Changing Xamarin Themes,styles per client approach - xamarin

Question

what approach would you use if you have a mobile app build using xamarin and this app is like a vanilla app.
Each client should be able to apply their own style to labels etc.. theme
Basically all the views/pages are the same for all the clients but the style per page will change for each individual client.
If this wasn't a mobile app I would have plugins within a folder and depending on the client i would drop the relative plugin in the pluginFolder eg:pluginClientA etc.. and this would be discovered at runtime usin mef.
Any suggestions

Answer 1

Set you styles up as dynamicresources as seen here https://developer.xamarin.com/guides/xamarin-forms/user-interface/styles/dynamic/
I only have 2 themes so I have them specified in xaml
<ResourceDictionary>
<Color x:Key="Primary">#337ab7</Color>
<Color x:Key="Accent">#96d1ff</Color>
<Color x:Key="BackgroundColor">#C0C0C0</Color>
<Color x:Key="TextColor">White</Color>
<!-- Buttons -->
<Style x:Key="buttonStyle" TargetType="Button">
<Setter Property="BorderRadius" Value="4" />
<Setter Property="FontSize" Value="48" />
<Setter Property="FontAttributes" Value="Bold" ></Setter>
<Setter Property="HeightRequest">
<Setter.Value>
<OnPlatform x:TypeArguments="x:Double" iOS="80" Android="80" />
</Setter.Value>
</Setter>
<Setter Property="WidthRequest">
<Setter.Value>
<OnPlatform x:TypeArguments="x:Double" iOS="150" Android="150" />
</Setter.Value>
</Setter>
</Style>
<Style x:Key="btnPrimary" TargetType="Button" BasedOn="{StaticResource buttonStyle}">
<Setter Property="TextColor" Value="{DynamicResource TextColor}" />
<Setter Property="BackgroundColor" Value="{DynamicResource Primary}" />
</Style>
<!--Light Theme-->
<Color x:Key="Primary-Light">#2196F3</Color>
<Color x:Key="BackgroundColor-Light">#FAFAFA</Color>
<Color x:Key="TextColor-Light">White</Color>
<!--Dark Theme-->
<Color x:Key="Primary-Dark">#1976D2</Color>
<Color x:Key="BackgroundColor-Dark">#C0C0C0</Color>
<Color x:Key="TextColor-Dark">Black</Color>
</ResourceDictionary>
So in the theme change event you can change the assigned colours
Resources ["Primary"] = Resources ["Primary-Dark"];