Android Livedata Observe Once Only (Kotlin)

ObserveOnceExtension.kt

fun <T> LiveData<T>.observeOnce(lifecycleOwner: LifecycleOwner, observer: Observer<T>) {
    observe(lifecycleOwner, object : Observer<T> {
        override fun onChanged(t: T?) {
            observer.onChanged(t)
            removeObserver(this)
        }
    })
}
//Using
liveData.observeOnce(this, Observer<Password> {
    if (it != null) {
        // do something
    }
})

ObserveOnceSample.kt

val liveData = viewModel.showSnackBar("Hi everyone")
liveData.observe(this, object: Observer<String> {
    override fun onChanged(text: String?) {
        liveData.removeObserver(this)
    }
})

Great, thanks for the reply!

Good Solution David, that Only work for me. All other solution not work for me and I didn't know why.

@kobeumut Thank you for this useful code

thanks for the solution, however for non-nullable variables with initial value, or for patterns with removing observer on certain conditions, this is helpful

fun <T> LiveData<T>.observeUntil(
    owner: LifecycleOwner,
    predicate: (T) -> Boolean,
    observer: (T) -> Unit
) {
    observe(owner, object: Observer<T> {
        override fun onChanged(value: T) {
            if(predicate(value)) {
                removeObserver(this)
            }
            observer(value)
        }
    })
}

this can be used as:

val mutLiveData = MutableLiveData(0)

mutLiveData.observeUntil(viewLifecycleOwner, { it == 10}) {
    /* code goes here... */
}

Nice!

I have implemented that but when the device configuration changes get the result again. what could we do in that case?

set flag on config change will cost a lot as I have implemented that in many places so, I am looking for optimal solutions