ext_func_sample.kt

/**
 * Extension for view visibility
 */
fun View.visible() {
    visibility = View.VISIBLE
}

fun View.gone() {
    visibility = View.GONE
}

/**
 * How to use the code above
 */
class MyActivity : Activity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        val progressBar = finViewById<ProgressBar>(R.id.progress_bar)
        
        // Call the view extension
        progressBar.visible()
        progressBar.gone()
    }
}