Density of screen in iOS and Universal WIndows App - xamarin.ios

Question

Hi I need to know the density of screen in windows 10/8/8.1 and iOS.
I got screen density in Android using DisplayMetrics but I find no such option/property available in UWP and iOS.
So Is there any property through which I can get screen density in UWP and IOS.

Answer 1

UPDATE - June 8th 2018
Xamarin has released Xamarin.Essentials!
Xamarin.Essentials provides developers with cross-platform APIs for their mobile applications.
Android, iOS, and UWP offer unique operating system and platform APIs that developers have access to all in C# leveraging Xamarin. Xamarin.Essentials provides a single cross-platform API that works with any Xamarin.Forms, Android, iOS, or UWP application that can be accessed from shared code no matter how the user interface is created.
https://github.com/xamarin/Essentials
You can now query the device's display information without having to manage all of the individual platform code pieces.
Device Display Information - https://learn.microsoft.com/en-us/xamarin/essentials/device-display
How-To:
Add a reference to Xamarin.Essentials in your class:
using Xamarin.Essentials;
The following information is exposed through the API:
// Get Metrics
var mainDisplayInfo = DeviceDisplay.MainDisplayInfo;
// Orientation (Landscape, Portrait, Square, Unknown)
var orientation = mainDisplayInfo.Orientation;
// Rotation (0, 90, 180, 270)
var rotation = mainDisplayInfo.Rotation;
// Width (in pixels)
var width = mainDisplayInfo.Width;
// Height (in pixels)
var height = mainDisplayInfo.Height;
// Screen density
var density = mainDisplayInfo.Density;
Useful Links:
(Github) Xamarin.Essentials - https://github.com/xamarin/Essentials
(Blog) Xamarin.Essentials - https://blog.xamarin.com/xamarin-essentials-cross-platform-apis-mobile-apps/
(Docs) Getting Started with Essentials - https://learn.microsoft.com/en-us/xamarin/essentials/get-started
Original Post (Before Xamarin.Essentials existed)
Below, I'm storing the specific OS's screen details in static vars, located in the Xamarin Forms App class
These all appear to work in my testing.
(copy/pasted from my github page - https://github.com/mattregul/Xamarin_Screensize)
Android (MainActivity.cs) - Jump to Github Page
// Store off the device sizes, so we can access them within Xamarin Forms
// Screen Width = WidthPixels / Density
// Screen Height = HeightPixels / Density
App.DisplayScreenWidth = (double)Resources.DisplayMetrics.WidthPixels / (double)Resources.DisplayMetrics.Density;
App.DisplayScreenHeight = (double)Resources.DisplayMetrics.HeightPixels / (double)Resources.DisplayMetrics.Density;
App.DisplayScaleFactor = (double)Resources.DisplayMetrics.Density;
iOS (AppDelegate.cs) - Jump to Github Page
// Store off the device sizes, so we can access them within Xamarin Forms
App.DisplayScreenWidth = (double)UIScreen.MainScreen.Bounds.Width;
App.DisplayScreenHeight = (double)UIScreen.MainScreen.Bounds.Height;
App.DisplayScaleFactor = (double)UIScreen.MainScreen.Scale;
Note In all Windows examples screensize is the root project namespace
UWP (App.xaml.cs) - Jump to Github Page
// You decided which is best for you...
// Do you want Size of the App's View
// or
// Do you want the Display's resolution
// ######################################
// Size of App's view
screensize.App.DisplayScreenHeight = Windows.UI.ViewManagement.ApplicationView.GetForCurrentView().VisibleBounds.Height;
