Useful design patterns for working with FragmentManager on Android

Question

When working with fragments, I have been using a class composed of static methods that define actions on fragments. For any given project, I might have a class called FragmentActions, which contains methods similar to the following:

public static void showDeviceFragment(FragmentManager man){
 String tag = AllDevicesFragment.getFragmentTag();
 AllDevicesFragment fragment = (AllDevicesFragment)man.findFragmentByTag(tag);
 if(fragment == null){
 fragment = new AllDevicesFragment();
 }
 FragmentTransaction t = man.beginTransaction();
 t.add(R.id.main_frame, fragment, tag);
 t.commit();
}

I'll usually have one method per application screen. I do something like this when I work with small local databases (usually SQLite) so I applied it to fragments, which seem to have a similar workflow; I'm not married to it though.

How have you organized your applications to interface with the Fragments API, and what (if any) design patterns do you think apply do this?

• Piotr: Why do you have one class responsible for showing all kind of fragment? Shouldn't it be a static method inside Fragment class inside?

Answer 1

The accepted pattern is to have a factory method inside your custom fragment class (typically called newInstance() but hey dealer's choice). So your fragment class should look something like this:

public class MyFragment extends Fragment
{
 public static MyFragment newInstance()
 {
 MyFragment newFragment = new MyFragment();
 // add any bundle arguments here if needed
 return newFragment;
 }
 // rest of fragment class...
}

Then, when you create a fragment and add it to the backstack, instead of saying:

MyFragment fragment = new MyFragment();

You can use the factory method instead of the 'new' keyword.