dart

问题 I'm new to both Flutter and Dart, and I'm trying to use the Camera Plugin to understand how things work. All examples I find have this part: List<CameraDescription> cameras; Future<Null> main() async { cameras = await availableCameras(); runApp(new CameraApp()); } Is there some way I could do this inside the initState() method? I guess this is also a more general question regarding async work required before the initState -method is run. (As the initState -method cannot be async). My goal is

问题 I'm using ScrollController for SingleChildScrollView widget where I want to detect when scroll start, end/stop and still scrolling? How can I detect, I'm using Listene scrollController = ScrollController() ..addListener(() { scrollOffset = _scrollController.offset; }); Also try with _scrollController.position.activity.velocity but didn't help me. Also there are _scrollController.position.didEndScroll(); _scrollController.position.didStartScroll(); But how can I use it? 回答1: From this link

问题 I'm using ScrollController for SingleChildScrollView widget where I want to detect when scroll start, end/stop and still scrolling? How can I detect, I'm using Listene scrollController = ScrollController() ..addListener(() { scrollOffset = _scrollController.offset; }); Also try with _scrollController.position.activity.velocity but didn't help me. Also there are _scrollController.position.didEndScroll(); _scrollController.position.didStartScroll(); But how can I use it? 回答1: From this link

问题 For example, I am trying to obtain data emitted for multiple streams at once, but 2 or more of these streams emit data of the same type, lets say a string. My question is, is it possible to use MultiProvider and use multiple StreamProvider (or any provider, but I am interested in this case) of the same type while still being able to access the data emitted by each one of them? A solution for this is using a StreamBuilder when using common data types but I really like what the MultiProvider

问题 For example, I am trying to obtain data emitted for multiple streams at once, but 2 or more of these streams emit data of the same type, lets say a string. My question is, is it possible to use MultiProvider and use multiple StreamProvider (or any provider, but I am interested in this case) of the same type while still being able to access the data emitted by each one of them? A solution for this is using a StreamBuilder when using common data types but I really like what the MultiProvider

问题 For example, I am trying to obtain data emitted for multiple streams at once, but 2 or more of these streams emit data of the same type, lets say a string. My question is, is it possible to use MultiProvider and use multiple StreamProvider (or any provider, but I am interested in this case) of the same type while still being able to access the data emitted by each one of them? A solution for this is using a StreamBuilder when using common data types but I really like what the MultiProvider

问题 For example, I am trying to obtain data emitted for multiple streams at once, but 2 or more of these streams emit data of the same type, lets say a string. My question is, is it possible to use MultiProvider and use multiple StreamProvider (or any provider, but I am interested in this case) of the same type while still being able to access the data emitted by each one of them? A solution for this is using a StreamBuilder when using common data types but I really like what the MultiProvider

问题 I am trying to make a simple chat app, so I created a scaffold and my body, will be the messages and my bottomNavigationBar would be my typing field and sending icon. I added a text field but when typing the navigation bar is hidden by the keyboard. this is the code of my BottomNavigationBar : bottomNavigationBar: new Container( height: ScreenSize.height/12, /*color: Colors.red,*/ child: new Row( mainAxisAlignment: MainAxisAlignment.spaceEvenly, children: <Widget>[ new Column(

问题 I am trying to make a simple chat app, so I created a scaffold and my body, will be the messages and my bottomNavigationBar would be my typing field and sending icon. I added a text field but when typing the navigation bar is hidden by the keyboard. this is the code of my BottomNavigationBar : bottomNavigationBar: new Container( height: ScreenSize.height/12, /*color: Colors.red,*/ child: new Row( mainAxisAlignment: MainAxisAlignment.spaceEvenly, children: <Widget>[ new Column(

问题 I need to display long text, which will occupy several screens/pages. I have to add some features also, so I would like to implement my own text displaying component. I found two classes that corresponds to this task: TextPainter use TextSpan for text use paint(canvas, offset) for painting Paragraph use "queue" for text and styles for them use Canvas.drawParagraph(paragraph, offset) for painting What is the difference between them and which one to use?! If the text contains 100 lines and only