Why is an error generated when I declare a nested static Fragment class as private?

Question

I created an activity for my Android project and decided to change the access modifier for the nested Fragment class to "private", I figured that the outer Activity class is the only element of my program that needs to access this Fragment class. When I go to build in eclipse I receive the following error message "This Fragment class should be public ....", why is this error generated?

"`private static class PlaceholderFragment extends ListFragment {...."`

Answer 1

因为Android框架可能需要通过反射来调用Fragment的no-arg构造函数，如果该类是私有的，它就无法执行。