dart

问题 Let us say I have the concrete classes Cat, Dog, and Parrot, and the following interface: class HasGuid { HasGuid.fromId(String id); } My goal is to guarantee that Cat, Dog, and Parrot all have a fromId named constructor. So, I can make calls like: Cat.fromId("Whiskers") =returns> [A Future<Cat> object with id "Whiskers"] Dog.fromId("Fido") =returns> [A Future<Dog> object with id "Fido"] Parrot.fromId("Polly") =returns> [A Future<Parrot> object with id "Poly"] fromId is making a call across

问题 How to change checkbox border-color in flutter? By default, it is showing black but I want it in grey. 回答1: CheckBox's border color comes from unselectedWidgetColor of your ThemeData . Add following ThemeData to your MaterialApp MaterialApp( title: 'Flutter Demo', debugShowCheckedModeBanner: false, theme: ThemeData( primarySwatch: Colors.blue, unselectedWidgetColor: Colors.red, // <-- your color ), home: MyHomePage(title: 'Flutter Demo Home Page'), ); If you don't want to add color to the

问题 An event is received from native code using EventChannel . Content is String, and I'd like to show it with SnackBar . But Scaffold.of returns null. And I found nothing to get BuildContext of Scaffold created by Widget Build(...) . The code is like this: @override void initState() { super.initState(); showMsg.receiveBroadcastStream().listen( (event) => setState(() { Scaffold.of(context).showSnackBar(new SnackBar( content: new Text(event.toString()), )); }), onError: (event) => {} ); 回答1: EDIT

问题 An event is received from native code using EventChannel . Content is String, and I'd like to show it with SnackBar . But Scaffold.of returns null. And I found nothing to get BuildContext of Scaffold created by Widget Build(...) . The code is like this: @override void initState() { super.initState(); showMsg.receiveBroadcastStream().listen( (event) => setState(() { Scaffold.of(context).showSnackBar(new SnackBar( content: new Text(event.toString()), )); }), onError: (event) => {} ); 回答1: EDIT

问题 How can I change ripple effect color in Flutter? 回答1: Wrap your widget in Theme and provide the data as data: ThemeData(splashColor: Colors.red) 回答2: An example for the @CopsOnRoad's answer. (Like-Button) Theme( data: ThemeData(splashColor: Colors.red[200]), child: Material( elevation: 0, shape: CircleBorder(), clipBehavior: Clip.hardEdge, color: Colors.transparent, child: InkWell( child: Padding( padding: const EdgeInsets.all(10), child: Icon( Icons.favorite, color: _isLiked ? Colors.red :

问题 How can I change ripple effect color in Flutter? 回答1: Wrap your widget in Theme and provide the data as data: ThemeData(splashColor: Colors.red) 回答2: An example for the @CopsOnRoad's answer. (Like-Button) Theme( data: ThemeData(splashColor: Colors.red[200]), child: Material( elevation: 0, shape: CircleBorder(), clipBehavior: Clip.hardEdge, color: Colors.transparent, child: InkWell( child: Padding( padding: const EdgeInsets.all(10), child: Icon( Icons.favorite, color: _isLiked ? Colors.red :

问题 I add an firebase database Listener to my flutter project as below: databaseReference = database.reference().child("community_board"); databaseReference.onChildAdded.listen(_onEntryAdded); databaseReference.onChildChanged.listen(_onEntryChanged); For Kotlin and swift of firebase, I have to remove the listener in onPause()/onDestroy(). May I know how to remove the firebase database listener in flutter? 回答1: var sub1 = databaseReference.onChildAdded.listen(_onEntryAdded); var sub2 =

问题 I add an firebase database Listener to my flutter project as below: databaseReference = database.reference().child("community_board"); databaseReference.onChildAdded.listen(_onEntryAdded); databaseReference.onChildChanged.listen(_onEntryChanged); For Kotlin and swift of firebase, I have to remove the listener in onPause()/onDestroy(). May I know how to remove the firebase database listener in flutter? 回答1: var sub1 = databaseReference.onChildAdded.listen(_onEntryAdded); var sub2 =

问题 I am using FirebaseMessaging to push notifications on my app. So I can handle these notification with this code : firebaseMessaging.configure( onLaunch: (Map<String, dynamic> msg) { print("onLaunch called"); }, onResume: (Map<String, dynamic> msg) { print("onResume called"); }, onMessage: (Map<String, dynamic> msg) { print("onMessage called : " + msg.toString()); }); When I receive a notification, I want to display this little '1' on my icon in my appbar My problem is : I don't know how to

问题 I am using FirebaseMessaging to push notifications on my app. So I can handle these notification with this code : firebaseMessaging.configure( onLaunch: (Map<String, dynamic> msg) { print("onLaunch called"); }, onResume: (Map<String, dynamic> msg) { print("onResume called"); }, onMessage: (Map<String, dynamic> msg) { print("onMessage called : " + msg.toString()); }); When I receive a notification, I want to display this little '1' on my icon in my appbar My problem is : I don't know how to