Question

如何知道FirebaseRecyclerAdapter查询是否为零，是否存在

我在

上找到了一些说明

https://github.com/firebase/FirebaseUI-Android/tree/master/database

它说：

数据和错误事件

使用FirebaseRecyclerAdapter时，您可以   希望每次数据更改时或有数据更改时执行一些操作   一个错误。为此，请重写onDataChanged（）和onError（）   适配器的方法：

FirebaseRecyclerAdapter adapter = new FirebaseRecyclerAdapter<Chat, ChatHolder>(options) {
    // ...

    @Override
    public void onDataChanged() {
        // Called each time there is a new data snapshot. You may want to use this method
        // to hide a loading spinner or check for the "no documents" state and update your UI.
        // ...
    }

    @Override
    public void onError(DatabaseError e) {
        // Called when there is an error getting data. You may want to update
        // your UI to display an error message to the user.
        // ...
    }
};

当我尝试如下使用时：

mAdapter = new FirebaseRecyclerAdapter<Place, PlaceViewHolder>(options)
        {

            @Override
            public void onDataChanged(DataSnapshot dataSnapshot)
            {
                // Called each time there is a new data snapshot. You may want to use this method
                // to hide a loading spinner or check for the "no documents" state and update your UI.
                // ...
                if (dataSnapshot.exists())
                {
                    Log.d(TAG,"data exists");

                }
                else
                {
                    Log.d(TAG,"No data exists");
                }
            }

            @NonNull
            @Override
            public PlaceViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i)
            {

错误消息是：

方法不会从其超类覆盖方法

那我该如何解决这个问题，谢谢。

Answer 1

我从另一个页面找到了答案：

https://www.programcreek.com/java-api-examples/?api=com.firebase.ui.database.FirebaseRecyclerAdapter

@Override
            public void onDataChanged()
            {
                // Called each time there is a new data snapshot. You may want to use this method
                // to hide a loading spinner or check for the "no documents" state and update your UI.
                // ...
                if (getItemCount() == 0)
                {
                    Log.d(TAG,"No data exists");
                }
                else
                {
                    Log.d(TAG,"data exists");
                }
            }

如何知道FirebaseRecyclerAdapter查询是否为零，是否存在

1 个答案: