I have a simple case, this is my layout:
ListView(
shrinkWrap: true,
children: [
Text("Row 1"),
Text("Row 2")
],
)
I want it to take only as much space in horizontal plane as its child widgets. Unfortunately, it expands to the whole width of the screen, which is the default behaviour of ListView.
Is there any way to make it take only as much space as necessary? The equivalent for Android would be wrap_content.
There are a lot of similar questions on this topic, but usually they are really looking for an alignment (so content aligned within their boundaries), whereas I'm looking for rows not taking all width (so having as small boundaries as possible).
Also I don't want to limit the size to some precise number, I want it to be flexible depending on the children width.
Related
I have a Row with three elements:
A Text which can be arbitrary short or long (called text in code)
A Wrap of elements which can be arbitrary short or long (called wrap in code)
An element of fixed size at the end (called fixed in code)
If it is possible to fit everything in one line, I want that all elements are displayed without any wrapping:
Only once it does not fit in one line, elements are allowed to wrap. I don't particularly care in that case, which element wraps first. I think it would be optimal to minimize the resulting vertical height, but this aspect is not that important to me.
My current code is:
return Row(mainAxisAlignment: MainAxisAlignment.spaceBetween, children: [
Flexible(child: Text(text, softWrap: true,)),
Flexible(child: wrap),
fixed,
]);
Unfortuantely the text and wrap element, each always take up exactly 50% of the available space in this case (due to the flex weight being 1 by default). So if either element takes more than 50% space it starts wrapping although it could take space from the other if that one is small.
How can I achieve no wrapping as long as it can be layout without wrapping?
I am coming to Flutter from a web background, where I am used to defining screen elements in terms of percentages of the height and width of the screen, or of elements that contain them.
I just completed a course.
Now that I am enthused and want to start building an app, I am a little confused, as the course only spoke of heights & widths in absolute pixel values. I can see this being problematic with different aspect rations, and especially with different orientations.
Is there a canonical approach to this? The official docs also seem to use absolute pixel values, so maybe I am missing a fundamental point.
A search suggests that I might use MediaQuery and then scale everything according to that. But, I don't see widespread use of that in code samples.
Is there a non-opinionated standard approach?
I am a little confused, as the course only spoke of heights & widths in absolute pixel values.
Actually, flutter uses density independent pixels (dp) for width/height arguments. dp actually scale with resolution, meaning 1 dp is displayed as the same PHYSICAL distance on every device. You don't have to worry about your elements being displayed at different sizes, just because the resolution of the screen they're on changes.
To be precise, flutter calls them logical pixel and:
By definition, there are roughly 38 logical pixels per centimeter, or about 96 logical pixels per inch, of the physical display.
So think about them as you would think about cm.
I am used to defining screen elements in terms of percentages of the height and width of the screen
Nonetheless, you might want to layout your widgets in a relative fashion (relative to the screen or the parent). For that purpose, flutter has different solutions:
Flexible
Expanded
Wrap
MediaQuery
LayoutBuilder
GridView
other layout options
Is there a non-opinionated standard approach?
It is a very opinionated question to begin with, but for example, Material design is a common standard for mobile-design. Flutters layout widgets are based around this approach.
But in the end, it is your design choice. For example, to achieve a responsive layout grid you could use Wrap, or you could use LayoutBuilder and determine yourself how you would like to layout rows and columns.
I would recommend you to scale widgets based on the size of the screen. This allows your application to be more flexible and adjust to various platforms and sizes such as large tablets or small phones. In order to do this, I recommend you to use the widget FractionallySizedBox which allows you to size widgets using a percentage of the screen size. For example, if you want a button widget to fill up 50 percent of a screen's width you can use the following code:
Container(
alignment: Alignment.center,
child: FractionallySizedBox(
widthFactor: 0.5,
child: FlatButton(
onTap: () {},
child: Text("PRESS HERE")
)
)
)
This code creates a button positioned in the center of the screen with a width of 50 percent of the screen size's width. You can also change the height of the button with the heightFactor field. By using this code the button widget will scale up and scale down for different screen sizes while still maintaining a size of half of the screen's width. For more resources, you should check out this video by the Flutter Team: https://youtu.be/PEsY654EGZ0 and their website on the FractionallySizedBox here: https://api.flutter.dev/flutter/widgets/FractionallySizedBox-class.html.
