How to change iconics button programmatically 
I want to change **gmd_book** if bookmark isn't null. If null **gmd_bookmark**

xml;
```xml
                           <com.mikepenz.iconics.view.IconicsButton
                            android:id="@+id/ib_bookmark"
                            android:layout_width="48dp"
                            android:layout_height="48dp"
                            android:layout_weight="1"
                            android:layout_margin="5dp"
                            android:background="@drawable/circle"
                            android:gravity="center"
                            android:text="{gmd_bookmark}"
                            android:textColor="@color/colorWhite"
                            android:textSize="24dp" />
```

Activity;
```
               if (bookmark != null){
                  //  ib_bookmark.                 
                }
```