i am trying to use Caliburn Micro in my windows phone 7 project.
But i got a nullreferenceexception when navigate the page.
namespace Caliburn.Micro.HelloWP7 {
public class MainPageViewModel {
readonly INavigationService navigationService;
public MainPageViewModel(INavigationService navigationService) {
this.navigationService = navigationService;
}
public void GotoPageTwo() {
/*navigationService.UriFor<PivotPageViewModel>()
.WithParam(x => x.NumberOfTabs, 5)
.Navigate();*/
navigationService.UriFor<Page1ViewModel>().Navigate();
}
}
}
namespace Caliburn.Micro.HelloWP7
{
public class Page1ViewModel
{
readonly INavigationService navigationService;
public Page1ViewModel(INavigationService navigationService)
{
this.navigationService = navigationService;
}
}
}
can anyone tell me what's the problem of my code? thanks in advance.
here is bootstrapper:
public class ScheduleBootstrapper : PhoneBootstrapper
{
PhoneContainer container;
protected override void Configure()
{
container = new PhoneContainer(RootFrame);
container.RegisterPhoneServices();
container.PerRequest<MainPageViewModel>();
container.PerRequest<MainContentViewModel>();
container.PerRequest<Page1ViewModel>();
AddCustomConventions();
}
static void AddCustomConventions()
{
ConventionManager.AddElementConvention<Pivot>(Pivot.ItemsSourceProperty, "SelectedItem", "SelectionChanged").ApplyBinding =
(viewModelType, path, property, element, convention) =>
{
if (ConventionManager
.GetElementConvention(typeof(ItemsControl))
.ApplyBinding(viewModelType, path, property, element, convention))
{
ConventionManager
.ConfigureSelectedItem(element, Pivot.SelectedItemProperty, viewModelType, path);
ConventionManager
.ApplyHeaderTemplate(element, Pivot.HeaderTemplateProperty, viewModelType);
return true;
}
return false;
};
ConventionManager.AddElementConvention<Panorama>(Panorama.ItemsSourceProperty, "SelectedItem", "SelectionChanged").ApplyBinding =
(viewModelType, path, property, element, convention) =>
{
if (ConventionManager
.GetElementConvention(typeof(ItemsControl))
.ApplyBinding(viewModelType, path, property, element, convention))
{
ConventionManager
.ConfigureSelectedItem(element, Panorama.SelectedItemProperty, viewModelType, path);
ConventionManager
.ApplyHeaderTemplate(element, Panorama.HeaderTemplateProperty, viewModelType);
return true;
}
return false;
};
}
protected override object GetInstance(Type service, string key)
{
return container.GetInstance(service, key);
}
protected override IEnumerable<object> GetAllInstances(Type service)
{
return container.GetAllInstances(service);
}
protected override void BuildUp(object instance)
{
container.BuildUp(instance);
}
}
I had this too, and tracked it down as follows:
As you know, Caliburn.Micro uses convention-over-configuration to locate Views for ViewModels, and vice-versa, which means we need to follow the conventions. My mistake was to have the namespace's inconsistent for the View and ViewModel
In my case, I had
MyWP7App.DetailsViewModel, and
MyWP7App.Views.DetailsView
--> I renamed the VM's namespace to be MyWP7App.ViewModels.DetailsViewModel, and it worked out fine. I think I could have moved the view into MyWP7App.DetailsView for a good result, too...
