dart

问题 In my program, this error comes in my laptop only. I typed the exact code as of the tutorial, but in tutorial, it is working fine, and i am getting this error - Closure call with mismatched arguments: function '[]' Receiver: Closure: () => Map<String, dynamic> from Function 'data':. Tried calling: []("message") Found: []() => Map<String, dynamic> This is my code, in which error is coming. If you want full details of functions, you can comment it out, and i will provide you the same in

问题 I have a dashboard , represented by grid, that supposed to delete item on long press event (using flutter_bloc), but it deletes last item instead of selected. All debug prints show, that needed element actually removed from list, but view layer still keeps it. My build function code: Widget build(BuildContext context) { double pyxelRatio = MediaQuery.of(context).devicePixelRatio; double width = MediaQuery.of(context).size.width * pyxelRatio; return BlocProvider( bloc: _bloc, child:

问题 I have a dashboard , represented by grid, that supposed to delete item on long press event (using flutter_bloc), but it deletes last item instead of selected. All debug prints show, that needed element actually removed from list, but view layer still keeps it. My build function code: Widget build(BuildContext context) { double pyxelRatio = MediaQuery.of(context).devicePixelRatio; double width = MediaQuery.of(context).size.width * pyxelRatio; return BlocProvider( bloc: _bloc, child:

问题 class _NavBarState extends State<NavBar> { int _currentIndex = 0; final List<Widget> _children = [ HomeScreen(), SignUpScreen(), ForgetPassword(), LoginScreen(), ]; void onTappedBar(int index) { setState(() { _currentIndex = index; }); } @override Widget build(BuildContext context) { return Scaffold( body: _children[_currentIndex], bottomNavigationBar: BottomNavigationBar( onTap: onTappedBar, currentIndex: _currentIndex, type: BottomNavigationBarType.fixed, items: [ BottomNavigationBarItem(

问题 I am getting this error in Dart: "Missing concrete implementation of "state.build"" The first method is the following: class MyHomePage extends StatefulWidget { // String titleInput; // String amountInput; @override MyHomePageState createState() => MyHomePageState(); } class MyHomePageState extends State<MyHomePage> { final List<Transaction> _userTransactions = [ // Transaction( // id: "t1", // title: "New Shoes", // amount: 69.99, // date: DateTime.now(), // ), // Transaction( // id: "t2", /

问题 I have a big problem. If I want to encrypt my video file, my application is freezing until that method finishing. But there is no error. How can I code my application does not freeze. thanks. Future sifrele() async { String realPath = "/storage/emulated/0/Android/data/com.android.xxxx/files"; var crypt = AesCrypt('sefa'); try { crypt.setOverwriteMode(AesCryptOwMode.on); String encFilepaths = await crypt.encryptFile( realPath + '/WhatCarCanYouGetForAGrand.mp4', realPath + '/video.mp4.aes');

问题 I am getting this error in Dart: "Missing concrete implementation of "state.build"" The first method is the following: class MyHomePage extends StatefulWidget { // String titleInput; // String amountInput; @override MyHomePageState createState() => MyHomePageState(); } class MyHomePageState extends State<MyHomePage> { final List<Transaction> _userTransactions = [ // Transaction( // id: "t1", // title: "New Shoes", // amount: 69.99, // date: DateTime.now(), // ), // Transaction( // id: "t2", /

问题 i hope everyone is safe i am using flutter,and i want to calculate distance between two locations so i have installed geolocator 6.0.0+1 from pub.dev here, with that i can find the location of user but i cannot use the inbuilt method called ** distanceBetween()** which is used to calculate the distance between two latitudes and longitudes, it shows me a error whis says **The method 'distanceBetween' isn't defined for the type '_RegisterState'. ** i have used the method as shown in the

问题 What is the difference between Future and Completer ? I am not looking for documentation part on either, instead I would like to see an example showing the real difference between the two. 回答1: Completer is a helper class for creating Future whereas Future is a Type . All asynchronous functions return Future, but with Completer it is possible to create synchronous function that returns Future as well. Also you can chain that synch functions with then etc. Completer object is one way process,

问题 When I run: $ flutter build web I'm getting the error Missing index.html. The flutter app is displaying in the browser, but in VS Code it reads "No Device." How can I debug, or fix this problem? 回答1: It would help to see the output of your flutter doctor, but I am guessing that your project is not configured for web. If you haven't already, you need to switch to the flutter beta channel like so: $ flutter channel beta $ flutter upgrade $ flutter config --enable-web At this point, running