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flutter appbar width

appBar: AppBar(
          title: Text('AppBar Height'),
          toolbarHeight: 100.0, // double
          automaticallyImplyLeading: false, // hides back button
        ),

height appbar flutter

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

flutter how to find the appbar size

var height = AppBar().preferredSize.height;

get appbar size flutter

var height = AppBar().preferredSize.height;

flutter appbar default size

Flutter appbar default size : 56 logical pixels