Under the covers
the call to Navigate() invokes DeterminePageName() which, in turn, invokes ViewLocator.LocateTypeForModelType
This, like the rest of CM is overridable, but the default implementation looks like this:
public static Func<Type, DependencyObject, object, Type> LocateTypeForModelType = (modelType, displayLocation, context) => {
var viewTypeName = modelType.FullName.Substring(
0,
modelType.FullName.IndexOf("`") < 0
? modelType.FullName.Length
: modelType.FullName.IndexOf("`")
);
Func<string, string> getReplaceString;
if (context == null) {
getReplaceString = r => { return r; };
}
else {
getReplaceString = r => {
return Regex.Replace(r, Regex.IsMatch(r, "Page$") ? "Page$" : "View$", ContextSeparator + context);
};
}
var viewTypeList = NameTransformer.Transform(viewTypeName, getReplaceString);
var viewType = (from assembly in AssemblySource.Instance
from type in assembly.GetExportedTypes()
where viewTypeList.Contains(type.FullName)
select type).FirstOrDefault();
return viewType;
};
If you follow the debugger through, you end up with a collection viewTypeList that contains MyWP7App.DetailsView, and a type whose full name is MyWP7App.Views.DetailsView, and the viewType returned is therefore null... this is the cause of the NullReferenceException.
I'm 99% sure the NameTransformer.Transform call will perform a pattern-match and transform the ViewModels in the namespace of the VM to Views in the namespace of the View it's trying to locate...
Related
I am coming up to speed on Xamarin. I am using "Mastering Xamarin.Forms: App architecture techniques for building multi-platform, native mobile apps with Xamarin.Forms 4, 3rd Edition" as a guide. This had me create a custom navigation service.
Here is the implementation (I skipped the interface for brevity)
namespace wfw_dispenser.Services
{
public class XamarinFormsNavService : INavService
{
readonly IDictionary<Type, Type> _map = new Dictionary<Type, Type>();
public event PropertyChangedEventHandler CanGoBackChanged;
public INavigation XamarinFormsNav { get; set; }
public bool CanGoBack => XamarinFormsNav.NavigationStack?.Any() == true;
public async Task GoBack()
{
if (CanGoBack)
{
await XamarinFormsNav.PopAsync(true);
OnCanGoBackChanged();
}
}
public async Task NavigateTo<TVM>()
where TVM : BaseViewModel
{
await NavigateToView(typeof(TVM));
if (XamarinFormsNav.NavigationStack.Last().BindingContext is BaseViewModel)
{
((BaseViewModel)XamarinFormsNav.NavigationStack.Last().BindingContext).Init();
}
}
public async Task NavigateTo<TVM, TParameter>(TParameter parameter)
where TVM : BaseViewModel
{
await NavigateToView(typeof(TVM));
if (XamarinFormsNav.NavigationStack.Last().BindingContext is BaseViewModel<TParameter>)
{
((BaseViewModel<TParameter>)XamarinFormsNav.NavigationStack.Last().BindingContext).Init(parameter);
}
}
public void RemoveLastView()
{
if (XamarinFormsNav.NavigationStack.Count< 2)
{
return;
}
var lastView = XamarinFormsNav.NavigationStack[XamarinFormsNav.NavigationStack.Count - 2];
XamarinFormsNav.RemovePage(lastView);
}
public void ClearBackStack()
{
if (XamarinFormsNav.NavigationStack.Count < 2)
{
return;
}
for (var i = 0; i < XamarinFormsNav.NavigationStack.Count - 1; i++)
{
XamarinFormsNav.RemovePage(XamarinFormsNav.NavigationStack[i]);
}
}
public void NavigateToUri(Uri uri)
{
if (uri == null)
{
throw new ArgumentException("Invalid URI");
}
Device.OpenUri(uri);
}
async Task NavigateToView(Type viewModelType)
{
if (!_map.TryGetValue(viewModelType, out Type viewType))
{
throw new ArgumentException("No view found in view mapping for " + viewModelType.FullName + ".");
}
// Use reflection to get the View's constructor and create an instance of the View
var constructor = viewType.GetTypeInfo()
.DeclaredConstructors
.FirstOrDefault(dc => !dc.GetParameters().Any());
var view = constructor.Invoke(null) as Page;
var vm = ((App)Application.Current).Kernel.GetService(viewModelType);
view.BindingContext = vm;
await XamarinFormsNav.PushAsync(view, true);
}
public void RegisterViewMapping(Type viewModel, Type view)
{
_map.Add(viewModel, view);
}
void OnCanGoBackChanged() => CanGoBackChanged?.Invoke(this, new PropertyChangedEventArgs("CanGoBack"));
}
}
It appears to me that there is a NavigateTo that takes a parameter. I tried it and it kind of goes nowhere without any errors in the log. There's nothing in the text about this method to explain how to use it.
