Develop Reference

Flutter column shows extra space between widgets in Android

Column widget is showing extra space between consecutive widgets even when using simple containers with their padding set to 0. I have tried using SizedBox, setting mainAxisSize to min but nothing seems to be working.
Moreover this issue is only appearing in Android OS and not on Web or iOS.
My Code:
Scaffold(
backgroundColor: Colors.yellow,
appBar: AppBar(
title: Text(title),
),
body: Center(
child: Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Container(
padding: EdgeInsets.zero,
height: 50,
color: Colors.black,
),
Container(
padding: EdgeInsets.zero,
height: 100,
color: Colors.black,
),
SizedBox(
height: 20,
),
Container(
height: 150,
color: Colors.black,
)
],
),
),
)
Output:
I have zoomed the image a bit to on the right to display the gap better. There is a line of space appearing between the 2 containers. I have placed another container of 150 height below the column to show the difference between complete opaque and space. I have recreated this same behaviour on Pixel 3 Emulator as well as OnePlus 6T device.
Can anybody help me with a fix to this. I know this can be solved using Stack and Positioned but I was hoping to find out if this is an issue in Flutter SDK or a fixable widget behaviour.

That's a pretty annoying effect indeed. And though I can't tell you why this is happening, playing around with it a bit, it seems that giving the Container a BoxDecoration with a Border instead of a color removes the artifacts:
Scaffold(
backgroundColor: Colors.yellow,
appBar: AppBar(
title: Text('title'),
),
body: Center(
child: Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Container(
decoration: BoxDecoration(
border: Border.all(color: Colors.black),
color: Colors.black,
),
padding: EdgeInsets.zero,
height: 51,
//color: Colors.black,
),
Container(
decoration: BoxDecoration(
border: Border.all(color: Colors.black),
color: Colors.black,
),
padding: EdgeInsets.zero,
height: 100,
),
Container(
decoration: BoxDecoration(
border: Border.all(color: Colors.black),
color: Colors.black,
),
height: 150,
//color: Colors.black,
)
],
),
),
)

For me answer didn't work (probably because i had clipPath over container but i found similar solution)
decoration: BoxDecoration(
border: Border.all(width: 0, color: Colors.yourColor),
color: Colors.yourColor,
),
In all containers at your column

Rounded Tab Bar in Flutter

I am new to flutter and creating a project where the design contains rounded top navigation. In flutter we have tab bars. So I searched around but could not find the solution. There were solution for rounded tabs but not the tab bar as whole. Is it even possible or is there a work around it.

You can create custom tab bar using Container and Stack to positioned Container on top.
Something like this.
Container(
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height,
child: Stack(
children: <Widget>[
Positioned(
top: 0,
child: Container(
width: MediaQuery.of(context).size.width,
height: 80,
decoration: BoxDecoration(
color: Colors.blue,
borderRadius: BorderRadius.all(Radius.circular(25.0))
),
child: Row(
children: <Widget>[
//icons buttons
],
),
),
)
],
)
),

How do I set the background colour/image to be stacked above another expanded widget? Or is there another way

Currently the only way I could make this kind of curved effect would be through making 2 container, making 1 a child of another and making 1 container's colour into the background colour.
However I cannot replicate this effect if the background is an image. Could anyone assist?
Example of the code I use:
Scaffold(
body: SafeArea(
child: Column(
children: <Widget>[
Container(
height: 100,
color: Color(0xFF0D6068),
),
Expanded(
child: Container(
color: Color(0xFF0D6068),
child: Container(
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.only(
topLeft: Radius.circular(50),
topRight: Radius.circular(50),
)),
),
))
],
)),
);

You can make use of a Stack widget to achieve this, such that the background color or image would be at the back then the curved container would be stacked on it. Here is an example code.
Stack(children <Widget> [
Image.asset(''),
Container()
]
)
Instead of using an image asset, you can make use of BoxDecoration with the decoration parameter of a container. The BoxDecoration has an image parameter where you can provide your image with a DecorationImage() widget.

How to create a custom stack in sliver appear in flutter?

Hi Everyone I am creating a profile page for a flutter app.
The SliverAppBar needs to show the below view when in the expanded state:
And below view when the user scrolls the silver list.
As you see this is a custom stack that I can create.
I don't know how to do it in slivers in a flutter.
Any links would also be highly appreciated to learn in-depth about flutter and slivers especially.
Code for the collapsed stack:
Stack(
alignment: Alignment.topRight,
children: <Widget>[
Container(
margin: EdgeInsets.only(top: 12),
width: 2000,
height: 80,
decoration: BoxDecoration(boxShadow: [
BoxShadow(blurRadius: 5.0, color: Colors.black87)
])),
Container(
margin: EdgeInsets.only(right: 20, top: 5),
decoration: BoxDecoration(
shape: BoxShape.circle,
boxShadow: [
BoxShadow(blurRadius: 5.0, color: Colors.black87)
],
border: Border.all(color: Colors.cyan, width: 3.0)),
child: CircleAvatar(
backgroundImage: AssetImage(
"assets/images/food/avocado-f.jpg"),
radius: 50,
),
)
],
),

You should use SliverPersistentHeader and create your own SliverPersistentHeaderDelegate.
In the build method you add your Stack view and you can use Transform or SizedBox to scale and transform the circle depending on the height of the header.
There is a nice tutorial that explains how to use this widget
https://medium.com/flutter-community/how-to-code-a-dynamic-header-in-flutter-e171ec2231bf

Flutter mask a circle into a container

I want to add a circle effect over a container, but I want the circle to not extend the dimensions of the container, but instead get clipped by it. This is what I'm trying to achieve:
As you can see the white circle naturally would extend the red container but instead, I'm trying to make it stay into the borders. How can I do it?

The simplest way to do this is to using an overlap and cliprect.
class OverlapSquare extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Container(
height: 200,
decoration: BoxDecoration(
borderRadius: BorderRadius.circular(10),
color: Colors.red,
),
child: ClipRect(
clipBehavior: Clip.hardEdge,
child: OverflowBox(
maxHeight: 250,
maxWidth: 250,
child: Center(
child: Container(
decoration: BoxDecoration(
color: Colors.white,
shape: BoxShape.circle,
),
),
),
),
),
);
}
}
The OverFlowBox allows the circle to draw outside the bounds of its parent, and then the cliprect cuts it back to the edge.
Just an FYI - on my device I'm getting a tiny red line at the top & bottom of the white circle. I'm fairly sure that's a recently-introduced bug in flutter as I'm also seeing something similar if I put a white border around the container. I've raised an issue on github for that.

ClipRRect worked best for me.
See reference video: https://www.youtube.com/watch?v=eI43jkQkrvs&vl=en
ClipRRect(
borderRadius: BorderRadius.cirular(10),
child: myContainerWithCircleWidget,
);