title: datasnapshot.getvalue() does not work and crashes app
body: <p>I am trying to get data from firebase real-time database in the form of <code>BusInformation.class</code>. But my app crashes while setting the class type of snapshot at this point: <code>ds.getValue(BusInformation.class);</code></p>
  
  <p>I am getting the following error:</p>
  
  <pre><code>com.google.firebase.database.DatabaseException: Class com.example.muzammil.bustracking.app_classes.BusInformation does not define a no-argument constructor. If you are using ProGuard, make sure these constructors are not stripped.
          at com.google.android.gms.internal.firebase_database.zzku.zza(Unknown Source)
          at com.google.android.gms.internal.firebase_database.zzkt.zzb(Unknown Source)
          at com.google.android.gms.internal.firebase_database.zzkt.zza(Unknown Source)
          at com.google.firebase.database.DataSnapshot.getValue(Unknown Source)
  </code></pre>
  
  <p>Following is code for BuInformation.java class:</p>
  
  <pre><code>public class BusInformation {
      private String id, username,phone;
      private LatLng position;
      private String destination;
  
      public BusInformation(String id, String username, String phone,  String destination,LatLng position) {
          this.id = id;
          this.username = username;
          this.phone = phone;
          this.position = position;
          this.destination = destination;
      }
  }
  </code></pre>
  
  <p>In Firebase database the data exist exactly in this form.</p>
  
  <p>The code for getting data from firebase:</p>
  
  <pre><code> public void getUpdatesFromFirebase(DataSnapshot dataSnapshot){
          for(DataSnapshot ds : dataSnapshot.getChildren()){
              if(ds.exists()) {
                  busInfo = ds.getValue(BusInformation.class);  //App crashes at this point
  
              }
  
          }
      }
  </code></pre>
  
  <p>Any body please tell me what is wrong with the code...</p>