You can also do the cast in Fragment.onAttach() if you want to fail quickly in the case of someone forgetting to implement the interface.
On Sun, Feb 27, 2011 at 8:59 PM, davemac <davemac...@gmail.com> wrote: > A little more formally, have your activity implement an interface such > as OnMyFragmentListener, so that the activity must implement a method > like onFragmentDidSomething(). When your fragment wants to send > something to the activity, it can do the following: > > ((OnMyFragmentListener)getActivity()).onFragmentDidSomething(...); > > You will get a ClassCastException in your fragment if the activity > didn't implement the interface, but the really nice thing is that from > your fragment's point of view, it doesn't have to care exactly which > activity did the invoking. The cast is to the interface, not the > activity. You could put the Listener interface definition inside your > fragment class to keep things nice and clean. > > - dave > > On Feb 27, 9:58 pm, Gregg Reno <gregg.r...@gmail.com> wrote: > > OK, that makes sense. Thanks Dianne. > > -Gregg > > On Feb 27, 2011 9:53 PM, "Dianne Hackborn" <hack...@android.com> wrote: > > > > > Fragment.getActivity().doSomething(). > > > > > A little more formally, define an interface for the fragment to call > back > > on > > > the activity it is running in, which each activity using that fragment > can > > > implement. > > > > > On Sun, Feb 27, 2011 at 6:39 PM, Gregg Reno <gregg.r...@gmail.com> > wrote: > > > > >> Maybe this covered earlier in this thread and I'm still not > > >> understanding it. I like the idea of a each fragment communicating > > >> back to the activity rather than to other fragments. Then the activity > > >> can decide whether it needs to send information to other fragments. > > > > >> So is there an existing mechanism for a fragment to send a message to > > >> the activity? If not, I guess I could just create a handler in the > > >> activity and pass the handler pointer to the fragment so it can send a > > >> message to the activity. > > > > >> My use case is the activity is responsible for all changes to the > > >> action bar and to showing or hiding various fragments. > > > > >> Thanks, > > >> -Gregg Reno > > > > >> -- > > >> You received this message because you are subscribed to the Google > > >> Groups "Android Developers" group. > > >> To post to this group, send email to > android-developers@googlegroups.com > > >> To unsubscribe from this group, send email to > > >> android-developers+unsubscr...@googlegroups.com > > >> For more options, visit this group at > > >>http://groups.google.com/group/android-developers?hl=en > > > > > -- > > > Dianne Hackborn > > > Android framework engineer > > > hack...@android.com > > > > > Note: please don't send private questions to me, as I don't have time > to > > > provide private support, and so won't reply to such e-mails. All such > > > questions should be posted on public forums, where I and others can see > > and > > > answer them. > > > > > > -- > You received this message because you are subscribed to the Google > Groups "Android Developers" group. > To post to this group, send email to android-developers@googlegroups.com > To unsubscribe from this group, send email to > android-developers+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/android-developers?hl=en > -- Dianne Hackborn Android framework engineer hack...@android.com Note: please don't send private questions to me, as I don't have time to provide private support, and so won't reply to such e-mails. All such questions should be posted on public forums, where I and others can see and answer them. -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
