ShowDialog来自initState Flutter中调用的一个异步函数

Question

我正在编写代码来检查用户是否安装了正确的应用程序版本，否则将他重定向到Playstore以更新应用程序。

我使用firebase_remote_config来存储变量，以保留我希望用户使用的最小版本。

Package_info获取用户app信息。

url_launcher从应用程序重定向到playstore

我的问题是，我检查版本的方法是异步的，它需要在进入应用程序的第一个屏幕之前向用户显示对话框。

我在initState中执行它。但是build方法在我的异步函数结束之前构建第一个屏幕，并且我的ShowDialog没有渲染。

我如何在第一次构建之前首先显示我的异步函数的结果?

这是我的代码经过一些更新，但不显示导航到另一个屏幕之前的对话框

class Splashscreen extends StatefulWidget {

@override
_SplashscreenState createState() => _SplashscreenState();
}
class _SplashscreenState extends State<Splashscreen> {
@override
void initState() {
super.initState();
SchedulerBinding.instance.addPostFrameCallback((_) {
versionCheck(context);
});
}

Future versionCheck(context) async {
//Get Current installed version of app
final PackageInfo info = await PackageInfo.fromPlatform();
double currentVersion =
double.parse(info.version.trim().replaceAll(".", ""));
//Get Latest version info from firebase config
final RemoteConfig remoteConfig = await RemoteConfig.instance;
try {
// Using default duration to force fetching from remote server.
await remoteConfig.fetch(expiration: const Duration(seconds: 10));
await remoteConfig.activateFetched();
remoteConfig.getString('force_update_current_version');
double nVersion = double.parse(remoteConfig
.getString('force_update_current_version')
.trim()
.replaceAll(".", ""));
if(nVersion > currentVersion){
showDialog(
context: context,
builder: (_) => new AlertDialog(
title: new Text("You are not up to date"),
content: new Text("To use the application, you must update it"),
actions: <Widget>[
FlatButton(
child: Text('Go To Store'),
onPressed: () {
_launchURL(PLAY_STORE_URL);
},
)
],
)
);
}
} on FetchThrottledException catch (exception) {
print(exception);
} catch (exception) {
print(
'Unable to fetch remote config. Cached or default values will be used');
}
}

_launchURL(String url) async {
if (await canLaunch(url)) {
await launch(url);
} else {
throw 'Could not launch $url';
}
}


@override
Widget build(BuildContext context) {
return ScopedModelDescendant<UserModel>(builder: (context, child, model) {
return new SplashScreen(
seconds: 4,
navigateAfterSeconds:
model.isSignedIn ? HomePage() : SuggestLoginPage(),
image: new  Image.asset('assets/images/logo.png', fit: BoxFit.cover,),
backgroundColor: Color(0xff131921),
styleTextUnderTheLoader: new TextStyle( ),
photoSize: 100.0,

loaderColor: Colors.white
);
});
}
}

Answer 1

在应用程序第一次运行时创建一个启动画面，显示您的徽标或加载器

class SplashScreen extends StatefulWidget {
@override
_SplashScreenState createState() => _SplashScreenState();
}

cclass _SplashScreenState extends State<SplashScreen> {
@override
void initState() {
super.initState();
SchedulerBinding.instance.addPostFrameCallback((_) {
checkVersion();
});
}
Future checkVersion({String payload}) async {
var upToDate = false;
if (upToDate)
print('Navigate to Home');
else
return showDialog(
context: context,
builder: (_) => new AlertDialog(
title: new Text("You are not up to date"),
content: new Text("To use the application, you must update it"),
actions: <Widget>[
FlatButton(
child: Text('Go To Store'),
onPressed: () {
//navigate to store
},
)
],
)
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Colors.white,
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
"Stackowerflow",
style: TextStyle(
fontFamily: "Josefin",
fontSize: 55,
fontWeight: FontWeight.bold,
color: Colors.grey,
),
),
Image.asset('assets/images/splash.gif',width: 500,
height: 500,),
],
),
),
);
}

不要忘记在main.dart中运行这个闪屏

现在你可以把你的函数添加到checkVersion如果是最新的，那么返回home或者你想重定向的任何东西如果不是，那么重定向到商店