Useful Activity's extension functions.

ActivityExt.kt

inline fun <reified T : Activity> Activity.launchActivity(extras: Bundle? = null) {
    val intent = Intent(this, T::class.java).apply {
        extras?.let { putExtras(it) }
    }
    startActivity(intent)
}

inline fun <reified T : Any> Activity.extra(key: String, default: T) = lazy {
    val value = intent?.extras?.get(key)
    if (value is T) value else default
}