问题
I need to detect TabBar when I swipe then print somethings on console, how I can do that? This is my code.
bottomNavigationBar: new Material(
color: Colors.blueAccent,
child: new TabBar(
onTap: (int index){ setState(() {
_onTap(index);
});},
indicatorColor: Colors.white,
controller: controller,
tabs: <Widget>[
new Tab(icon: new Icon(Icons.shopping_basket)),
new Tab(icon: new Icon(Icons.store)),
new Tab(icon: new Icon(Icons.local_offer)),
new Tab(icon: new Icon(Icons.assignment)),
new Tab(icon: new Icon(Icons.settings)),
],
)
),
回答1:
You need to add a listener to your tab controller - maybe in initState.
controller.addListener((){
print('my index is'+ controller.index.toString());
});
回答2:
Here is a full example. Use a TabController and add a callback using addListener.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Demo',
home: MyTabbedPage(),
);
}
}
class MyTabbedPage extends StatefulWidget {
const MyTabbedPage({Key key}) : super(key: key);
@override
_MyTabbedPageState createState() => _MyTabbedPageState();
}
class _MyTabbedPageState extends State<MyTabbedPage> with SingleTickerProviderStateMixin {
var _context;
final List<Tab> myTabs = <Tab>[
Tab(text: 'LEFT'),
Tab(text: 'RIGHT'),
];
TabController _tabController;
@override
void initState() {
super.initState();
_tabController = TabController(vsync: this, length: myTabs.length);
_tabController.addListener(_handleTabSelection);
}
void _handleTabSelection() {
if (_tabController.indexIsChanging) {
switch (_tabController.index) {
case 0:
Scaffold.of(_context).showSnackBar(SnackBar(
content: Text('Page 1 tapped.'),
duration: Duration(milliseconds: 500),
));
break;
case 1:
Scaffold.of(_context).showSnackBar(SnackBar(
content: Text('Page 2 tapped.'),
duration: Duration(milliseconds: 500),
));
break;
}
}
}
@override
void dispose() {
_tabController.dispose();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
bottom: TabBar(
controller: _tabController,
tabs: myTabs,
),
),
body: Builder(
builder: (context) {
_context = context;
return TabBarView(
controller: _tabController,
children: myTabs.map((Tab tab) {
final String label = tab.text.toLowerCase();
return Center(
child: Text(
'This is the $label tab',
style: const TextStyle(fontSize: 36),
),
);
}).toList(),
);
},
),
);
}
}
回答3:
Warp your tab in BottomNavigationBar . it will give you option onTap() where you can check which tab will clicked.
using this code you will also redirect to particular page when you tap on Tab
import 'package:flutter/material.dart';
class BottomBarList extends StatefulWidget {
@override
_BottomBarListState createState() => _BottomBarListState();
}
class _BottomBarListState extends State<BottomBarList> {
int bottomSelectedIndex = 0;
int _selectedIndex = 0;
List<Widget> _widgetOptions = <Widget>[
AllMovieList(),
MovieDescription(),
];
@override
Widget build(BuildContext context) {
return Scaffold(
// appBar: AppBar(),
bottomNavigationBar: bottomBar(),
body:_widgetOptions.elementAt(_selectedIndex),
);
}
bottomBar() {
return BottomNavigationBar(
type: BottomNavigationBarType.shifting,
unselectedItemColor: Colors.grey,
items: const <BottomNavigationBarItem>[
BottomNavigationBarItem(
icon: Icon(Icons.tv),
title: Text('Home'),
),
BottomNavigationBarItem(
icon: Icon(Icons.star),
title: Text('Business'),
),
],
currentIndex: _selectedIndex,
selectedItemColor: Colors.black,
backgroundColor: Colors.orange,
onTap: _onItemTapped,
);
}
void _onItemTapped(int index) {
setState(() {
_selectedIndex = index;
});
}
}
回答4:
We can listen to tab scroll notification by using NotificationListener Widget
class HomePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: NotificationListener(
onNotification: (scrollNotification) {
