dart | 易学教程

Flutter ScreenState Dispose method exception

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问题 When I try to navigate away from one screen to another in flutter, I am getting an exception stating that the ScreenState that I am changing away from does not call super.dispose() in its dispose method. However, the overriden dispose method clearly calls super.dispose() . Attached are the relevant class and the logs. Any help would be greatly appreciated. Class: import 'package:flutter/material.dart'; import 'package:flutter/widgets.dart'; import 'package:kickit/screens/feed_screen.dart';

How to recognize dynamic keys while using JsonSerializable in Flutter?

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问题 Let's assume, until recently, I was getting the bellow Json response { "AA": { "product": { "id":"111", "type":"C" } } } And, I have written the bellow, model.dart to convert from json to object model.dart @JsonSerializable() class ResponseGate { @JsonKey(name: "AA") AA aa; ResponseGate({this.aa}); factory ResponseGate.fromJson(Map<String, dynamic> json) => _$ResponseGateFromJson(json); } @JsonSerializable() class AA { @JsonKey(name: "product") Product product; AA(this.product); factory AA

StreamProvider not updating List

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问题 I have a StreamController which should update a List but it doesn't happen: class LocationService { StreamController<List<bg.Geofence>> geofencesController = StreamController<List<bg.Geofence>>(); updateGeofences(geofences) { logger.i('listing geofences $geofences'); geofencesController.add(List.from(list)); } } When I call updateGeofences I got many geofences in logs. But widget are not rebuilt! Here is my providers setup: class MyApp extends StatelessWidget { @override Widget build

Stack position not accurate

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问题 I want to add red blinking dot on the container when it is tapped, but the dot position is not accurate. How to fix? MyApp import 'package:flutter/material.dart'; import 'blinking_dot.dart'; void main() => runApp(MyApp()); class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Flutter Demo', theme: ThemeData( primarySwatch: Colors.blue, ), home: MyHomePage(title: 'Flutter Demo Home Page'), ); } } class MyHomePage extends StatefulWidget

Flutter pdf generation too slow with image

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问题 im working on a pdf generator app in flutter, but when i want to add an image to the pdf, it takes too long also i wanted to know how it is possible to add multiple images. Im using 3 libraries, image picker - pdf - printing here is my code: Future getImage() async { var image = await ImagePicker.pickImage(source: ImageSource.gallery); final tempDir = await getTemporaryDirectory(); final path = tempDir.path; int rand = new Math.Random().nextInt(10000000); imge.Image imagee = imge.decodeImage

How to highlight text of specific letters in Flutter?

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问题 I am trying to highlight two letters 'Rs' in specific, any special characters like '% or !' and numbers like 1234 etc. I already have half my answer from this question - How to highlight text in Flutter? but i'm not sure how to edit it for letters as I am new to RegEx? import 'package:flutter/material.dart'; void main() => runApp(MyApp()); class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Flutter Demo', debugShowCheckedModeBanner:

在应用开发中，我为什么选择 Flutter 而不是 React Native ？

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Python实战社群 Java实战社群长按识别下方二维码，按需求添加扫码关注添加客服进Python社群▲ 扫码关注添加客服进Java社群 ▲ 作者 | Sanket Doshi 译者 | 核子可乐策划 | 李俊辰来源丨前端之巅（ID：frontshow）作为一位开发人员，我想在本文中与大家聊聊跨平台开发领域的两大核心选项——Flutter 与 React Native 框架，并介绍我自己为什么更偏爱 Flutter。时至今日，React Native 与 Flutter 已经成为两大领先跨平台开发框架。这两套框架之所以极具人气，是因为它们不仅能够简化开发、代码重用等常规工作，同时提供高度原生化的界面外观以及强有力的技术支持。虽然二者的价值主张相似，但有很多方面仍存在不少差别。双方都能帮助开发人员更快、更轻松地构建并发布应用程序，但作为成熟度更高的框架选项，React Native 的社区规模更大；而 Flutter 则提供更多内置工具，可帮助用户减少对第三方工具的依赖。我之所以更倾向于 Flutter，当然是觉得它在很多方面比 React Native 的表现更好。在解释具体原因之前，咱们不妨先聊聊这些框架的基本情况，以及它们分别适合处理的应用项目类型。 React Native React Native 是由 Facebook 公司于 2015

get String from nested Map in dart

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问题 My Map: {Info: {name: Austin, Username: austinr}} I'm using this line to get the myName variable to be set as "Austin" String myName = map["name"] as String; However.. this line seems to set the string "myName" to null. just looking for a way to extract my name and Username from the map Thanks 回答1: I am able to run the following code successfully. var map = {"Info":{"name": "Austin", "Username": "austinr"}}; String myString = map["Info"]["name"] as String; print(myString); The output is

why flutter has stopped to launch my app on ios

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问题 All of a sudden I cant run my flutter app that uses firebase. Apparently there's a problem with the pod install process, some dependency incompatibility. Given the fact that I haven't changed anything in the yaml file and the app worked perfectly this morning, I assume is some problem with the tools and not with my source code. The problem appeared after a flutter plugin update, but I don't know if the two things are related. This is the build output: Launching lib/main.dart on iPhone XR in

Why List() constructor is not accessible in Dart's null safety?

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问题 With NNBD, you're not allowed to initialise the list using the default constructor: List<int> foo = List(); // Compile time error However, you can still do: List<int> foo = []; // No error So, what's the difference between the two? Either both of them should show the error or none of them. 回答1: The List constructor had two uses: new List() to create an empty growable list, equivalent to [] . new List(n) to create a fixed-length list of length n filled with null values With null safety, the