RowSelected - NullReferenceException [英] RowSelected - NullReferenceException
问题描述
我试图这样做,当我在 UITableView 上按下一行时,它会将一些数据发送到另一个 UIViewController 并创建一个序列.
I am trying to make so when I press a row on my UITableView, it will send some data to another UIViewController and make a seque.
但是在测试时,它给了我:
However when testing it out, it gives me:
System.NullReferenceException 已抛出对象引用未设置到一个对象的实例
System.NullReferenceException has been thrown Object reference not set to an instance of an object
错误似乎显示在这里:
viewController.NavigationController.PushViewController (detail, true);
这是我的RowSelected"
Here is my "RowSelected"
public override void RowSelected (UITableView tableView, NSIndexPath indexPath)
{
Console.WriteLine ("Row: " + tableItems [indexPath.Row].Heading);
//new UIAlertView("Row Selected", tableItems[indexPath.Row].Heading, null, "OK", null).Show();
tableView.DeselectRow (indexPath, true);
// Specially for Storyboard !!
var detail = viewController.Storyboard.InstantiateViewController("detail") as HolsteinItemViewController;
detail.Title = tableItems[indexPath.Row].Heading;
detail.LoadUrl (tableItems[indexPath.Row].SubHeading);
viewController.NavigationController.PushViewController (detail, true);
}
异常捕获:
System.NullReferenceException: Object reference not set to an instance of an object
at Holstein.TableSource.RowSelected (MonoTouch.UIKit.UITableView tableView, MonoTouch.Foundation.NSIndexPath indexPath) [0x0008e] in /Users/Emil/Projects/Holstein/Holstein/Code/TableSource.cs:41
at at (wrapper managed-to-native) MonoTouch.UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
at MonoTouch.UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0004c] in /Developer/MonoTouch/Source/monotouch/src/UIKit/UIApplication.cs:38
at Holstein.Application.Main (System.String[] args) [0x00008] in /Users/Emil/Projects/Holstein/Holstein/Main.cs:16
TableSource.cs 第 46 行
viewController.NavigationController.PushViewController (detail, true);
Main.cs 第 16 行
UIApplication.Main (args, null, "AppDelegate");
推荐答案
您的 viewController.NavigationController
属性为 null.根据 iOS UIViewController
参考 这里
Your viewController.NavigationController
property is null. According to iOS UIViewController
reference here
如果接收器或其祖先之一是导航的孩子控制器,此属性包含拥有的导航控制器.如果视图控制器未嵌入在导航控制器.
If the receiver or one of its ancestors is a child of a navigation controller, this property contains the owning navigation controller. This property is nil if the view controller is not embedded inside a navigation controller.
显然,该视图控制器不是 UINavigationController
堆栈的一部分.
Apparently, that view controller is not part of a UINavigationController
stack.
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