I read everywhere on internet, in flutter everything is a widget but what actually widget is.I thinks its simply contain a bunch of properties that flutter need to render something on screen.But If widget is same as UI component then why we specially called it (Widget),like other languages we simply called UI components.Is Widgets same as UI component?
A widget is just a class that extends either the StatefulWidget or StatelessWidget classes.
It is also not really true that everything in flutter is a widget, but a lot of things are widgets. There are a hierarchy of widgets from the whole app itself to the containers or texts you have on the page, and everything in between. Lots of code you write for your app might be outside of these widget classes, and just interact with them.
Related
Working on a game project where:
I have a BottomNavigationBar navigating betwen my custom Widgets where one of them is a FlameGame. I don't want to unload and reload the widgets when player navigates as it will be frequent and expensive.
I have followed this and now my custom Widgets are being preserved, except for the FlameGame.
Tried adding AutomaticKeepAliveClientMixin. Wanted me to implement 12 overrides... Any suggestions?
Wrapped my GameWidget in another custom widget of mine that implements the KeepAlive mixin.
It works now.
I'm quite new to flutter and I'm trying to figure out the best way to build my widgets in the aspect of good performance while I have three choices:
1- Stateful Wigdet.
2- Stateless Widget.
3- Widget function(){} with a StatefulBuilder if needed.
Thanks.
A StatefulWidget has State, which means that you can change stuff inside the widget without needing to destroy it and create a new version. They work slower than StatelessWidget but are better for checkboxes or screens which need to be frequently updated.
A StatelessWidget is locked, and you cannot change values once it is initiated. In order to change things inside the widget, you need to re-call the build function to build an updated version. They are quite fast but are best used for static screens.
Widget function(){} widgets are custom-made. Essentially, you can take any existing widget and modify it, adding childs and other widgets to it. However, the widget type normally inherits from a StatefulWidget or StatelessWidget. These can cover basically everything.
The core concept of StatelessWidget and StatefulWidget is confusing to me.
According to flutter documentary:
A widget is either stateful or stateless.
If a widget can change—when a user interacts with it, for example—it’s stateful.
A stateless widget never changes. Icon, IconButton, and Text are examples of stateless widgets. Stateless widgets subclass StatelessWidget.
so mainly if you have something on the screen that changes when user interacts with it, you should use stateful widget for it and otherwise, you should use stateless widget.
for example if you have a plus button on the screen and a a number on the screen which should be increased every time the user press it, you should use stateful widget to notify flutter that the text on the screen should be changed and rerendered.
for more information you can check here.
In the Flutter docs they say that a Widget is a mutable configuration (description) for an Element, which I have no problem understanding.
But then we have the stateless widget, which extends the Widget class, and must implement a build method. The two classes look like they do the same job, can any one explain the difference ?
Thanks.
Widget is just an interface. You're never gonna use it directly, and this class does absolutely nothing.
It exists just for the compiler to know that your program is type-safe.
every thing with flutter made with widgets there is no widget only it is Stateless widgets and statefull widgets
and the stateless is static and the other is dynamic
stateless for fixed layouts if you need any dynamic programming like(validation, requests, listeners for buttons and others..)
you need to use Statefull widgets
for more information see here..
difference between stateless and statefull widgets
I am learning Dart/flutter and trying to understand how Widgets system works. But I can't understand what difference between stateless and stateful widgets? For example I have button. What type it have?
Let's imagine two cases.
I send text to button and it's display it.
I send text to button and it's change color.
What will be if I will create not proper Widget type?
There are 3 kind of widgets, not just 2.
Stateful widget
Stateless widget
Inherited widget
A stateless widget is like a constant. It is immutable. If you want to change what is displayed by a stateless widget, you'll have to create a new one.
Stateful widgets are the opposite. They are alive and can interact with the user. Stateful widgets have access to a method named setState, which basically says to the framework "Hello, I want to display something else. Can you redraw me please ?".
Finally, Inherited widget is a mixt of both worlds. It is immutable and stateless. But another widget (whatever it is) can subscribe to that inherited widget.
Which means that when you replace your inherited widget by a new one, all the widgets that has subscribed to the old one will be redrawn.
In the end, a stateful widget will usually be used like a Controller.
A stateless widget will be used like a View.
And the inherited widget will be your configuration file or your Model.
According to flutter.io:
Stateless widget
Stateless widgets are immutable, meaning that their properties can’t
change — all values are final.
Here is doc.
Stateful widget
Stateful widgets maintain state that might change during the lifetime
of the widget. Implementing a stateful widget requires at least two
classes: 1) a StatefulWidget class that creates an instance of 2) a
State class. The StatefulWidget class is, itself, immutable, but the
State class persists over the lifetime of the widget.
As a example if you want to change text in text widget when a button press, you have to use StatefulWidget and it will let you to change the state of a variable.
But in StatelessWidget you cannot do that because it doesn't keep state.
Read more from doc.
This tutorial will help anyone who trying to understand these two.
Check out the Flutter Interactivity Tutorial.
If your widget's build method depends entirely on its immutable constructor arguments, you should use a StatelessWidget because they're simpler. If you want to store some persistent private data that you expect to mutate over time, use a StatefulWidget and store the data on the State.