// This method saves the application state before entering background state. It fires the event OnBackgroundEntering to collect
// state data from the current subscriber and saves it to the local storage.
public async Task <bool> SaveStateAsync()
{
if (OnBackgroundEntering == null)
{
return(false);
}
try
{
SuspensionState suspensionState = new SuspensionState()
{
SuspensionDate = DateTime.Now
};
Type target = OnBackgroundEntering?.Target.GetType();
SuspendAndResumeArgs onBackgroundEnteringArgs = new SuspendAndResumeArgs(suspensionState, target);
OnBackgroundEntering?.Invoke(this, onBackgroundEnteringArgs);
await ApplicationData.Current.LocalFolder.SaveAsync(StateFilename, onBackgroundEnteringArgs);
return(true);
}
catch (Exception)
{
// TODO WTS: Save state can fail in rare conditions, please handle exceptions as appropriate to your scenario.
return(false);
}
}
// This method restores application state when the App is launched after termination, it navigates to the stored Page passing the recovered state data.
protected override async Task HandleInternalAsync(LaunchActivatedEventArgs args)
{
SuspendAndResumeArgs saveState = await GetSuspendAndResumeData();
if (saveState?.Target != null && typeof(Page).IsAssignableFrom(saveState.Target))
{
NavigationService.Navigate(saveState.Target, saveState.SuspensionState);
}
}
public async Task RestoreSuspendAndResumeData()
{
SuspendAndResumeArgs saveState = await GetSuspendAndResumeData();
if (saveState != null)
{
OnDataRestored?.Invoke(this, saveState);
}
}
public async Task <SuspendAndResumeArgs> GetSuspendAndResumeData()
{
SuspendAndResumeArgs saveState = await ApplicationData.Current.LocalFolder.ReadAsync <SuspendAndResumeArgs>(StateFilename);
if (saveState?.Target != null && typeof(Page).IsAssignableFrom(saveState.Target))
{
return(saveState);
}
return(null);
}