How Can I get a page transition programmatically after getting biometric authentication result true without any button press event in advance? - flutter

Question

I am creating an app in flutter implemented local_auth plugin.
I would like this flow below.
1.background page(BioAuthScreen) is up
2.simultaneously authenticateWithBiometrics dialog is up.
3.if result is true, get the page transition to HomeScreen(folloing comment // 3),
if I pressed the button (the code following comment // 4),
It's work.(up the dialog, if the result is true, the page transition OK).
But I wouldn't like button in background page.
if I put the code following comment // 1 or // 2, the dialog is up, if the result is true,
but background page still there. there's no error.
This is the code.
class BioAuthScreen extends StatefulWidget {
BioAuthScreen({Key key, this.initFlag = false}) : super(key: key);
final bool initFlag;
#override
_BioAuthScreenState createState() => _BioAuthScreenState();
}
class _BioAuthScreenState extends State<BioAuthScreen>
with WidgetsBindingObserver {
final LocalAuthentication _localAuthentication = LocalAuthentication();
bool _isAuthenticated;
#override
void initState() {
super.initState();
WidgetsBinding.instance.addObserver(this);
// 1
/* WidgetsBinding.instance.addPostFrameCallback((_) async {
await _getAuthenticated();
}); */
}
#override
void didChangeDependencies() async {
super.didChangeDependencies();
await Future.delayed(const Duration(milliseconds: 700));
// 2
// await _getAuthenticated();
}
#override
void dispose() {
WidgetsBinding.instance.removeObserver(this);
super.dispose();
}
#override
void didChangeAppLifecycleState(AppLifecycleState state) {
super.didChangeAppLifecycleState(state);
if (state == AppLifecycleState.inactive) {
} else if (state == AppLifecycleState.paused) {
Navigator.pushReplacement(
context, MaterialPageRoute(builder: (context) => BioAuthScreen()));
} else if (state == AppLifecycleState.resumed) {}
}
Future<List<BiometricType>> _getListOfBiometricTypes() async {
List<BiometricType> listOfBiometrics;
try {
listOfBiometrics = await _localAuthentication.getAvailableBiometrics();
} on PlatformException catch (e) {
print(e);
}
print(listOfBiometrics);
return listOfBiometrics;
}
Future<void> _getAuthenticated() async {
var result = false;
var availableBiometricTypes = await _getListOfBiometricTypes();
try {
if (availableBiometricTypes.contains(BiometricType.face) ||
availableBiometricTypes.contains(BiometricType.fingerprint)) {
result = await _localAuthentication.authenticateWithBiometrics(
localizedReason: '生体認証',
useErrorDialogs: true,
stickyAuth: false,
);
}
} on PlatformException catch (e) {
print(e);
}
if (!mounted) return;
print('result: $result');
// 3
if (result) {
await Navigator.pushNamed(context, Constants.homeScreenRoute);
}
}
#override
Widget build(BuildContext context) {
final screenWidth = MediaQuery.of(context).size.width;
final screenHeight = MediaQuery.of(context).size.height;
return SafeArea(
child: Scaffold(
body: FractionallySizedBox(
widthFactor: 1,
heightFactor: 1,
child: DecoratedBox(
decoration: const BoxDecoration(
color: CustomColors.midBlue,
),
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
const Padding(
padding: EdgeInsets.all(40.0),
),
// Title
AuthTitleComponent(),
SizedBox(height: screenHeight * 0.28),
ButtonTheme(
minWidth:
screenWidth > 600 ? screenWidth * 0.6 : screenWidth * 0.7,
height: 45,
child: RaisedButton(
elevation: 3.0,
color: CustomColors.lightBlue,
// 4
onPressed: () async {
await _getAuthenticated();
},
child: Text(
'BioMetricAuthLogin',
style: Theme.of(context)
.textTheme
.headline2
.copyWith(color: Colors.white),
),
),
),
],
),
),
),
),
);
}
}

Answer 1

I was able to replicate the reported behavior using the code snippets you've provided. LocalAuthentication.authenticate catches PlatformException when biometric auth is called through didChangeAppLifecycleState.
This seems to be a bug and I've filed this as an issue here. I'm using Flutter version 2.0.0 stable and local_auth 1.1.0 for reference.