An important rule when dealing with fragments—especially those that you add at -runtime—is that the fragment must have a container {@link android.view.View} in the layout in -which the fragment's layout will reside.
+An important rule when dealing with fragments—especially when adding fragments at +runtime—is that your activity layout must include a container {@link android.view.View} +in which you can insert the fragment.
The following layout is an alternative to the layout shown in the previous lesson that shows only one fragment at a time. In order to replace