make common module ViewDataCache.

app/src/main/java/chat/rocket/android/helper/Avatar.java

@@ -65,14 +65,9 @@ public class Avatar {
    * render avatar into imageView.
    */
   public void into(final ImageView imageView) {
-    Object tag = imageView.getTag();
-    if (tag != null && tag instanceof String) {
-      String username = (String) tag;
-      if (this.username.equals(username)) {
-        return;
-      }
+    if (ViewDataCache.isStored(username, imageView)) {
+      return;
     }
-    imageView.setTag(this.username);
 
     final Context context = imageView.getContext();
     Picasso.with(context)

app/src/main/java/chat/rocket/android/helper/ViewDataCache.java

+package chat.rocket.android.helper;
+
+import android.view.View;
+import hugo.weaving.DebugLog;
+
+/**
+ * save String to setTag.
+ */
+public class ViewDataCache {
+
+  /**
+   * stores str if not stored. returns true if already stored.
+   */
+  @DebugLog
+  public static boolean isStored(String str, View view) {
+    if (view.getTag() != null && view.getTag() instanceof String
+        && ((String) view.getTag()).equals(str)) {
+      return true;
+    }
+    view.setTag(str);
+    return false;
+  }
+}