![]() ![]() For implementing platform-specific features such as geolocation or bluetooth, we can take advantage of the DependencyService. One of my favorite features of Xamarin.Forms is that we have access to 100% of the controls and APIs for iOS, Android, and Windows. Adding the attribute to all the screens that defined in storyboard/xib solve the issue for ships with over 40 pages, layouts, and controls for you to mix-and-match to build great native cross-platform user interfaces. Also, it will no longer call into ViewDidLoad method during design time. The screen should not showing in the Toolbox‘s Custom Components section now. public partial class ViewController : UIViewControllerĪfter that, clean and rebuild the solutions. To remove the screen from being use as a custom components, we will need manually add an DesignTimeVisible attribute for the ViewController class and set the flag to false. This is the reason why the ViewController‘s ViewDidLoad method is getting call during design time. Attempt 2: Set the ViewController DesignTimeVisible flag to falseĬhecking in the UI Designer, you will find that under the Toolbox, the ViewController is also showing as a custom component. In addition, this method seems not working for views that inherit from UITableViewController. However, it is kind of troublesome to add this checking every time. This method can solve the problem and the view is able to render correctly in UI Designer again. Public class AppDelegate : UIApplicationDelegate Then in ViewDidLoad method, I will check only when IsDesignTime is false, I will run the code. By default it is set to true and it will set to false when called into FinishedLaunching method in AppDelegate. I have defined a boolean IsDesignTime in AppDelegate.cs. ![]() Xamarin bugzilla code#Attempt 1: Do not run code in ViewDidLoad during design time ![]() This is the reason why there is NullReferenceException when render. ![]() In the ViewDidLoad method, I have some code that is dependency injection which is not available during design time. In this mode, all custom view is not rendered.Ĭhecking in the log files and you might get the following errors: System.NullReferenceException: Object reference not set to an instance of an objectĪt +c_async5.MoveNext () in /Users/builder/data/lanes/4470/6c2f6737/source/md-addins///IPhoneDesignerSession.cs:774 Reasons & SolutionsĪfter checking into the log file, found out that the UI Designer actually call into UIViewController‘s (those that defined in the storyboard/xib) ViewDidLoad method. Problem 2: UI Designer took very long time to load and not able to render custom viewĪfter UI Designer is startup, it will show a warning bar at the top. There are many different errors but this is the most common error: System.NullReferenceException Recently when trying to open iOS UI Designer to edit storyboard/xib file, I have encounter some problems. This issue is also reported in Xamarin BugZilla: Problem 1: ViewControler is rendered but with error exclamation mark ![]()
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