Apps How to handle errors in LiveData + MVVM + Retrofit?

[Nixon3333]

Hi! I have a problem with handling errors from retrofit.
MainActivity:

private void initRecyclerView() {

    mProgressDialog = new ProgressDialog(this);
    recyclerView = binding.rvTasks;
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    adapter = new TaskAdapter();
    recyclerView.setAdapter(adapter);

    LiveData<Result<List<Task>>> result = viewModel.getTasks();

    result.observe(this, tasks -> handleTasks(tasks));

}

private void handleTasks(Result<List<Task>> tasks) {
    if (tasks.getError() != null)
        adapter.setTaskCollection(tasks.getResult());
    else {
        List<Task> list = new ArrayList<>();
        list.add(0, new Task(1, 1, "Title", "Body"));
        adapter.setTaskCollection(list);
    }
}

Result class:

public class Result<T> {

private final T result;
private final Throwable error;

private Result(@Nullable T result, @Nullable Throwable error) {
   this.result = result;
   this.error = error;
}

@NonNull
public static <T> Result<T> success(@NonNull T result) {
   return new Result(result, null);
}

@NonNull
public static <T> Result<T> error(@NonNull Throwable error) {
   return new Result(null, error);
}

@Nullable
public T getResult() {
   return result;
}

@Nullable
public Throwable getError() {
   return error;
}

And ViewModel:

public LiveData getTasks() {
   return LiveDataReactiveStreams.fromPublisher(
           Observable.just(retrofitApi.getTasks()
           .map(Result::success)
           .onErrorReturn(Result::error)
           .subscribeOn(Schedulers.io())
           .observeOn(AndroidSchedulers.mainThread()))
           .toFlowable(BackpressureStrategy.MISSING));
}

App crashed with ClassCastException. I know this exception, but don't know how to wrap data correctly?

 

[23tony]

Can you share the stack trace of the error too?