When is a Fragment created in the Activity's onCreate accessible?

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http://stackoverflow.com – I am creating & attaching a fragment in my activity onCreate method : FragmentManager fragmentManager = getSupportFragmentManager(); FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction(); mSlateFragment = new SlateFragment(); fragmentTransaction.add(R.id.root, mSlateFragment); fragmentTransaction.commit(); After that, I also setup my seekbars to their default values, to do this, I have to access the mSlateFragment object that has just been created : mSlateFragment.mSlate.setProperty(33); this call however provokes a crash of my app. making this call in onStart (HowTos)