我有以下示例(在iPhone X,iOS 11上测试):
import 'package:flutter/material.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
@override
Widget build(BuildContext context) {
return new ListView(
children: <Widget>[
new Container(
height: 40.0,
color: Colors.blue,
),
new Container(
height: 40.0,
color: Colors.red,
),
new Container(
height: 40.0,
color: Colors.green,
),
]
);
}
}
在这种情况下,ListView的行为与预期的一样。我可以滚动到视口之外,并且ListView会再次反弹(典型的iOS行为)。但是,当我添加ScrollController来跟踪偏移量时,滚动的行为会发生变化:
import 'package:flutter/material.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
ScrollController _controller = new ScrollController();
@override
Widget build(BuildContext context) {
return new ListView(
controller: _controller,
children: <Widget>[
new Container(
height: 40.0,
color: Colors.blue,
),
new Container(
height: 40.0,
color: Colors.red,
),
new Container(
height: 40.0,
color: Colors.green,
),
]
);
}
}
在这种情况下,将无法再滚动。为什么在添加ScrollController时无法再滚动?此外,添加physics: new BouncingScrollPhysics(),
到ListView也无济于事。
谢谢你的帮助 :)
要始终启用滚动,ListView
您可以在AlwaysScrollableScrollPhysics
类中包装所需的原始滚动体。更多细节在这里。如果需要,可以指定aparent
或依靠默认值。
这是添加了选项的示例:
import 'package:flutter/material.dart';
void main() => runApp(new MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return new MaterialApp(
title: 'Flutter Demo',
theme: new ThemeData(
primarySwatch: Colors.blue,
),
home: new MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => new _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
ScrollController _controller = new ScrollController();
@override
Widget build(BuildContext context) {
return new ListView(
physics: const AlwaysScrollableScrollPhysics(), // new
controller: _controller,
children: <Widget>[
new Container(
height: 40.0,
color: Colors.blue,
),
new Container(
height: 40.0,
color: Colors.red,
),
new Container(
height: 40.0,
color: Colors.green,
),
]
);
}
}
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