I probably have to do something in the "catching" view model for this. Can someone help me out?
First, you must extend from the parameterized version of BaseViewModel. In your case, since you are passing in a PaymentRequest, this would be:
public class CheckoutViewModel : BaseViewModel<PaymentRequest>
Then BaseViewModel<T> has a virtual Init method that you can implement
public class BaseViewModel<TParameter> : BaseViewModel
{
protected BaseViewModel(INavService navService, IAnalyticsService analyticsService)
: base(navService, analyticsService)
{
}
public override void Init()
{
Init(default(TParameter));
}
public virtual void Init(TParameter parameter)
{
}
}
I am trying to integrate the Event Aggregator into my app and following the online documentation, I haven't quite been able to get it to work and also am unable to find a complete example to look at. The app I am trying to build is a simple search engine for our internal knowledge base, so all it has is 3 views - the main search page (the root page), the results page and a details page.
Below I've just added what I think is the relevant code so far for debugging this error I am getting on build. If you need any more snippets, then more than happy to provide!
Admittedly, I really dont know how the bootstrapper works - have just been following tutorials and documentation thus far.
My code is as follows:
Bootstrapper.cs
namespace CleverBot
{
class Bootstrapper : BootstrapperBase
{
private readonly SimpleContainer _container = new SimpleContainer();
public Bootstrapper()
{
Initialize();
}
protected override void OnStartup(object sender, StartupEventArgs e)
{
base.OnStartup(sender, e);
DisplayRootViewFor<ShellViewModel>();
}
protected override void Configure()
{
_container.Singleton<IEventAggregator, EventAggregator>();
_container.RegisterPerRequest(typeof(DetailedDocumentViewModel), null, typeof(DetailedDocumentViewModel));
_container.RegisterPerRequest(typeof(SearchPageViewModel), null, typeof(SearchPageViewModel));
_container.RegisterPerRequest(typeof(SearchResultsViewModel), null, typeof(SearchResultsViewModel));
_container.RegisterPerRequest(typeof(ShellViewModel), null, typeof(ShellViewModel));
}
protected override object GetInstance(Type serviceType, string key)
{
return _container.GetInstance(serviceType, key);
}
protected override IEnumerable<object> GetAllInstances(Type serviceType)
{
return _container.GetAllInstances(serviceType);
}
protected override void BuildUp(object instance)
{
_container.BuildUp(instance);
}
}
}
And my ShellViewModel.cs looks like this:
namespace CleverBot.ViewModels
{
public class ShellViewModel : Conductor<object>
{
private readonly IEventAggregator _eventAggregator;
public ShellViewModel(IEventAggregator eventAggregator)
{
_eventAggregator = eventAggregator;
Startup.Init<SolrModel>("http://localhost:8983/solr/brain_drive");
ShowSearchPage();
}
public void ShowSearchPage()
{
ActivateItem(new SearchPageViewModel(_eventAggregator));
}
}
}
And finally, my SearchPageViewModel.cs looks like:
namespace CleverBot.ViewModels
{
public class SearchPageViewModel : PropertyChangedBase
{
private string _searchTerm;
private readonly IEventAggregator _eventAggregator;
