dart

问题 I'm new with Flutter. I want to display DropdownMenuItem from my list variable. Check out my code. // my list variable List listUserType = [ {'name': 'Individual', 'value': 'individual'}, {'name': 'Company', 'value': 'company'} ]; // items property in DropdownMenuItem return DropdownButtonFormField<List<Map>>( decoration: InputDecoration( prefixIcon: Icon(Icons.settings), hintText: 'Organisation Type', filled: true, fillColor: Colors.white, errorStyle: TextStyle(color: Colors.yellow), ),

问题 void main() { foo().catchError((error) { print('Error caught = $error'); }); } Future<void> foo() { throw Future.error('FooError'); } As I read the docs: This is the asynchronous equivalent of a "catch" block. If I use catch block, the error is caught. But my catchError isn't able to catch the error, but according to docs it should. Am I doing something wrong? Note: I know I can use return instead of throw and the error will be then caught in catchError as stated by @CopsOnRoad here. My

问题 I have a navigation_bar.dart file that handles changing to new pages within my app. Within it, I am using the bottomNavigationBar to build out four different pages based on what tab is currently selected like so: class NavigationBar extends StatefulWidget { @override _NavigationBarState createState() => _NavigationBarState(); } class _NavigationBarState extends State<NavigationBar> { int _selectedIndex = 0; final List<Widget> _pageOptions = <Widget>[ Page1(), Page2(), Page3(), Page4(), ];

问题 I'm trying to make countdowns to date and put each countdown in an ItemView in a ListView. I have already the Listview.buillder() but I don't know how to make countdowns which have different values and put them in the Listview. I have seen that there is another similar question but I can't solve my problem with it. Here is my code : home_screen.dart import 'package:flutter/material.dart'; import 'package:cached_network_image/cached_network_image.dart'; import '../recyclerview/data.dart';

问题 I am just learn about Flutter for website. I need to add some google map javascript API and using google_maps dependencies on pub.dev I follow the example from here, but after debugging with VSCode , i found that I cannot interact with the map at all. No hand tools to drag the map, ore even just to click the maps mode (satellite or map mode). I have tried several example from the example link, from the basics to the controlled example. But I still cannot interact with it. No error on terminal

问题 I'm still new to the dart flutter. now I'm trying to pull data from the REST API. following the script that I have made: class ChatCard { final String chatdetail_id; final String chatdetail_userfullname; final String chatdetail_userurlphoto; final String chatdetail_message; final int chatdetail_isread; final String chatdetail_datetime; ChatCard({ this.chatdetail_id, this.chatdetail_userfullname, this.chatdetail_userurlphoto, this.chatdetail_message, this.chatdetail_isread, this.chatdetail

问题 I want to change the color on the tap of the container. So I just for loop to show container and change color when index is the same. But the issue is index is changing but the color is not. I have checked by the print value of currentIndex is changing but don't know why the color isn't changing I am using a stateful widget Code List categories = [ {'CatID': 0, 'CatName': 'All'}, {'CatID': 1, 'CatName': 'Computer Hardware'}, {'CatID': 2, 'CatName': 'Computer Software'}, {'CatID': 3, 'CatName'

问题 I am trying to test a simple repository class which make a network call using the Dio package that is a dependency injection. Requirement of the Http.post is to send a Map object to a URL with the headers of 'Content-Type': 'application/json . You can see this below: class AuthenticateUserRemoteDataSourceImpl implements AuthenticateUserRepository { final Dio httpClient; AuthenticateUserRemoteDataSourceImpl({@required this.httpClient}); @override Future<Either<Failure, AuthenticateUser>>

问题 I have a stateful Page A that contains a widget which is present in a seperate stateful class. The widget fetches a number from sharedPreferences in its initState method and show it and when i click on the widget, it routes to Page B, Page B contains a function that change the number in the sharedPreferences. when i go back i dont see the changes but when i reopen the app or switch to a different tab and come back, i do. 回答1: In page A, when you go to page B use, Navigator.pushNamed(context,

问题 I have a chip. How do I get the chip to disappear when the user has deleted it? I do not understand the code at all from Flutter Docs. I've tried everything. Chip( deleteIcon: Icon(Icons.close, size: 15,), label: Text('Delete me!'), deleteButtonTooltipMessage: 'erase', onDeleted: () {setState(() {print("I want to erase this chip, and eat chips");}); }, ) The docs suggest that this chip (Chip) can be erased. But they don't give much in the way of examples. 回答1: I am assuming that you have this