【发布时间】：2021-06-09 16:15:22
【问题描述】：
我不明白为什么在 Positioned 小部件中，我收到一个错误，即子参数未定义以及 AnimatedContainer 中的“持续时间”参数未定义。
我先查了官方文档，不知道为什么不行。
https://api.flutter.dev/flutter/widgets/Positioned-class.html
https://api.flutter.dev/flutter/widgets/AnimatedContainer-class.html
class _DetailsPageState extends State<DetailsPage> {
var selectedCard = 'WEIGHT';
@override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Color(0xFF7A9BEE),
appBar: AppBar(
leading: IconButton(
onPressed: () {
Navigator.of(context).pop();
},
icon: Icon(Icons.arrow_back_ios),
color: Colors.white,
),
backgroundColor: Colors.transparent,
elevation: 0.0,
title: Text('Details',
style: TextStyle(
fontFamily: 'Montserrat',
fontSize: 18.0,
color: Colors.white)),
centerTitle: true,
actions: <Widget>[
IconButton(
icon: Icon(Icons.more_horiz),
onPressed: () {},
color: Colors.white,
)
],
),
body: ListView(children: [
Stack(children: [
Container(
height: MediaQuery.of(context).size.height - 82.0,
width: MediaQuery.of(context).size.width,
color: Colors.transparent),
Positioned(
top: 75.0,
child: Container(
decoration: BoxDecoration(
borderRadius: BorderRadius.only(
topLeft: Radius.circular(45.0),
topRight: Radius.circular(45.0),
),
color: Colors.white),
height: MediaQuery.of(context).size.height - 100.0,
width: MediaQuery.of(context).size.width)),
Positioned(
top: 30.0,
left: (MediaQuery.of(context).size.width / 2) - 100.0,
child: Hero(
tag: widget.heroTag,
child: Container(
decoration: BoxDecoration(
image: DecorationImage(
image: AssetImage(widget.heroTag),
fit: BoxFit.cover)),
height: 200.0,
width: 200.0))),
Positioned(
top: 250.0,
left: 25.0,
right: 25.0,
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(widget.foodName,
style: TextStyle(
fontFamily: 'Montserrat',
fontSize: 22.0,
fontWeight: FontWeight.bold)),
SizedBox(height: 20.0),
Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
Text(widget.foodPrice,
style: TextStyle(
fontFamily: 'Montserrat',
fontSize: 20.0,
color: Colors.grey)),
Container(height: 25.0, color: Colors.grey, width: 1.0),
Container(
width: 125.0,
height: 40.0,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(17.0),
color: Color(0xFF7A9BEE)),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: <Widget>[
InkWell(
onTap: () {},
child: Container(
height: 25.0,
width: 25.0,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(7.0),
color: Color(0xFF7A9BEE)),
child: Center(
child: Icon(
Icons.remove,
color: Colors.white,
size: 20.0,
),
),
),
),
Text('2',
style: TextStyle(
color: Colors.white,
fontFamily: 'Montserrat',
fontSize: 15.0)),
InkWell(
onTap: () {},
child: Container(
height: 25.0,
width: 25.0,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(7.0),
color: Colors.white),
child: Center(
child: Icon(
Icons.add,
color: Color(0xFF7A9BEE),
size: 20.0,
),
),
),
)
],
),
)
],
),
SizedBox(height: 20.0),
Container(
height: 150.0,
child: ListView(
scrollDirection: Axis.horizontal,
children: <Widget>[
_buildInfoCard('WEIGHT', '300', 'G'),
SizedBox(width: 10.0),
_buildInfoCard('CALORIES', '267', 'CAL'),
SizedBox(width: 10.0),
_buildInfoCard('VITAMINS', 'A, B6', 'VIT'),
SizedBox(width: 10.0),
_buildInfoCard('AVAIL', 'NO', 'AV')
],
)
),
SizedBox(height: 20.0),
Padding(
padding: EdgeInsets.only(bottom:5.0),
child: Container(
decoration: BoxDecoration(
borderRadius: BorderRadius.only(topLeft: Radius.circular(10.0), topRight: Radius.circular(10.0), bottomLeft: Radius.circular(25.0), bottomRight: Radius.circular(25.0)),
color: Colors.black
),
height: 50.0,
child: Center(
child: Text(
'\$52.00',
style: TextStyle(
color: Colors.white,
fontFamily: 'Montserrat'
)
),
),
),
)
],
))
])
]));
}
Widget _buildInfoCard(String cardTitle, String info, String unit) {
return InkWell(
onTap: () {
selectCard(cardTitle);
},
child: AnimatedContainer(
duration: Duration(milliseconds: 500),
curve: Curves.easeIn,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(10.0),
color: cardTitle == selectedCard ? Color(0xFF7A9BEE) : Colors.white,
border: Border.all(
color: cardTitle == selectedCard ?
Colors.transparent :
Colors.grey.withOpacity(0.3),
style: BorderStyle.solid,
width: 0.75
),
),
height: 100.0,
width: 100.0,
child: Column(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Padding(
padding: const EdgeInsets.only(top: 8.0, left: 15.0),
child: Text(cardTitle,
style: TextStyle(
fontFamily: 'Montserrat',
fontSize: 12.0,
color:
cardTitle == selectedCard ? Colors.white : Colors.grey.withOpacity(0.7),
)),
),
Padding(
padding: const EdgeInsets.only(left: 15.0, bottom: 8.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
Text(info,
style: TextStyle(
fontFamily: 'Montserrat',
fontSize: 14.0,
color: cardTitle == selectedCard
? Colors.white
: Colors.black,
fontWeight: FontWeight.bold)),
Text(unit,
style: TextStyle(
fontFamily: 'Montserrat',
fontSize: 12.0,
color: cardTitle == selectedCard
? Colors.white
: Colors.black,
))
],
),
)
]
)
)
);
}
selectCard(cardTitle) {
setState(() {
selectedCard = cardTitle;
});
}
}
【问题讨论】：
-
我刚刚复制了您的代码并构建了它，定位的小部件或动画容器没有错误。你在哪一行得到错误？还是出现在每个位置？
-
你运行的是哪个版本？
-
我在 windows 上运行 Flutter 2.2.0 版
-
不能让它工作，不知道为什么。
标签： flutter