public SearchPageViewModel(IEventAggregator eventAggregator)
{
_eventAggregator = eventAggregator;
}
public string SearchTerm
{
get { return _searchTerm; }
set
{
_searchTerm = value;
NotifyOfPropertyChange(() => SearchTerm);
}
}
public void BasicSearchButton()
{
// Build the new query object
var queryResult = new SolrQuery(_searchTerm);
// Execute the query, while also applying all the options
var Result = ExecuteQuery(queryResult);
// Publish the result, to be picked up by SearchResults VM
_eventAggregator.PublishOnUIThread(Result);
}
private SolrQueryResults<SolrModel> ExecuteQuery(SolrQuery query)
{
var solr = CommonServiceLocator.ServiceLocator.Current.GetInstance<ISolrOperations<SolrModel>>();
QueryOptions options = getQueryOptions();
var docs = solr.Query(query, options);
return docs;
}
private QueryOptions getQueryOptions()
{
var facetPivotQuery = new SolrFacetPivotQuery()
{
Fields = new[] { new PivotFields("created_year", "created_month") },
MinCount = 1
};
QueryOptions options = new QueryOptions
{
Facet = new FacetParameters
{
Queries = new ISolrFacetQuery[]
{
new SolrFacetFieldQuery("type"),
new SolrFacetFieldQuery("source"),
facetPivotQuery
}
},
Highlight = new HighlightingParameters
{
Fields = new[] { "text", "id", "author" },
Fragsize = 150,
Snippets = 200,
MaxAnalyzedChars = -1
}
};
return options;
}
}
}
Is anyone able to shed any light on why I am getting the System.NullReferenceException error? I know what it means but I don't see how I am getting it as am just starting out with this framework.
Thanks in advance!
It looks like I had to register the following:
_container.Singleton<IWindowManager, WindowManager>();
in my bootstrapper.cs, so now it looks like:
namespace CleverBot
{
class Bootstrapper : BootstrapperBase
{
private SimpleContainer _container = new SimpleContainer();
public Bootstrapper()
{
Initialize();
}
protected override void OnStartup(object sender, StartupEventArgs e)
{
DisplayRootViewFor<ShellViewModel>();
}
protected override void Configure()
{
_container.Singleton<IEventAggregator, EventAggregator>();
// THE FOLLOWING WAS ADDED
_container.Singleton<IWindowManager, WindowManager>();
GetType().Assembly.GetTypes()
.Where(type => type.IsClass)
.Where(type => type.Name.EndsWith("ViewModel"))
.ToList()
.ForEach(viewModelType => _container.RegisterPerRequest(
viewModelType, viewModelType.ToString(), viewModelType));
}
protected override object GetInstance(Type serviceType, string key)
{
return _container.GetInstance(serviceType, key);
}
protected override IEnumerable<object> GetAllInstances(Type serviceType)
{
return _container.GetAllInstances(serviceType);
}
protected override void BuildUp(object instance)
{
_container.BuildUp(instance);
}
}
}
I'm currently working on a Xamarin.iOS project that uses a web-api to gather data. However, I'm running into some problems trying to pass the user input from a textfield to the Tableview that gets the result from the api.
To do this I've followed the example on the MvvmCross documentation.
The problem is that the input from the Textfield never reaches the 'Filter' property in my TableviewController's viewmodel. I think I'm not passing the string object correctly to my IMvxNavigationService when called.
