检查 Firebase 数据库中是否存在某些键值并执行一些操作 Android

Question

I want to check if a specific value of a key exists in the Realtime Database or not and perform some action based on it.

I have the following data:

"Orders" : {
"03403426747" : {
  "17" : {
    "State" : "(4) Canceled",
    "address" : "yubt",
    "date" : "Feb 28, 2022",
    "discount" : "0",
    "name" : "uk",
    "phone" : "0311111111",
    "time" : "15:33:58 PM",
    "totalAmount" : "3778"
  },
  "18" : {
    "State" : "(1) Approved",
    "address" : "yubt",
    "date" : "Feb 28, 2022",
    "discount" : "120",
    "name" : "uk",
    "phone" : "03111111111",
    "time" : "16:01:58 PM",
    "totalAmount" : "7703"
  }
 }
}

I want to check If any order from these has has "State" value other than "(3) Completed" & "(4) Canceled" .

if anyone's order has a value other than these, I want to remove that user from the list which contains users with pending orders. and if at any time that user has new order or older order State changed I want to again add that user to the list.

Answer 1

I want to check If any order from these has has "State" value other than "(3) Completed" & "(4) Canceled".

There is no way you can query the Realtime Database using a negation. What you can do instead is to create a separate query for each "other" state and join the results on the client.

However, if you consider at some point in time to try using Cloud Firestore , then you should consider using not equal (!=) query or if it fits your needs the not-in query.

Answer 2

After a long time, my brain light burned and I came up with a solution.

Create a data class for OrderState

public class OrderState {
public static int ordersCount = 0;

public static boolean state = false;

public static void update(boolean state){
    if (state){
        ordersCount = ordersCount + 1;
        OrderState.state = true;
    }else
        if (!state && ordersCount > 0){
                ordersCount = ordersCount - 1;
            if (ordersCount < 1) OrderState.state = false;
        }
}

public static void reset(){
    ordersCount = 0;
    state = false;
}
}

On FirebaseRecyclerAdapter -> onBindViewHolder

//if order not canceled or completed. it will update OrderState, 
//ordersCount + 1 and state to true

if (adminOrders.getState().equals(Prevalent.orderStateNew) ||
                            adminOrders.getState().equals(Prevalent.orderStateApproved) ||
                            adminOrders.getState().equals(Prevalent.orderStateShipped) ||
                            adminOrders.getState().equals(Prevalent.orderStateApproved)){
                        OrderState.update(true);
                    }

                    changeUserWithOrderState();

On changing state of order by admin

//if the order is not already cancelled or completed, reduce one order from OrderState as it will be readded automatically upon Recycler refresh.

if (!adminOrders.getState().equals(Prevalent.orderStateCanceled) &&
                                        !adminOrders.getState().equals(Prevalent.orderStateCompleted)) OrderState.update(false);

Al last if the user does not has any order with states New, Approved, and Shipped OrderState.orderCount = 0; OrderState.state = false; and upon updating the database it will set the state to false.

private void changeUserWithOrderState() {
    DatabaseReference userWithOrder = FirebaseDatabase.getInstance().getReference()
            .child(Prevalent.usersWithOrders)
            .child(userPhoneKey);

   
    HashMap<String, Object> map = new HashMap<>();
    map.put(Prevalent.orderState, String.valueOf(OrderState.state));
    userWithOrder.updateChildren(map).addOnCompleteListener(task -> {
        //Changed state based upon OrderState.state value...
    });
}