RecyclerView 未填充数据

Question

我正在尝试使用 SQLite 数据库内容中的数据加载 recyclerview。但它不起作用

这就是我所做的

活动课

public class ViewMembership extends AppCompatActivity {
private  RecyclerView recyclerView;
private  membership_view_recycler_adapter m;

private  DBHelper dbHelper;


public List<membership_recycler_model> membershipList=new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_view_membership);
    dbHelper=new DBHelper(this);

    ////////////////////////////////////////////////////////////////////////////

    recyclerView=(RecyclerView) findViewById(R.id.View_Membership_Recycler);
    m=new membership_view_recycler_adapter(membershipList);
    RecyclerView.LayoutManager layoutManager=new LinearLayoutManager(getApplicationContext());
    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setItemAnimator(new DefaultItemAnimator());

    recyclerView.addItemDecoration(new DividerItemDecoration(this, LinearLayoutManager.VERTICAL));

    recyclerView.setAdapter(m);

    prepare_membership();

    //////////////////////////////////////////////////////////////////////////

}
public void  prepare_membership()
{
    System.out.println("#######################Prepare_membership called");
    membershipList=dbHelper.membership_for_recycler_view();
   m.notifyDataSetChanged();
}}

适配器类

public class membership_view_recycler_adapter extends RecyclerView.Adapter<membership_view_recycler_adapter.MyViewHolder> {

public class MyViewHolder extends RecyclerView.ViewHolder {
    public TextView name,region;
    public MyViewHolder(View itemView) {
        super(itemView);
        name=(TextView) itemView.findViewById(R.id.membership_name_textview);
        region=(TextView) itemView.findViewById(R.id.membership_region_textview);
    }
}


public membership_view_recycler_adapter(List<membership_recycler_model> membership_list) {
    this.membership_list = membership_list;
}

private List<membership_recycler_model> membership_list;



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

@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
    membership_recycler_model membership=membership_list.get(position);
    holder.name.setText(membership.getMembership_name());
    holder.region.setText(membership.getRegion());
}

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

我没有编译错误，应用程序没有抛出任何异常。 dbHelper.membership_for_recycler_view() 返回适当的值。我对 Android 有点陌生。我在教程的帮助下做到了这一点。我做错了什么？

Answer 1

我认为问题是你在打电话

prepare_membership()

稍后运行并使用空列表将数据传递给适配器。尝试进行以下更改：

1. 在适配器中添加新方法 -

        public void refreshData(List<membership_recycler_model> membership_list){
             this.membership_list.clear();
             this.membership_list.addAll(membership_list);
             notifyDataSetChanged();
         }
   

2. 在prepare_membership()函数中从数据库获取列表后调用此方法，即

   m.refreshData(membershipList)

`