Android-如何从Fragment访问父活动中的getter方法

Question

I have a FragmentActivity that has the values I needed to be used in a Fragment.

This is the way I do it, but I have no idea on how to access the getter in the FragmentActivity.

ItemDetailActivity

public class ItemDetailActivity extends FragmentActivity implements ActionBar.TabListener {

    public String getItem_id() {
        return item_id;
    }

    public String getUser_id() {
        return user_id;
    }
    ...
}

ItemPhotosFragment

public class ItemPhotosFragment extends Fragment {
    public ItemPhotosFragment() {
        user_id = getActivity().getUser_id();
    }
}

As you can see in the FragmentActivity, I'm implementing TabListener. So I'm want to pass the values to all tabs (fragments).

How do I do this? Is accessing from getActivity a best practice because I saw some of the solutions here suggesting it.

Answer 1

type cast into parent activity:

write this code in onActivityCreated inside your fragment not in constructor:

user_id =((ItemDetailActivity )getActivity()).getUser_id();

It's about fragment's life-cycle . onActivityCreated is called when fragment becomes part of the activity and this is the first callback from where getActivity() doesn't return null

Answer 2

There are two ways of doing this:

1. While initializing the fragment in activity, you can do myFragment.setArguments(Bundle bundle) and you can put your params in this bundle.
2. The other way is mentioned in above example.

Answer 3

Above solution provided are good. i think the same can be done in a much cleaner way using delegation pattern. Here is the link for this. http://developer.android.com/training/basics/fragments/communicating.html#DefineInterface