How to filter ListAdapter?

Question

I have an adapter that is extended by ListAdapter, I use submit list to update the ui but when I use it when the user change the search query it displays other I items in the list however when I log the filtered list it is correct and the filtered items is correct.

Here is how I filter the list and submit it to the adapter :

 searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                if (newText.equals("")) {
                    refreshData();
                } else {
                    List<Teacher> list = new ArrayList<>(originalList.stream().filter(item -> item.name.toLowerCase().trim().contains(newText.toLowerCase().trim())).collect(Collectors.toList()));
                    if (!teachersAdapter.getCurrentList().equals(list)) {
                        teachersAdapter.submitList(null);
                        teachersAdapter.submitList(list);
                        if (!teachersAdapter.getCurrentList().equals(list)) {
                            teachersAdapter.submitList(null);
                            teachersAdapter.submitList(list);
                        }
                    }
                }
                return false;
            }

        });

and this is the DiffUtil for the adapter

    public TeachersAdapter(TeacherClicks teacherClicks) {
        super(new DiffUtil.ItemCallback<Teacher>() {
            @Override
            public boolean areItemsTheSame(@NonNull Teacher oldItem, @NonNull Teacher newItem) {
                return oldItem.id.equals(newItem.id);
            }

            @Override
            public boolean areContentsTheSame(@NonNull Teacher oldItem, @NonNull Teacher newItem) {
                return newItem.equals(oldItem) && newItem.toString().equals(oldItem.toString());
            }
        });
        this.teacherClicks = teacherClicks;
    }

This is the behavior resulted

result

I tried a lot of things but none of them works

Answer 1

If you are using LiveData to observe changes in your data make sure to update it on the main thread using postValue like this:

MutableLiveData<List<Teacher>> liveDataList = new MutableLiveData<>();
List<Teacher> list = new ArrayList<>(originalList.stream().filter(item -> item.name.toLowerCase().trim().contains(newText.toLowerCase().trim())).collect(Collectors.toList()));
liveDataList.postValue(list);

Also you dont need to call submitList(null) before submitting a new list, simply just use :

teachersAdapter.submitList(list);

More, you need to simplify your areContentsTheSame method like this:

@Override
public boolean areContentsTheSame(@NonNull Teacher oldItem, @NonNull Teacher newItem) {
    return true; 
}

And lastly check if your "Teacher" class has a correct implementation of the equals method. The areItemsTheSame and areContentsTheSame methods in the DiffUtil.ItemCallback rely on this method.

This changes may help you to solve your problem.