How to track error on stripe tap-on-mobile on android device on tap behind device screen?

Question

I have followed the development from this github repository but I have added only tap on mobile feature with real android device that have NFC support.

Terminal SDK verion used is:

com.stripe:stripeterminal:2.15.0
com.stripe:stripeterminal-localmobile:2.15.0

In my app I have a MainActivity and 2 fragments ( say Fragment1 and Fragment2). Fragment 1 : Selection of amount from a set of values nothing else added here (MainActivity first load this fragment) Fragment 2 : Show selected amount and Connecting reader and Processing Payment is added in this fragment

Issues faced on my Fragment 2 is added with Processing payment is added below.

val config = ConnectionConfiguration.LocalMobileConnectionConfiguration("xxxxxxxxxxxxxxx");
Terminal.getInstance().connectLocalMobileReader(
firstReader,
config,
object : ReaderCallback {

    override fun onSuccess(reader: Reader) {
        Log.d("Custom Log", "Connected to mobile device");
        val params = PaymentIntentParameters.Builder()
                                            .setAmount(30)
                                            .setCurrency("gbp")
                                            .build();

        Terminal.getInstance().createPaymentIntent(params, object: PaymentIntentCallback {

            override fun onSuccess(paymentIntent: PaymentIntent) {
                // Placeholder for collecting a payment method with paymentIntent
                val collectConfig = CollectConfiguration.Builder()
                                                        .updatePaymentIntent(true)
                                                        .build();

                val cancelable = Terminal.getInstance().collectPaymentMethod(paymentIntent,
                    object : PaymentIntentCallback {

                        override fun onSuccess(paymentIntent: PaymentIntent) {
                        val pm = paymentIntent.paymentMethod
                        val card = pm?.cardPresentDetails ?: pm?.interacPresentDetails
                        // Placeholder for business logic on card before processing paymentIntent

                        Terminal.getInstance().processPayment(paymentIntent, object : PaymentIntentCallback {
                            override fun onSuccess(paymentIntent: PaymentIntent) {
                                // Placeholder for notifying your backend to capture paymentIntent.id
                                Log.d("Custom Log","Process Payment : "+paymentIntent.id);

                            }

                            override fun onFailure(exception: TerminalException) {
                                // Placeholder for handling the exception
                                Log.d("Custom Log","Error errorMessage : " + exception.errorMessage);
                            }
                        })

                        }

                        override fun onFailure(exception: TerminalException) {
                        // Placeholder for handling exception
                        }

                    })

            }

            override fun onFailure(exception: TerminalException) {
                Log.d("Custom Log","Error ReaderCallback : " + exception.errorMessage)
            }
        })
    }
    override fun onFailure(e: TerminalException) {
        Log.d("Custom Log","Error ReaderCallback : " + e.errorMessage)
    }
});

In the above code, collectPaymentMethod brings a white screen for tap behind, I think this is a new system activity to handle NFC card reading.I have few questions here regarding customisation

q1: Is it possible to customize this screen view ?

q2: On tapping on this screen with a live card it show success message with green screen, even though the card is invalid for test payment, How can I customise this in error case

q3: Screen automatically closes and goes to MainActivity : Fragment1 , How can I catch the the closing and move to fragment2 insted of fragment1. I could'nt find a callback function to handle such cases

My tapto screen and success case screen is attached below

In processPayment of the above code, it fall into onFailure with the error: Your card was declined. Your request was in test mode, but used a non test (live) card. For a list of valid test cards

How can I handle this error with a custom message or info in app.

As a summary, i need to do some customisation with the white screen of the above screenshot, but i couldnt find any documentations or example of that. Someone please help me to sort out these cases

Thanks in advance