Unfortunately, I still stumble from time to time over the render engine complain about vertical or horizontal unlimited widget size. Example:
Column(
mainAxisSize: MainAxisSize.min,
children: [
Column(
mainAxisSize: MainAxisSize.min,
children: [
Text('1'),
Expanded(
flex: 1,
child: Text('X'),
),
Text('2 ')
]),
],
)
Error message:
======== Exception caught by rendering library ===============
The following assertion was thrown during performLayout(): RenderFlex children have
non-zero flex but incoming height constraints are unbounded.
When a column is in a parent that does not provide a finite height
constraint, for example if it is in a vertical scrollable, it will try
to shrink-wrap its children along the vertical axis. Setting a flex on
a child (e.g. using Expanded) indicates that the child is to expand to
fill the remaining space in the vertical direction. These two
directives are mutually exclusive. If a parent is to shrink-wrap its
child, the child cannot simultaneously expand to fit its parent.
Consider setting mainAxisSize to MainAxisSize.min and using
FlexFit.loose fits for the flexible children (using Flexible rather
than Expanded). This will allow the flexible children to size
themselves to less than the infinite remaining space they would
otherwise be forced to take, and then will cause the RenderFlex to
shrink-wrap the children rather than expanding to fit the maximum
constraints provided by the parent.
In the above example, the Expanded() has a flex factor. Which other widget does not have?
Could you outline an abstract algorithm, by which I could determine, if a certain child is allowed to be an Expanded()?
Related
I created a simple web app with Flutter.
The app layout is divided in two vertically zones: on the left there is a small top-bottom menu, on the right there is the main content inside a DataTable.
I wrapped the DataTable inside a SingleChildScrollView and everything worked fine.
The left side, on the other hand, keeps giving me a vertical overflow.
The tree on the left side is as follows:
Row(
children: [
//Left side menu
Flexible(
Container(
Column()
), //Container
), //Flexible
//Right side
Flexible(...),
],
), //Row
Obviously it is a very simplified version.
I've tried to insert a SingleChildScrollView in almost all places (Column, Container, Flexible), but it doesn't work and it always returns the error.
A RenderFlex overflowed by 174 pixels on the bottom.
Any solutions?
Thank you!
My approach would be to use MediaQuery to get current height and width of the web window. Then spilt the available width in the ratio of 2:7 maybe? You can play around with the ratio.
Now, lets keep the body of Scaffold to be Container with width as MediaQuery.of(context).size.width and height as ... .height. Now Row with childrens be 2 Expanded widgets with flex 2 and flex 7 respectively. Now we have to portion in the screen in the ratio 2:7.
On the left side, as you said, you need a menu, let it be
Expanded(
flex:2,
child: Column())
And on the other side be-
Expanded(
flex:7,
child: Container(
child: SingleChildScrollView() ///then add your stuff for scrolling purposes.
)
)
learn more about MediaQuery here
learn more about Expanded here
I want to layout a row in flutter with dynamic height items inside the row.
example:
there 2 widgets inside the row (A and B).
Widget A is a small content filled Widget (height 100px).
The height of B is bigger (eg.. 500px.)
the row should now have the height of the biggest child (B).
How can i say that child A autosize to 500px?
I know ... i can wrap the row into a SizedBox with 500px an set the crossAxisAlignment of the row to stretch... but that is not what I want ...
Is there a way to auto size all childs inside of a row to the heightest ?
You can use IntrinsicHeight widget like so with row's crossAxisAlignment set to CrossAxisAlignment.stretch.
IntrinsicHeight(
child: Row(
crossAxisAlignment: CrossAxisAlignment.stretch,
children: [
WidgetA(),
WidgetB(),
],
),
)
I have a column with 2 children. The first child has a fixed height, and the second child has dynamic content.
I want the first child to be at the head of the screen, and the second child to be in the vertical middle.
So i added an empty third child and made the first and third child Flexible so that they shared vertical space equally:
Column(
children: [
Flexible(
child: Column(
children: [_firstChild()],
),
),
_secondChild(),
Flexible(child: Container()),
],
)
This works when the content of the second child is short.
But if the second child gets tall, it clips the first child:
Isn't the Flexible supposed to distribute only the empty space when fit: FlexFit.loose? I tried both the fit possibilities. I've tried to put the first child inside a SizedBox and an Align
I've tried to make the third child a Spacer. Nothing has worked so far. The empty third child is taking half of the remaining vertical space.
EDIT:
When the second child's height is too much to make it vertically centered without clipping the first child, i want it to just behave like a default Column with MainAxisAlignment.start (like the first image)
What about this:
Stack(children:[
Center(child: SecondChild()),
Align(alignment: Alignment.topCenter, child: FirstChild()),
])
In a row widget, with the crossAxisAlignment: CrossAxisAlignment.center property, all the widgets inside of the row will be vertically centred inside the Row, as expected.
But how do I do if I want only one of them aligned for exmample to the start, something like the picture below:
I can think of some ways to do it, like adding a Column in the last widget, and play with the main axis aligment, Expanded...etc etc but seems like a lot of boilerplate code for such a simple output, ther might be out there a simpler and more elegant way to achieve this??
You can wrap widget 4 in a Container and set the height as widget 3 and add Alignment.topCenter
Ah, stumbled across this and found a solution.
Wrap widgets 3 and 4 in another Row and set the inner Row to CrossAxisAlignment.start.
Row(
children: [
LargeWidget('w1'),
LargeWidget('w2'),
Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
LargeWidget('w3'),
SmallWidget('w4'),
],
),
],
);
This frees you from having to know the height of each widget.
I'm trying to build a "semi-responsive" widget. It has a fixed number of relatively large children that always fit on the screen horizontally (A, B and C) and a variable list of small children that not always fit horizontally together with A, B, and C. My idea is to have the widget look like the first picture when the screen is wide, and as a second when the screen is more narrow, and as a third when there's no space for smaller widgets at all. What I'm getting is the third only. As if Wrap always tries to put as many children horizontally as possible. I want it to minimize width instead.
My pseudocode:
Card(
child: Wrap(
children: [
Row(children: [A(), B(), C()]),
Wrap(children: [1(), 2(), 3(), 4(), 5()]),
]
),
);
Any idea how to "squeeze" Wrap vertically? Using standard layout widgets if possible.
You can archive that using the alignment property in the Wrap widget.
Card(
child: Wrap(
alignment: WrapAlignment.end,
children: [
Row(children: [A(), B(), C()]),
1(), 2(), 3(), 4(), 5(),
],),
);
check it out in dartpad gist