Android: Coroutines with Blinking TextView

I want to make a blinking text function. I found that can be easily done by Kotlin Coroutines and LifecycleOwner.

withTimeout

With Kotlin Coroutines, you can set a timer in one line.

val SEC = 1000L
withTimeout(duration * SEC) {
    ...
}

Well, you need to run it under a scope. In Android, I can choose LifecycleScope from LifecycleOwner.

Blink of TextView

To flash a TextView, you just need to make it VISIBLE and GONE.

repeat(31) { i ->
    if (i%2 == 0)
        errorTV.visibility = View.VISIBLE
    else
        errorTV.visibility = View.GONE
    delay(300)
}

This block will blink 15 times.

Combination

fun flashError(
    viewLifecycleOwner: LifecycleOwner,
    errorTV: TextView,
    duration: Long, // second
    delay: Long, // ms
) {
    val SEC = 1000L
    viewLifecycleOwner.lifecycleScope.launch {
        withTimeout(duration * SEC) {
            repeat(31) { i ->
                if (i%2 == 0)
                    errorTV.visibility = View.VISIBLE
                else
                    errorTV.visibility = View.GONE
                delay(delay)
            }
        }
    }
}

This is a stand-alone function. I stored it in UiHelper.kt. I will use it to blink the error message in my app.

Test #1

To show an error about Email-Not-Found.

// Blink the error message
private fun showErrorMsg(message: String) {
    customerEmailEt.requestFocus()
    progressBar.visibility = View.GONE
    emailNotFoundTV.text = message

    flashError(
        viewLifecycleOwner,
        emailNotFoundTV,
        10,
        300
    )
}

Let’s run.

It flashes 15 times.

Test #2

The app needs to show a Product-Not-Found error.

// Blink the error message
private fun showErrorMsg(message: String) {
    productPB.visibility = View.GONE
    productNotFoundTV.visibility = View.VISIBLE
    productNotFoundTV.text = message

    flashError(
        viewLifecycleOwner,
        productNotFoundTV,
        10,
        300
    )
    pidEt.requestFocus()
}

I have a blink ended cycles after 15 times.

Working Fine!