activity中加载或切换fragment

fun AppCompatActivity.addFragment(fragment: Fragment, containerId: Int) =
    supportFragmentManager.inTransaction { add(containerId, fragment) }

fun AppCompatActivity.replaceFragment(fragment: Fragment, containerId: Int) =
    supportFragmentManager.inTransaction { replace(containerId, fragment) }

inline fun FragmentManager.inTransaction(func: FragmentTransaction.() -> FragmentTransaction) =
    beginTransaction().func().commit()