Setting a default theme in App.xaml can cause issues on new pages

[juliandc1969]

If, as suggested a 'default theme' is defined in App.xaml, any new pages created will use this 'theme' and not the current theme that has been 'merged'. for example. a simple 2 page app MainPage - containing a page link to SettingsPage SettingsPage - contains a switch that toggles between dark and light themes and a 'back button'

if you: Navigate to Settings page. Toggle the theme from light (the default theme in App.xaml) to dark using the 'merge method' shown - observe the page correctly change theme. Navigate back to MainPage - observe theme is correct. Navigate to the SettingsPage once again - observe the theme has reverted to 'Light' without reaching any code that merges the light theme into the resource dictionary.

To Fix: Remove the default theme from App.xaml In App.xaml.cs App constuctor: Merge in the default theme OR Determine the previously saved theme and merge that.

It may be worth noting this effect on the page so others aren't caught by it.

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Document Details

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• ID: 3f353ff4-2d18-218c-f0d5-b3110e476c4d
• Version Independent ID: a1cec8f2-969c-23c5-a252-b417afcacff6
• Content: Theme a Xamarin.Forms Application - Xamarin
• Content Source: docs/xamarin-forms/user-interface/theming/theming.md
• Product: xamarin
• Technology: xamarin-forms
• GitHub Login: @davidbritch
• Microsoft Alias: dabritch