I see people usually initialize the controller like this, initializing it in initState() method.
late VideoPlayerController _videoPlayerController;
#override
void initState() {
super.initState();
_videoPlayerController = VideoPlayerController.network(
"https://assets.mixkit.co/videos/preview/mixkit-spinning-around-the-earth-29351-large.mp4");
}
but then I realize if I just put the controller like this without initState()just put the controller after the variables with late in before the variables, everything works fine. So what is the difference?
class _VideoDetailScreenState extends State<VideoDetailScreen> {
late VideoPlayerController _videoPlayerController = VideoPlayerController.network(
"https://assets.mixkit.co/videos/preview/mixkit-spinning-around-the-earth-29351-large.mp4");
As from the official documentation:
The framework calls initState. Subclasses of State should override initState to perform one-time initialization that depends on the BuildContext or the widget, which are available as the context and widget properties, respectively, when the initState method is called.
Related
Im using getx and i want to call api after bage build, because this api its not necessary part of the page build.. What i know is this way
#override
void initState(){
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_){
});
}
But what about getx best way ?
the Getx package offers lifecycle methods that are very convenient in you're cases, what you need here is to use the onReady(), which is called one frame after the onInit() is executed, you can say that its equivalent to the:
#override
void initState(){
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_){
// Here is the code which will be executed exactly after initState using StatefulWidget
});
}
you can use onReady() like this:
class TextController extends GetxController {
#override
void onInit() {
/*...*/
}
void onReady() {
// Here is the code which will be executed exactly after onInit using Getx
}
}
Let's say I created a ScrollController in a statefullWidget like so:
late ScrollController controller;
#override
void initState() {
super.initState();
controller = ScrollController();
}
#override
void dispose() {
controller.dispose();
super.dispose();
}
Using this controller indside the widget is easy.
But, if I want to access that controller from another screen, I have to pass it as a parameter maybe like so:
Navigator.pushNamed(context, '/another-screen', arguments: controller);
But, What if the screens are totally independent? (I can't pass it as an argument) I thought of using Provider to globally provide the controller. But now, I can't dispose it.
try to add on global late ScrollController controller;
and then initialise that variable
you can declare on main.dart late ScrollController controller;
I am trying to use a tab bar controller , what is the right way to add it
Just declare the tabController globally inside your state class and initialise it inside init state as you did, then you can access it inside your build method.
late TabController tabController;
void initState(){
tabController=TabController(vsync:this,length:3);
}
now use accordingly tab controller inside build method.
Try to declare tabController globally inside your state class and init it inside init state see the documentation for more details :
class _JobApplication... extendes State<...> ..{
late TabController _tabController;
#override
void initState() {
super.initState();
_tabController = TabController(vsync: this, length: 3);
}
}
declare in state
late TabController _tabController;
Assign in initstate
#override
void initState() {
super.initState();
_tabController = TabController(vsync: this, length: 3);
}
I want to create a TextController in the initState and then dispose of it like a good boy in dispose. But for some reason, the controller is not avaiable outside of the intiState:
class _InputFieldEnterThingState extends State<InputFieldEnterThing> {
#override
void initState() {
TextEditingController textController =
TextEditingController(text: 'placeholder');
super.initState();
}
#override
void dispose() {
textController.dispose();
super.dispose();
}
It tells me "textController" is not defined in dispose() ... same, if I try using it in the build method. It's, as if the varialbe is strictly local in initState. I feel I'm missing something super obvious, but cannot find it.
The textController is a local variable in the initState method, you need to make him global and the dispose method will recognize him.
The way to do that:
class _InputFieldEnterThingState extends State<InputFieldEnterThing> {
TextEditingController textController; // make him global
#override
void initState() {
textController = // without redefine
TextEditingController(text: 'placeholder');
super.initState();
}
#override
void dispose() {
textController.dispose();
super.dispose();
}
Since you declared the variable textController inside initState the variable is only accessible in initState. If you want to access textController e.g. in dispose, you have to declare it outside the initState.
class _InputFieldEnterThingState extends State<InputFieldEnterThing> {
late TextEditingController textController;
#override
void initState() {
textController = TextEditingController(text: 'placeholder');
super.initState();
}
#override
void dispose() {
textController.dispose();
super.dispose();
}
what is the difference between running a method before super.initState() and after super.initState()
#override
void initState() {
super.initState();
getCurrentUser();
}
#override
void initState() {
getCurrentUser();
super.initState();
}
Explanation for framework: Dart is class based object oriented programming language, so when you build a widget you extend it from a base class StatelessWidget or StatefulWidget. initState is lifecycle method in flutter widget (as you might know) which is only available to override in StatefulWidgets and it called only once. So, it call initState of base class which is StatefulWidget thats why you call super.initState()which in turn creates BuildContext and attached State.
Now your question: I didn't find anything different in calling a method before or after super.initState(). Event I tried adding addPostFrameCallback before super.initState() and it worked fine.
Even super.mounted is also true in both cases.
Suggestion
Dart/Flutter documentation "suggests" to call super.initState() as first method before your body implementation.
But if we look at how it is implemented Documentation
#protected
#mustCallSuper
void initState() {
assert(_debugLifecycleState == _StateLifecycle.created);
}
it's possible to see that it contains only an assert(). the assert built-in function it's called only in DEBUG mode, not in production mode. So, at the end of the day, it really doesn't matter, because the super.initState() would practically do nothing.