你可以用is:

class B
val a: A = A()
if (a is A) { /* do something */ }
when (a) {
  someValue -> { /* do something */ }
  is B -> { /* do something */ }
  else -> { /* do something */ }
}

你可以这样检查

 private var mActivity : Activity? = null

then

 override fun onAttach(context: Context?) {
    super.onAttach(context)

    if (context is MainActivity){
        mActivity = context
    }

}

你可以用is:

class B
val a: A = A()
if (a is A) { /* do something */ }
when (a) {
  someValue -> { /* do something */ }
  is B -> { /* do something */ }
  else -> { /* do something */ }
}

其他解决方案:KOTLIN

val fragment = supportFragmentManager.findFragmentById(R.id.fragment_container)

if (fragment?.tag == "MyFragment")
{}

可以在运行时使用is操作符或其否定形式!is来检查对象是否符合给定类型。

例子:

if (obj is String) {
    print(obj.length)
}

if (obj !is String) {
    print("Not a String")
}

自定义对象的另一个例子:

我有一个CustomObject类型的obj。

if (obj is CustomObject) {
    print("obj is of type CustomObject")
}

if (obj !is CustomObject) {
    print("obj is not of type CustomObject")
}

when和is的结合:

when (x) {
    is Int -> print(x + 1)
    is String -> print(x.length + 1)
    is IntArray -> print(x.sum())
}

摘自官方文件