How do I manually call the ViewModel observer second time?

Question

I have two Fragment-s with RecyclerView and LiveData both. When I made some changes in second fragment, I need to update RecyclerView in first fragment.
So after update second fragment I need to trigger onChange method in first fragment.
Code from first fragment:

item_viewmodel.getAllCategoryModel().observe(getViewLifecycleOwner(), new Observer<List<Items>>() {
    @Override
    public void onChanged(List<Items> myLists) {
       //Observer is already registered, but I need to call it manully from second fragment.
    }
});

How can I do this?

score 0 · Answer 1 · answered Sep 06 '21 at 16:03

0

You can achieve this by using Shared viewmodel, create a instance of viewmodel in both the fragments and use accordingly, for more details visit this page link

answered Sep 06 '21 at 16:03

Manan jain

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1
1
6

score 0 · Answer 2 · answered Sep 06 '21 at 16:12

You should try use Transformations.switchMap() method, put that the first livedata depends of the second livedata by the method describe above

Here is an example class that holds a typed-in name of a user String (such as from an EditText) in a MutableLiveData and returns a LiveData containing a List of User objects for users that have that name. It populates that LiveData by requerying a repository-pattern object each time the typed name changes.

This ViewModel would permit the observing UI to update "live" as the user ID text changes.

 class UserViewModel extends AndroidViewModel {
 MutableLiveData<String> nameQueryLiveData = ...

 LiveData<List<String>> getUsersWithNameLiveData() {
     return Transformations.switchMap(
         nameQueryLiveData,
             name -> myDataSource.getUsersWithNameLiveData(name));
 }

 void setNameQuery(String name) {
     this.nameQueryLiveData.setValue(name);
 }
}

Here more about this...

If you want more specific answer please post all code about your viewModel

score 0 · Answer 3 · answered Sep 06 '21 at 16:26

0

I assume best way would be to use by activityViewModels() kotlin property delegate in fragments and share the host activity's Viewmodel for cross fragment communication.

More about usage here

answered Sep 06 '21 at 16:26

Rajan Kali

12,627
3
25
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Well, I tried things like in this tutorial: https://youtu.be/ACK67xU1Y3s but only one onChange method in single fragment is trigger. I observe same item as it is in this video and when I am in frag A change something only onChange method in frag A is trigger. Analogy it is with frag B. Is that what you meant with the SharedViewModel on this video? – Rivke Sep 07 '21 at 16:54

How do I manually call the ViewModel observer second time?

3 Answers3