有选择地从 Firebase 检索数据到 FirebaseRecyclerAdapter

Question

在我的 Android 应用程序中，我使用 RecyclerView 和 CardView。 RecyclerView 的内容是从 Firebase 实时数据库中获取的。为此，我使用了 FirebaseUI 中的 FirebaseRecyclerAdapter。数据库中的条目对应于 class Bus.

的 POJO

public class Bus {
    private String source;
    private String destination;
    private long available;
    private String date;
    private long fare;

    Bus() {

    }

    Bus(String source,String destination,long available,String date,long fare) {
        this.source = source;
        this.destination = destination;
        this.available = available;
        this.date = date;
        this.fare = fare;
    }

    public long getAvailable() {
        return available;
    }

    public long getFare() {
        return fare;
    }

    public String getDate() {
        return date;
    }

    public String getDestination() {
        return destination;
    }

    public String getSource() {
        return source;
    }

    public void setAvailable(long available) {
        this.available = available;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public void setDestination(String destination) {
        this.destination = destination;
    }

    public void setFare(long fare) {
        this.fare = fare;
    }

    public void setSource(String source) {
        this.source = source;
    }

}

在 activity 中，我接受用户的来源、目的地和日期。我的意图是只显示 RecyclerView 中的相关数据。这是我的 FirebaseRecyclerAdapter 代码：

FirebaseRecyclerAdapter<Bus,BusViewHolder> firebaseRecyclerAdapter = new     FirebaseRecyclerAdapter<Bus,BusViewHolder>(Bus.class,R.layout.bus_card,BusViewHolder.class,mDatabase) {
        @Override
        protected void populateViewHolder(BusViewHolder viewHolder,Bus model,int position) {
            if(model.getSource().equals(source) && model.getDestination().equals(destination) && model.getDate().equals(date)) // This is the criteria for displaying the card
            {
                viewHolder.setSource(model.getSource());
                viewHolder.setDestination(model.getDestination());
                viewHolder.setAvailable(model.getAvailable());
                viewHolder.setDate(model.getDate());
                viewHolder.setFare(model.getFare());
            }
        }

    };
    recyclerView.setAdapter(firebaseRecyclerAdapter);

这是我的 ViewHolder:

public static class BusViewHolder extends RecyclerView.ViewHolder {
    View mView;

    public BusViewHolder(View itemView) {
        super(itemView);
        mView = itemView;
    }

    public void setSource(String source) {
        TextView src = mView.findViewById(R.id.source);
        src.setText("Source " + source);
    }

    public void setDestination(String destination) {
        TextView dest = mView.findViewById(R.id.destination);
        dest.setText("Destination " + destination);
    }

    public void setDate(String date) {
        TextView dte = mView.findViewById(R.id.date);
        dte.setText("Date " + date);
    }

    public void setAvailable(long available) {
        TextView avail = mView.findViewById(R.id.available);
        avail.setText("Available Seats " + Long.toString(available));
    }

    public void setFare(long fare) {
        TextView fre = mView.findViewById(R.id.fare);
        fre.setText("Fare " + Long.toString(fare));
    }
}

这个方法的问题是显示了相关的卡片，但是对于不满足条件的数据却有空卡片。是否可以选择性地将数据检索到 FirebaseRecyclerAdapter 中？目前，在 RecyclerView 中创建的卡片总数等于数据库中的条目总数。

Answer 1

我使用 query 对象从 Realtime Database 中有选择地检索。由于 query 不支持多个 orderby 子句，我不得不在我的节点中添加一个额外的字段。这是更新后的 firebaserecycleradapter

query = mDatabase.orderByChild("sourcedestinationdate").equalTo(source+destination+date);
FirebaseRecyclerAdapter<Bus,BusViewHolder> firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Bus,BusViewHolder>(Bus.class,R.layout.bus_card,BusViewHolder.class,query) {
        @Override
        protected void populateViewHolder(BusViewHolder viewHolder,Bus model,int position) {
            viewHolder.setSource(model.getSource());
            viewHolder.setDestination(model.getDestination());
            viewHolder.setAvailable(model.getAvailable());
            viewHolder.setDate(model.getDate());
            viewHolder.setFare(model.getFare());
        }
    };
    recyclerView.setAdapter(firebaseRecyclerAdapter);

注意FirebaseRecyclerAdapter中的最后一个参数是query。

有选择地从 Firebase 检索数据到 FirebaseRecyclerAdapter

Selective retrieval of data from Firebase to FirebaseRecyclerAdapter

android

firebase

android-recyclerview

firebase-realtime-database

firebaseui