我正在开发一个应用程序,遇到一个问题,其中SingleChildScrollView从顶部开始:
如何使它像这样从底部开始:
滚动视图在屏幕的上半部分topContent
中实现:
final topContent = Stack(
children: <Widget>[
Container(
padding: EdgeInsets.only(left: 10.0),
height: MediaQuery.of(context).size.height * 0.5,
decoration: new BoxDecoration(
image: new DecorationImage(
image: new AssetImage("assets/images/drones1.jpg"),
fit: BoxFit.cover,
),
)),
Container(
height: MediaQuery.of(context).size.height * 0.5,
padding: EdgeInsets.all(40.0),
width: MediaQuery.of(context).size.width,
decoration: BoxDecoration(color: Color.fromRGBO(58, 66, 86, .9)),
child: SingleChildScrollView( //scroll view implemented here
child: Center(
child: topContentText,
),
),
),
Positioned(
left: 8.0,
top: 60.0,
child: InkWell(
onTap: () {
Navigator.pop(context);
},
child: Icon(Icons.arrow_back, color: Colors.white),
),
)
],
);
更新:我分配了一个控制器,并按照下面的link's示例尝试使用SchedulerBinding.instance.addPostFrameCallback调用滚动控制器的jumpTo函数,但它给了我一个例外,其结果与在不向下滚动的位置之前:
import 'package:garuda_academy_app/Constants.dart';
import 'Lesson.dart';
import 'package:flutter/material.dart';
import 'package:flutter/scheduler.dart';
class DetailPage extends StatefulWidget {
final Lesson lesson;
DetailPage({Key key, this.lesson}) : super(key: key);
@override
_DetailPageState createState() => _DetailPageState(lesson: lesson);
}
class _DetailPageState extends State<DetailPage> {
final Lesson lesson;
ScrollController _scrollController;
_DetailPageState({this.lesson});
@override // I use the SchedularBinding here
void initState() {
super.initState();
SchedulerBinding.instance.addPostFrameCallback((_) =>
_scrollController.jumpTo(_scrollController.position.maxScrollExtent));
}
@override
Widget build(BuildContext context) {
final levelIndicator = Container(
child: Container(
child: LinearProgressIndicator(
backgroundColor: Color.fromRGBO(209, 224, 224, 0.2),
value: lesson.indicatorValue,
valueColor: AlwaysStoppedAnimation(Colors.green)),
),
);
final course = Container(
padding: const EdgeInsets.all(7.0),
decoration: new BoxDecoration(
border: new Border.all(color: Colors.white),
borderRadius: BorderRadius.circular(5.0)),
child: new Text(
lesson.course,
style: TextStyle(color: Colors.white),
),
);
final topContentText = Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
SizedBox(height: 120.0),
Icon(
Icons.flight,
color: Colors.white,
size: 40.0,
),
Container(
width: 90.0,
child: new Divider(color: Colors.green),
),
SizedBox(height: 10.0),
Text(
lesson.title,
style: TextStyle(color: Colors.white, fontSize: 45.0),
),
SizedBox(height: 30.0),
Row(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Expanded(flex: 1, child: levelIndicator),
Expanded(
flex: 6,
child: Padding(
padding: EdgeInsets.only(left: 10.0),
child: Text(
lesson.level,
style: TextStyle(color: Colors.white),
))),
Expanded(flex: 1, child: course)
],
),
],
);
final topContent = Stack(
children: <Widget>[
Container(
padding: EdgeInsets.only(left: 10.0),
height: MediaQuery.of(context).size.height * 0.5,
decoration: new BoxDecoration(
image: new DecorationImage(
image: new AssetImage(lesson.imagePath),
fit: BoxFit.cover,
),
)),
Container(
height: MediaQuery.of(context).size.height * 0.5,
padding: EdgeInsets.all(40.0),
width: MediaQuery.of(context).size.width,
decoration: BoxDecoration(color: Color.fromRGBO(58, 66, 86, .9)),
child: SingleChildScrollView(
controller: _scrollController, // Where I pin the ScrollController
child: Center(
child: topContentText,
),
),
),
Positioned(
left: 8.0,
top: 60.0,
child: InkWell(
onTap: () {
Navigator.pop(context);
},
child: Icon(Icons.arrow_back, color: Colors.white),
),
)
],
);
final bottomContentText = Text(
lesson.content,
style: TextStyle(fontSize: 18.0),
);
final downloadButton = Container(
padding: EdgeInsets.symmetric(vertical: 16.0),
width: MediaQuery.of(context).size.width,
child: RaisedButton(
onPressed: () => {},
color: Color.fromRGBO(58, 66, 86, 1.0),
child:
Text(DETAIL_PAGE_DOWNLOAD, style: TextStyle(color: Colors.white)),
));
final bottomContent = Container(
width: MediaQuery.of(context).size.width,
padding: EdgeInsets.all(40.0),
child: Center(
child: Column(
children: <Widget>[bottomContentText, downloadButton],
),
),
);
return Scaffold(
body: Column(
children: <Widget>[topContent, bottomContent],
),
);
}
}
异常: I / flutter(1567):引发了另一个异常:NoSuchMethodError:在null上调用了吸气剂“ position”。
答案 0 :(得分:0)
我通过定义ScrollController时进一步添加(通过更新)解决了这个问题:
ScrollController _scrollController = new ScrollController(
initialScrollOffset: 0.0,
keepScrollOffset: true,
);