if (scrollNotification is ScrollUpdateNotification) {
_onStartScroll(scrollNotification.metrics);
}
},
child: _buildTabBarAndTabBarViews(),
);
}
_onStartScroll(ScrollMetrics metrics) {
print('hello world');
}
}
回答5:
Swipe functionality is not provided by onTap() function, for that TabController is used
class TabBarDemo extends StatefulWidget {
@override
_TabBarDemoState createState() => _TabBarDemoState();
}
class _TabBarDemoState extends State<TabBarDemo>
with SingleTickerProviderStateMixin {
TabController _controller;
int _selectedIndex = 0;
List<Widget> list = [
Tab(icon: Icon(Icons.card_travel)),
Tab(icon: Icon(Icons.add_shopping_cart)),
];
@override
void initState() {
// TODO: implement initState
super.initState();
// Create TabController for getting the index of current tab
_controller = TabController(length: list.length, vsync: this);
_controller.addListener(() {
setState(() {
_selectedIndex = _controller.index;
});
print("Selected Index: " + _controller.index.toString());
});
}
@override
Widget build(BuildContext context) {
return MaterialApp(
home: Scaffold(
appBar: AppBar(
bottom: TabBar(
onTap: (index) {
// Should not used it as it only called when tab options are clicked,
// not when user swapped
},
controller: _controller,
tabs: list,
),
title: Text('Tabs Demo'),
),
body: TabBarView(
controller: _controller,
children: [
Center(
child: Text(
_selectedIndex.toString(),
style: TextStyle(fontSize: 40),
)),
Center(
child: Text(
_selectedIndex.toString(),
style: TextStyle(fontSize: 40),
)),
],
),
),
);
}
}
Github: https://github.com/jitsm555/Flutter-Problems/tree/master/tab_bar_tricks
Output:
回答6:
I ran into a similar issue and following is what I did to accomplish the same: -
import 'package:flutter/material.dart';
import '../widgets/basic_dialog.dart';
import 'sign_in_form.dart';
import 'sign_up_form.dart';
class LoginDialog extends StatefulWidget {
@override
_LoginDialogState createState() => _LoginDialogState();
}
class _LoginDialogState extends State<LoginDialog>
with SingleTickerProviderStateMixin {
int activeTab = 0;
TabController controller;
@override
void initState() {
super.initState();
controller = TabController(vsync: this, length: 2);
}
@override
Widget build(BuildContext context) {
return NotificationListener(
onNotification: (ScrollNotification notification) {
setState(() {
if (notification.metrics.pixels <= 100) {
controller.index = 0;
} else {
controller.index = 1;
}
});
return true;
},
child: BasicDialog(
child: Container(
height: controller.index == 0
? MediaQuery.of(context).size.height / 2.7
: MediaQuery.of(context).size.height / 1.8,
padding: const EdgeInsets.all(8.0),
child: Column(
mainAxisSize: MainAxisSize.min,
children: <Widget>[
TabBar(
controller: controller,
tabs: <Widget>[
Padding(
padding: const EdgeInsets.all(5.0),
child: Text('Sign In'),
),
Padding(
padding: const EdgeInsets.all(5.0),
child: Text('Sign up'),
),
],
),
Expanded(
child: TabBarView(
controller: controller,
children: <Widget>[
Padding(
padding: const EdgeInsets.all(8.0),
child: SingleChildScrollView(
child: SignInForm(),
),
),
// If a container is not displayed during the tab switch to tab0, renderflex error is thrown because of the height change.
controller.index == 0
? Container()
: Padding(
padding: const EdgeInsets.all(8.0),
child: SingleChildScrollView(
child: SignUpForm(),
),
),
],
),
)
],
),
),
),
);
}
}
回答7:
You can disable swiping effect on TabBarView by adding:
physics: NeverScrollableScrollPhysics(),
and declaring one TabController and assigning that to your TabBar and TabBarView:
TabController _tabController;
来源：https://stackoverflow.com/questions/55485466/how-to-detect-tabbar-change-in-flutter