Retrieve data in Android using Firebase

Question

I'm a newbie to Firebase and I'm trying to get data from cloud to my project

DatabaseReference userRef = ref.child(user.getUid());

    userRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            UserDoctor userDoctor = dataSnapshot.getValue(UserDoctor.class);
            tempName = userDoctor.getName();
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

But the problem is I couldn't assign the string to the tempName, it returned "null"

This is my debug window

And the UserDoctor class is here

public class UserDoctor {
public String address;
public String major;
public String mobile;
public String name;
public String workplace;

public UserDoctor(){}

public UserDoctor(String _address, String _major, String _mobile, String _name, String _workplace){
    name = _name;
    address = _address;
    major = _major;
    mobile = _mobile;
    workplace = _workplace;
}

public String getName() {
    return name;
}

}

Thank you very much!

As your debug window shows, the name of the doctor is being property read and set. The problem is not reading the data from Firebase. The problem is more likely *when* you are trying to use `tempName`. Data is read from Firebase asynchronously and most likely simply hasn't been read yet when you are using `tempName`. See my answer here for a long explanation: http://stackoverflow.com/questions/33203379/setting-singleton-property-value-in-firebase-listener — Frank van Puffelen, Mar 23 '17 at 16:03
@FrankvanPuffelen First of all, thanks for your answer, I've read the link you gave but I'm so confused and don't know what to do with this. So I can't use the semaphore, right?. Can you suggest me a way to get the doctor's name? — Phụng Nguyễn Lê Gia, Mar 23 '17 at 16:19
Your code already *gets* the doctor's name. But you show nowhere how your using it. Typically you'll need to move all the code that *uses* `tempName` *into* `onDataChange()`. — Frank van Puffelen, Mar 23 '17 at 17:07
intent.putExtra("userName", tempName); I already did it, but it seemed not worked well — Phụng Nguyễn Lê Gia, Mar 24 '17 at 01:04
That depends on where you use that code. If the link I provided (which is the most likely cause, I'm quite certain of that) doesn't help you solve the problem, please edit your question to include a [single, minimal snippet of code that completely reproduces the problem](http://stackoverflow.com/help/mcve) (read the link, it's quite useful). — Frank van Puffelen, Mar 24 '17 at 03:23

Retrieve data in Android using Firebase

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