As an Android developer, you may have come across the term AndroidViewModel. It’s a clever way to separate your application’s data and state handling from Fragments or Activities, usually referred to as “dumb views.” While this library has served well over the years, it is important to note that it is now deprecated. However, understanding its rationale and how to use it can still be beneficial for existing projects. Let’s delve into how to implement and utilize AndroidViewModel effectively.

Before We Begin: Important Notice

The AndroidViewModel library has been deemed deprecated. Google’s Android Architecture Components are now the preferred choice for new projects. Despite this, the INLOOPX team will continue maintaining the library without a specific support end deadline. Thus, you don’t need to migrate your existing projects, as there will be no new feature development associated with this library.

The Basic Idea Behind AndroidViewModel

The core idea of AndroidViewModel is to keep an instance of a ViewModel class with your Fragment or Activity throughout its lifecycle, even during orientation changes. Think of it like a trusty backpack you take everywhere; it carries all your important supplies (data) and keeps them safe as you navigate through different terrains (activity states).

How to Implement AndroidViewModel

Implementing AndroidViewModel involves a few clear steps:

1. Create an interface: Start by defining an interface for your view. For example, we can name it IUserListView.
2. Create your ViewModel class: Extend the AbstractViewModel to create a ViewModel class, like UserListViewModel.
3. Associate Fragments or Activities with ViewModel: Each Fragment or Activity should extend either ViewModelActivityBase or ViewModelBaseFragment.
4. Set the model view: Make sure to call setModelView() once your view is created and initialized.

Code Snippets to Illustrate Implementation

Here’s what the implementation looks like in code:

public interface IUserListView extends IView {
    public void showUsers(List users);
}

public class UserListViewModel extends AbstractViewModel {
    ...
}

public class UserListFragment extends ViewModelBaseFragment 
                                    implements IUserListView {
    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        ButterKnife.inject(this, view);
        setModelView(this);
    }
}

The code demonstrates how each component communicates to create a well-structured application.

Event Handling: From View to ViewModel and Back

Once you have your ViewModel and Fragment set up, handling user interactions is seamless:

getViewModel().onDeleteUserClicked(userId);
getViewOptional().showUsers(userList);

These methods allow your Fragment to communicate with the ViewModel and receive updates efficiently. The getViewOptional() method ensures that you’ll always have a result, whether the view is currently available or not.

Data Binding Support

AndroidViewModel supports data binding. You can extend the ViewModelBaseBindingFragment to incorporate data binding easily:

@Override
public ViewModelBindingConfig getViewModelBindingConfig() {
    return new ViewModelBindingConfig(R.layout.fragment_sample_binding, requireActivity());
}

This feature eliminates boilerplate code and allows for a cleaner architecture.

Troubleshooting Common Issues

Even with the best implementations, hiccups can occur:

• If your ViewModel isn’t restoring state, ensure you use ViewModelStatePagerAdapter for consistent behavior with FragmentStatePagerAdapter.
• Always check that the arguments you pass during onCreate are correctly fetched and utilized.

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Conclusion

AndroidViewModel offers a robust way to handle data in your Android applications while maintaining a clean architecture. Though deprecated for new projects, its insights and methodologies remain relevant for existing applications. At fxis.ai, we believe that such advancements are crucial for the future of AI, as they enable more comprehensive and effective solutions. Our team is continually exploring new methodologies to push the envelope in artificial intelligence, ensuring that our clients benefit from the latest technological innovations.