kotlin 扩展函数

https://www.kotlincn.net/docs/reference/extensions.html

扩展函数在android中的应用

fun AppCompatActivity.replaceFragmentInActivity(fragment: Fragment, @IdRes frameId: Int) {    supportFragmentManager.transact {        replace(frameId, fragment)    }}fun AppCompatActivity.addFragmentToActivity(fragment: Fragment, tag: String) {    supportFragmentManager.transact {        add(fragment, tag)    }}private inline fun FragmentManager.transact(action: FragmentTransaction.() -> Unit) {    beginTransaction().apply {        action()    }.commit()}