How to write a double back button pressed to exit app using flutter

Question

I\'m new to flutter, and I saw many android apps can exit when double press back button.

The first time press back button, app shows a toast\"press again to exit app

Answer 1

If you want a snackbar you should provide a scaffold key as it's related to a scaffold, so this key should make the trick of calling a snackbar outside of it's scaffold parent.

Here is a solution :

class Home extends StatelessWidget {

  final GlobalKey _scaffoldKey = new GlobalKey();

  @override
  Widget build(BuildContext context) {
  return WillPopScope(
    onWillPop: () async{
        DateTime initTime = DateTime.now();
        popped +=1;
        if(popped>=2) return true;
        await _scaffoldKey.currentState.showSnackBar(
        SnackBar(
            behavior: SnackBarBehavior.floating,
            content: Text('Tap one more time to exit.',textAlign: TextAlign.center,),
            duration: Duration(seconds: 2),
        )).closed;

        // if timer is > 2 seconds reset popped counter
        if(DateTime.now().difference(initTime)>=Duration(seconds: 2)) {
        popped = 0;
        }
        return false;
        },
    child: Scaffold(
        key: _scaffoldKey,
        appBar: AppBar(title : Text("Demo")),
        body: Text("body")
    );
  )
}