Pixels To Xamarin.Forms Font Size - xamarin.forms

Question

i am using Xamarin forms and i have a project that requires the font size to be 32 pixels. I kept searching on google however i could not find an answer on how to convert this pixels in Xamarin device-independent units. I would greatly appreciate some help.
Thank you.

Answer 1

Xamarin uses DIU (device-independent units) about everywhere.
Have a look at https://learn.microsoft.com/en-us/xamarin/xamarin-forms/creating-mobile-apps-xamarin-forms/summaries/chapter05
I had a similiar issue and found out via trial and error that Xamarin.Essentials.DeviceDisplay.MainDisplayInfo.Density returns the amount of pixels per DIU on the device (tested on iPod Touch, Nokia 8 and Firetablet).
So this should be correct:
myLabel.FontSize = 32 / Xamarin.Essentials.DeviceDisplay.MainDisplayInfo.Density;
But as Jason has stated, you might want to check your requirements, because the more pixels are on the device, smaller the font gets. Thats why people use DIU in the first place :-)
It is probably better to have a look at how big the font is on the customers homepage. Maybe measure it there in inches, centimeters or whatever fits you and then do the math to convert that to DIUs (see link above, 64 DIU = 1 centimeter).

Answer 2

You could use custom renderer to invoke native method to set 32 pixels.Based on Button control, you can create a custom Button in Xamaarin forms as follows:
public class MyButton : Button
{
}
Then Andoird solution create the custom rendere class as follows:
[assembly: ExportRenderer(typeof(Xamarin.Forms.MyButton), typeof(CustomButtonRenderer))]
namespace AppShellTest.Droid
{
[Obsolete]
public class CustomButtonRenderer: ButtonRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
{
base.OnElementChanged(e);
if (Control != null)
{
// do whatever you want to the UITextField here!
Control.SetTextSize(Android.Util.ComplexUnitType.Px, 32);
}
}
}
}
About other controls, also can create their custom renderers to do.
=================================Update===============================
The method that can convert dp to px or px to dp, you can check that whether it works for you.
public int dip2px(Context context, float dpValue)
{
float scale = context.Resources.DisplayMetrics.Density;
return (int)(dpValue * scale + 0.5f);
}
public int px2dip(Context context, float pxValue)
{
float scale = context.Resources.DisplayMetrics.Density;
return (int)(pxValue / scale + 0.5f);
}
Then renderer code will be:
public class CustomButtonRenderer: ButtonRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.Button> e)
{
base.OnElementChanged(e);
if (Control != null)
{
// do whatever you want to the UITextField here!
Control.SetTextSize(Android.Util.ComplexUnitType.Px, dip2px(32));
}
}
public int dip2px(float dpValue)
{
float scale = MainActivity.instance.Resources.DisplayMetrics.Density;
return (int)(dpValue * scale + 0.5f);
}
}
The MainActivity.instance declared in MainActivity that means the instance of MainActivity.
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
public static MainActivity instance { set; get; }
protected override void OnCreate(Bundle savedInstanceState)
{
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
instance = this;
base.OnCreate(savedInstanceState);
Xamarin.Essentials.Platform.Init(this, savedInstanceState);
global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
LoadApplication(new App());
}
...