How to retrieved data in Firebase to the Android Studio

Question

I need to retrieved data from database Firebase. But I have problem since when I try to retrieve the data, the application will stop.

this is the code for retrievedPoint.java

final FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference ref = database.getReference("reloadPoint");

ref.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        ReloadPoint rp = dataSnapshot.getValue(ReloadPoint.class);
        System.out.println(rp);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {
        System.out.println("The read failed: " + databaseError.getCode());
    }
});

ref.addChildEventListener(new ChildEventListener() {
    @Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        ReloadPoint newPost = dataSnapshot.getValue(ReloadPoint.class);
        System.out.println("Email: " + newPost.getmEmail());
        System.out.println("Point: " + newPost.getmPoint());
        System.out.println("User id: " + newPost.getmUserid());
    }

    @Override
    public void onChildChanged(DataSnapshot dataSnapshot, String s) {

    }

    @Override
    public void onChildRemoved(DataSnapshot dataSnapshot) {

    }

    @Override
    public void onChildMoved(DataSnapshot dataSnapshot, String s) {

    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

this the code for the ReloadPoint class.

public class ReloadPoint {

private String mEmail;
private String mPoint;
private String mUserid;

public ReloadPoint(String email, String point, String userid) {
   this.mEmail = email;
   this.mPoint = point;
   this.mUserid = userid;

}

public String getmEmail() {
 return mEmail;
}

public void setmEmail(String mEmail) {
    this.mEmail = mEmail;
}

public String getmPoint() {
  return mPoint;
}

public void setmPoint(String mPoint) {
  this.mPoint = mPoint;
}

public String getmUserid() {
    return mUserid;
}

public void setmUserid(String mUserid) {
   this.mUserid = mUserid;
}
}

This is the thing that I want to retrieve from Firebase. this is the child that I want to retrieve
This is the Android where the retrived data will appear if the retrieved process is success.retrievedPoint.xml
Result from log cat.Log cat result

Please help me.

Possible duplicate of [users does not define no argument constructor](https://stackoverflow.com/questions/47706601/users-does-not-define-no-argument-constructor) — orimdominic, Jul 16 '18 at 09:48
Possible duplicate of [Error in fetching data from firebase to recycler view](https://stackoverflow.com/questions/51035276/error-in-fetching-data-from-firebase-to-recycler-view) — Alex Mamo, Jul 16 '18 at 09:51

score 2 · Answer 1 · answered Jul 16 '18 at 09:42

2

As the error message implies, your ReloadPoint class needs a no-args constructor, e.g :

public ReloadPoint() {

}

answered Jul 16 '18 at 09:42

Arnaud

17,229
3
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score 2 · Answer 2 · answered Jul 16 '18 at 09:44

2

Please include a no-argument constructor in your ReloadPoint class like so

public ReloadPoint() {

}

see this question users does not define no argument constructor

answered Jul 16 '18 at 09:44

orimdominic

995
10
23

I put the code like you said above the apps working properly but the data cannot be retrieved @Dominic Orim – Nor Sakinah Jul 16 '18 at 15:59

Ticherhaz FreePalestine · Answer 3 · 2018-07-16T22:45:18.283

1

public class ReloadPoint {

private String mEmail;
private String mPoint;
private String mUserid;

//Ni hang lupa ni. apa la sakinah
//Klau da soklan lagi, hbungi kt insta id: nyrtron
public ReloadPoint(){

}

public ReloadPoint(String email, String point, String userid) {
   this.mEmail = email;
   this.mPoint = point;
   this.mUserid = userid;

}

public String getmEmail() {
 return mEmail;
}

public void setmEmail(String mEmail) {
    this.mEmail = mEmail;
}

public String getmPoint() {
  return mPoint;
}

public void setmPoint(String mPoint) {
  this.mPoint = mPoint;
}

public String getmUserid() {
    return mUserid;
}

public void setmUserid(String mUserid) {
   this.mUserid = mUserid;
}
}

I think I have found your problem.

DatabaseReference ref = database.getReference().child("reloadPoint").child("Waniyanazahri");

UPDATED ANSWER: Its look like you haven't call the class.

ref.addValueEventListener(new ValueEventListener() {
   @Override
   public void onDataChange(DataSnapshot dataSnapshot) {
      //Add this one
      ReloadPoint rp = new ReloadPoint();
      rp = dataSnapshot.getValue(ReloadPoint.class);
      System.out.println(rp);
    }
   @Override
   public void onCancelled(DatabaseError databaseError) {
   System.out.println("The read failed: " + databaseError.getCode());
   }
});

edited Jul 16 '18 at 22:45

answered Jul 16 '18 at 10:03

Ticherhaz FreePalestine

2,738
4
20
46

1

I did put the code that you said, and the application is working properly, but the data does not retrieved. @Zuhrain – Nor Sakinah Jul 16 '18 at 15:57
@NorSakinah I updated the answer. Please take a look. – Ticherhaz FreePalestine Jul 16 '18 at 17:47
I follow the code but it doesn't work and my app crashed. I checked the logcat, seem the ReloadPoint newPost = dataSnapshot.getValue(ReloadPoint.class); – Nor Sakinah Jul 16 '18 at 19:55
@NorSakinah check the updated answer – Ticherhaz FreePalestine Jul 16 '18 at 22:45
I will update to you later.By the way, is the ref.addChildEventListener(new ChildEventListener(){} is needed to retrieve the data? @Zuhrain – Nor Sakinah Jul 17 '18 at 01:33
actually, you just can use `addValueEventListener` only. I'm used to it. I know a little bit about the `addChildEventListener`. But most of my coding, I use `addValueEventListener` @NorSakinah – Ticherhaz FreePalestine Jul 17 '18 at 01:42
So can I just modify the code and delete 'addChildEventListener'? @Zuhrain – Nor Sakinah Jul 17 '18 at 02:11
yes and don't forget to transfer all the value that you want to display. – Ticherhaz FreePalestine Jul 17 '18 at 02:15
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/176097/discussion-between-nor-sakinah-and-zuhrain). – Nor Sakinah Jul 17 '18 at 03:03

How to retrieved data in Firebase to the Android Studio

3 Answers3