dart

问题 This is the error I am receiving. I tried flutter clean and changing the syntax of some lines but im new to dart and flutter so im not really sure. I reinstalled cocoa pods and ruby as well but Im receiving the same error. I also made sure to update ruby to the latest version. [!] Invalid `Podfile` file: no implicit conversion of nil into String. # from /Users/(name)/Downloads/Projects/doctor_consultation_app/ios/Podfile:57 # ------------------------------------------- # unless File.exist?

问题 I've developed a Rest API for my app. It sends to the app dates in the following format 2018-09-07T17:29:12+02:00 , where I guess +2:00 represents my timezone as part of one object. In my Flutter app, once I deserialize the received object, it substracts two hours to the actual received DateTime object. The class I'm trying to deserialize is defined as follows: import 'package:json_annotation/json_annotation.dart'; part 'evento.g.dart'; @JsonSerializable(nullable: false) class Evento { final

问题 I've developed a Rest API for my app. It sends to the app dates in the following format 2018-09-07T17:29:12+02:00 , where I guess +2:00 represents my timezone as part of one object. In my Flutter app, once I deserialize the received object, it substracts two hours to the actual received DateTime object. The class I'm trying to deserialize is defined as follows: import 'package:json_annotation/json_annotation.dart'; part 'evento.g.dart'; @JsonSerializable(nullable: false) class Evento { final

问题 This question already has answers here : How do I extend a List in Dart? (5 answers) Closed 6 years ago . Is it possible to extend a generic list with my my own specific list. Something like: class Tweets<Tweet> extends List<T> And how would a constructor look like, if I wanted to construct with my own constructor: Datasource datasource = new Datasource('http://search.twitter.com/search.json'); Tweets tweets = new Tweets<Tweet>(datasource); And how to call the parent constructor then, as this

问题 This question already has answers here : How do I extend a List in Dart? (5 answers) Closed 6 years ago . Is it possible to extend a generic list with my my own specific list. Something like: class Tweets<Tweet> extends List<T> And how would a constructor look like, if I wanted to construct with my own constructor: Datasource datasource = new Datasource('http://search.twitter.com/search.json'); Tweets tweets = new Tweets<Tweet>(datasource); And how to call the parent constructor then, as this

问题 This forEach works just fine var newMarkers = new List<Marker>(); providers.forEach((p) { var marker = markerFrom(p); newMarkers.add(marker); print("got one"); }); _markers = newMarkers; but this map doesn't ever get called when placed in the exact same place as the forEach : _markers = providers.map((p) => markerFrom(p)); Additionally, this is the markerFrom method: Marker markerFrom(FoodProvider provider) { var marker = new Marker(new MarkerOptions() ..map = _map ..position = new LatLng

问题 Consider the following code: StreamBuilder<QuerySnapshot> _createDataStream(){ return StreamBuilder<QuerySnapshot>( stream: Firestore.instance.collection("data").limit.(_myLimit).snapshots(), builder: (context, snapshot){ return Text(_myLimit.toString); } ); } I want that the StreamBuilder refreshes when the _myLimit Variable changes. It's possible doing it like this: void _incrementLimit(){ setState(() =>_myLimit++); } My Question is if there is another, faster way, except the setState((){})

问题 Consider the following code: StreamBuilder<QuerySnapshot> _createDataStream(){ return StreamBuilder<QuerySnapshot>( stream: Firestore.instance.collection("data").limit.(_myLimit).snapshots(), builder: (context, snapshot){ return Text(_myLimit.toString); } ); } I want that the StreamBuilder refreshes when the _myLimit Variable changes. It's possible doing it like this: void _incrementLimit(){ setState(() =>_myLimit++); } My Question is if there is another, faster way, except the setState((){})

问题 I'm trying to add multiple screens to my flutter app but can't get it to work. And there are no tutorials/ guides to do this. Does anyone have an example on how to accomplish this. Thanks in advance. 回答1: You can use the Navigator It's use is demonstrated in the Stocks example in https://github.com/flutter/flutter/blob/c8447c91a93cdee28eddb01ee3ace27b9362220f/packages/flutter/test/widgets/navigator_test.dart Navigator.pushNamed(context, '/second'); ... onTap: () => Navigator.pop(context),

问题 I have bound my flutter-iOS app to firebase and i'm also using firebase-messaging and cloud functions for sending notifications via subscribing to topics, i'm using the APNs push notifications key of apple developer account. when i use the option runner>flutter run main.dart in release mode to build my app on my phone, fcm notifications doesn't work anymore, while it works in development mode, anyone can help me fix this? this is my index.json code: const functions = require('firebase