preferredsizewidget appbar flutter code example

Example 1: height appbar flutter

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

Example 2: flutter appbar widget

Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('AppBar Title', textAlign: TextAlign.center),
      ),