/* 拡張したメソッドの一部 */
public fun <V : View> View.bindView(id: Int, exInit: (V) -> V)
        : ReadOnlyProperty<View, V> = required(id, viewFinder, exInit)
@Suppress("UNCHECKED_CAST")
private fun <T, V : View> required(id: Int, finder: T.(Int) -> View?, exInit:(V) -> V)
        = Lazy({t: T, desc -> exInit(t.finder(id) as V? ?: viewNotFound(id, desc)) })