title: You cannot start a load on a not yet attached View or a Fragment where getActivity() returns null
body: <p>I am using FragmentStatePagerAdapter to show around 5 fragments in an activity.On each activity I am showing the images which I am fetching from FirebaseListAdapter/FirebaseRecyclerAdapter. As it is FragmentStagePagerAdapter adjacent views/Fragments will be initialized even they are not visible.If the tabs are scrolled in a fast manner (forward/backward) App is crashing with above mentioned error.I found out some similar issues on the internet but not able to fix this issue.I am also getting <strong>You cannot start a load for a destroyed activity</strong> error if I am starting a new activity(In activity I am showing images from firebase in a grid view) and closing it immediately(pressing the back button)
  I am using following code.</p>
  
  <pre><code>adapt= new FirebaseListAdapter&lt;MyClassStudent&gt;(getActivity(), MyClassStudent.class, R.layout.mychild_grid_template, myRef) {
              @Override
              protected void populateView(final View v, MyClassStudent model, int position) {
                  final TextView uname = (TextView) v.findViewById(R.id.mychild_uname);
  
                  final CircleImageView profileImage=(CircleImageView)v.findViewById(R.id.mychild_image);
                  studRef.child(model.getUsername()).addListenerForSingleValueEvent(new ValueEventListener() {
                      public void onDataChange(DataSnapshot dataSnapshot) {
                          Child child=dataSnapshot.getValue(Child.class);
                          uname.setText(child.getUsername());
                          Glide.with(getActivity()).load(child.getProfileImage()).into(profileImage);
                      }
  
                      @Override
                      public void onCancelled(DatabaseError databaseError) {
  
                      }
                  });
              }
          };
  </code></pre>
  
  <p>Stack Trace:</p>
  
  <pre><code>E/UncaughtException: java.lang.NullPointerException: You cannot start a load on a not yet attached View or a  Fragment where getActivity() returns null (which usually occurs when getActivity() is called before the Fragment is attached or after the Fragment is destroyed).
                           at com.bumptech.glide.util.Preconditions.checkNotNull(Preconditions.java:27)
                           at com.bumptech.glide.Glide.getRetriever(Glide.java:509)
                           at com.bumptech.glide.Glide.with(Glide.java:563)
                           at com.mycompany.educareteacher.FragmentStudents$2$1.onDataChange(FragmentStudents.java:184)
                           at com.google.firebase.database.zzp.onDataChange(Unknown Source)
                           at com.google.android.gms.internal.tl.zza(Unknown Source)
                           at com.google.android.gms.internal.vg.zzHW(Unknown Source)
                           at com.google.android.gms.internal.vm.run(Unknown Source)
                           at android.os.Handler.handleCallback(Handler.java:739)
                           at android.os.Handler.dispatchMessage(Handler.java:95)
                           at android.os.Looper.loop(Looper.java:148)
                           at android.app.ActivityThread.main(ActivityThread.java:5438)
                           at java.lang.reflect.Method.invoke(Native Method)
                           at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:738)
                           at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:628)
  D/FA: Logging event (FE): app_exception(_ae), Bundle[{firebase_event_origin(_o)=crash, firebase_screen_class(_sc)=ClassDetailActivity, firebase_screen_id(_si)=-4663411025690523798, timestamp=1500710706898, fatal=1}]
  V/FA: Recording user engagement, ms: 3544
  D/FA: Logging event (FE): user_engagement(_e), Bundle[{firebase_event_origin(_o)=auto, engagement_time_msec(_et)=3544, firebase_screen_class(_sc)=ClassDetailActivity, firebase_screen_id(_si)=-4663411025690523798}]
  E/AndroidRuntime: FATAL EXCEPTION: main
                    Process: com.mycompany.com.educareteacher, PID: 5154
                    java.lang.NullPointerException: You cannot start a load on a not yet attached View or a  Fragment where getActivity() returns null (which usually occurs when getActivity() is called before the Fragment is attached or after the Fragment is destroyed).
                        at com.bumptech.glide.util.Preconditions.checkNotNull(Preconditions.java:27)
                        at com.bumptech.glide.Glide.getRetriever(Glide.java:509)
                        at com.bumptech.glide.Glide.with(Glide.java:563)
                        at com.mycompany.educareteacher.FragmentStudents$2$1.onDataChange(FragmentStudents.java:184)
                        at com.google.firebase.database.zzp.onDataChange(Unknown Source)
                        at com.google.android.gms.internal.tl.zza(Unknown Source)
                        at com.google.android.gms.internal.vg.zzHW(Unknown Source)
                        at com.google.android.gms.internal.vm.run(Unknown Source)
                        at android.os.Handler.handleCallback(Handler.java:739)
                        at android.os.Handler.dispatchMessage(Handler.java:95)
                        at android.os.Looper.loop(Looper.java:148)
                        at android.app.ActivityThread.main(ActivityThread.java:5438)
                        at java.lang.reflect.Method.invoke(Native Method)
                        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:738)
                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:628)
  </code></pre>
  
  <p>How Can I solve this issue?</p>