Page State Step-by-Step

The Windows Phone life cycle is not terribly complicated, but it can be the source of some LifeCycle  confusion, and managing the life-cycle can be intimidating to new Windows Phone programmers.  This posting will review the basic life-cycle of a Windows Phone application and will show you what you need to do to preserve state and give your users a rewarding phone experience.

Reviewing the Life Cycle

When your application is launched (e.g., from the start menu) the Application Launching event is fired. You can hook this event in App.xaml.cs in the Application_Launching event handler, as described in yesterday’s posting on Fast Application Switching.

Once the application is started, and every time the user navigates to your page, you  will receive the OnNavigatedTo method, after which your page will be in the Running state.

If the user starts a new application your application receives the Application Deactivated event and is put in the Dormant state.  If the phone runs low on memory, your application may be Tombstoned.

From either Tombstoned or Dormant your application may be terminated or it may be restored.  What we care about right now is what happens when your application is restored.

If your application is Dormant, you not only don’t have to take any action when you are restored, you don’t want to take any action; all your state was preserved when you were dormant, and you are ready to go.

If on the other hand, your application was tombstoned, then you do want to restore your page state when you return so that it appears to the user that your application was running (or at least dormant) while it was switched away.

Managing Page State

The best way to see how to manage Page State is to build a small application.  Open Visual Studio and create a new Windows Phone application and on the main page add a prompt and a TextBox for the user’s name, and a CheckBox for whether the user is a Geek, as shown in the following code,

Read more: Jesse Liberty
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