When building a Phonegap application for the Windows Phone platform, it defaults to not enabling fast resume. To back up a bit, when you use the back key to return to a WP8 application, it resumes where you left off. However, when you return to the application via other means, such as the start menu, the application will restart. There are some reasons why you might want this, but I personally can’t think of many for the average user. Normally I want to return to my same place in the application regardless of how I’m getting to the application (one exception is with alerts, where the user does need to see the alert within the application itself).
So, if you want to have your Phonegap application fast resume, you need to change a setting the AppManifest file for the WP8 app. With Phonegap, it will be at the following path off of your application’s home directory…
Find the DefaultTask element and add ActivationPolicy=”Resume”.
<DefaultTask ActivationPolicy="Resume" Name="_default" NavigationPage="MainPage.xaml" />
For more information, this is a great read on fast resume.