I have tried both writing the code out of the book and importing it. There are no errors, though when i run the activity the display is empty. I run the debugger and in the "Activity Thread" it highlights:

if (list == null) {

Out of:

public void registerOnActivityPausedListener(Activity activity,
OnActivityPausedListener listener) {
synchronized (mOnPauseListeners) {
ArrayList<OnActivityPausedListener> list = mOnPauseListeners.get(activity);
if (list == null) {
list = new ArrayList<OnActivityPausedListener>();
mOnPauseListeners.put(activity, list);
}
list.add(listener);
}
}


Please help. None of the fragments activities are working.

I'm currently working through this book and also have problems with the Fragments code. There are no errors, but I noticed LinearLayout is highlighted in the main.xml file. With a message "set android:baselineAligned="false" for better performance.
I'm new to Android. Would a RelativeLayout for this particular exercise? I don't really know the difference...