title: Error in jjoe64 GraphView Library
body: <p>someone can help me? I found this error and I can't find the resolution to my problem. This is the Android Error:</p>
  
  <pre><code>09-15 18:26:47.434 3096-3096/com.example.user.navigationdrawer E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.user.navigationdrawer, PID: 3096
    java.lang.IllegalArgumentException: new x-value must be greater then the last value. x-values has to be ordered in ASC.
    at com.jjoe64.graphview.series.BaseSeries.appendData(BaseSeries.java:388)
    at com.example.user.navigationdrawer.SeventhFragment$1.onDataChange(SeventhFragment.java:75)
    at com.firebase.client.Query$1.onDataChange(Query.java:158)
    at com.firebase.client.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:45)
    at com.firebase.client.core.view.DataEvent.fire(DataEvent.java:45)
    at com.firebase.client.core.view.EventRaiser$1.run(EventRaiser.java:38)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5417)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
  </code></pre>
  
  <p>And This is my code:</p>
  
  <pre><code>package com.example.user.navigationdrawer;
  
  import android.app.Activity;
  import android.app.Fragment;
  import android.content.Intent;
  import android.os.Bundle;
  import android.provider.ContactsContract;
  import android.support.annotation.Nullable;
  import android.view.LayoutInflater;
  import android.view.View;
  import android.view.ViewGroup;
  import android.widget.Toast;
  
  import com.firebase.client.DataSnapshot;
  import com.firebase.client.Firebase;
  import com.firebase.client.FirebaseError;
  import com.firebase.client.ValueEventListener;
  import com.google.firebase.auth.FirebaseAuth;
  import com.google.firebase.auth.FirebaseUser;
  import com.jjoe64.graphview.GraphView;
  import com.jjoe64.graphview.series.BarGraphSeries;
  import com.jjoe64.graphview.series.DataPoint;
  import com.jjoe64.graphview.series.LineGraphSeries;
  import com.jjoe64.graphview.series.Series;
  
  public class SeventhFragment extends Fragment{
  
  GraphView graphView;
  FirebaseAuth auth;
  FirebaseUser user;
  Firebase mRef;
  LineGraphSeries&lt;DataPoint&gt; series;
  
  View myView;
  
  @Nullable
  @Override
  public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
      myView = inflater.inflate(R.layout.seventh_layout, container, false);
      graphView = (GraphView) myView.findViewById(R.id.graph);
  
      auth = FirebaseAuth.getInstance();
      user = auth.getCurrentUser();
  
      if (user == null){
          Activity activity = getActivity();
          Toast.makeText(activity, "Per accedere a questa funzione devi aver effettuato il login.", Toast.LENGTH_SHORT).show();
          startActivity(new Intent(activity, LoginActivity.class));
      }
  
      graphView.getViewport().setXAxisBoundsManual(true);
      graphView.getViewport().setMinX(0.0);
      graphView.getViewport().setMaxX(24);
      // set manual Y bounds
      graphView.getViewport().setYAxisBoundsManual(true);
      graphView.getViewport().setMinY(0.0);
      graphView.getViewport().setMaxY(2000);
  
      graphView.getViewport().setScrollable(true);
  
      series = new LineGraphSeries&lt;DataPoint&gt;();
  
      mRef = new Firebase("my url" );
      mRef.addListenerForSingleValueEvent(new ValueEventListener() {
          @Override
          public void onDataChange(DataSnapshot dataSnapshot) {
              final double Valore = dataSnapshot.getValue(double.class);
              series.appendData(new DataPoint(1, Valore), false, 24); //what number must i write here?
          }@Override
          public void onCancelled(FirebaseError firebaseError) {
          }});
  
      mRef = new Firebase("my url" );
      mRef.addListenerForSingleValueEvent(new ValueEventListener() {
          @Override
          public void onDataChange(DataSnapshot dataSnapshot) {
              final double Valore = dataSnapshot.getValue(double.class);
              series.appendData(new DataPoint(2, Valore), false, 25); //what number must i write here?
          }@Override
          public void onCancelled(FirebaseError firebaseError) {
  
          }});
  
      graphView.addSeries(series);
      return myView;
  }}
  </code></pre>
  
  <p>I want to set in the graph the data i recived from FireBase but it gives me an error. I'm using the library: com.jjoe64:graphview:4.1.0'
  HELP!</p>