Thursday, April 5, 2018

android kotlin - AlertDialog yes no cancel button example

AlertDialog Yes No Cancel Button
The AlertDialog is a subclass of Dialog that can display one, two, or three Buttons. It can display a text message. Developers can display a more complex View on the alert dialog window using a custom View.

The following android application development tutorial will demonstrate to us how we can display an alert dialog with yes, no, and a cancel button inside it. The code is written in Kotlin programming language. We created the AlertDialog using the native android SDK API.

To create an alert dialog we have to initialize an instance of AlertDialog.Builder object. This AlertDialog Builder object can define the alert dialog’s various properties such as button, message, icon and etc. Finally, we can create an AlertDialog using this builder instance.

So how can we display the yes, no, and cancel buttons inside the alert dialog? Using the AlertDialog Builder instance developers can set its Positive, Negative, and Neutral buttons. Simply we can call the Positive button to the ‘yes’ button, the Negative button to the ‘no’ button, and the Neutral button to the ‘cancel’ button. We also can set the click listeners for those buttons using AlertDialog Builder API. The android SDK display the following buttons inside a dialog window in a good format and position.

This android kotlin tutorial code is written in an android studio IDE. Copy the code and paste it into your android studio IDE and run it on an emulator to see how we create an AlertDialog with yes, no and cancel buttons in an android application.

And how we handle the click events for the alert dialog’s specified button objects in an application. We displayed screenshots of the emulator screen, which also help you to understand the code without running it on an android device or emulator.
MainActivity.kt

package com.cfsuman.kotlintutorials

import android.os.Bundle
import android.widget.Button
import android.widget.TextView
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity


class MainActivity : AppCompatActivity() {
    private lateinit var context:MainActivity
    private lateinit var textView:TextView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // Get the context
        context = this;

        // Get the widgets reference from XML layout
        textView = findViewById(R.id.textView)
        val button = findViewById<Button>(R.id.button)

        // Button click listener
        button.setOnClickListener{
            // Show the yes, no and cancel buttons on an alert dialog
            showDialog()
        }
    }


    // Method to show an alert dialog with yes, no and cancel button
    private fun showDialog(){
        // Late initialize an alert dialog object
        lateinit var dialog:AlertDialog

        // Initialize a new instance of alert dialog builder object
        val builder = AlertDialog.Builder(context)

        // Set a title for alert dialog
        builder.setTitle("Title of AlertDialog.")

        // Set a message for alert dialog
        builder.setMessage("I am alert dialog message.")

        // Set the alert dialog positive/yes button
        builder.setPositiveButton("YES"){_, _ ->
            textView.text = "Positive (Yes) button clicked."
        }

        // Set the alert dialog negative/no button
        builder.setNegativeButton("NO"){_, _ ->
            textView.text = "Negative (No) button clicked."
        }

        // Set the alert dialog neutral/cancel button
        builder.setNeutralButton("CANCEL"){_, _ ->
            textView.text = "Neutral (Cancel) button clicked."
        }

        // Initialize the AlertDialog using builder object
        dialog = builder.create()

        // Finally, display the alert dialog
        dialog.show()
    }
}
activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/rootLayout"
    android:background="#FEFEFA"
    android:padding="24dp">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Show Dialog"
        android:textAllCaps="false"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="32dp"
        android:fontFamily="sans-serif"
        android:textSize="24sp"
        app:layout_constraintStart_toStartOf="@+id/button"
        app:layout_constraintTop_toBottomOf="@+id/button" />

</androidx.constraintlayout.widget.ConstraintLayout>
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