java - Firebase 全局保存 query.addValueEventListener 数据

Question

我想将从查询中检索到的数据保存到全局类变量，例如 .RoomType，但是当它存在于 query.addValueEventListener 的范围时，数据永远不会保存。当我在其范围内执行 Log.w("Value", "value is "+ RoomType ); 时，它会输出检索到的数据。我如何在全局范围内保存这些数据？

这是我的代码:

public class DatabaseManager {


public static String RoomName, RoomType, BuildingName;
static int RoomLevel;
public  Double RoomLat, RoomLang ;




//connecting to Firebase database by creating database reference
private static FirebaseDatabase mDatabase;

public static FirebaseDatabase getDatabase() {
    if (mDatabase == null) {
        //Retrieving an instance of the database
        mDatabase = FirebaseDatabase.getInstance();

        //Enabling database for offline use for events where there is no internet connection
        mDatabase.setPersistenceEnabled(true);

    }
    return mDatabase;
}




public  void getresults(DatabaseReference myref, String data){
    Query query=  myref.child("rooms").orderByChild("RoomName").equalTo(data);
    query.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if (dataSnapshot.exists()) {




                for (DataSnapshot Node : dataSnapshot.getChildren()) {



                    RoomType = Node.child("RoomType").getValue().toString();
                    BuildingName = Node.child("BuildingName").getValue().toString();
                    RoomLevel = Node.child("RoomLevel").getValue(Integer.class);
                    RoomLat = Node.child("RoomLat").getValue(Double.class);
                    RoomLang = Node.child("RoomLang").getValue(Double.class);


                }

            }

            Log.w("Value", " value is "+ RoomType );
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }


    });

    Log.w("Value at end ", " value is "+ RoomType );


}


}

Answer 1

尝试像这样初始化 RoomType 变量 RoomType = "";