如何通知一个片段另一个片段上发生了一些事情

Question

i have 2 fragments on the screen, how can i notify the 2nd that something happened on the 1st? now I am using this solution:

    companion object {
    private val onFullScreenPressedEvent = SingleLiveEvent<Boolean>()
    val onFullScreenPressed: LiveData<Boolean> = onFullScreenPressedEvent
}

and observe onFullScreenPressed from second fragment

Answer 1

Your best bet would be to use a ViewModel tied to the Activity of the Fragments (so shared between fragments), and modify the liveData there.

example Viewmodel

class MyActivityViewModel : ViewModel(){

    private val onFullScreenPressedEvent = SingleLiveEvent<Boolean>()
    val onFullScreenPressed: LiveData<Boolean> = onFullScreenPressedEvent

fun onFullScreen(){
    onFullScreenPressedEvent.call()
}}

For example, by using implementation "androidx.fragment:fragment-ktx:1.4.0" you can do in fragment A

private val viewModelA: MyActivityViewModel by activityViewModels()

and call the code that will change the event viewModelA.onFullScreen()

Then in Fragment B

private val viewModelB: MyActivityViewModel by activityViewModels()

and observe the liveData you trigger in Fragment A viewModelB.onFullScreenPressed.observe(viewLifecycleOwner, myObserver)