screensize.App.DisplayScreenWidth = Windows.UI.ViewManagement.ApplicationView.GetForCurrentView().VisibleBounds.Width;
// Size of screen's resolution
//screensize.App.DisplayScreenWidth = Windows.Graphics.Display.DisplayInformation.GetForCurrentView().ScreenHeightInRawPixels;
//screensize.App.DisplayScreenHeight = Windows.Graphics.Display.DisplayInformation.GetForCurrentView().ScreenWidthInRawPixels;
// Pixels per View Pixel
// - https://msdn.microsoft.com/en-us/windows/uwp/layout/design-and-ui-intro#effective-pixels-and-scaling
// - https://msdn.microsoft.com/en-us/windows/uwp/layout/screen-sizes-and-breakpoints-for-responsive-design
screensize.App.DisplayScaleFactor = Windows.Graphics.Display.DisplayInformation.GetForCurrentView().RawPixelsPerViewPixel;
Windows Phone 8.1 (App.xaml.cs) - Jump to Github Page
// Size of App's view
screensize.App.DisplayScreenHeight = Windows.UI.ViewManagement.ApplicationView.GetForCurrentView().VisibleBounds.Height;
screensize.App.DisplayScreenWidth = Windows.UI.ViewManagement.ApplicationView.GetForCurrentView().VisibleBounds.Width;
// Pixels per View Pixel
// - https://msdn.microsoft.com/en-us/windows/uwp/layout/design-and-ui-intro#effective-pixels-and-scaling
// - https://msdn.microsoft.com/en-us/windows/uwp/layout/screen-sizes-and-breakpoints-for-responsive-design
screensize.App.DisplayScaleFactor = Windows.Graphics.Display.DisplayInformation.GetForCurrentView().RawPixelsPerViewPixel;
Windows 8.1 (App.xaml.cs) - Jump to Github Page
// Size of App's view
screensize.App.DisplayScreenHeight = Window.Current.Bounds.Height;
screensize.App.DisplayScreenWidth = Window.Current.Bounds.Width;
screensize.App.DisplayScaleFactor = 1; // No scaling here? If you find a scaling for Windows 8.1, please let me know :)
Xamarin Forms Page (App.cs) - Jump to Github Page
namespace screensize
{
public class App : Application
{
public static double DisplayScreenWidth = 0f;
public static double DisplayScreenHeight = 0f;
public static double DisplayScaleFactor = 0f;
public App()
{
string ScreenDetails = Device.OS.ToString() + " Device Screen Size:\n" +
$"Width: {DisplayScreenWidth}\n" +
$"Height: {DisplayScreenHeight}\n" +
$"Scale Factor: {DisplayScaleFactor}";
// The root page of your application
var content = new ContentPage
{
Title = "Xamarin_GetDeviceScreensize",
Content = new StackLayout
{
VerticalOptions = LayoutOptions.Center,
Children = {
new Label {
HorizontalTextAlignment = TextAlignment.Center,
FontSize = Device.GetNamedSize (NamedSize.Large, typeof(Label)),
Text = ScreenDetails
}
}
}
};
MainPage = new NavigationPage(content);
}
}
}

Answer 2

This list lists the ios device dpi information. You can also use GBDeviceInfo thrid-party tool to get the screen density for IOS device like this [GBDeviceInfo deviceInfo].displayInfo.pixelsPerInch;
IOS:
iPhones
iPhone 1/3G/3GS 320 x 480 163 ppi
iPhone 4/4S 640 x 940 326 ppi
iPhone 5/5C/5S 640 x 1136 326 ppi
iPhone 6/6S 750 x 1334 326 ppi
iPhone 6 Plus/6S Plus 1080 x 1920 401 ppi
Without downsampling: 1242 x 2208 461 ppi
Except for the 6th generation (= 5th) iPod touch,
all the models are equal to their iPhone counterparts
iPads
iPad 1/2 768 x 1024 132 ppi
iPad 3/4/Air/Air 2 1536 x 2048 264 ppi
iPad Mini 1 768 x 1024 163 ppi
iPad Mini 2/3/4 1536 x 2048 326 ppi
iPad Pro 2737 x 2048 264 ppi
Apple Watches
Apple Watch 38 mm 272 x 340 326 ppi
Apple Watch 42 mm 312 x 390 326 ppi
I found API in the UWP to retrieve the device dpi. Windows.Graphics.Display.DisplayInformation. You can try it.