The FractionallySizedBox however is only one of many different approaches to making your flutter app fit to different screen sizes. Another approach is to use the AspectRatio Widget. Below is an example of this:
Container(
alignment: Alignment.center,
child: AspectRatio(
aspectRatio: 3/2
child: FlatButton(
onTap: () {},
child: Text("PRESS ME")
)
)
)
This code will create a button with a 3 to 2 ratio between its width and height. If the screen size changes the button will increase or decrease in size accordingly while again maintaining the 3 to 2 ratio. If you want more information the Flutter team also has a video on it (https://youtu.be/XcnP3_mO_Ms) along with some documentation here:(https://api.flutter.dev/flutter/widgets/AspectRatio-class.html).
Both widgets are perfectly fine and are considered standard practice to use but I personally use FractionallySizedBox more.
I hope my answer was helpful.
My widget tree looks like this :
Container(
child : Wrap(
alignment: WrapAlignment.center,
direction: Axis.horizontal,
spacing: 8,
children: _getWidgets(),
)
)
Now, this container is inside a column with other containers and therefore has a dynamic height based on the phone.
The _getWidgets() also returns a dynamic number of widgets. So, if the number of widgets exceed a certain limit, it overflows (easily fixable by enabling scroll).
What I want is to show only the number of widgets that fit in the given space without enabling scroll. Is this possible ?
For example, if I have 7 widgets, I calculate it will start overflowing at the 5th position, hence I only render 4 widgets.
I get a strange margin under my GridView:
This image is from an IOS simulator, here's how it looks on a smaller screen on Android where the margin appears to be gone or a lot smaller:
Here's the code:
Column(
children: [
GridView.count(
shrinkWrap: true,
crossAxisCount: 8,
children: tiles
),
Text('mamma')
]
)
Each element in the grid (tiles) is an EmptyTile widget:
class EmptyTile extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Container(
decoration: BoxDecoration(
color: bgColor,
border: Border.all(color: borderColor)
)
);
}
}
I really can't figure out what this margin is or where it comes from, whether it has something to do with shrinkWrap or something else.
How can I remove this margin?
EDIT:
As requested here's the fullscreen images without the simplified example.
IOS:
Android:
Try this. by default it has padding and you should set padding to zero.
GridView.builder(
padding: EdgeInsets.all(0),
The difference in layout you experience comes from a combination of things:
How GridView manages its size.
How widgets are placed in a Column.
GridView tiles and size
When you build a GridView, its width and height are implicitly deduced from the crossAxisCount parameter and the constraints given by its parent.
The constraints are the limits in size in which the widget is allowed to draw.
The crossAxisCount defines how many tiles should fit in one line (row or column). Depending on its scrollDirection, it will either try to fill all the available width or height. By default this direction is set to Axis.vertical, which means that the width will be filled.
So when we come back to your example, this means that the size of each tile will depend on the width of the Column containing your grid, divided by the number of tiles you set in crossAxisCount. This size will be both the width and the height of every tile in your GridView.
Once Flutter knows the size of each of your tiles, it sets them on each row, until all tiles are placed or there isn't any available space.
Column layout
Now that we know more about GridView, we need to understand how Column builds its layout.
Columns allocates space to each widget in its children, following an algorithm best describes in the docs.
tl;dr:
Your GridView will only fill its own height in the Column, leaving the rest as free space. This is why you get empty space in your Column.
Possible fix
I actually don't really see how this is a problem. GridViews are supposed to only extend to display their children, so it totally makes sense for it to stop when it completed.
The thing is, most of the times this ind of grids are not used with a finite list of children, and more likely with a growing list.
If you only want to have one line of tiles, that will extend using the available space, you could use a simple Row.
If you want multiple lines of tiles, with non-square tiles, you need to dive a little deeper into GridView.custom.
Edit after question was updated with more screenshots:
It is possible that you need to rethink your layout so that the player panels are in the same Column than the game board. You will have a much better control over the layout this way.
I have encountered a problem with scaled items in a Column layout.
(My problem is not with Text widgets. My actual code has a complex widget that's scaled on user input. But I will demonstrate the problem with Text widgets instead.)
I have two Text items below each other in a Column.
The first item is scaled up inside a Transform.
Column(children: [
Transform(transform: Matrix4.identity()..scale(4.0), child:
Text("I should not float over the thing below, despite being scaled."),
),
Text("But unfortunately this happens and it pains me greately."),
]);
The first item now floats above the second. See screenshot:
I want the layout to automatically adjust itself to new scale transformation.
Or I want the first Text to be cropped to a certain size (I've played around with SizedBox and FittedBox but got nowhere fast when used with a scale transformation).
Can anyone suggest a solution?
That's a feature of Transform. If you don't want that, don't use transform.
You could just instead do
new Text("foo", textScaleFactor: 4.0,)