RecyclerView 与游标 Adapter 的实现

Question

如何实现带光标的RecyclerView。我试图实现 this code but this code uses some class to store each row but I did not want to make some class for the sake of storing each row of the cursor. And also I found this article ，它说我们在使用光标时不需要制作 class 。我很困惑使用哪种方法以及如何使用它。我试图实现 Whosebug 上存在的大部分代码，但它们几乎都是一样的。

我也用这个尝试了我的代码：

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.MyViewHolder>{
    private Cursor cursor;
    public class MyViewHolder extends RecyclerView.ViewHolder{
        TextView title,text;
        CardView cd;
        LinearLayout ll;
        public MyViewHolder(View v){
            super(v);
            title = v.findViewById(R.id.childTitleView);
            text = v.findViewById(R.id.childTextView);
            cd = v.findViewById(R.id.parentCardView);
            ll = v.findViewById(R.id.ll);
         }

    }

    public RecyclerViewAdapter(Cursor c){
        this.cursor = c;
    }

    @Override
    public int getItemCount() {
        return cursor.getCount();
    }

    @Override
    public void onBindViewHolder(final MyViewHolder holder, final int position) {
        cursor.moveToNext();
        String t = cursor.getString(cursor.getColumnIndex(RecordContract.RecordEntry.COLUMN_TITLE));
        String d = cursor.getString(cursor.getColumnIndex(RecordContract.RecordEntry.COLUMN_TEXT));
        holder.title.setText(t);
        holder.text.setText(d);
        holder.cd.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View view) {
                Toast.makeText(view.getContext(), ""+position, Toast.LENGTH_SHORT).show();
                //holder.ll.setBackgroundColor(Color.parseColor("#000"));
                holder.cd.setBackgroundColor(Color.parseColor(view.getResources().getString(R.color.blueGreen)));
                return true;
            }
        });

    }

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

这是我的 MainActivity

 protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mdb = new RecordDbHelper(getApplicationContext());

        RecyclerView rv = findViewById(R.id.recylerViewId);
        rv.setLayoutManager(new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL));
        rv.setItemAnimator(new DefaultItemAnimator());
        Cursor c = getCursor();
        RecyclerViewAdapter rva = new RecyclerViewAdapter(c);
        rv.setAdapter(rva);
  }

   public Cursor getCursor(){
        SQLiteDatabase db = mdb.getReadableDatabase();
        String[] projection = {
            RecordContract.RecordEntry._ID,  RecordContract.RecordEntry.COLUMN_TEXT,
            RecordContract.RecordEntry.COLUMN_TITLE};
        String selection = null;
        String[] selectionArgs = null;
        String tableName = RecordContract.RecordEntry.TABLE_NAME;
        Cursor c = db.query(tableName,projection,selection,selectionArgs,null,null,null);
        return c;
    }

好吧，这会在 RecyclerView 中显示文本但是当将新数据添加到数据库时，应用程序需要重新启动。它不会自行刷新。

Answer 1

Well this show the text in the RecyclerView

它不会可靠地这样做。在 onBindViewHolder() 中，将 moveToNext() 替换为 moveToPosition(position)。现在，您忽略了 position 参数，这意味着一旦您开始滚动（特别是向后滚动），您就会运行遇到问题。

But when a new data is added to the database then the app requires to start again. It does not refresh itself.

这与 CursorAdapter 与 AdapterView 的工作方式没有什么不同，例如 ListView。

当你更新数据库时，你需要得到一个新的Cursor并交给你的RecyclerViewAdapter。您的 RecyclerViewAdapter 然后可以调用 notifyDataSetChanged() 告诉 RecyclerView 重绘自己。

RecyclerView 与游标 Adapter 的实现

Implementation of RecyclerView with cursor Adapter

android

android-recyclerview

android-cursor

sectionedrecyclerviewadapter