如何在firebase中获取嵌套子的值？

Question

（https://i.stack.imgur.com/qXm2W.png）

我想获得产品ID，产品名称，数量等的价值，我怎样才能获得所有这些价值

Answer 1

如果您想从单个食物对象（0）获取该数据，请使用以下代码：

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference zeroRef = rootRef.child("Request").child(uid).child("foods").child("0");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        String discount = dataSnapshot.child("discount").getValue(String.class);
        String price = dataSnapshot.child("price").getValue(String.class);
        String productId = dataSnapshot.child("productId").getValue(String.class);
        String productName = dataSnapshot.child("productName").getValue(String.class);
        String quantity = dataSnapshot.child("quantity").getValue(String.class);
        Log.d("TAG", discount + " / " + 
                price + " / " + 
                productId + " / " + 
                productName + " / " + 
                quantity);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
zeroRef.addListenerForSingleValueEvent(eventListener);

如果您将拥有更多单个对象，请使用以下代码：

String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference foodsRef = rootRef.child("Request").child(uid).child("foods");
ValueEventListener eventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String discount = ds.child("discount").getValue(String.class);
            String price = ds.child("price").getValue(String.class);
            String productId = ds.child("productId").getValue(String.class);
            String productName = ds.child("productName").getValue(String.class);
            String quantity = ds.child("quantity").getValue(String.class);
            Log.d("TAG", discount + " / " + 
                    price + " / " + 
                    productId + " / " + 
                    productName + " / " + 
                    quantity);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
foodsRef.addListenerForSingleValueEvent(eventListener);

假设Request节点是您的Firebase根的直接子节点，并且其下的第一个直接子节点是用户ID。

修改

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference requestRef = rootRef.child("Request");
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String discount = ds.child("foods").child("0").child("discount").getValue(String.class);
            String price = ds.child("foods").child("0").child("price").getValue(String.class);
            String productId = ds.child("foods").child("0").child("productId").getValue(String.class);
            String productName = ds.child("foods").child("0").child("productName").getValue(String.class);
            String quantity = ds.child("foods").child("0").child("quantity").getValue(String.class);
            Log.d("TAG", discount + " / " + 
                    price + " / " + 
                    productId + " / " + 
                    productName + " / " + 
                    quantity);
        }
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {}
};
requestRef.addListenerForSingleValueEvent(valueEventListener);