com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.test.consti.last.QuestionEntry

Question

I'm building a social app that will save and retrieve data from firebase. But I'm getting this error

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.test.consti.last.QuestionEntry at com.google.android.gms.internal.zzear.zzb(Unknown Source) at com.google.android.gms.internal.zzear.zza(Unknown Source) at com.google.firebase.database.DataSnapshot.getValue(Unknown Source) at com.test.consti.last.FirebaseHelper.fetchData(FirebaseHelper.java:28) at com.test.consti.last.FirebaseHelper.access$000(FirebaseHelper.java:17) at com.test.consti.last.FirebaseHelper$1.onChildAdded(FirebaseHelper.java:36) at com.google.android.gms.internal.zzdri.zza(Unknown Source) at com.google.android.gms.internal.zzdwu.zzbvb(Unknown Source) at com.google.android.gms.internal.zzdxa.run(Unknown Source) at android.os.Handler.handleCallback(Handler.java:730) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:176) at android.app.ActivityThread.main(ActivityThread.java:5419) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:525) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862) at dalvik.system.NativeStart.main(Native Method)

This is my FirebaseHelper. There i'm to retrieve data from firebase database ( only "Questions" childs contents)

public class FirebaseHelper {
 DatabaseReference db;
 Boolean saved=null;
 ArrayList<QuestionEntry> questionEntries =new ArrayList<>();
public FirebaseHelper(DatabaseReference db)  {
    this.db=db;
    }
private void fetchData (DataSnapshot dataSnapshot){
questionEntries.clear();
for (DataSnapshot ds :dataSnapshot.getChildren()){
//There is the error
    QuestionEntry questionEntry = ds.getValue(QuestionEntry.class);
    questionEntries.add(questionEntry);
}
}
public ArrayList<QuestionEntry> retreive (){
db.addChildEventListener(new ChildEventListener() {
    @Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        fetchData(dataSnapshot);
    }

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

    @Override
    public void onChildRemoved(DataSnapshot dataSnapshot) {

    }

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

    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});
return questionEntries;
}

Then this is QuestionEntry

public class QuestionEntry {
public String question_title;

public String question_id;
public   String tag_id;
public   String tag_name;
public   String question_content;
public String question_date;
public    String question_username;
public String interet;


public QuestionEntry(){

}

public void setQuestion_title(String question_title) {
    this.question_title = question_title;
}

public void setQuestion_id(String question_id) {
    this.question_id = question_id;
}

public void setTag_id(String tag_id) {
    this.tag_id = tag_id;
}

public void setTag_name(String tag_name) {
    this.tag_name = tag_name;
}

public void setQuestion_content(String question_content) {
    this.question_content = question_content;
}

public void setQuestion_date(String question_date) {
    this.question_date = question_date;
}

public void setQuestion_username(String question_username) {
    this.question_username = question_username;
}

public void setInteret(String interet) {
    this.interet = interet;
}

public String getQuestion_title() {
    return question_title;
}

public String getQuestion_id() {
    return question_id;
}

public String getTag_id() {
    return tag_id;
}

public String getTag_name() {
    return tag_name;
}

public String getQuestion_content() {
    return question_content;
}



public String getQuestion_username() {
    return question_username;
}

public String getInteret() {
    return interet;
}

public String getQuestion_date() {
    return question_date;
}
}

this is my firebase database structure this my Acticity

this is my Activity

    public class Actu extends Fragment {
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        v = inflater.inflate(R.layout.activity_actu, container, false);
        lv = (ListView) v.findViewById(R.id.actu_rv);
        db = FirebaseDatabase.getInstance().getReference("Questions");
        helper = new FirebaseHelper(db);
        adapter = new QuestionAdapter(getContext(),helper.retreive());
        lv.setAdapter(adapter);


        return v;        }
}

I've already post the content to firebase

Peter Haddad Peter Haddad · Accepted Answer · 2017-10-28T15:14:30

change the fetchData method into this:

private void fetchData (DataSnapshot dataSnapshot){
questionEntries.clear();
QuestionEntry questionEntry = dataSnapshot.getValue(QuestionEntry.class);
questionEntries.add(questionEntry);
 }

the for loop is looping through the children of node questions and since the children contains strings you are getting that error.

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.test.consti.last.QuestionEntry

1 Answers