I have a simple chat page with a ChatBloc and a ReplyBox widget, a message box with a send button.
The I would like the ReplyBox to be reusable, so not to have specific knowledge of the ChatBloc. However, I'd like to be able to control the text in the ReplyBox from the bloc. This is proving very difficult because the text field expects to use a TextEditingController.
What I've tried:
Using TextFormField initialValue to pass into the widget the text from the bloc. Doesn't rebuild when the value changes.
Forcing a rebuild using Key. Text is updated but focus is lost.
Making it a stateful widget with a TextEditingController, not taking the text value from the bloc, and just clearing when the button is pressed. This works ok, but it's not flexible. For example, the message would be cleared if there is a sending error, which it shouldn't.
I haven't tried managing the TextEditingController in the bloc. It seems like not the right thing to do.
I see the 3rd method is promising with StatefullWdiget and TextEditingController to solve your problem.
I would have another bloc for the ReplyBox with events like Reset, Update, etc.
In the widget I would connect the state of the ChatBloc to ReplyBloc.
In drawing may be something like this:
I have asked a similar question on the repository of BLoC library. Quoting the answer provided to me by Felix Angelov, the creator itself:
I don't recommend that. The proper way imo is to maintain a TextEditingController and call clear when you want to clear the input.
You can read the answer here plus you can also check the entire question.
Related
I'm struggling to figure out how to use Riverpod for the following scenario.
I have a file called textformfields.dart with 3 TextFormFields
I have another file called buttons.dart (which is widely used in the whole project) which generates an ElevatedButton
I have another file called submitProject.dart which returns a Scaffold and calls the textformfields.dart and the buttons.dart
My goal is to disable the button, if at least one of the 3 TextFormFields is empty.
I really have no idea how to start, since I'm not really familiar with State Management and Riverpod yet.
Can you give me some tips?
I am designing an application that uses setState to refresh a screen with all its widgets, however I would like to know if there is a way to exclude a particular widget (conainer) and all its children, as if I were treating it as a new page.
I tried to use Navigator.push (context, MaterialPageRoute), but it didn't work, I would like to treat the widget as a separate page. I appreciate any help
Short answer: You can't.
Long answer: You can change where the setState is called, create a separate StatefulWidget that contains only the ones that need to be rebuilded. However in most of the cases this is not possible because of the order you need to show your widgets or many other factors. That's when State Managements tools come in handy. You should try to learn how to use Provider, Riverpod or BLoC (which i personally recommend). If you want something a litte bit easier you can start learning how to use InheritedWidget starting in the documentation right here.
use const if possible. if not,
use StatefulBuilder , if you call setState inside this widget, the outside widget is not touched. Maybe it will suit what you need
i have a page named displayData . On it there is a button if i click on it it shows DraggableScrollableSheet normally it has a button done when i click on it the icon of the page on the bakground (DisplayData) must change .i used a variable in a setState but it doesn't work it's true on the DraggableScrollableSheet but always false in display data
any help !
for this type of cases, there are several solutions, I recommend the use of providers, in this way with the use of 'extends ChangeNotifier' you will be able to detect the changes made without having to use the setState and you will be able to call from any class (or page ) the variables you need
you can use callback methods from on widget to another, if you have much complicated scenario then I suggest using state management libraries like Provider, RiverPod or Bloc.
also
Could you share your code here
In Flutter does avoiding setState() achieve anything?
I have a StatefulWidget (screen) where I use Widgets that handle their own state completely with the exception of the FAB button. The Fab button is disabled or enabled when data has changed in order to allow the update of the DB when data has changed. I posted a question on SO as to how to use Provider to handle that and thus prevent the need to setState(), and implemented that with Provider.
When looking at another screen to implement something similar, I wondered if another solution may be better. This screen also contains Widgets that all handle their own state - TextFields with TextEditControllers, so the only place I was calling setState() was to enable or disable the FAB. I had previously created a Stateful Widget to create a CheckBox with its own state because the standard CheckBox doesn't have state. It's fairly simple and only 50 lines of code. So, I did the same with the FAB, I created a Stateful Widget (CustomFab) that encapsulates a FAB. When it needs to be enabled or disabled, it is called to set its own state, and returns a FAB that is either enabled or disabled with the appropriate color. Because I have other similar screens, I can use that same component with them.
Does it achieve anything by avoiding setState() in this situation (for mobile and Web), and if so, which is the best way to handle that (Custom-Widget or Provider or another)?
setState is merely avoided in Flutter development for two main reasons:
It rebuilds the whole widget, which may hinder performance on consecutive calls if not used correctly.
using setState only as a state management couples the business logic to the UI, which may reduce code re-usability and maintainability.
In simple apps, there are no significant issues in using setState. However, if you need more control over your code, I suggest going for more complex state management patterns.
Is it possible to do inter widget communication via something like a notification/event bus?
I need to be able to tell one widget to react to something that happened in another and didn't want to create a hard link.
The notification listener will only fire is if it is higher in the widget tree than both of the widgets so that isn't probably a viable solution.
There are lots of ways to do this depending on your use case.
You could have them be AnimatedWidgets that are passed a ValueNotifier or ChangeNotifier as the listenable. You can see this pattern in the Gallery's animation example.
You could use StreamBuilder to have your widgets rebuild automatically when new events come in on a Stream. There aren't a lot of examples of this in the main Flutter repo, but it's something that you're likely to need once you start using plugins or doing network I/O.
You could use a GlobalKey to get currentState and have one State call methods on the other. This is how snackbars work (example).
You can also extend InheritedWidget to provide widgets with information that wasn't passed as a constructor argument, and they'll automatically be marked for rebuild when that information changes. This is how Themes work, for example.
If you can provide more details on what your widgets do / what their relationship is, or ideally a code snippet I can help you decide which approach would make the most sense for your situation.