当我有两个recyclerview数据源，但是只有一个数据源被更改时，如何在recyclerview中使用notifyDataSetChanged（）

Question

Currently, I have two Lists holding data of different types. I pass the two lists to the recyclerview's constructor. But the constructor doesn't get called on notifyDataSetChanged() , so how would I repopulate the Lists I create in the adapter's constructor, using the parameters? Also, how do I re-intialize the count variable so my little hack works?

Here's my code -

public class SomeAdapter extends RecyclerView.Adapter<PrefAdapter.PrefViewHolder> {

    LayoutInflater inflater;
    List<Class1> SomeList1;
    List<Class2> SomeList2;
    int count = 0;

    public PrefAdapter(Context context, List<Class1> SomeList1, List<Class2> SomeList2) {
        inflater = LayoutInflater.from(context);
        this.SomeList1 = SomeList1;
        this.SomeList2 = SomeList2;
    }

    @Override
    public PrefViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = inflater.inflate(R.layout.row, parent, false);
        return new SomeViewHolder(view);
    }

    @Override
    public void onBindViewHolder(SomeViewHolder holder, int position) {
        if(count >= SomeList2.size()) {
            if (nameAndNumberList.size() > 0) {
                holder.name.setText(SomeList1.get(count-SomeList2.size()).getName());
                holder.number.setText(SomeList1.get(count-SomeList2.size()).getNumber());
                count+=1;
            }
        }else {
            holder.name.setText(SomeList2.get(position).getName());
            holder.number.setText(SomeList2.get(position).getNumber());
            count+=1;
        }
    }


    @Override
    public int getItemCount() {
        return SomeList1.size()+SomeList12.size();
    }

Update -

Turns out I was being really stupid. Just removed the count variable. position does the job of count. I need to get some sleep.

Answer 1

The best idea is repopulate the data in the existing List . For example:

SomeList1.clear();
SomeList1.addAll(list2);

Now invoke the notifyDataSetChanged() , so the data in the recyclerview's is updated

adapter.notifyDataSetChanged()

Answer 2

In your constructor, you're setting this.SomeList1 to the SomeList1 that was passed in. This makes it so that this.SomeList1 points to the same list instance as the code that passed it to the constructor.

Since they're pointing to the same list instances, you can update them as you see fit in the calling code, and the adapter will be none the wiser. Calling notifyDataSetChanged after changes were made will cause the adapter to refresh itself. This causes getItemCount to be re-evaluated. Since the lists are now updated, you'll get the updated count.

// Initialize adapter. Empty lists.
List<Class1> list1 = new ArrayList<>();
List<Class2> list2 = new ArrayList<>();
PrefAdapter adapter = new PrefAdapter(context, list1, list2);

// Set adapter on recycler view.
...

// Update lists. First list has 1 item, second list has 2.
list1.add(new Class1());
list2.add(new Class2());
list2.add(new Class2());

// Notify adapter that data has changed.
// This causes the adapter to refresh itself.
// Since the list instances are the same,
// when getItemCount is re-evaluated, it will return 3.

adapter.notifyDataSetChanged();