I'm experimenting with the Architecture Components, and I want to build a ViewModel for each item of a RecyclerView. I'm not sure if that is formally correct or I should stick with the "old way".
I have this adapter:
public class PostAdapter extends RecyclerView.Adapter<PostAdapter.PostViewHolder> {
private List<Post> list;
public static class PostViewHolder extends RecyclerView.ViewHolder{
final ItemPostBinding binding;
public PostViewHolder(ItemPostBinding binding){
super(binding.getRoot());
this.binding = binding;
}
}
@Override
public PostViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
ItemPostBinding binding = DataBindingUtil
.inflate(LayoutInflater.from(parent.getContext()), R.layout.item_post,
parent, false);
return new PostViewHolder(binding, parent.getContext());
}
@Override
public void onBindViewHolder(PostViewHolder holder, int position) {
holder.binding.setPost(list.get(position));
holder.binding.executePendingBindings();
}
@Override
public int getItemCount() {
return list == null ? 0 : list.size();
}
public void setList(List<Post> list){
this.list = list;
notifyDataSetChanged();
}
}
which works fine but it's very basic. how do I update it so each item has it's own ViewModel associated? is that even possible?
EDIT: playing with it, I've tried to put in ViewModels the following way:
public class PostAdapter extends RecyclerView.Adapter<PostAdapter.PostViewHolder> {
private List<Post> list;
public static class PostViewHolder extends RecyclerView.ViewHolder{
final ItemPostBinding binding;
private final Context context;
private GalleryItemViewModel viewModel;
public PostViewHolder(ItemPostBinding binding, Context context){
super(binding.getRoot());
this.binding = binding;
this.context = context;
}
public Context getContext(){
return context;
}
public void setViewModel(GalleryItemViewModel viewModel){
this.viewModel = viewModel;
binding.setViewModel(viewModel);
}
}
@Override
public PostViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
ItemPostBinding binding = DataBindingUtil
.inflate(LayoutInflater.from(parent.getContext()), R.layout.item_post,
parent, false);
return new PostViewHolder(binding, parent.getContext());
}
@Override
public void onBindViewHolder(PostViewHolder holder, int position) {
GalleryItemViewModel vm = ViewModelProviders.of((FragmentActivity) holder.getContext()).get(GalleryItemViewModel.class);
vm.setPost(list.get(position));
holder.setViewModel(vm);
}
@Override
public int getItemCount() {
return list == null ? 0 : list.size();
}
public void setList(List<Post> list){
this.list = list;
notifyDataSetChanged();
}
}
it works but is that the correct way to do it?
Funny, but answer - This is correct way, should be accepted :)
You can make some code clean-up and remove GalleryItemViewModel
from PostViewHolder
, because you are creating hard reference and not using it.
Then dirrectly in onBindViewHolder()
use it like holder.binding.setViewModel(vm);
This is a link with MVVM code example that can help you.