This question already has answers here:
Passing data to StatefulWidget and accessing it in it's state in Flutter
(7 answers)
Closed 1 year ago.
I have this Stateful class and I wanna took "Data" from Stateful class to State class
Here is my code:
class PlayMode extends StatefulWidget {
final Data data;
PlayMode({this.data}); // Pass this to State class
#override
State<StatefulWidget> createState() {
return new PlayModeState();
}
}
How it can be done?
In your PlayModeState class, simply use
widget.data
Related
createState:
Creates the mutable state for this widget at a given location in the tree.
https://api.flutter.dev/flutter/widgets/StatefulWidget/createState.html
Now, in code:
class A extends StatefulWidget {
#override
_AState createState() => _AState();
}
class _AState extends State<A> {
}
Here we create a separate class named _AState which inherits from a predefined class named State?
So, what is createState' role here? How does it create a mutable state for us?
With createState you tell the StatefulWidget which class to use as state for this widget. And you tell it here that it needs to create an instance of _AState for this widget.
By the way, it is also recommended to write it as
State<A> createState() => _AState();
It still works the way you wrote it but the IDE might complain about
Avoid using private types in public APIs
Saying the return type is State<A> instead of _AState removes this warning.
In order to create a stateful widget in a flutter, it uses the createState() method. Stateful Widget means a widget that has a mutable state.
I have a situation where I want to create multiple flutter StatefulWidgets based on the same state class. The problem I run into seems clear, the state widget needs to know the properties of the parent that calls createState. There has to be a way to accomplish this without having to copy paste large amounts of code.
What I have so far is a state class that looks like this:
abstract class XxxState<T extends StatefulWidget> extends State<T>
{ TextEditingController textController; // instantiated by initState().
}
to accomplish what I want I create several abstract methods that the subclass will override to implement it's function. The problem is when I create the class I want to instantiate I don't know how to connect the new StatelessWidget to the state class that overrides the XxxState class.
class YyyWidget extends StatefulWidget {
#override
_YyyState createState() => _YyyState();
}
class _YyyState<YyyWidget> extends XxxState {
/// In this class widget.xxx looks to StatefulWidget and not YyyWidget
}
Any reference for how this should be done would be appreciated.
All one has to do is learn how to subclass a StatefulWidget correctly and all works as expected.
abstract class YyyWidget extends StatefulWidget { ... }
// Do not do the createState here
// Someone edited the question and removed the abstract from the code,
// thereby changing the question to one they thought they could answer.
Then create the abstract state
abstract class YyyState<Page extends XxxWidget>
extends State<Page> {
{
TextEditingController textController;
...
}
Then the subclass calls
class ZzzWidget extends XxxWidget {
// Do the create state here
#override
_AaaState createState() => _AaaState();
}
and the subclass state is
class _AaaState extends YyyState<AaaWidget> {
//inside this class widget.field gets state from AaaWidget
}
I don't even remember what the original post was, So maybe deleting the question is the better option here.
This question already has answers here:
Make flutter application fullscreen
(13 answers)
Closed 2 years ago.
I have tried different things from different sites and articles but i cannot get rid the black bar on top
it's been asked here
tl;dr
add this piece code to the main function, before runApp()
SystemChrome.setEnabledSystemUIOverlays([])
code:
void main() {
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setEnabledSystemUIOverlays(<SystemUiOverlay>[]);
runApp(MyApp());
}
the screen you want to make will be like this
class SplashScreen extends StatefulWidget {
#override
_SplashScreenState createState() => _SplashScreenState();
}
class _SplashScreenState extends State<SplashScreen> {
#override
Widget build(BuildContext context) {
return Scaffold();
}
}
result:
without SystemChrome.setEnabledSystemUIOverlays([]):
I'm currently learning Flutter. I tried to deep dive into Flutter Widget life-cycle, and I wonder why StatefulWidget are written like this :
class Example extends StatefulWidget {
#override
_ExampleState createState() => _ExampleState();
}
class _ExampleState extends State<Example> {
// initState
// setState
// ...
#override
Widget build(BuildContext build) {
...
}
}
but not :
class Example extends StatefulWidget {
// initState
// setState
// ...
#override
Widget build(BuildContext build) {
...
}
}
I think the latter makes the source simple. But I don't know why they're using the former style ?
The reason why StatefulWidget uses a separate State class and not having build method inside its body is because all fields inside a Widget are immutable, and this includes all its sub-classes.
You might have noticed that StatelessWidget has its build and other associated methods defined inside it, but that was possible due to the nature of StatelessWidget which is rendered completely using the provided info, and doesn't expect any future change in its State.
In the case of StatefulWidget, State information occasionally change (or expected to change) during the course of the app, thus this information isn't suitable for storage in a final field (build) to satisfy Widget class conditions (all fields are immutable). That's why State class is introduced. You just have to override the createState function to attach your defined State to your StatefulWidget, and let all that change happens in a separate class.
This question already has answers here:
Passing data to StatefulWidget and accessing it in it's state in Flutter
(7 answers)
Closed 3 years ago.
I have a string that contains an information that was passed from previous classes. But i need to use that variable in the state class.
Class of stateful widget that contains the information (String text):
class CreateLevelScreen extends StatefulWidget {
String text;
CreateLevelScreen({Key key, #required this.text}) : super(key: key);
#override
State<StatefulWidget> createState() => _CreateLevelState();
}
State class of stateful widget to retrieve that information text too.
class _CreateLevelState extends State<CreateLevelScreen> {
//need to pass text in here to use it too.
}
When you say
class _CreateLevelState extends State<CreateLevelScreen>
it means _CreateLevelState will manage the state of CreateLevelScreen
so the variables are directly accessible as widget.<variable_name>
thus you have widget.textto be used in _CreateLevelState class if there is a variable text in your CreateLevelScreen class.
You can use text in _CreateLevelState using widget.text.