add v4 fragment support

[dlemures]

It failed, could you fix it?

[yaming116]

@dlemures dependency to be optional build failed,i need remove it?

[dlemures]

It seems that none of the previous solutions work:

• compile dependency -> We don't want to include support library in every app (see https://github.com/robolectric/robolectric/issues/1369)
• optional / provided dependency -> It doesn't work in apps where the support library is not included, because Dart uses android.support.v4.app.Fragment

You will need to create a new sibling module (dart-support?) so if the app uses support fragment, users will need to include dart-support instead of dart: compile 'com.f2prateek.dart:dart-support:XXX'

One possible approach:

• Create class com.f2prateek.dart.support.Dart inside the new module dart-support
• com.f2prateek.dart.support.Dart extends from com.f2prateek.dart.Dart and adds the methods for support fragments
• for the enum, you can create a interface with the method public Object getExtra(Object source, String key) and both Dart classes define an enum which extends it. (in case we want to keep the enum approach...)

What do you think? @yaming116 @stephanenicolas

[dlemures]

I think it is a bit overkilling to make so many changes for a shortcut. From the support fragment we can always use:

Dart.inject(this, getArguments)