In Flutter, I have a bottom navigator bar and there are 4 different bottom navigator bar items in it. In the 4th menu item, I have a checkbox widget. While browsing in the navigation bar items I would like the checked or unchecked items situation remains. For example if I uncheck this widget I would like it to stay still "unchecked" while browsing in other navigation bar items. How can I do this? I tried to use key parameter of checkbox but I failed.
You should use AutomaticKeepAliveClientMixin
to keep state Alive while you browse between your items.Extend your state class with it and create an override method wannaKeepAlive and set it to true.Here is an example of a widget using AutomaticKeepAliveClientMixin.
class Example extends StatefulWidget {
#override
_ExampleState createState() => _ExampleState();
}
class _ExampleState extends State<Example> with AutomaticKeepAliveClientMixin {
#override
Widget build(BuildContext context) {
return Container(
);
}
#override
// TODO: implement wantKeepAlive
bool get wantKeepAlive => true;
}
Welcome to State management!
Official guideline for state management from Flutter team.
I would recommend to read everything starting from introduction to state management.
Related
In my case we have 3 tabs in TabController and in all of this pages we have some data which we want to use them, now on each tab when we are swiping between them we don't have previous data and length of box values is 0, you suppose we have three tab as:
screen_a
screen_b
screen_c
into screen_a we have:
class Home extends StatefulWidget {
const Home({Key? key}) : super(key: key);
#override
State<StatefulWidget> createState() =>MyHome();
}
class MyHome extends State<Home> {
late Box<Level> _level;
late List<Level> levels ;
late VideoPlayerController _controller;
#override
void initState() {
super.initState();
_level = Hive.box<Level>('level');
levels = _level.values.toList();
}
#override
Widget build(BuildContext context) {
now on starting application we have many data on screen_a and after swiping on screen_b and going back to screen_a we don't have any data in hive :| :|
what's the problem?
You should store your tabs' data in a bloc or controller class that does not lose state and data when switching between tabs.
It depends on your overall use case and how you want your TabViews to behave, but you can work with the AutomaticKeepAliveClientMixin to ensure that your state of the StatefulWidget stays intact when switching tabs. This also ensures that the content of your StatefulWidget does not have to be rebuild when switching tabs, but will still use resources (just to keep in mind for performance considerations when working with more complex scenarios):
class MyHome extends State<Home> with AutomaticKeepAliveClientMixin {
/// Here you can either add custom logic to determine when
/// this tab should be kept "alive" - for now returning [true]
/// will work out.
#override
bool get wantKeepAlive => true;
...
I have a MainScreen() file where I defined two Widgets, side by side:
Left menu (ListTiles).
Main View (rest of screen, to the right).
My issue is that I need to tap the ListTiles on the left and dynamically change the Widget loaded on the Main View.
Any suggestions?
The main view must be stateful for this to work, as you need to trigger a rerender once you tap one of the tiles. You want to pass a callback function from your main screen to your menu of list tiles.
Your best bet is to setup an enum and have each listtile provide the callback with its own enum value.
Once you have the callback in your list of tiles, you can easily pass it onward to the individual tiles. Then, execute the callback function onTap and provide it with the correct enum value.
On your main screen, you just show the correct widget by looking at the current enum value.
class MainScreen extends StatefulWidget {
const MainScreen({Key? key}) : super(key: key);
#override
_MainScreenState createState() => _MainScreenState();
}
class _MainScreenState extends State<MainScreen> {
MyEnum _currentTile = MyEnum.Home;
void _callbackFunction(MyEnum tileOption) {
setState(() {
_currentTile = tileOption;
});
}
#override
Widget build(BuildContext context) {
return MyCustomListTile((MyEnum tile) => _callbackFunction(tile) );
}
}
I have made a TabBarView with a TabBar and each tab has its own navigator stack
when navigating through the navigator stack of the first tab and at some point swiping to another tab
and swiping back to the previous tab, the previous tab navigator stack has reset like it has build again
how to handle this situation
I want each tab navigator stack to hold its history when swiping to another tabs
I've figured out the solution and it is simply just wrap the nested Navigator with a stateful widget and use the state of the stateful widget with the mixin AutomaticKeepAliveClientMixin and implement the (must be implemented method)
#override
bool get wantKeepAlive => true;
as the following example
class NotificationsNavigator extends StatefulWidget {
#override
_NotificationsNavigatorState createState() => _NotificationsNavigatorState();
}
class _NotificationsNavigatorState extends State<NotificationsNavigator> with
AutomaticKeepAliveClientMixin {
#override
bool get wantKeepAlive => true;
#override
Widget build(BuildContext context) {
return new Navigator(
key: someKey,
onGenerateRoute: notificationsOnGenerateRoutes,
initialRoute: '/',
);
}
}
How do I preserve my data when I navigate between two different tabs in Flutter... Basically what I want to achieve is, on one side of the tab, I see users data, and on the other side of the tab, I want to be able to copy some of those user data and paste into some textfields on the other tab without losing the data in the text fields when I navigate back and forth and still also preserving the level of scrolling I might have done on the tab where the users data show.
You need to use AutomaticKeepAliveClientMixin This will ensure the State instance is not destroyed when leaving the screen.Extend your every tabview's state class with it and create an override method wannaKeepAlive and set it to true.Here is an example of a widget using AutomaticKeepAliveClientMixin.
class Example extends StatefulWidget {
#override
_ExampleState createState() => _ExampleState();
}
class _ExampleState extends State<Example> with AutomaticKeepAliveClientMixin {
#override
Widget build(BuildContext context) {
return Container(
);
}
#override
// TODO: implement wantKeepAlive
bool get wantKeepAlive => true;
}
I have used TabBarView as my page holder for BottomNavigationBar instead of Indexed stack. But this does refresh the page every time tab is changed. The state is not maintained. What to do?
Using AutomaticKeepAliveClientMixin flutter.dev
class _SampleScaffoldSate extends State<SampleScaffold> with AutomaticKeepAliveClientMixin {
// ... other code
#override
bool get wantKeepAlive => true;
}