In flutter, Is there any difference between these layouts? -
Expanded
SizedBox.expand
BoxConstraints.expand()
If all are same, why there are multiple layout classes/functions for same functionality?
As far as I know.
Expanded widget can only used inside of Row, Column and Flex. It helps to expand the children based on the flex value. By default - it's 1.
SizedBox.expand - It will expand the child as large as it's parent allows. You can put anywhere unlike Expanded.
BoxConstraints.expand - Usually takes as object of ConstrainedBox constraints property.
From the documentation -
Creates box constraints that expand to fill another box constraints.
If width or height is given, the constraints will require exactly the
given value in the given dimension.
Related
I need a grid that contains children of fixed sizes.
GridView expands its children, which is not what I need. The grid should simply size itself according to it's children by setting the crossAxisCount.
My current solution is to use simple columns and rows, but that's so much boilerplate code for just a common widget.
You will have to do it dynamically, and supply the value of the crossAxisCount dynamically
My Flutter UI has a Row widget with and arbitrary number Widgets in it. I would like to move all of those widgets over to the right by a fixed amount. But the caveat is, if the other widgets grow in width such that the available horizontal space is consumed, the spacing widget will relinquish its space.
The Spacer widget does not work for me, as it does not allow you to specify a fix maximum. It only allows a flex value, which is a function of the width of the other content in the row. I want this spacer to take up a fixed amount of space regardless of the width of the other content of the row (unless all the room is used up).
Try using sizedBox or FractionallySizedBox as explained in this answer
https://stackoverflow.com/a/63430801/8213343
In a flutter app, what is the difference between a Container inside a Row and a Row inside Container?
In flutter in each time I want to make an app, I took minutes to ask my self
which one should I choose?
In flutter Row and Column provide a way to use the Flex layout system aka FlexBox.
In short Flex is a one-dimensional layout system, where in the children can be aligned on the main-axis or cross-axis, the main axis can be defined as horizontal or vertical.
A Container in Flutter is a general-purpose widget that gives you access to a range of properties like padding, decoration, size etc. A full-list is available at the API Docs
To answer your question,
A Container in a Row is like we said above, a child of a Flex, which means it will respect the properties of alignment set by the parent (MainAxisAlignment/CrossAxisAlignment )
A Row in a Container, is the opposite of that which means that, the Row or Column will respect properties set on the Container that is for example the Decoration or Size properties amongst others.
Containers with no children try to be as big as possible unless the incoming constraints are unbounded, in which case they try to be as small as possible. Containers with children size themselves to their children. The width, height, and constraints arguments to the constructor override this.
Question
What does the incoming constraint mean in Flutter?
According to Google's flutter documentation on understanding constraints:
A widget gets its own constraints from its parent [the "incoming constraint" you are asking about]. A constraint is just a set of 4 doubles: a minimum and maximum width, and a minimum and maximum height.
Then the widget goes through its own list of children. One by one, the widget tells its children what their constraints are (which can be different for each child), and then asks each child what size it wants to be.
Then, the widget positions its children (horizontally in the x axis, and vertically in the y axis), one by one.
And, finally, the widget tells its parent about its own size (within the original constraints, of course).
I suggest you read that entire URL for more details. The Google people are writing some amazingly clear documentation.
i'm trying to set widgets sizes according to screen height. For example i have 3 widgets inside my body, the first and second one should be 20% from whole screen size, the third one - the rest.
The problem is that i have CupertinoSliverNavigatoinBar and CupertinoTabBar, so i can't calculate height of my third widget.
I'm trying to implement this thing.
According to documentation, CupertinoTabBar height is 50.0. To verify this you can check the source code of CupertinoTabBar and there is constant which called _kTabBarHeight.
But for your particular problem I think you should use Expanded widget with flex property.