Question

I have a checkbox. On it’s checked event I want to turn off IdleDetectionMode and on unchecked event I want to turn on. This is the code :-

private void chkRunInBackground_Checked(object sender, RoutedEventArgs e)
        {
            PhoneApplicationService.Current.ApplicationIdleDetectionMode = IdleDetectionMode.Disabled;

        }

        private void chkRunInBackground_Unchecked(object sender, RoutedEventArgs e)
        {
            PhoneApplicationService.Current.ApplicationIdleDetectionMode = IdleDetectionMode.Enabled;

        }

The checked event runs fine but on unchecked event I get, IdleDetection mode cannot be started once it is disabled. Why is this restriction applied and what can I do to work around it?

Answer 1

From MSDN:

In the current release, application
idle detection cannot be enabled in a
single application instance once it
has been disabled. Doing so throws an
exception. In future releases this may
be supported, so your application may
choose to disable application idle
detection when it is no longer needed
and catch the expected exception.

The following code snippet shows an implementation of this.

// Custom function to turn off idle detection. This will throw an exception in the current release.
public void TryReenableApplicationIdleDetection()
{
    bool didEnable = false;
    try
    {
        Microsoft.Phone.Shell.PhoneApplicationService.Current.ApplicationIdleDetectionMode =
            Microsoft.Phone.Shell.IdleDetectionMode.Enabled;
        didEnable = true;
    }
    catch (InvalidOperationException ex)
    {
        // This exception is expected in the current release.
    }

    // possibly use the value of didEnable to decide what to do next
    // if it is 'true' then your app will be deactivated 
    // if it is 'false' then your app will keep running
}