//SOLVED: one of the containers inside the stack had an margin attribute that margins symetrically. Changed it to EdgeInsets.only(left:..,top:..)
I want to let my ListView start after the blue part of my page. But there is an blank and redundant space that doesn't allow me to start at expected point.
the blank space that i get
Here is my code:
Column(children:[Stack(some other code),Expanded(child:ListView(..))]);
The space is there because you have wrapped Stack(some other code) inside Column.
This is what you should do if you want the ListView to be over some other code,
Stack(
children:[
//some other code,
Column(
children:[
Expanded(
child : ListView(...)
),
...
According to documentation:
By default, ListView will automatically pad the list's scrollable extremities to avoid partial obstructions indicated by MediaQuery's padding. To avoid this behavior, override with a zero padding property.
To remove it wrap the ListView into a MediaQuery.removePadding:
MediaQuery.removePadding(
context: context,
removeTop: true,
child: ListView(...))
Related
I want to built a split screen for larger devices. One half should be as small as possible but as large as needed and the other half should occupy the rest of the screen.
I figured I'd use a Row containing two Scaffolds (one wrapped in a Expanded widget) like so:
Row(children: [
Scaffold(appBar: MyAppBar1(), body: Container()),
Expanded(child: Scaffold(appBar: MyAppBar2(), body: Container())),
])
However, I get the following error message when wrapping a Scaffold inside a Row:
RenderCustomMultiChildLayoutBox object was given an infinite size during layout.
I know that I could just wrap the Scaffold inside a SizedBox with a fixed width, but I want the Scaffold to automatically take the right size.
Scaffold itself doesn't have a width constraint, so it will try to occupy as much space as possible (if I'm remembering correctly), and Row on its part won't try to constrain it, hence the error.
You have two options:
wrap the Scaffold in another Expanded, then use the flex argument on both the Expanded to give them size relative to each other (i.e., if one has flex: 1 and the other flex: 2, the second one will have twice the size of the first)
wrap the Scaffold in a ConstrainedBox and set the constraints yourself, which I guess in this case would be the maxWidth set on the smaller side
As others pointed out, anyway, if you don't really need another Scaffold, you can simply use two Column and get a similar result.
You do not need to use two Scaffolds. Use two columns inside one Column in Scaffold. Wrap the second Column with Expanded. This way your first part will take as much space as needed and the second part will take the remaining space.
home: Scaffold(
body: Column(
children: [
Column(
children: [],
),
Expanded(
child: Column(
children: [],
),
),
],
),
)
Why does a ListView completely ignore imposed constraints?
#override
Widget build(BuildContext context) {
return Padding(
child: Container(
constraints: BoxConstraints(maxWidth: 500),
child: ListView(
children: buildList(data),
),
),
);
}
The displayed ListView does not seem to be bothered at all with the maxWidth:500 of the parent container (same if replaced with a ConstrainedBox) and all elements (which are Rows) go full screen width.
Why?
The solution is to work with width of children instead, but still I'd much rather constrain the entire listView, and also if there's a constraint, shouldn't everything inside be forced not to exceed it?
EDIT: After hours of trying various things it finally works. Turns out the list view needed to a child of a Center, otherwise it would not pay any attention to SizedBoxes, ConstrainedBoxes, Containers etc. you'd put on it or its children and stretch full screen no matter what.
What are the parent widgets of the Padding(child: Container(... list view ))? I mean are you sure that a parent is not imposing its constraints on its children? Try do replace your ListView with Container(color: Colors.red, height: 100) and see if it respects the constraints. If it does not, there probably is a parent widget with infinite width constraint or something like that!
A solution can be wrap your Container with an UnconstrainedBox but I would recommend first checking my first point :D
Sorry if this is a dup, I see a lot of questions regarding text wrapping, but not generic widget wrapping in a row.
I have a dynamic row of buttons within a row. I'd like to wrap the buttons to create a second row if the list becomes longer than the width of the screen. Is it possible to do this automatically, or do I need to manually detect and create the correct number of rows.
If the latter, does anybody have pointers to measuring a widget's width vs screen width? Right now I'm doing something like:
...
return Row(
children: List.generate(count*2 + 1, (i) {
if (i %2 == 0) {
return Spacer();
}
return RaisedButton(child: Text((i / 2).round().toString(), onPressed: (){...});
});
Row is useful when you need to organize child widgets in a single line. Wrap with default direction is an alternative to Row that moves child widgets to the next line if there is no enough space
I'm creating a widget that presents a Stack inside a Container. Inside the Stack there is a dynamic Column inside a Positioned widget, which sticks the Column to the Bottom.
I am trying to wrap the Stack in a SingleChildScrollView, that if the dynamic Column will have lots of children it will be able to scroll.
But after I add the scroll view I get this error message:
RenderStack object was given an infinite size during layout.
A scrollView doesn't have height, it will use infinite height for it's children. So the stack should be wrapped in a sizedBox widh a known height in case that you want that. If you want the stack to fill the screen then remove the singleChildScrollview completely. And if you want the stack to be scrollable from the inside. Just add SingleChildScrollView inside the stack
return Scaffold(
body: Container(
color: Colors.blue[100],
child: Stack(
children: [
Positioned.fill(child: SingleChildScrollView(child: MyColumn()))
],
),
),
);
EDIT 1:
Ok the problem is the layout itself. Since you only use the stack to position the image. And you know the widht and height of the image, and the background shape fills all the items. We could
Isolate the stack only to the image, and use padding and some calculation to have the layout build in a similar way.
Then render everything else inside a normal column
My implementation https://dartpad.dev/230b14d8f0b22b45929a75c208786257
From the RenderStack documentation:
First, the non-positioned children (those with null values for top, right, bottom, and left) are laid out and initially placed in the upper-left corner of the stack. The stack is then sized to enclose all of the non-positioned children. If there are no non-positioned children, the stack becomes as large as possible.
Since all of your Stack's children are positioned, Stack will match the maximum size constraint passed down by the SingleChildScrollView. This size has infinite height, so the Stack is forced to have infinite height as well.
To fix this, you will need to find another way to accomplish what you want. One option that comes to mind involves a ConstrainedBox providing a minimum height (obtained from a LayoutBuilder), a non-positioned Column, and a bottomCenter alignment on the Stack itself. This is similar to the first code sample in the SingleChildScrollView documentation:
LayoutBuilder(
builder: (context, constraints) {
return SingleChildScrollView(
child: ConstrainedBox(
// This ensures that the Stack fills the entire viewport,
// even if the Column is small.
constraints: BoxConstraints(
minHeight: constraints.maxHeight,
),
child: Stack(
// Place the only non-positioned child (the column) at the bottom
alignment: Alignment.bottomCenter,
children: [
Column(
mainAxisSize: MainAxisSize.min,
children: [ /* ... */ ]
)
]
)
)
);
}
)
I want to show a bottom sheet after the user tap on the FAB button. At first, it was working properly but I didn't know why it suddenly started to appear in full height/expanded state mode all the time.
I've tried with all type of bottom sheet listed in the document. It has the same problem.
// _scaffoldKey.currentState
// .showBottomSheet((context) => AccountView());
showModalBottomSheet(
context: context, builder: (context) => AccountView());
In the AccountView is a ListView, Currently, there's only one item. The bottom sheet height should only be equaled to the height of the ListTile. But it appears in full height instead.
You can use shrinkWrap: true, property in ListView or you can put AccountView() in a container and give it height.
Turn out I need to set shrinkWrap in the column to true.
Column(
shrinkWrap: true,
...
)