https://docs.flutter.dev/development/ui/interactive
A stateless widget never changes. Icon, IconButton, and Text are examples of stateless widgets. Stateless widgets subclass StatelessWidget.
https://api.flutter.dev/flutter/material/IconButton-class.html
An icon button is a picture printed on a Material widget that reacts to touches by filling with color (ink).
Icon buttons are commonly used in the AppBar.actions field, but they can be used in many other places as well.
If the onPressed callback is null, then the button will be disabled and will not react to touch.
When this button reacts to user touches, that means it is interactive? Then why does it fall under Stateless category?
The icon button is reactive, it reacts to touches. But can not change its state.
Stateless means the Widget can not recompose but it does can react to userevents like tapping. Look Textfield it has the ability to recompose it self whenever the text changed, So it means it is changing its UI state which is called a 'Stateful Widget'.
I hope you understood Cheers!
Related
I am using a DropdownButton in a Flutter app, and when you click it and the drop down appears, it overlays a webview that I'm using.
That all works perfectly, however webviews in Flutter, when run as a web app (which this is) trap all UI interactions and don't allow clicks to flow through to the Flutter UI elements.
There is a PointerInterceptor component that handles this perfectly, all I need to be able to do is wrap all of the DropdownMenuItems that appear inside of a single pointer interceptor (because if I individually wrap them then there is a really bad performance hit).
However - the DropdownMenuItems appear in the widget tree directly under the MaterialApp widget - and that is too high in the tree for me to wrap in a PointerInterceptor.
That is the reason that I want to know :
Is it possible to specify where in the widget tree the DropdownMenuItem widgets' appear when a DropdownMenuButton is clicked ?
I'm fairly new to Riverpod but it seems that using a ConsumerWidget as the body of a screen is a bad practice because the screen is rebuilt when not needed.
For example:
the main widget (the screen itself) is a ConsumerWidget
somewhere in the hierarchy I have a list of clickable buttons, for which I'm watching a ChangeNotifierProvider to update a selected index (only one button can be clicked at a time).
It seems that whenever I click one button to update the index (and change the color of the button), the main widget's Build method is called, along with the items in my list.
However, when using just a Consumer widget inside the itemBuilder method of my ListView, clicking one button no longer triggers the build method of the main widget.
So, is it considered a good practice to just use Consumer widgets where needed?
I'm using cardview on listview. And cardView has a icon.I wanna change icon color. When i click icon ,color is changed very well but whole listView is reloaded and goes to top of the listView. How can i change icon color withot refreshing listView?
connect the color to a variable and on an event change the variable using an terinary function then setState on the stateful widget.
Widgets vs helper method.
enter link description here
Here you can make a separate widget. That should be a stateful class. Otherwise, you can use any state management.
My app has a screen that is composed of several buttons and text labels which are conditionally visible based on the selection of the buttons (for example, a yes/no radio button asking whether you were exposed to a covid-positive individual, which would cause another radio button asking whether the encounter lasted more than 15 minutes to be displayed).
I know that stateless widgets for screens are preferable due to their improved performance, so I am trying to keep the screen widget stateless
The radio buttons in the example are actually custom statefull widgets wrapping a ToggleButton, so I would have the condition (controlling the visibility of widget) to flow between the main stateless widget and the statefull child widgets (with the toggle buttons)
When we want to achieve a button, we can choose raisedButton in flutter lib, also can a Container with onTap() function. So what's the difference between the two and which one should we choose in different situation?
Container function doesnot have onTap option, but you can achieve it by wrapping it in Guesture detector or Inkwell. There are no changes in the backend. But Raised button gives you the elevation, and animation on tap. You can also do it in the container, but it requires you to manually do it.
If you want a simple button quickly use RaisedButton.
If you want a more complex one, use Container or mixture of Containers, RaisedButton etc.
I am gonna offer something different... A tale of a treasure that is known to have answers to many questions, use cases and sometimes even examples. The name of this treasure is: official documentation. ;)
RaisedButton
A raised button is based on a Material widget whose Material.elevation increases when the button is pressed. Use raised buttons to add dimension to otherwise mostly flat layouts, e.g. in long busy lists of content, or in wide spaces. Avoid using raised buttons on already-raised content such as dialogs or cards.
Container
A convenience widget that combines common painting, positioning, and
sizing widgets.
GestureDetector
A widget that detects gestures. Attempts to recognize gestures that
correspond to its non-null callbacks. If this widget has a child, it
defers to that child for its sizing behavior. If it does not have a
child, it grows to fit the parent instead. By default a
GestureDetector with an invisible child ignores touches; this behavior
can be controlled with behavior. GestureDetector also listens for
accessibility events and maps them to the callbacks. To ignore
accessibility events, set excludeFromSemantics to true. See
flutter.dev/gestures/ for additional information. Material design
applications typically react to touches with ink splash effects. The
InkWell class implements this effect and can be used in place of a
GestureDetector for handling taps.
InkWell
A rectangular area of a Material that responds to touch. For a variant
of this widget that does not clip splashes, see InkResponse... The
InkWell widget must have a Material widget as an ancestor. The
Material widget is where the ink reactions are actually painted. This
matches the material design premise wherein the Material is what is
actually reacting to touches by spreading ink.
Well, technically you are right, they can both react to a click event. But a RaisedButton will have all the styles specific to the target platform taken care of for you (it inherits from MaterialButton).
note that it's the same in html: you can use a regular div with a click handler or use a button tag. The button will have a few styles already taken care of for you...