Ẩn keyboard trong flutter

FocusScope.of(context).requestFocus(new FocusNode());

Check the device in Flutter

f (Platform.isIOS) {
  print('is a IOS');
} else if (Platform.isAndroid) {
  print('is a Andriod');
} 

Copy text in flutter

Clipboard.setData(new ClipboardData(text: text));

a snackbar in flutter

final snackBar = SnackBar(content: Text('Yay! A SnackBar!'));

// Find the Scaffold in the widget tree and use it to show a SnackBar.
Scaffold.of(context).showSnackBar(snackBar);