如何从firebase检索嵌套数据

Question

这是我的 firebase 中的数据结构：

我无法检索所有“menukedai”数据。通过使用下面的代码，“menukedai”的数据没有出来。供您参考，“menukedai”的数据将来自用户。

这是我的尝试：

foodDatabaseRef = FirebaseDatabase.getInstance().getReference("uploads").child("menukedai");

foodDatabaseRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
            foodmenu foodmenu = postSnapshot.getValue(foodmenu.class);
            fooddata.add(foodmenu);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        Toast.makeText(foodlist.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
    }
});

这是我的美食菜单课。

package com.example.trialfoodbuddy;

public class foodmenu {
    private String Foodimage;
    private String Foodname;
    private CharSequence Foodprice;

    public foodmenu(){
        //empty constructor needed
    }
    public foodmenu(String foodimage, String foodname, CharSequence foodprice){
        Foodimage = foodimage;
        Foodname = foodname;
        Foodprice = foodprice;
    }

    public String getFoodimage(){
        return Foodimage;
    }

    public String getFoodname(){
        return Foodname;
    }

    public CharSequence getFoodprice(){
        return Foodprice;
    }

    public void setFoodimage(String foodimage){
        Foodimage = foodimage;
    }

    public void setFoodname(String foodname){
        Foodname = foodname;
    }

    public void setFoodprice(CharSequence foodprice){
        Foodprice = foodprice;
    }
}

Answer 1

我相信您想要获取嵌套在“menukedai”下的信息，因此您需要为该信息添加另一个循环

foodDatabaseRef = FirebaseDatabase.getInstance().getReference("uploads");
foodDatabaseRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot uploadSnapshot : dataSnapshot.getChildren()) {
            // this is where you actually getting the information 
            for(DataSnapshot menuItemSnapshot : uploadSnapshot.child("menukedai").getChildren()){
                foodmenu foodmenu = menuItemSnapshot.getValue(foodmenu.class);
                fooddata.add(foodmenu);
            }
        }
    }
    // Log the values and check them to make sure you getting the data you want if always nice so I added it for you here
    Log.i("Values","My values are:"+foodmenu);
    @Override
    public void onCancelled(DatabaseError databaseError) {
        Toast.makeText(foodlist.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
    }
});

通常来说，您应该始终在数据库中的类中使用变量名，因此当您提取信息时，您的构造函数会知道为您的类中的哪个变量分配什么值。