https://dart.dev/guides/language/effective-dart/usage#avoid-late-variables-if-you-need-to-check-...
PS C:\flutter> flutter doctor -v[√] Flutter (Channel beta, 3.24.0-0.2.pre, on Microsoft Windows [Version 10.0.22631.3958], locale nb-NO)• Flutter version 3.24.0-0.2.pre on channel beta at c:\Flutter\flutter• Upstream repository https://github.com/flutter/flutter.git• Framework ...
initializeApp(), builder: (context, snapshot) { // Check for errors if (snapshot.hasError) { return SomethingWentWrong(); } // Once complete, show your application if (snapshot.connectionState == ConnectionState.done) { return MyAwesomeApp(); } // Otherwise, show something whilst ...
如果_selectedDate属性没有默认值，请将其设置为可空值：
[glyph.uid]; // Check if glyph with this `uid` really exists if (!targetGlyph) { return; } targetGlyph.selected(!!glyph.selected); targetGlyph.code(glyph.code || targetGlyph.originalCode); targetGlyph.name(glyph.css || targetGlyph.originalName); }); }); // load selection state ...
Thanks to the late final, the future is lazily initialized only once so the API calls triggered by execute() are also executed one time only. It would have been absolutely WRONG if we fetched the HTTP data directly inside the build method: 1 2 3 4 5 6 7 8 9 10 11 12 13 class _...
UserRepository(); Stream<AppResult<ScreenState>> invoke() { return CombineLatestStream.combine2( _userRepository.getUserData(), _booksRepository.getBooks(), (userDataResponse, booksResponse) { // Here we need to check if we got success on both streams if (userDataResponse is AppResult.data ...
It's possible for the controller variable to equalnull, for example, in a case where you provide an incorrect State Machine name. So, before we proceed to the next step, we need to check if thecontrollervariable holding theStateMachineControllerisnull. If it isn’t, we can proceed with th...
However, only the child node in the Provider is used to query the data of the nearest parent node's InheritedElement and the top-level Widget parallel layout function. The most classic refresh mechanism of the Provider is completely useless!
class _MyHomePageState extends State<MyHomePage> { late Timer timer; // Define timer variable here // Rest of your code... // This will call when the state object is initiate @override void initState() { super.initState(); // Initialize the timer here timer = Timer.periodic(const Durat...