NickName:Luke Ask DateTime:2011-04-06T19:57:54

Modal View destructor not being called when InputAccessoryView is overriden

I am presenting a UIViewController modally and that view contains various UITextFields. I've overriden the modal views InputAccessoryView so that it shows a simple view, with one button that will ResignFirstResponder from every UITextField, thus dismissing the keyboard.

Recently I've been really cracking down on memory related issues so all my controllers now have a destructor. I've noticed that whenever the keyboard is shown with this overriden InputAccessoryView whenever the Modal View is dismissed the destructor will not be called. Does this mean that the UIViewController is not being destroyed? Am I incorrectly displaying the InputAccessoryView?

The InputAccessoryView code is as follows:

bool accessoryViewInit = false;
UIView accessoryView = new UIView(new RectangleF(0,0,320,30));

public override UIView InputAccessoryView 
{
    get 
    {
        if (!accessoryViewInit)
        {
            accessoryView.BackgroundColor = UIColor.FromRGBA(0.0f, 0.0f, 0.f, 0.5f);
            UIButton dismiss = new UIButton(new RectangleF(50,1, 200, 28));
            dismiss.BackgroundColor = UIColor.Blue;
            dismiss.SetTitle("Close Keyboard", UIControlState.Normal);
            dismiss.TouchUpInside += delegate(object sender, EventArgs e) {
                field1.ResignFirstResponder();
                field2.ResignFirstResponder();
                field3.ResignFirstResponder();
            };
            accessoryView.AddSubview(dismiss);
        }       
        return accessoryView;
    }
}

I have a feeling that is due to the fact I'm assigning a delegate to the TouchUpInside event for the button, is it keeping a reference to this, thus stopping the whole controller from being destroyed?

I've created a sample project which can be found at https://github.com/lukewhitt/InputAccessoryView-test

To recreate the problem: Run app, Present modal view by touching big red button. Now, if you dismiss the view without showing the keyboard, the destructor will be called. If you make on the UITextFields first responder (showing the keyboard and the InputAccessoryView) then dismiss the modal controller, the destructor won't be called.

EDIT

It would appear this is a bug in Monotouch that will be fixed in an up-coming release. In order to get around the problem, it seems you can't use anonymous delegates when assigning to events. So the dismiss.TouchUpInside would become:

public override UIView InputAccessoryView {
// code before
    dismiss.TouchUpInside += HandleDismissTouch;
// rest of code
}

private void HandleDismissTouch (object sender, EventArgs e)
{
    field1.ResignFirstResponder();
    field2.ResignFirstResponder();
    field3.ResignFirstResponder();
}

then in the code that dismisses the modal controller, I've added the following:

if (dismiss != null)
{
    dismiss.TouchUpInside -= HandleDismissTouch;
    dismiss.Dispose();
    dismiss = null;
}

which causes the destructor to be called!

Copyright Notice：Content Author:「Luke」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/5565947/modal-view-destructor-not-being-called-when-inputaccessoryview-is-overriden