Alert Dialog

An Alert dialog is a pop up on the screen which gives or asks some information from the user. like the one given below

<meta http-equiv="content-type" content="text/html; charset=utf-8">Future<void> _neverSatisfied() async {
  return showDialog<void>(
    context: context,
    barrierDismissible: false, // user must tap button!
    builder: (BuildContext context) {
      return AlertDialog(
        title: Text('Rewind and remember'),
        actions: <Widget>[
          FlatButton(
            child: Text('Regret'),
            onPressed: () {
              Navigator.of(context).pop();
            },
          ),
        ],
      );
    },
  );
}

Flat Button

A Flat Button can be customized with an outline or a fill or even navigate to another page.

<meta http-equiv="content-type" content="text/html; charset=utf-8">FlatButton(
    onPressed: (){
    //Here comes the onPressed Code
    },
    child: //here comes the child it can be a text or even a another widget
),

App Bar

An App bar is a top portion in your screen which things like a top bar and can contain icons, menus, and whatnot

To create an App bar use this code

appBar: AppBar(
    title: const Text(
    'App Bar',
    ),
),