问题
I have the following example (tested on an iPhone X, iOS 11):
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,
),
]
);
}
}
In this case the ListView acts like expected. I can scroll beyond the viewport and the ListView bounces back again (typical iOS behavior). But when I add a ScrollController to track the offset, the behavior of the scrolling changes:
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,
),
]
);
}
}
In this case the scrolling is not possible anymore. Why is it that when I add a ScrollController, that the scrolling is not possible anymore? Also adding physics: new BouncingScrollPhysics(), to the ListView does not help.
Thanks for any help :)
回答1:
To always have the scroll enabled on a ListView you can wrap the original scroll phisics you want with the AlwaysScrollableScrollPhysics class. More details here. If you want you can specify a parent or rely on the default.
Here is your example with the option added:
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,
),
]
);
}
}
回答2:
Creates scroll physics using AlwaysScrollableScrollPhysics that always lets the user scroll.
For scroll with bouncing effect Just supply physics: BouncingScrollPhysics(parent: AlwaysScrollableScrollPhysics) to your scroller. That will make it always scrollable, even when there isn't content that overflows
const BouncingScrollPhysics(parent: AlwaysScrollableScrollPhysics())
Here is full example
ListView(
padding: EdgeInsets.all(8.0),
physics: const BouncingScrollPhysics(parent: AlwaysScrollableScrollPhysics()),
children: _listData.map((i) {
return ListTile(
title: Text("Item $i"),
);
}).toList(),
);
回答3:
Just add AlwaysScrollableScrollPhysics
ListView(
physics: const AlwaysScrollableScrollPhysics(),
children : [...]
}
回答4:
I found a solution how to track the offset with lists that have a smaller content height than the viewport. Use a NotificationListener together with a CustomScrollView in the build() method like this:
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 NotificationListener(
onNotification: _handleScrollPosition,
child: new CustomScrollView(
slivers: [
new SliverList(
delegate: new SliverChildListDelegate([
new Container(
height: 40.0,
color: Colors.blue,
),
new Container(
height: 40.0,
color: Colors.red,
),
new Container(
height: 40.0,
color: Colors.green,
),
])
)
]
)
);
}
bool _handleScrollPosition(ScrollNotification notification) {
print(notification.metrics.pixels);
return true;
}
}
As long as there is no solution with a ScrollController only (or a "better" (more elegant)) solution, I will accept this as the answer.
回答5:
I think this solution is better without CustomScrollView. Just use NotificationListener to wrap the ListView.
Widget noti = new NotificationListener(
child:listView,
onNotification: (ScrollNotification note){
print(note.metrics.pixels.toInt());
},
);
I have test it , Bounce is effective
回答6:
**
Use container height for scrolling and also use physics: AlwaysScrollableScrollPhysics(), controller: controller,
**
Container(
width: 400,
child: Drawer(
child: Stack(children: [
Container(
height: MediaQuery.of(context).size.height-80,
child: ListView(
controller: controller,
padding: EdgeInsets.zero,
physics: AlwaysScrollableScrollPhysics(),
children: [
Container(
height: 300,
padding: EdgeInsets.symmetric(vertical: 20, horizontal: 10),
child: DrawerHeader(
child:Stack(children: [
Center(
child: Column(
children: [
nullCatcher(image) == "" ? Image.asset("assets/images/doctor.png",height: 90,width: 90,) : Image.network(
"$image",
height: 90,
width: 90,
),
SizedBox(width: 30,),
Text("$name",style: TextStyle(color: Colors.grey[700],fontWeight: FontWeight.bold,fontSize: 25),),
Text("$specialty",style: TextStyle(color: Colors.grey[600]),),
],
),
),
Positioned(
right: 0,bottom: 10,
child: Text("Version: 1.0.0",style: TextStyle(color: Colors.orange),))
],),
),
),
ListTile(
contentPadding: EdgeInsets.zero,
title: Container(
height: 70,
padding: EdgeInsets.symmetric(horizontal: 30),
decoration: drawerListDecoration,
child: Row(
children: [
Container(
height: 35,width: 35,
decoration: BoxDecoration(
color: Theme.of(context).accentColor,
borderRadius: BorderRadius.circular(100)
),
child: Icon(Icons.attach_file,color: Colors.white,size: 20,)),
SizedBox(width: 20,),
Text('Create Appointment'),
],
)),
onTap: () {
Navigator.pushReplacement(context, MaterialPageRoute(builder: (__)=>CreateAppointment()));
// Update the state of the app.
// ...
