c# - MonoTouch Dialog--Null 导航控制器

Question

我正在寻找一种在GlassButton单击时更改屏幕的方法。我刚刚开始学习 Monotouch.Dialog。我已经做了以下尝试来处理这个问题。

public override void ViewDidLoad ()
    {

        button.TouchUpInside += (sender, e) => {
            this.NavigationController.PushViewController(list, true);
        };
    } 

list 是 a UIViewController，但在单击时this.NavigationController.PushViewController(list, true);被指向一个空引用异常。 list已经实例化并且不为空，但是，this.NavigationController为空。我怎样才能解决这个问题？

GlassButton button = new GlassButton (new RectangleF(0, 0, 200, 50));
List list = new List ();
public static EntryElement lastName = new EntryElement (null, "Enter Last Name", null);
public static EntryElement firstName = new EntryElement (null, "Enter First Name", null);
public static EntryElement middleInitial = new EntryElement (null, "Enter Middle Initial", null);

    public practice () : base (UITableViewStyle.Grouped, null)
    {
        Root = new RootElement ("Level 1") {
            new Section() {
                new RootElement("Level 2") {
                    new Section("Individual Information") {
                        lastName, firstName, middleInitial
                    },

                    new Section("Submit") {
                        button
                    }
                }
            }
        };
    }

Answer 1

我有同样的问题并通过派生子类来解决DialogViewController

public class CustomDialogViewController : DialogViewController
{
        public CustomDialogViewController(RootElement root)
            : base(null, true)
        {
            base.Root = root;
        }
}

在我的主视图控制器中，我在 ViewDidLoad() 中使用了以下内容：

var root = new RootElement("Customer form");
// code to generate section and add into root
CustomDialogViewController customDialogViewController = new CustomDialogViewController(root);
var navigationController = new UINavigationController(customDialogViewController);

this.AddChildViewController(this.navigationController);
this.View.AddSubview(this.navigationController.View);