The executing sequence in the code with android studio development

manpreet Best Answer 3 years ago

I was trying to realize the executing sequence in my code. It's a user register function in my app,when I call the function, the output is as following(suppose that Account exist): test1 Account exist but my expected output is that: Account exist test1 I don't know where is the problem,can anyone help me solve the question? thanks in advance.

private boolean checkAccountExist(final String userID){
FirebaseDatabase.getInstance().getReference("userAccount").child(userID);
    cDB = FirebaseDatabase.getInstance().getReference("userAccount");
    cDB.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            if(dataSnapshot.child(userID).exists()){
                System.out.println("Account Exist");
            }
            else{
                System.out.println("Account isn't exist");
            }
        }
        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {}
    });
    System.out.println("test1");
    return true;
}

my expected output is that: Account exist test1 but actually output is : test1 Account exist

manpreet 3 years ago

All Firebase APIs are asynchronous for a very good reason. You will need to learn how to do asynchronous programming in order to work with it. There is really no easy way around it.

You should not try to turn an asynchronous API in a synchronous, blocking API, because that runs the risk of crashing your app with an Application Not Responding dialog if that runs on the main thread and the database takes longer than a few seconds to respond (because the connection is slow, or there is a lot of data). The fact that the API is asynchronous protects you from this disaster.