如何將ArrayList從Adapter傳遞給activity？

Question

我需要將ArrayList list_add發送到活動，但我不知道我怎么能這樣做，如果可以在主活動上共享它以便將來使用它。 任何人都可以幫我實現一個方法嗎？ 下面有一個mainAdatper for recyclerview，我有一個list_add並希望將它傳遞給主要活動，之后我可以將它添加到

class MainAdapter extends RecyclerView.Adapter <MainAdapter.ViewHolder> {

    private static int lastCheckedPos = 0;
    ArrayList<String> list_add = new ArrayList<>();
    ArrayList<String> lista_show;
    private Context context;
    String t;    

    public MainAdapter(ArrayList<String> lista_shows, Context context) {
        lista_show = lista_shows;
    }

    @Override
    public MainAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from (parent.getContext ()).inflate (R.layout.row,parent,false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final MainAdapter.ViewHolder holder, final int position) {

        holder.mdevice.setText (lista_show.get (position));
        holder.cardView.setOnLongClickListener (new View.OnLongClickListener () {
            @Override
            public boolean onLongClick(View v) {
                t = lista_show.get(position);
                if (list_add.contains(t)) {
                    Toast.makeText(v.getContext (), t+"Already Selected", Toast.LENGTH_SHORT).show();
                } else {
                    list_add.add(t);
                    holder.cardView.setCardBackgroundColor(Color.parseColor("#60B5EC"));
                    Toast.makeText(v.getContext (), t+"Added", Toast.LENGTH_SHORT).show();
                }
                return true;
            }
        });

        holder.cardView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                t = lista_show.get (position);
                holder.cardView.setCardBackgroundColor(Color.WHITE);
                if (! list_add.contains(t)) {
                    Toast.makeText(v.getContext (), "Long press for add", Toast.LENGTH_SHORT).show();
                } else {
                    list_add.remove(t);
                    Toast.makeText(v.getContext (), t+"Removed", Toast.LENGTH_SHORT).show();
                }
            }
        });

    }

    @Override
    public int getItemCount() {
        return lista_show.size ();
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

        public TextView mdevice;
        CardView cardView;

        public ViewHolder( View itemView) {
            super (itemView);
            mdevice = itemView.findViewById (R.id.device);
            cardView = itemView.findViewById (R.id.mcardview);
        }
    }
}

Answer 1

1. 添加回調接口：

public interface ListOwner {
  void push(ArrayList<String> list);
}

2. 在適配器中設置參考：

private ListOwner listOwner;

public MainAdapter(ArrayList<String> lista_shows, Context context, ListOwner owner) {
  this.lista_show = lista_shows;
  this.listOwner = owner;
}

3. 在需要時在適配器中調用它：

if (listOwner != null) {
  listOwner.push(list_add);
}

4. 當然，通過您的活動實現ListOwner ：

public class MyActivity extends AppCompatActivity implements ListOwner {
 // all code

  // create instance of adapter:
  mAdapter = new MainAdapter(list_show, MyActivity.this, MyActivity.this);


  @Override
  public void push(ArrayList<String> list) {
     // you have the list here
  }
}

PS

您可以省略接口並直接傳遞對Activity引用（ MyActivity中的MyActivity ）