LessonContentSingleton lcs = LessonContentSingleton.getInstance();

lcs.setupContext(this);
lcs.populateContent(bookNum, lessonNum);

studyMain_Fragment = Lesson_StudyMain_Fragment.create();
studyWriting_Fragment = Lesson_StudyWriting_Fragment.create();
typing_Fragment = Lesson_Typing_Fragment.create();
studyMorePhrase_Fragment = Lesson_StudyMorePhrase_Fragment.create();
testing_Fragment = Lesson_Testing_Fragment.create();
bookSearch_Fragment = Book_Search_Fragment.create();

fragmentList.add(studyMain_Fragment);
fragmentList.add(studyWriting_Fragment);
fragmentList.add(typing_Fragment);
fragmentList.add(studyMorePhrase_Fragment);
fragmentList.add(testing_Fragment);
fragmentList.add(bookSearch_Fragment);

.........
每次点击Drawer item(选课)时：

lcs.populateContent(bookNum, lessonNum);
LessonViewPagerAdapter mPagerAdapter = new LessonViewPagerAdapter(getFragmentManager());
mViewPager.setAdapter(mPagerAdapter);
......

private class LessonViewPagerAdapter extends FragmentStatePagerAdapter {
public LessonViewPagerAdapter(FragmentManager fm) {
super(fm);
}

@Override
public Fragment getItem(int position) {
return fragmentList.get(position);
}

@Override
public int getCount() {
return 6;//fragmentList.size();
}
}

新的Adapter，并没有生成新的(6个)Fragment, 只是使用保存在fragmentList中的Fragments, 软件能很好地运行。