adding floating action button flutter code example

Example 1: set floating action button invisible flutter

floatingActionButton: new Visibility( 
        visible: false,
        child: new FloatingActionButton(
          onPressed: _incrementCounter,
          tooltip: 'Increment',
          child: new Icon(Icons.add),
        ),
      ),

Example 2: floatingactionbutton flutter

Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: const Text('Floating Action Button'),
    ),
    body: Center(
      child: const Text('Press the button below!')
    ),
    floatingActionButton: FloatingActionButton(
      onPressed: () {
        // Add your onPressed code here!
      },
      child: Icon(Icons.navigation),
      backgroundColor: Colors.green,
    ),
  );
}