dart

问题 I can do region blocks in android studio like this. //region Description Your code here //endregion But how to the same with flutter ? 回答1: In the IntelliJ or Android Studio IDE, you can use REGION folding as written in your question, works fine. REGION folding also works with //#region (both tested in the IntelliJ IDE CE 2019.3.3 and Android Studio IDE 3.4.1): // with and without spaces after double slashes //#region Description Your code here //#endregion // #region Description Your code

问题 I have some code and when I run it produces an error, saying: NoSuchMethod: the method 'XYZ' was called on null What does that mean and how do I fix it? 回答1: Why do I get this error? Example As a real world comparison, what just happened is this conversation: Hey, how much gas is left in the tank of the car? What are you talking about, we don't have a car. That is exactly what is happening in your program. You wanted to call a function like _car.getGasLevel(); but there is no car , the

问题 I have some code and when I run it produces an error, saying: NoSuchMethod: the method 'XYZ' was called on null What does that mean and how do I fix it? 回答1: Why do I get this error? Example As a real world comparison, what just happened is this conversation: Hey, how much gas is left in the tank of the car? What are you talking about, we don't have a car. That is exactly what is happening in your program. You wanted to call a function like _car.getGasLevel(); but there is no car , the

问题 I want to group all list tiles according dates which are same and show them under sticky bar as shown in the picture. I get the dates from sqlite database. The data from the database is in format like this: 21-01-2020. It should show Today, tomorrow and date for example 28 Nov 2020 as in the picture. ListView.builder( ... return listTile( title: Text(items[position0].dates), //dates from database, returns 21-01-2020 ), ), At last I just want results like the below picture by comparing dates

问题 i have been trying to get the download URL for my images in firebase storage so I can add it to my listview builders "NetworkCatched Images" for each of my items in the list, as you can see from my code below, I first declared a variable at the beginning of my stateful class called "URL" so I could change the value by making it equal to the download URL i get from firebase storage, but it seems like the async function I'm using doesn't even run because i made sure it prints out the value of

问题 @override Widget build(BuildContext context) { return BlocProvider<HomeBloc>( create: (context) { return HomeBloc(homeRepo: HomeRepository()); }, child: BlocProvider.of<HomeBloc>(context).state is HomeStateLoading ? CircularProgressIndicator() : Container()); } I am confused with the error: BlocProvider.of() called with a context that does not contain a Bloc of type HomeBloc. No ancestor could be found starting from the context that was passed to BlocProvider.of<HomeBloc>(). Didn't I just

问题 I have a database and retrieving my Data from firestore. class ProductProvider with ChangeNotifier { UserModel userModel; List<UserModel> userModelList = []; Future<void> getUserData() async { List<UserModel> newList = []; User currentUser = FirebaseAuth.instance.currentUser; QuerySnapshot userSnapshot = await FirebaseFirestore.instance .collection("Manufacturer-Accounts") .get(); userSnapshot.docs.forEach( (element) { if (currentUser.uid == element.data()['Manufacturer_ID']) { userModel =

问题 I have Doubt when understand, Compile-time constant and runtime constant in Dart language, I am a beginner in dart language, I searched in google there is no article that covers this question, So thanks in advance 回答1: There are no "run-time constants" in Dart, not the way the word "constant" is generally used. All constants are compile-time constants , meaning that their entire value can be determined at compile-time, they are deeply immutable, and the compiler can canonicalize the objects

问题 I am new to flutter, I have successfully retrieved the user email and username from Azure AD Auth. But I want to display this in Text widget in home screen. How can I send the username from the Signin class to home screen and display the name? Signin class _SignInState extends State<SignIn> { MsalMobile msal; bool isSignedIn = false; @override void initState() { super.initState(); MsalMobile.create('assets/auth_config.json', authority).then((client) { setState(() { msal = client; });

问题 I am new to flutter, I have successfully retrieved the user email and username from Azure AD Auth. But I want to display this in Text widget in home screen. How can I send the username from the Signin class to home screen and display the name? Signin class _SignInState extends State<SignIn> { MsalMobile msal; bool isSignedIn = false; @override void initState() { super.initState(); MsalMobile.create('assets/auth_config.json', authority).then((client) { setState(() { msal = client; });