我正在颤抖地调用RESFUL NODE API，以获取有关向服务器提供电子邮件和密码的一些数据，并且它运行良好。我没有将这些数据存储在任何数据库中，因为我是从api中的某个地方抓取数据并将其发送回用户的。现在，我想在数据更改时通知用户。我所苦苦挣扎的是，如何知道是否以JSON的形式更改了或不更改，因为由于异步行为，我的api不管数据是否更改，其api都会以不同的顺序返回数据。那么，如何在数据更改时通知我的用户？这是我的flutter应用程序代码：
class UserPage extends StatefulWidget{
Map formData;
UserPage(formData){
this.formData = formData;
}
@override
State<StatefulWidget> createState() {
// TODO: implement createState
return _UserPageState();
}
}
class _UserPageState extends State<UserPage> {
List AssignmentData;
List<dynamic> newData;
String LoginFailedMsg ='';
FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin;
void ValidateResponse() async{
await http.post("xxxxxxxxxxxxxxxxxxxxxx",
headers: {
'Content-type': 'application/x-www-form-urlencoded',
'Accept' : 'application/json'
},
body: widget.formData
).then((response){
if(response.statusCode == 200){
// Login Successful
setState(() {
Fluttertoast.showToast(
msg: "Assignments Refreshed",
toastLength: Toast.LENGTH_SHORT,
gravity: ToastGravity.BOTTOM,
timeInSecForIos: 1
);
AssignmentData = json.decode(response.body);
});
}
else{
//Login Failed
setState(() {
LoginFailedMsg = response.body;
print(LoginFailedMsg);
});
}
});
}
@override
void initState() {
// TODO: implement initState
ValidateResponse();
flutterLocalNotificationsPlugin = new FlutterLocalNotificationsPlugin();
var android = new AndroidInitializationSettings('@mipmap/ic_launcer');
var ios = new IOSInitializationSettings();
var initSettings = new InitializationSettings(android, ios);
flutterLocalNotificationsPlugin.initialize(initSettings,onSelectNotification: onSelectNotification);
}
Future onSelectNotification(String payload){
debugPrint('payload:$payload');
showDialog(context: context,builder: (_)=>
new AlertDialog(
title: new Text('Notification'),
content: new Text('$payload')
)
);
}
@override
Widget build(BuildContext context){
final AssignmentImage = Image.asset('assets/assignment_img.png',fit: BoxFit.fitWidth,);
return new Scaffold(
backgroundColor: Colors.white,
appBar: new AppBar(
title: Text('Pending Assignments'),
backgroundColor: Colors.red,
actions: <Widget>[
IconButton(
icon: Icon(Icons.refresh),
color: Colors.black,
tooltip: 'Refresh Assignments',
onPressed: ValidateResponse,
)
],
),
body: new Column(
children: <Widget> [Text(LoginFailedMsg),
new Expanded(child: ListView.builder(
shrinkWrap: true,
itemCount: AssignmentData == null ? 0 : AssignmentData.length,
itemBuilder: (BuildContext context,int index) {
return new Column(
children: <Widget>[SizedBox(height: 15,),
Text(
AssignmentData[index]['course'],
style: TextStyle(
fontSize: 15,
fontWeight: FontWeight.bold
),
),
SizedBox(height: 15,),
new ListView.builder(
physics: ClampingScrollPhysics(),
shrinkWrap: true,
itemCount: AssignmentData[index]['pending_assignment'].length,
itemBuilder: (BuildContext context, int NoOfAssignments){
return new Container(
margin: const EdgeInsets.all(5.0),
padding: const EdgeInsets.all(3.0),
decoration: new BoxDecoration(
border: new Border.all(color: Colors.white12),
color: Colors.white,
boxShadow: [BoxShadow(color: Colors.black,blurRadius:4.0, ),]
),
child: new Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: [
Text(
'Name: '+AssignmentData[index]['pending_assignment'][NoOfAssignments]['name'],
style: TextStyle(
fontSize: 15,
fontStyle: FontStyle.italic,
fontWeight: FontWeight.w600
),
),
SizedBox(height: 20,),
Text(
'Due Date: '+AssignmentData[index]['pending_assignment'][NoOfAssignments]['dueDate'],
style: TextStyle(
fontSize: 15,
fontStyle: FontStyle.italic,
fontWeight: FontWeight.w500
),
),
SizedBox(height: 20,),
RaisedButton(
elevation: 6,
child: Text(
'Link: Open it',
style: TextStyle(
fontSize: 15,
fontStyle: FontStyle.italic
),
),
onPressed: () => LauncUrl(AssignmentData[index]['pending_assignment'][NoOfAssignments]['assignmentLink']).launchURL(),
)
]
)
);
}
)
]
);
})
)
]
)
);
}
}
注意：我仅初始化了通知，而未在任何地方使用它。