android kotlinでのactivity?.let{ }のactivityについて kotlingoogleandroidkotlin ( < )kotlin "activity?" nullActivity Android Studiokotlin activity?.println("OK") unresolved reference activity override fun onCreateDialog(savedInstanceState: Bundle): Dialog { return activity?.let { .... } ?: throw IllegalStateException("Activity cannot be null") } OOPer activityDialogFragment(Fragment)(JavagettergetActivity()Kotlin) "Activity! getActivity() Return the Activity this fragment is currently associated with." activity activity? activity class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) activity?.println("OK") } }

## _nullActivity_

Kotlinnull

`activity``DialogFragment`(`Fragment`)(Javagetter`getActivity()`Kotlin)

`FragmentActivity?`Nullable`?.`safe call

* `activity``null``let``null``null`





* * *

## _activity?.println("OK") unresolved reference _

()

`FireMissilesDialogFragment``activity`()()`activity`

Android Studiokotlin`activity`?

`println`Kotlin

`activity`


activity?.let {
println(it)
}




* * *

Kotlin

* * *



### _"Activity! getActivity() Return the Activity this fragment is currently associated with." activity_

AndroidKotlin

KotlinJava
Calling Java from Kotlin

Getters and Setters

Java`get()`getter`set(...)`setter(setter)()Kotlin

AndroidKotlin`activity...``activity``getActivity()`getter