Question

在我的片段中，当我运行app时，RecyclerView已经显示了一些数据。实际上我想要在某些类别基础上刷新数据时，如果特定类别中不存在数据，我会得到空数组。现在我想将null设置为RecyclerView适配器，这样它就会因为null数组而刷新并显示任何内容。

这是片段中的刷新代码函数，它无法正常工作：

 new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                Log.d(TAG, "run: fragment 2"+searchTxt);
                if(dataStoredArrayList!=null) {
                    dataStoredArrayList.clear();
                    myRecyclerAdapter.notifyDataSetChanged();
                }
                mparser = new SecondParseDataClass(context);
                mparser.setOnDataRetrievalCallback(new OnDataRetrievalCallback() {
                    @Override
                    public void onDataRetrieval(ArrayList<DataStored> dataSet) {
                        if(dataSet!=null) {
                            dataStoredArrayList.addAll(dataSet);
                            myRecyclerAdapter.notifyDataSetChanged();
                        }
                        else{
                            dataStoredArrayList=null;
                            myRecyclerAdapter.notifyDataSetChanged();
                        }
                    }
                });
                mparser.execute("http://192.168.3.10/testing.php", "2",searchTxt);

            }
        }, 0);

Answer 1

使用dataStoredArrayList.clear()代替dataStoredArrayList=null。

Answer 2

我使用这个完美运行的适配器类

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import java.util.ArrayList;
import in.kpis.structure.R;


/**
 * Created by user on 6/21/2016.
 */
public class AdapterDemo extends BaseRecyclerViewAdapter<AdapterDemo.MyViewHolder> {

    private ArrayList<String> list = new ArrayList<>();
    private Context context;

    class MyViewHolder extends RecyclerView.ViewHolder {
//        private ImageView ivHorizontalImage;

        MyViewHolder(View view) {
            super(view);
//            ivHorizontalImage = (ImageView) view.findViewById(R.id.ivHorizontalImage);
        }
    }

    public void insertItemInList(String beanChat) {
        if (list == null) list = new ArrayList<>();
        list.add(beanChat);
        notifyItemInserted(list.size() - 1);
    }


    public void insertItemsInList(ArrayList<String> myList) {
        for (String beanChat : myList) {
            insertItemInList(beanChat);
        }
    }

    public ArrayList<String> getList() {
        if (list == null) list = new ArrayList<>();
        return list;
    }

    public void clearList() {
        if (list == null) return;
        list.clear();
        notifyDataSetChanged();
    }


    public AdapterDemo(Context context) {
        this.context = context;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.layout_nothing_to_display, parent, false);

        return new MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
    }

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

，您的代码将缩减为

 new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                Log.d(TAG, "run: fragment 2"+searchTxt);
                adapterDemo.clearList();
                mparser = new SecondParseDataClass(context);
                mparser.setOnDataRetrievalCallback(new OnDataRetrievalCallback() {
                    @Override
                    public void onDataRetrieval(ArrayList<DataStored> dataSet) {
                        if(dataSet!=null) {
                            adapterDemo.insertItemsInList(dataSet);
                        }
                        else{
                            adapterDemo.clearList();
                        }
                    }
                });
                mparser.execute("http://192.168.3.10/testing.php", "2",searchTxt);

            }
        }, 0);

我逐个插入项目，因为它使用recycler view提供默认动画效果。

如何将Null设置为RecyclerView适配器在片段中

2 个答案: