fragment.md

DialogFragment/Fragment

DialogFragment/Fragment lifecycle

• onAttach()
• onCreate()
• onCreateDialog()
  • DialogFragment only
• onCreateView()
• onViewStateRestored()
• onStart()
• onResume()
• onDismiss()
  • DialogFragment only
• onPause()
• onSaveInstanceState()
• onStop()
• onDestroyView()
• onDestroy()
• onDetach()

Note that onRestoreInstanceState() does not exist in Fragment(s).

DialogFragment listener

• DialogFragment.dialog.setOnShowListener()

Fragment listener

• onConfigurationChanged()

FragmentContainerView

is a container to which multiple fragments can be added.

View in Fragment

• is the root of a fragment's layout.
• is created by onCreateView().
• is detached from a fragment by onDestroyView().

FragmentManager

FragmentManager.findFragmentById(...)

• gets fragments that provide a UI in the activity layout.

FragmentManager.findFragmentByTag(...)

• gets fragments whether or not they provide a UI in the activity layout.
• Despite the documentation, I have found that findFragmentByTag() can get fragments that are detached and not in the back stack.

FragmentManager.getFragments()

• does not include fragments that are detached.
• https://developer.android.com/guide/components/fragments#Managing

FragmentActivity.getSupportFragmentManager()

• returns a FragmentManager associated with the activity.
  • which can place a fragment in <androidx.fragment.app.FragmentContainerView> in the activity's layout file.
• FragmentActivity is namely an Activity.

Fragment.getParentFragmentManager()

• returns a FragmentManager associated with the fragment's activity.
  • which can place a child fragment in <androidx.fragment.app.FragmentContainerView> in the activity's layout file.

Fragment.getChildFragmentManager()

• returns a private FragmentManager associated with the fragment.
  • which can place a child fragment in <androidx.fragment.app.FragmentContainerView> in the fragment's layout file.

Fragment back stack or simply back stack

• is NOT a collection of Fragment(s) but a collection of FragmentTransaction(s).
• is managed by the parent activity.
  • https://developer.android.com/guide/components/fragments#Transactions
• Fragment = childFragmentManager = fragment back stack = 1 : 1 : 1
• In a Fragment, the following removes all the existing fragments, and then add a FragmentA

fragmentManager.commit {
    replace(FragmentA)
}

FragmentManager

• When FragmentManager.popBackStack() is called, the following happens in sequence.
  1. FragmentManager.primaryNavigationFragment.childFragmentManager.popBackStack() is called.
  2. If the above returns false, FragmentActivity.supportFragmentManager.popBackStack() is called.
  3. If the above returns false, the app quits.

FragmentTransaction

FragmentTransaction.remove(...)

• calls Fragment.onDestroy() and Fragment.onDetach() if FragmentTransaction.addToBackStack(...) is NOT called in the same transaction.
• calls up to Fragment.onDestroyView() if FragmentTransaction.addToBackStack(...) is called in the same transaction.

FragmentTransaction.addToBackStack()

• adds a FragmentTransaction in the back stack instead of adding an Fragment in the back stack.
• will run the sequence of the operations of the transaction in the reverse order when the Up or Back button is pressed.

FragmentTransaction.attach(...)

• attaches a fragment to the UI.
• calls Fragment.onCreateView().

FragmentTransaction.detach(...)

• detaches a fragment to the UI.
• calls Fragment.onDestroyView().