Flutter:为iOS和Android添加应用程序更新对话框

Question

我目前正在开发通知功能，因此当有新的更新可用时，用户会收到一个对话框，他可以在其中选择是否更新。我用Firebase Remote Config来做这件事，在那里我有一个名为"；force_update_current_version"；然后我添加版本的值进行检查。但我确实有以下错误。

谢谢你的帮助，祝你在新的一年里有一个健康的开始。

Main.dart代码

import 'checkUpdate.dart';
@override
void initState() {
try {
versionCheck(**context**);
} catch (e) {
print(e);
}
**super**.initState();
}

上下文错误：未定义的名称"context"。请尝试将名称更正为已定义的名称，或定义名称。

super错误："super"调用的上下文无效。

checkUpdate.dart代码

import 'package:flutter/material.dart';
import 'dart:io';
import 'package:firebase_remote_config/firebase_remote_config.dart';
import 'package:url_launcher/url_launcher.dart';
import 'package:package_info/package_info.dart';
import 'package:flutter/cupertino.dart';
const APP_STORE_URL = 'https://apps.apple.com/us/app/appname/idAPP-ID';
const PLAY_STORE_URL =
'https://play.google.com/store/apps/details?id=APP-ID';
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: 0));
await remoteConfig.activateFetched();
remoteConfig.getString('force_update_current_version');
double newVersion = double.parse(remoteConfig
.getString('force_update_current_version')
.trim()
.replaceAll(".", ""));
if (newVersion > currentVersion) {
_showVersionDialog(context);
}
} on FetchThrottledException catch (exception) {
// Fetch throttled.
print(exception);
} catch (exception) {
print('Unable to fetch remote config. Cached or default values will be '
'used');
}
}
//Show Dialog to force user to update
_showVersionDialog(context) async {
await showDialog<String>(
context: context,
barrierDismissible: false,
builder: (BuildContext context) {
String title = "New Update Available";
String message =
"There is a newer version of app available please update it now.";
String btnLabel = "Update Now";
String btnLabelCancel = "Later";
return Platform.isIOS
? new CupertinoAlertDialog(
title: Text(title),
content: Text(message),
actions: <Widget>[
FlatButton(
child: Text(btnLabel),
onPressed: () => _launchURL(**Config**.APP_STORE_URL),
),
FlatButton(
child: Text(btnLabelCancel),
onPressed: () => Navigator.pop(context),
),
],
)
: new AlertDialog(
title: Text(title),
content: Text(message),
actions: <Widget>[
FlatButton(
child: Text(btnLabel),
onPressed: () => _launchURL(**Config**.PLAY_STORE_URL),
),
FlatButton(
child: Text(btnLabelCancel),
onPressed: () => Navigator.pop(context),
),
],
);
},
);
}
_launchURL(String url) async {
if (await canLaunch(url)) {
await launch(url);
} else {
throw 'Could not launch $url';
}
}

App and Play Store的配置错误：未定义的名称"Config"。请尝试将名称更正为已定义的名称，或定义名称。

Answer 1

1. 在checkUpdate.dart中，我们需要导入公开RemoteConfig类的firebase_remote_config包：

import 'package:firebase_remote_config/firebase_remote_config.dart';

请确保先安装它。

2. versionCheck()函数应从StatefulWidget调用，因此，调用它的好地方应该在第一个屏幕Widget内，例如：

class FirstScreen extends StatefulWidget {
const FirstScreen({ Key key }) : super(key: key);
@override
_FirstScreenState createState() => _FirstScreenState();
}
class _FirstScreenState extends State<FirstScreen> {
@override
void initState() {
super.initState();
WidgetsBinding.instance
.addPostFrameCallback((_) => versionCheck(context));
}
@override
Widget build(BuildContext context) {
return Container(color: const Color(0xFFFFE306));
}
}