="Show Alert Dialog"

Button in android has the following properties:
id, padding, textSize, text, textColor, background, layout_margin etc.

Now go to AlertDialogActivity.kt and add the unique id of Button which is available in activity_alert_dialog file.

val btn = findViewById<Button>(R.id.btn)

Set the onClickListener event on the button instance

btn.setOnClickListener{

}

Create a variable instance of dialog inside button onclick method.

val dialog = AlertDialog.Builder(this)

Then set a title, message on dialog reference by using this

dialog.setTitle("Delete Wallpaper")
dialog.setMessage("Do you really want to delete?")

Now, set a positive button on a dialog instance using

dialog.setPositiveButton("Yes", DialogInterface.OnClickListener { dialog, which ->
Toast.makeText(
this,
"Hello",
Toast.LENGTH_SHORT
).show()
dialog.dismiss()
})

Use Negative Button in dialog

dialog.setNegativeButton("No", DialogInterface.OnClickListener{
dialog, which ->
dialog.dismiss()
})

For displaying the dialog on screen and close the dialog use these

dialog.show()
dialog.dismiss()

Now run the application in emulator or real device, you will see the output shown below.

OUTPUT:

Complete source code for Android Alert Dialog example:

activity_alert_dialog.xml file

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:gravity="center"
tools:context=".AlertDialogActivity">

AlertDialogActivity.kt file

import android.content.DialogInterface
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.Toast
import androidx.appcompat.app.AlertDialog

class AlertDialogActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_alert_dialog)
val btn = findViewById(R.id.btn)

btn.setOnClickListener{
val dialog = AlertDialog.Builder(this)
dialog.setTitle("Delete Wallpaper")
dialog.setMessage("Do you really want to delete?")
dialog.setPositiveButton("Yes", DialogInterface.OnClickListener { dialog, which ->
Toast.makeText(
this,
"Hello",
Toast.LENGTH_SHORT
).show()
dialog.dismiss()
})
dialog.setNegativeButton("No", DialogInterface.OnClickListener{
dialog, which ->
dialog.dismiss()
})

dialog.show()
}
}
}

Conclusion: We have covered the topic How to show an Alert Dialog on click of Button to Android by using Kotlin.

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