Adding platform specific magic to cross-platform Xamarin Forms apps
Xamarin Forms is a fantastic abstraction on top of iOS, Android, Windows and Mac. It allows you to write one UI that is shared between platforms using the underlying UI controls native to each OS. The downside to this is the lowest-common-denominator model - only the features that are available on all platforms are provided out of the box. Luckily Xamarin provides a swathe of techniques to allow you to add platform specific tweaks. In this session we will look at some of these techniques, from the small number of platform specifics provided out of the box by Xamarin, to writing effects and implementing your own custom renderers. Each technique will be demonstrated with a live coded example showing just how easy they are to get working. By the end of this session you will have an understanding of the different tools you can use to make platform-specific tweaks to the UI, and be able to write your own effects and custom renderers.
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Adding platform specific magic to cross-platform Xamarin Forms apps
- 19. @JimBobBennett aka.ms/ [assembly: ExportRenderer(typeof(Entry), typeof(MyEntryRenderer)) ] public class MyEntryRenderer : EntryRenderer { … }
Editor's Notes
- Write once, run everywhere - iOS, Android, UWP, WPF, macOS, Linux, Tizen, Native UI To most Forms IS Xamarin Fast to market - EROAD Inspect
- To make Forms work on all platforms means it’s a lowest common denominator model Only features that work on all platforms are available Simplicity was key as well, so only the basics were ported
- Beautiful design - part of it is good typography. Designers love fonts and want different weights all over the place Not easy in Forms
- Problem - designer wants light fonts. How can we do this?
- Look at two ways to do it - effects, custom renderers Only going to cover iOS and Android, but principles apply to all platforms
- Effects - lightweight ways to manipulate underlying controls Attach to a control to allow you to tweak the underlying control
- Forms - wraps native controls in Forms controls Put an entry on the screen, on iOS you get a UITextField, Android gives an EditText Effects attach to these controls Effects are NOT control specific - can attach to any control
- Demo on for iOS and Android Effect for font
- Two parts - platform effect for the platform, routing effect in core project Effects have an Id with a two part key - resolution group name and effect name Platform specific - resolution group name registered in assembly as first part of key Effect exported by name Allows multiple effect NuGets with same effect name to not clash. Effects can be read off control to evaluate properties
- All forms controls use renderers to convert from Forms to Native These renderers are open, so you can tweak to suit, or write your own
- All forms controls use renderers to convert from Forms to Native These renderers are open, so you can tweak to suit, or write your own
- ExportRenderer tells Xamarin Forms which renderer to use for a control
- You can export your own renderers to ‘override’ the default from Xamarin Forms Own renderers derived from the Xamarin ones with customizations
- Demo on for iOS and Android Renderer Renderer has control and element - native control and Forms element
- Effects when you want to tweak certain controls only, and want to add effects to multiple types Renderers for tweaking all controls of one type