com.google.firebase.database.DatabaseException

Question

When I start the activity, it is showing the error:

Class com.rcpl.agni.Artist does not define a no-argument constructor.If you are using ProGuard, make sure these constructors are not stripped.

protected void onStart() {
        super.onStart();
        ref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                //artistList.clear();
                for(DataSnapshot artistSnapshot : dataSnapshot.getChildren()){
                    Artist artist = artistSnapshot.getValue(Artist.class);
                    Toast.makeText(MainActivity.this, artist.getArtistName(), Toast.LENGTH_SHORT).show();

                }

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
    }

Artist.java

package com.rcpl.agni;

/**
 * Created by Dell-pc on 23-01-2018.
 */

public class Artist {
    String artistId;
    String artistName;
    String artistGenre;

    public Artist(String artistId, String artistName, String artistGenre) {
        this.artistId = artistId;
        this.artistName = artistName;
        this.artistGenre = artistGenre;
    }

    public String getArtistId() {
        return artistId;
    }

    public String getArtistName() {
        return artistName;
    }

    public String getArtistGenre() {
        return artistGenre;
    }
}

Frank van Puffelen · Accepted Answer · 2020-02-28 22:07:37Z

9

To solve this, you just need to add the public no-argument constructor to your Artist class.

public Artist() {}

Remember, when the Firebase Realtime Database SDK deserializes objects coming from the database, it requires that any objects to a have a public no-argument constructor. This is needed to instantiate that particular object. All the fields within the object are set by using public setter methods or direct access to public members.

If you don't use a public no-arg constructor, the SDK doesn't know how to create an instance of the class. Most serialization libraries will have the same requirement.

edited Feb 28, 2020 at 22:07

Frank van Puffelen

603k85 gold badges895 silver badges868 bronze badges

answered Jan 23, 2018 at 16:15

Alex Mamo

139k18 gold badges171 silver badges202 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Alex Mamo Over a year ago

@RosárioPereiraFernandes Indeed and this is because we almost answered in the same time with the only one solution that solves OP's problem. Firebase requires this constructor in order to use it's correct, but why? Everytime is good practice not only to solve the problem so to explain to the OP's a little more about that process.

Rosário P. Fernandes Over a year ago

I Agree. That's why I removed my comment.

Rosário P. Fernandes · Accepted Answer · 2018-01-23 16:13:12Z

I believe the error is pretty self-explanatory. You just need to add an empty constructor to your Artist class:

package com.rcpl.agni;

/**
 * Created by Dell-pc on 23-01-2018.
 */

public class Artist {
    String artistId;
    String artistName;
    String artistGenre;

    public Artist(){}

    public Artist(String artistId, String artistName, String artistGenre) {
        this.artistId = artistId;
        this.artistName = artistName;
        this.artistGenre = artistGenre;
    }

    public String getArtistId() {
        return artistId;
    }

    public String getArtistName() {
        return artistName;
    }

    public String getArtistGenre() {
        return artistGenre;
    }
}

Firebase requires this constructor in order to use it when you call artistSnapshot.getValue(Artist.class);

Jose Antonio · Accepted Answer · 2019-11-28 14:03:10Z

0

add the non-argument in the Data class

Run the app with a clear logcat:

answered Nov 28, 2019 at 14:03

Jose Antonio

9101 gold badge16 silver badges28 bronze badges

Collectives™ on Stack Overflow

com.google.firebase.database.DatabaseException

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related