Question

所以我的Firebase中有一些数据。它的结构是

（假设有更多数据）我想获取banknoteType =＆＃34; 100_dollar＆＃34;和userId =＆＃34; 1057 ...＆＃34;

   DatabaseReference database = FirebaseDatabase.getInstance().getReference("userBanknoteAmount");
    Query firebaseQuery = database.orderByChild(1057...).equalTo(1057...);
            firebaseQuery.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                     //todo
                    }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {
                    Log.w("onCancelledError", "loadPost:onCancelled", databaseError.toException());
                }
            });

但是onDataChange事件并没有发生......我在误解什么？编辑：我正在尝试调试它，onDataChange和onCancelled断点都没有停止

编辑2：我正在使用的当前代码是

 DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
    DatabaseReference userBanknoteAmountRef = rootRef.child("userBanknoteAmount");
    Query firebaseQuery = userBanknoteAmountRef.orderByChild("userId");//.equalTo(userId);
    firebaseQuery.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                Log.d("test", "onDataChange: "+postSnapshot);
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.wtf("onCancelledError", "loadPost:onCancelled", databaseError.toException());
        }
    });

编辑3：https://i.stack.imgur.com/iBkcx.png

Answer 1

Firebase实时数据库不允许您链接多个过滤方法。如果您想获取以下内容的记录：userId="1057..."，请更改以下代码行：

Query firebaseQuery = database.orderByChild(1057...).equalTo(1057...);

与

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference userBanknoteAmountRef = rootRef.child("userBanknoteAmount");
Query firebaseQuery = userBanknoteAmountRef.orderByChild("userId").equalTo(1057...);

如果您希望获得banknoteType ="100_dollar"和userId="1057..."的所有记录，请参阅 post 中的答案。

根据您编辑的帖子，请同时更改以下代码：

Log.d("test", "onDataChange: "+postSnapshot);

到

Log.d("test", "onDataChange: "+postSnapshot.child("userId").getValue(String.class));

Firebase查询无效（onDataEvent未触发）

1 个答案: