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?

CodePudding user response：

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

CodePudding user response：

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

CodePudding user response：

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