Dart “集团架构”;getter x在null上被调用;
根据文档,我试图使用Bloc架构来设置子窗口小部件的颜色状态,但它根本不起作用。以下是我的相关档案: 飞镖 在显示>stream:colorBloc.colorStream的行上 以下是日志中的具体错误:Dart “集团架构”;getter x在null上被调用;,dart,flutter,stream,bloc,Dart,Flutter,Stream,Bloc,根据文档,我试图使用Bloc架构来设置子窗口小部件的颜色状态,但它根本不起作用。以下是我的相关档案: 飞镖 在显示>stream:colorBloc.colorStream的行上 以下是日志中的具体错误: I/flutter (18865): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════ I/flutter (18865): The foll
I/flutter (18865): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (18865): The following NoSuchMethodError was thrown building dropDownMenu(dirty, state:
I/flutter (18865): dropDownMenuState#7edb3(ticker inactive)):
I/flutter (18865): The getter 'colorStream' was called on null.
I/flutter (18865): Receiver: null
I/flutter (18865): Tried calling: colorStream
我尽可能地关注文档,但是我看不到他们初始化这个流的任何地方,或者任何类似的地方。我真的不理解这个错误,也不知道如何解决它。有人对streams有任何经验吗?在调用'of'方法时,您没有传入BlocBase子类 使用
colorBloc=BlocProvider.of(上下文)代码>
而不是
colorBloc=BlocProvider.of(上下文)代码>
编辑:
再次查看代码,您不需要该行,因为ColorBloc驻留在当前类中,而不是小部件树上。只需删除该行即可使用上面的ColorBloc实例。你就是一个传奇,伙计!这完全消除了错误。应用程序仍然没有实际更新此小部件的颜色。我已经接受了你的回答,但我还有一个问题:如果有人能看一下吗?从我读过的和测试过的所有内容来看,它应该工作得很好,但它什么也没做。不客气!让我检查一下,看看能不能帮上忙。
import 'dart:async';
import 'package:ultimate_mtg/model/blocprovider.dart';
import 'dart:ui';
import 'dart:math';
class ColorBloc extends BlocBase {
// streams of Color
StreamController streamListController = StreamController<Color>.broadcast();
// sink
Sink get colorSink => streamListController.sink;
// stream
Stream<Color> get colorStream => streamListController.stream;
// function to change the color
changeColor() {
colorSink.add(getRandomColor());
}
@override
dispose() {
streamListController.close();
}
}
// Random Colour generator
Color getRandomColor() {
Random _random = Random();
return Color.fromARGB(
_random.nextInt(256),
_random.nextInt(256),
_random.nextInt(256),
_random.nextInt(256),
);
}
import 'package:flutter/material.dart';
import 'dart:math';
import 'package:ultimate_mtg/model/colorBloc.dart';
import 'package:ultimate_mtg/model/blocprovider.dart';
// ignore: camel_case_types
class dropDownMenu extends StatefulWidget {
final Function() onPressed;
final String tooltip;
final IconData icon;
final _callback;
dropDownMenu({Key key, this.onPressed, this.tooltip, this.icon, @required void singlePlayerCallbacks(String callBackType), @required StatefulWidget styleMenu } ):
_callback = singlePlayerCallbacks;
@override
dropDownMenuState createState() => dropDownMenuState();
}
// ignore: camel_case_types
class dropDownMenuState extends State<dropDownMenu>
with SingleTickerProviderStateMixin {
bool isOpened = false;
AnimationController _animationController;
Animation<double> _translateButton;
Curve _curve = Curves.easeOut;
double _fabHeight = 58;
double menuButtonSize = 55;
Color menuButtonTheme;
ColorBloc colorBloc = ColorBloc();
@override
initState() {
_animationController =
AnimationController(vsync: this, duration: Duration(milliseconds: 600))
..addListener(() {
setState(() {});
});
_translateButton = Tween<double>(
begin: 0.0,
end: _fabHeight,
).animate(CurvedAnimation(
parent: _animationController,
curve: Interval(
0.0,
1.0,
curve: _curve,
),
));
super.initState();
}
@override
dispose() {
_animationController.dispose();
super.dispose();
}
animate() {
if (!isOpened) {
_animationController.forward();
} else {
_animationController.reverse();
}
isOpened = !isOpened;
}
Widget backgroundColour() {
colorBloc = BlocProvider.of(context);
return StreamBuilder(
initialData: Colors.blue,
stream: colorBloc.colorStream,
builder: (BuildContext context, snapShot) => Container(
width: menuButtonSize,
height: menuButtonSize,
child: RawMaterialButton(
shape: CircleBorder(),
fillColor: Colors.black,
elevation: 5.0,
onPressed: (){},
child: Container(
height: menuButtonSize - 3,
width: menuButtonSize - 3,
decoration: BoxDecoration(
color: snapShot.data,
shape: BoxShape.circle,
),
child: Image.asset(
'lib/images/background_colour.png',
scale: 4,
),
),
),
),
);
}
Widget toggle() {
return Transform.rotate(
angle: _animationController.value * (pi * 2),
child: Container(
width: menuButtonSize,
height: menuButtonSize,
child: RawMaterialButton(
shape: CircleBorder(),
fillColor: Colors.black,
elevation: 5.0,
onPressed: animate,
child: SizedBox(
height: menuButtonSize - 3,
width: menuButtonSize - 3,
child: Image.asset('lib/images/ic_launcher.png'),
),
),
),
);
}
@override
Widget build(BuildContext context) {
return Stack(
children: <Widget> [
BlocProvider(
bloc: ColorBloc(),
child: Column(
mainAxisAlignment: MainAxisAlignment.start,
children: [
Stack(
children: <Widget>[
Transform(
transform: Matrix4.translationValues(
0,
_translateButton.value,
0,
),
child: backgroundColour(),
),
toggle(),
],
),
],
),
),
Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Container(
height: menuButtonSize,
width: menuButtonSize,
child: Opacity(
opacity: 0.0,
child: FloatingActionButton(
heroTag: null,
onPressed: animate,
),
),
),
SizedBox(
height: 3.0,
),
Container(
height: menuButtonSize,
width: menuButtonSize,
child: Opacity(
opacity: 0.0,
child: FloatingActionButton(
heroTag: null,
onPressed: isOpened == true? (){
widget?._callback('background');
} : () {},
),
),
),
],
),
],
);
}
}
Widget backgroundColour() {
colorBloc = BlocProvider.of(context);
return StreamBuilder(
initialData: Colors.blue,
stream: colorBloc.colorStream,
I/flutter (18865): ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
I/flutter (18865): The following NoSuchMethodError was thrown building dropDownMenu(dirty, state:
I/flutter (18865): dropDownMenuState#7edb3(ticker inactive)):
I/flutter (18865): The getter 'colorStream' was called on null.
I/flutter (18865): Receiver: null
I/flutter (18865): Tried calling: colorStream