如何使用viewholder作为生命周期所有者使用livingata和viewmodel？

Question

我有一个垂直滚动的recyclerview（verticalRV）。此recyclerview（horizo​​ntalRV）中的每个项目都是Horizo​​ntal recyclerview。

在verticalRV itemViewHodler中尝试从viewmodel获取数据并观察任何chages并相应地更新horizo​​ntalRV适配器。

但是观察者是onChanged方法没有得到调用。

我已经实现了LifecycleOwner接口来管理视图持有者的生命周期with livedata并相应地从垂直RV的适配器设置状态

public class VeritcalRVHolderItem implements LifecycleOwner {
    private static final String TAG = LDFeedListAdapterHolder.class.getSimpleName();
    private final FragmentActivity activity;
    private final RvHorizontalListAdapter adapter;
    private RecyclerView rvHorizontalList;


    public VeritcalRVHolderItem(Context context, View itemView, FragmentActivity activity) {
        super(context, itemView);
        this.activity = activity;
        rvHorizontalList = itemView.findViewById(R.id.rvHorizontalList);
        LinearLayoutManager layout = new LinearLayoutManager(getContext(), LinearLayout.HORIZONTAL, false);
        rvHorizontalList.setLayoutManager(layout);
        adapter = new RvHorizontalListAdapter(this.activity);
        rvHorizontalList.setAdapter(adapter);
        LDViewModel LDViewModel = ViewModelProviders.of(activity).get(LDViewModel.class);
        LDViewModel.getTopicsForFeed().observe(this, new Observer<List<Topic>>() {
            @Override
            public void onChanged(List<Topic> topics) {
                //adding live discussion model at first position
                adapter.updateLiveList(topics);
                adapter.notifyItemChanged(0);
                Log.d(TAG, "discussion model calls");
            }
        });
    }

    private LifecycleRegistry lifecycleRegistry;

    public void onAppear() {
        lifecycleRegistry.markState(Lifecycle.State.CREATED);
    }

    public void onDisappear() {
        lifecycleRegistry.markState(Lifecycle.State.DESTROYED);
    }

    @NonNull
    @Override
    public Lifecycle getLifecycle() {
        return lifecycleRegistry;
    }

}

请让我知道我在这里失踪了什么。

Answer 1

从我的角度来看，最好将数据观察到你的fragment或activity并将数据传递给recyclerview，在Recyclerview中覆盖方法getItemViewType，从getItemViewType你可以处理vertical项目和horizontal项目。

例：-

public class ViewModel extends AndroidViewModel {
   private MutableLiveData<Model> modelMutableLiveData;
   public ViewModel(@NonNull Application application) {
      super(application);
      modelMutableLiveData = new MutableLiveData<>();
   }

   public MutableLiveData<Model> getModelMutableLiveData() {
      return modelMutableLiveData;
   }

   public final void yourMethod(Model model) {
      // Do something
   }
}

片段类

public class Fragment extend BaseFragment {
    private void initViewModelData() {
       viewModel.getModelMutableLiveData().observe(this, new Observer<Model>() {
        @Override
        public void onChanged(@Nullable Model model) {
            if (model != null) {
                modelList.add(model);
                adapter.notifyItemInserted(modelList.size()- 1);
           }
        }
      });
    }
}

RecyclerViewAdapter

  class RecyclerViewAdater extend Adapter<ViewHolder>{
     @Override
     public int getItemViewType(int position) {
        return mDataList.get(position).getContainerType();
     }
  }

基于此，您可以编写您的recyclerView代码