},
),
ListTile(
contentPadding: EdgeInsets.zero,
title: Container(
height: 70,
padding: EdgeInsets.symmetric(horizontal: 30),
decoration: drawerListDecoration,
child: Row(
children: [
Container(
height: 35,width: 35,
decoration: BoxDecoration(
color: Theme.of(context).accentColor,
borderRadius: BorderRadius.circular(100)
),
child: Icon(Icons.attach_file,color: Colors.white,size: 20,)),
SizedBox(width: 20,),
Text('Appointment / Prescription List'),
],
)),
onTap: () {
Navigator.pushReplacement(context, MaterialPageRoute(builder: (__)=>AppointmentList()));
// Navigator.pop(context);
},
),
Container(
height: 70,
padding: EdgeInsets.symmetric(horizontal: 30 ),
color: Colors.grey[200],
child: Row(
children: [
Container(
height: 35,width: 35,
decoration: BoxDecoration(
color: Theme.of(context).accentColor,
borderRadius: BorderRadius.circular(100)
),
child: Icon(Icons.attach_file,color: Colors.white,size: 20,)),
SizedBox(width: 20,),
Text("Clinical Options:",style: TextStyle(fontWeight: FontWeight.bold,color: Colors.grey[600]),),
],
),
),
ListTile(
contentPadding: EdgeInsets.zero,
title: Container(
height: childHeight,
padding: EdgeInsets.only(left: childPaddeing),
// decoration: drawerListDecoration,
child: Row(
children: [
lineDesign(),
SizedBox(width: 20,),
Text('Chief Complain'),
],
)),
onTap: () {
Navigator.pushReplacement(context, MaterialPageRoute(builder: (__)=>AppointmentList()));
// Navigator.pop(context);
},
),
ListTile(
contentPadding: EdgeInsets.zero,
title: Container(
height: 50,
padding: EdgeInsets.symmetric(horizontal: 45),
decoration: drawerListDecoration,
child: Row(
children: [
lineDesign(),
SizedBox(width: 20,),
Text('On Examination'),
],
)),
onTap: () {
Navigator.pushReplacement(context, MaterialPageRoute(builder: (__)=>AppointmentList()));
// Navigator.pop(context);
},
),
ListTile(
contentPadding: EdgeInsets.zero,
title: Container(
height: 70,
padding: EdgeInsets.symmetric(horizontal: 30),
decoration: drawerListDecoration,
child: Row(
children: [
Container(
height: 35,width: 35,
decoration: BoxDecoration(
color: Theme.of(context).accentColor,
borderRadius: BorderRadius.circular(100)
),
child: Icon(Icons.attach_file,color: Colors.white,size: 20,)),
SizedBox(width: 20,),
Text('Examination Category'),
],
)),
onTap: () {
Navigator.pushReplacement(context, MaterialPageRoute(builder: (__)=>AppointmentList()));
// Navigator.pop(context);
},
),
ListTile(
contentPadding: EdgeInsets.zero,
title: Container(
height: 70,
padding: EdgeInsets.symmetric(horizontal: 30),
decoration: drawerListDecoration,
child: Row(
children: [
Container(
height: 35,width: 35,
decoration: BoxDecoration(
color: Theme.of(context).accentColor,
borderRadius: BorderRadius.circular(100)
),
child: Icon(Icons.attach_file,color: Colors.white,size: 20,)),
SizedBox(width: 20,),
Text('Diagnosis'),
],
)),
onTap: () {
Navigator.pushReplacement(context, MaterialPageRoute(builder: (__)=>AppointmentList()));
// Navigator.pop(context);
},
),
ListTile(
contentPadding: EdgeInsets.zero,
title: Container(
height: 70,
padding: EdgeInsets.symmetric(horizontal: 30),
decoration: drawerListDecoration,
child: Row(
children: [
Container(
height: 35,width: 35,
decoration: BoxDecoration(
color: Theme.of(context).accentColor,
borderRadius: BorderRadius.circular(100)
),
child: Icon(Icons.attach_file,color: Colors.white,size: 20,)),
SizedBox(width: 20,),
Text('Investigations'),
],
)),
onTap: () {
Navigator.pushReplacement(context, MaterialPageRoute(builder: (__)=>AppointmentList()));
// Navigator.pop(context);
},
),
],
),
),
Positioned(
bottom: 0,
left: 0,
right: 0,
child: ButtonTheme(
child: RaisedButton(
color: Colors.red[900],
onPressed: (){
if(blocState is LogoutInLoading){}else logoutAlert(blocContext);
},
child: Container(
height: 70,
child:blocState is LogoutInLoading ? Container( height: 20,width: 20,margin: EdgeInsets.symmetric(vertical: 25), child: CircularProgressIndicator(valueColor: AlwaysStoppedAnimation(Colors.white),),) : Row(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Text("Sign Out",style: TextStyle(color: Colors.white,fontWeight: FontWeight.bold,fontSize: 25),),
SizedBox(width: 20,),
Icon(Icons.logout,color: Colors.white,)
],
),
),
),
)
)
],),
),
);
来源：https://stackoverflow.com/questions/48081917/flutter-listview-not-scrollable-not-bouncing