Alert Dialog - How to show an Alert Dialog on Button click in Android Studio using Kotlin.

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 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">

</LinearLayout>

 

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

        <Button
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:id="@+id/btn"
        android:gravity="center"
        android:text="Show Alert Dialog"
     ></Button>

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:

Alert Dialog Example


 

Alert Dialog Example

 

 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">

    <Button
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:id="@+id/btn"
        android:gravity="center"
        android:text="Show Alert Dialog"></Button>
</LinearLayout>

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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