Flutter/UI/Button

body内にボタンを表示

body: Center(
       child: Column(
         mainAxisAlignment: MainAxisAlignment.center,
         children: <Widget>[
           Text(
             'hello',
           ),
           RaisedButton(
             child: Text('button1'),
             onPressed: () {
               // ボタン処理
             },
           ),
         ],
       ),
),

画面右下にボタンを表示

floatingActionButtonをScaffoldの項目に追加

return Scaffold(
     appBar: AppBar(
       title: Text(widget.title),
     ),
     body: Center(
       child: Column(
         mainAxisAlignment: MainAxisAlignment.center,
         children: <Widget>[
           Text(
             'hello',
           ),
         ],
       ),
     ),
     floatingActionButton: FloatingActionButton(
       onPressed:() {
              // ボタン処理
            },
       tooltip: 'Increment',
       child: Icon(Icons.add),
     ),
);