MutableLiveData retains old value even when the observer activity gets destroyed

Question

I have an activity which is observing livedata from repository. Now when the activity gets destroyed and then created again, i still get the old value from repository unless i fetch the new one manually.

Why is the mutablelivedata retaining its old value even after the observer activity is destroyed?

Do you use Dagger or Koin to inject ViewModel into activity? Or do you custom ViewModelFactory? — Miller Go Dev, Sep 18 '19 at 01:13
Please show code in your activity and repository where you get livedata — Miller Go Dev, Sep 20 '19 at 02:05
I was initializing MutableLiveData variables before instantiating the viewmodel. Now i initialise the variables in the viewmodel constructor and the problem is solved — Neelabh Anand, Sep 24 '19 at 17:31

score 2 · Answer 1 · answered Sep 17 '19 at 20:54

2

you can reduce lifetime of your ViewModel, in this case newly created ViewModel won't persist previous data.

Alternatively, you can manually call inside your activity

override fun onDestroy(){
    super.onDestroy()
    viewModel.clear()
}

inside viewmodel:

fun clear(){ myLiveData.value = defaultValue /*or null*/ }

or change MutableLiveData with LiveEvent
https://proandroiddev.com/livedata-with-single-events-2395dea972a8

answered Sep 17 '19 at 20:54

Lukas

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1

Yes currently i am clearing the viewmodel just like you suggested. But i think the livedata should clear itself when the activity gets destroyed. There should be a proper way to do this maybe. – Neelabh Anand Sep 19 '19 at 17:29

score 1 · Answer 2 · answered Oct 04 '22 at 05:55

You can use SingleLiveData<T> observer.

class SingleLiveData<T> : MutableLiveData<T?>() {

    override fun observe(owner: LifecycleOwner, observer: Observer<in T?>) {
        super.observe(owner, Observer { t ->
            if (t != null) {
                observer.onChanged(t)
                postValue(null)
            }
        })
    }
}

Now an instance of MutableLiveData<T> you can use SingleLiveData<T>. It will call only one time.

private val data = SingleLiveData<String>()

MutableLiveData retains old value even when the observer activity gets destroyed

2 Answers2