How to handle back button press in Kotlin Android

How to handle back button press in Kotlin Android.

Here's a step-by-step tutorial on how to handle the back button press in Kotlin for Android:

1. Create a new Kotlin Android project in Android Studio or open an existing project.

2. Open the activity where you want to handle the back button press. This is usually the main activity or the activity where you want to control the navigation flow.

3. Inside the activity class, override the onBackPressed() method. This method is called when the back button is pressed on the device.

override fun onBackPressed() {
    // Handle the back button press here
}

4. Inside the onBackPressed() method, you can add your custom logic to handle the back button press. For example, if you want to navigate back to the previous activity or fragment, you can use the finish() method to close the current activity.

override fun onBackPressed() {
    // Close the current activity
    finish()
}

5. If you want to show a confirmation dialog before allowing the user to navigate back, you can use the AlertDialog class. First, create an instance of AlertDialog.Builder and set the desired title, message, and button listeners.

override fun onBackPressed() {
    AlertDialog.Builder(this)
        .setTitle("Confirmation")
        .setMessage("Are you sure you want to exit?")
        .setPositiveButton("Yes") { dialog, _ ->
            // Close the current activity
            finish()
        }
        .setNegativeButton("No") { dialog, _ ->
            // Do nothing and dismiss the dialog
            dialog.dismiss()
        }
        .show()
}

6. You can also handle the back button press differently based on the current state of your app. For example, if you have a multi-step form and the user is on step 2, you can navigate back to step 1 instead of closing the activity.

override fun onBackPressed() {
    if (isOnStep2) {
        // Navigate back to step 1
        goToStep1()
    } else {
        // Close the current activity
        finish()
    }
}

7. Test your app by running it on an Android device or emulator. Press the back button and verify that your custom back button handling logic is executed.

That's it! You've successfully learned how to handle the back button press in Kotlin for Android. Feel free to customize the logic based on your app's requirements.