Mam problem z wywołanie strony po naciśnięciu buttona.
ViewModel
namespace TestApp
{
public sealed class MessageViewModel : BaseViewModel
{
#region Command
public ICommand ClickCommand { get; set; }
#endregion
public MessageModel MessageModel { get; set; }
private bool _isSelect;
public bool IsSelect
{
get
{
return _isSelect;
}
set
{
_isSelect = value;
OnPropertyChanged();
}
}
public MessageViewModel()
{
IsSelect = true;
MessageModel = new MessageModel
{
Message = "Hello World",
};
InitializeCommands();
}
private void InitializeCommands()
{
ClickCommand = new DelegateCommand(ClickCommandExecute);
}
private async void ClickCommandExecute()
{
// IsSelect = !IsSelect;
await NavigateToPage(new GuidPage());
}
public override void RemoveHandlers() { }
}
}
BaseView
namespace TestApp
{
/// <summary>
/// BaseViewModel
/// </summary>
public abstract class BaseViewModel : BaseNotifyPropertyChanged
{
#region Fields
private INavigation _navigation;
#endregion
#region Methods
public BaseViewModel()
{
}
public async Task NavigateToPage(ContentPage page, bool detailPage = false, bool removePrevious = false)
{
await _navigation.PushAsync(page);
}
public abstract void RemoveHandlers();
#endregion
}
}
Błąd
System.NullReferenceException: Object reference not set to an instance of an object
at TestApp.BaseViewModel+<NavigateToPage>c__async0.MoveNext () [0x00022] in /Users/xxx/Documents/xxx/Xamarin/TestApp/TestApp/TestApp/ViewModels/BaseViewModel.cs:27
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.4.0.128/src/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00047] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.4.0.128/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x0002e] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.4.0.128/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x0000b] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.4.0.128/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128
at System.Runtime.CompilerServices.TaskAwaiter.GetResult () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.4.0.128/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:113
at TestApp.MessageViewModel+<ClickCommandExecute>c__async0.MoveNext () [0x00022] in /Users/xxx/Documents/xxx/Xamarin/TestApp/TestApp/TestApp/ViewModels/MessageViewModel.cs:52
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.4.0.128/src/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143
at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>m__0 (System.Object state) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/10.4.0.128/src/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1018
at UIKit.UIKitSynchronizationContext+<Post>c__AnonStorey0.<>m__0 () [0x00000] in /Users/builder/data/lanes/3985/ba11e481/source/xamarin-macios/src/UIKit/UIKitSynchronizationContext.cs:24
at Foundation.NSAsyncActionDispatcher.Apply () [0x00000] in /Users/builder/data/lanes/3985/ba11e481/source/xamarin-macios/src/Foundation/NSAction.cs:163
at at (wrapper managed-to-native) UIKit.UIApplication:UIApplicationMain (int,string[],intptr,intptr)
at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Users/builder/data/lanes/3985/ba11e481/source/xamarin-macios/src/UIKit/UIApplication.cs:79
at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x00038] in /Users/builder/data/lanes/3985/ba11e481/source/xamarin-macios/src/UIKit/UIApplication.cs:63
at TestApp.iOS.Application.Main (System.String[] args) [0x00008] in /Users/monaco/Documents/workspace/Xamarin/TestApp/TestApp/iOS/Main.cs:17