Memory leaks with NavigationController and multiple UIViewController - ios

Question

In my application I manage 4 UIViewController :
First one for handle user login
Second one that display the menu
Third one for displaying the action available depending on the user entry in previous view.
Fourth one that show details infos about previous selected item on third view.
Third and Four are displaying a UIViewTable with item to select that are passed to the next UIViewController to display info.
So I made attention to not using hard link to each other. Parameters are passed when UIViewControlle are instantiate.
Here is the probleme that I'm dealing with :
When I pass from Third to Fourth, and then go back to Fourth, memory is never been released. Worth, when I return to Fourth it take the same amount of memory again.
After 3-4 round-trip the device memory is full. (Another strange behavior here with UIImageView that take 12Mo of memory any picture, no mater the picture size is 12Ko or 120Ko...)
Here is the code that is use to switch between controllers :
//First UIViewController, tagged as Root in storyboard
public partial class LoginController
{
//....some logic code here
//User ask for login by pressed a button , after an echange with a server
//for credential verification, if the server reply "ok" then I call the second
//UIViewController like this
void PushHomeScreen()
{
HomeController homeController = Storyboard.InstantiateViewController("home") as HomeController;
NavigationController.PushViewController(homeController, false);
}
}
public partial class HomeController
{
//....some logic code here
//The view displaying 3 UIButton that root to 2 different UIViewController.
//First one is deadend, and user can only go back. It will be used one time to select a dataset to download and use after.
//The two next use the same UIViewController, only the way that the controller handle the nexts user action is different :
//If user came from the Second then it display screen for retrieving user attendance
//If user came from the Third then it display screen for retrievin user survey.
//So here are the code behind:
private void BtnDownload_TouchUpInside(object sender, EventArgs e)
{
DownloadController downloadTrainingController = Storyboard.InstantiateViewController("downloadTraining") as DownloadController;
NavigationController.PushViewController(downloadTrainingController, false);
}
private void BtnSurvey_TouchUpInside(object sender, EventArgs e)
{
TrainingAndReviewListController trakningController = Storyboard.InstantiateViewController("trakning") as TrainingAndReviewListController;
trakningController.backgroundColor = "violet";
NavigationController.PushViewController(trakningController, false);
}
private void BtnTraining_TouchUpInside(object sender, EventArgs e)
{
TrainingAndReviewListController trakningController = Storyboard.InstantiateViewController("trakning") as TrainingAndReviewListController;
trakningController.backgroundColor = "red";
NavigationController.PushViewController(trakningController, false);
}
}
//I will not show you the DownloadController as it is not pertinent to the current probleme.
public partial class TrainingAndReviewListController
{
//To handle the back action, so user go from this to HomeController
void BtnHome_TouchUpInside(object sender, EventArgs e)
{
NavigationController.PopViewController(false);
}
private void Tablesource_OnRowSelected(object sender, DownloadTableSource.RowSelectedEventArgs e)
{
serviceController = Storyboard.InstantiateViewController("service") as ServiceController;
serviceController.backgroundColor = backgroundColor;
serviceController.training = e.training;
NavigationController.PushViewController(serviceController, false);
}
}
//Next are the final UIViewController on the storyboard. It consume a lot of memory in inspector due to 20 UIViewImage on it who each consume 12Mo of memory.
//When I come back from this Controller to the previous memory are never released, and if I return on it, it consume the same amount extra again
//One solution to prevent this is to instanciate him once in TrainingAndReviewListController as class attribute, and then reuse it. But it is not supposed to be the role
//of the NavigationController?
public partial class ServiceController
{
public string backgroundColor = "red";
public Training training;
//To handle the user action for going to the Home controller, this is not the action that cause memory leaks, altoutgh it will cause the same behavior I think.
void BtnHome_TouchUpInside(object sender, EventArgs e)
{
foreach (UIViewController uiviewcontroller in NavigationController.ViewControllers) {
if (uiviewcontroller.GetType() == typeof(HomeController)) {
NavigationController.PopToViewController(uiviewcontroller as HomeController, false);
}
}
}
void BtnGoBack_TouchUpInside(object sender, EventArgs e)
{
Console.WriteLine(NavigationController.ViewControllers.Count()); //It always log the same count, as if the controller is really be poped when i come back and pop again.
//But profilage show me that memory still used by this instance.
NavigationController?.PopViewController(false);
}
}