android double click to exit
private var doubleBackToExitPressedOnce = false
override fun onBackPressed() {
if (doubleBackToExitPressedOnce) {
super.onBackPressed()
return
}
this.doubleBackToExitPressedOnce = true
Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show()
Handler(Looper.getMainLooper()).postDelayed(Runnable { doubleBackToExitPressedOnce = false }, 2000)
}