title: transition name is null when trying to build a shared element lollipop transition
body: <p>I am trying to create a shared element transition in my app. I have a listview in activity1 and whith an image view in each element of my list. This image is also present in the second activity2 when the user click on item in the list. </p>
  
  <p>Problem is the following:</p>
  
  <pre><code> java.lang.IllegalArgumentException: Shared element name must not be null
               at android.app.ActivityOptions.makeSceneTransitionAnimation(ActivityOptions.java:470)
               at android.app.ActivityOptions.makeSceneTransitionAnimation(ActivityOptions.java:431)
               at android.support.v4.app.ActivityOptionsCompat21.makeSceneTransitionAnimation(ActivityOptionsCompat21.java:31)
               at android.support.v4.app.ActivityOptionsCompat.makeSceneTransitionAnimation(ActivityOptionsCompat.java:134)
               at com.frisbeeeapp.frisbeee.main_fragment.Main_All_Annonces$6$2.onItemClick(Main_All_Annonces.java:417)
               at android.widget.AdapterView.performItemClick(AdapterView.java:300)
               at android.widget.AbsListView.performItemClick(AbsListView.java:1143)
               at android.widget.AbsListView$PerformClick.run(AbsListView.java:3044)
               at android.widget.AbsListView$3.run(AbsListView.java:3833)
               at android.os.Handler.handleCallback(Handler.java:739)
               at android.os.Handler.dispatchMessage(Handler.java:95)
               at android.os.Looper.loop(Looper.java:135)
               at android.app.ActivityThread.main(ActivityThread.java:5221)
               at java.lang.reflect.Method.invoke(Native Method)
               at java.lang.reflect.Method.invoke(Method.java:372)
               at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
               at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
  </code></pre>
  
  <p>change_image_transform.xml :</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;transitionSet xmlns:android="http://schemas.android.com/apk/res/android"&gt;
      &lt;changeImageTransform /&gt;
  &lt;/transitionSet&gt;
  </code></pre>
  
  <p>And extract of imageview declared in layout of activity1:</p>
  
  <pre><code>&lt;ImageView
      android:id="@+id/allannonces_image"
      android:transitionName="transitionImg"
      android:layout_width="fill_parent"
      android:layout_height="270dp"
      android:scaleType="centerCrop"
      android:layout_below="@+id/allannonces_imageuser"
      android:layout_marginTop="18dp"/&gt;
  </code></pre>
  
  <p>And here is the code inside activity1:</p>
  
  <pre><code>list.setOnItemClickListener(new AdapterView.OnItemClickListener() {
      @Override
      public void onItemClick(AdapterView&lt;?&gt; parent, View view, int position, long id) {
  
          Annonce currentAnnonce = (Annonce) list.getAdapter().getItem(position);
          String titre = currentAnnonce.getTitle();
          String cat = currentAnnonce.getCategorie();
          String desc = currentAnnonce.getDescription();
          String etat = currentAnnonce.getEtat();
          String img = currentAnnonce.getImage();
          String prix = currentAnnonce.getPrix();
          String villeObj = currentAnnonce.getVilleObjet();
          String codePostal = currentAnnonce.getCode_postal();
          String departement = currentAnnonce.getDepartement();
          String avatarUser = currentAnnonce.getImageUser();
          String pseudoUser = currentAnnonce.getPseudoUser();
          String dateDebut = currentAnnonce.getDate_debut();
          String idAnnonce = currentAnnonce.getId();
          String emailUser = currentAnnonce.getEmailUser();
          String partel = currentAnnonce.getPartel();
          String parmail = currentAnnonce.getParmail();
  
          Intent myIntent = new Intent(Main_All_Annonces.this, Detail_annonce.class);
          myIntent.putExtra("titre", titre);
          myIntent.putExtra("cat", cat);
          myIntent.putExtra("desc", desc);
          myIntent.putExtra("etat", etat);
          myIntent.putExtra("img", img);
          myIntent.putExtra("prix", prix);
          myIntent.putExtra("villeObj", villeObj);
          myIntent.putExtra("codePostal", codePostal);
          myIntent.putExtra("departement", departement);
          myIntent.putExtra("avatarUser", avatarUser);
          myIntent.putExtra("pseudoUser", pseudoUser);
          myIntent.putExtra("dateDebut", dateDebut);
          myIntent.putExtra("idAnnonce", idAnnonce);
          myIntent.putExtra("emailUser", emailUser);
          myIntent.putExtra("partel", partel);
          myIntent.putExtra("parmail", parmail);
  
          myIntent.putExtra("parentAct", "AllAnnonces");
  
          if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.LOLLIPOP) {
              String transitionName = (String) view.getTag(R.id.allannonces_image);
              ActivityOptionsCompat options =
                      ActivityOptionsCompat.makeSceneTransitionAnimation(
                              Main_All_Annonces.this,
                              view,           // The view which starts the transition
                              transitionName  // The transitionName of the view we’re transitioning to
                      );
  
              // put more extras in the intent if you want, like the object clicked
              myIntent.putExtra("EXTRA_IMAGE_TRANSITION_NAME", transitionName);
              ActivityCompat.startActivity(Main_All_Annonces.this, myIntent, options.toBundle());
          }
          else {
              // Code to run on older devices
              startActivity(myIntent);
              overridePendingTransition(R.anim.left_to_right, R.anim.right_to_left);
          }
      }
  });
  </code></pre>
  
  <p>And the code inside onCreate of activity2:</p>
  
  <pre><code>ViewCompat.setTransitionName(image_txt, getIntent().getStringExtra("EXTRA_IMAGE_TRANSITION_NAME"));
          imageLoader.displayImage(img, image_txt);
  </code></pre>
  
  <p>An extract of imageview declared in layout of activity2:</p>
  
  <pre><code>    &lt;ImageView
           android:id="@+id/detail_annonce_image"
           android:transitionName="transitionImg"
           android:layout_width="fill_parent"
           android:layout_height="280dp"
           android:scaleType="centerCrop"
           android:src="@drawable/cover1" /&gt;
  </code></pre>