app bar size code example

Example 1: Flutter: Setting the height of the AppBar

appBar: PreferredSize(
  preferredSize: Size.fromHeight(100.0),
  child: AppBar(
    automaticallyImplyLeading: false, // hides leading widget
    flexibleSpace: SomeWidget(),
  )
),

Example 2: get app bar size

MediaQuery.of(context).padding.top + kToolbarHeight