仅当主机活动被破坏时如何从片段调用方法？

Question

I got a method() in the fragment. Fragment in host activity. So I need to call the method() from fragment ONLY when host activity was in onDestroy() . Maybe it suppose to be something like a static flag?

Answer 1

class MyActivity:  AppCompatActivity() {
    override fun onDestroy() {
        super.onDestroy()
        val fragment = supportFragmentManager.findFragmentById(R.id.my_fragment) as MyFragment
        if (fragment != null) {
            fragment.myMethod()
        }
    }
}

class MyFragment: Fragment() {
    fun myMethod() {
    }
}

Or use a ViewModel to handle communication between the activity and the fragment.

https://developer.android.com/topic/libraries/architecture/viewmodel#sharing

Answer 2

You can, by SupportFragmentManager, get a Fragment by layout id, tag or name. But the most important thing here is in some situations Activity.onDestroy() method could never be called. So be careful if you implement code that needs to be executed, like an unsubscribe logic or removing callbacks.