Is there any way in flutter in which we can size everything in our app depending on screen size like rem property in css. Because all widgets demand sizes in pixel sizes which can be different for different screen size.
Because all widgets demand sizes in pixel sizes
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.
But for relative layout there are some options:
Flexible
Expanded
MediaQuery
LayoutBuilder
GridView
other layout options
Related
as you might know there are two types of size in flutter app (physical,logical).
for margin and padding if we want the app to be responsive we must get context size (width,height).
for a reason I don't want to use MediaQuery.of(context).size so I'm using
Size screenSize = WidgetsBinding.instance.window.physicalSize;
double width = screenSize.width;
double height = screenSize.height;
in such case the size is physical and can't be used like before for padding and margin with edgeinsets.
what I'm asking is a way to either change physical pixel size to logical without using context and MediaQuery or a way to use physical pixels to give responsive margin and padding.
thanks in advance.
I tried to get the ratio with testing results it differs between devices so we can't use static ratio.
The ratio is not the ratio of height/width of physical size.
You can get the screen size without context like this:
var size = MediaQueryData.fromWindow(WidgetsBinding.instance.window).size;
now if you print this size, you can see it is equals to the size that you get from MediaQuery with context.
How to get the screen's (or pixel's) physical width and height in flutter?
is it possible?
I need to display exactly 1 cm on different screens programaticly
Thanks.
You can use:
MediaQuery.of(context).size
/// The size of the media in logical pixels (e.g, the size of the screen).
///
/// Logical pixels are roughly the same visual size across devices. Physical
/// pixels are the size of the actual hardware pixels on the device. The
/// number of physical pixels per logical pixel is described by the
/// [devicePixelRatio].
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.
Given any screen resolution, is there a way that I can figure out the amount of points in an inch? For instance, if I wanted to create an NSView that was 8.5 inches by 11 inches (like a sheet of a paper), is there an algorithm that will allow me to obtain the correct point values for the frame across many different types of Macs and screen resolutions?
It's not straightforward. I'm not sure there's a good way. I can provide an approach, but I haven't confirmed that this works reliably:
First, you can use CGDisplayScreenSize() to get the screen's physical size in millimeters. You can obtain the CGDirectDisplayID for a screen from NSScreen, which you can, in turn, get from the window. Obtain the screen's deviceDescription and get the value for the "NSScreenNumber" key. That may need to be cast to CGDirectDisplayID.
The problem from there is that the display mode may not fill the screen. It could be letterboxed or pillarboxed. Or, it might be stretched. This should be fairly uncommon these days, but still possible. You can obtain the display mode using CGDisplayCopyDisplayMode(). To determine if it's stretched, you can examine its ioFlags to see if they contain the bitmask kDisplayModeStretchedFlag (declared in IOKit).
If it's stretched, the screen's frame will have to be mapped to its size in millimeters separately for the X and Y axes. You assume the screen's frame.width (in points) maps to the full physical width, and similarly for the height.
If the mode is not stretched, you'll have to check the aspect ratio of the frame and the screen physical size to see if it's letter- or pillarboxed. If the aspect ratios are very close, then it's presumably not. That case is similar to the stretched case, but the width and height mappings should be equivalent.
If the aspect ratios differ significantly, then you compare them. If the screen's physical aspect ratio is larger than the frame's, then the screen is physically wider than the mode is using (pillarboxed). So, you compute the mapping from points to millimeters from the two heights. If the physical aspect ratio is smaller than the logical one, then the mode is letterboxed and you use the widths to compute the mapping.
I have a vertical Scroll List. I have developed this app for resolution 768*1024. In this resolution my List is working fine. But when I run my app in higher resolution(1440*2960) it leave some space around all 4 direction.
I have also tried with changing Layout element min height dynamically, but Spacing issue is still exist.
Vertical and horizontal layout set element position in (screen width/height divided by a number of elements) * element number, in other words, they space out all elements evenly across canvas space. To achieve what you want you either have to enable child control size -> height option or write a script that aligns your elements in the center of the screen and one after another taking in consideration their height.