To clarify, in my UserinputViewController I'm binding the textfield's text like so:
[MvxFromStoryboard(StoryboardName = "Main")]
public partial class SearchEventView : MvxViewController
{
public SearchEventView (IntPtr handle) : base (handle)
{
}
public override void ViewDidLoad()
{
base.ViewDidLoad();
MvxFluentBindingDescriptionSet<SearchEventView, SearchEventViewModel> set = new MvxFluentBindingDescriptionSet<SearchEventView, SearchEventViewModel>(this);
set.Bind(btnSearch).To(vm => vm.SearchEventCommand);
set.Bind(txtSearchFilter).For(s => s.Text).To(vm => vm.SearchFilter);
set.Apply();
}
}
The Viewmodel linked to this ViewController looks like this:
public class SearchEventViewModel : MvxViewModel
{
private readonly IMvxNavigationService _navigationService;
private string _searchFilter;
public string SearchFilter
{
get { return _searchFilter; }
set { _searchFilter = value; RaisePropertyChanged(() => SearchFilter); }
}
public SearchEventViewModel(IMvxNavigationService mvxNavigationService)
{
this._navigationService = mvxNavigationService;
}
public IMvxCommand SearchEventCommand {
get {
return new MvxCommand<string>(SearchEvent);
}
}
private async void SearchEvent(string filter)
{
await _navigationService.Navigate<EventListViewModel, string>(filter);
}
}
And finally, TableviewController's viewmodel looks like this:
public class EventListViewModel : MvxViewModel<string>
{
private readonly ITicketMasterService _ticketMasterService;
private readonly IMvxNavigationService _navigationService;
private List<Event> _events;
public List<Event> Events
{
get { return _events; }
set { _events = value; RaisePropertyChanged(() => Events); }
}
private string _filter;
public string Filter
{
get { return _filter; }
set { _filter = value; RaisePropertyChanged(() => Filter); }
}
public EventListViewModel(ITicketMasterService ticketMasterService, IMvxNavigationService mvxNavigationService)
{
this._ticketMasterService = ticketMasterService;
this._navigationService = mvxNavigationService;
}
public IMvxCommand EventDetailCommand {
get {
return new MvxCommand<Event>(EventDetail);
}
}
private void EventDetail(Event detailEvent)
{
_navigationService.Navigate<EventDetailViewModel, Event>(detailEvent);
}
public override void Prepare(string parameter)
{
this.Filter = parameter;
}
public override async Task Initialize()
{
await base.Initialize();
//Do heavy work and data loading here
this.Events = await _ticketMasterService.GetEvents(Filter);
}
}
Whenever trying to run, the string object 'parameter' in my TableviewController's Prepare function remains 'null' and I have no idea how to fix it. Any help is greatly appreciated!
I believe the issue is with your command setup
new MvxCommand<string>(SearchEvent);
As this command is being bound to a standard UIButton. It will not pass through a parameter value of your filter but null instead. So the string parameter generic can be removed. Additionally, as you want to execute an asynchronous method I would suggest rather using MvxAsyncCommand
new MvxAsyncCommand(SearchEvent);
Then in terms of SearchEvent method you can remove the parameter. The value of filter is bound to your SearchFilter property. It is this property's value that you want to send as the navigation parameter.
private async Task SearchEvent()
{
await _navigationService.Navigate<EventListViewModel, string>(SearchFilter);
}
container.RegisterType<IDataContextFactory<MyDataContext>, DefaultDataContextFactory<MyDataContext>>(new PerRequestLifetimeManager());
Created a PerRequestLifetimeManager using OperationContext but it does not seem call setValue function at all, it always trys to go to GetValue() function which always retruns null since nothing has been set.
My goal is to create a lifetimeManager for dbconetxt that will give me a new dbContext per method call. transient is not an option since it won;t work for join query.
public class WcfOperationContext : IExtension<OperationContext>
{
private readonly IDictionary<string, object> items;
private WcfOperationContext()
{
items = new Dictionary<string, object>();
}
public IDictionary<string, object> Items
{
get { return items; }
}
public static WcfOperationContext Current
{
get
{
WcfOperationContext context = OperationContext.Current.Extensions.Find<WcfOperationContext>();
if (context == null)
{
context = new WcfOperationContext();
OperationContext.Current.Extensions.Add(context);
}
return context;
}
}
public void Attach(OperationContext owner) { }
public void Detach(OperationContext owner) { }
}
public class PerRequestLifetimeManager : LifetimeManager
{
private string key;
public PerRequestLifetimeManager()
{
key = Guid.NewGuid().ToString();
}
public override object GetValue()
{
if (WcfOperationContext.Current == null)
{
return null;
}
else
{
return WcfOperationContext.Current.Items[key];
}
}
public override void RemoveValue()
{
if (WcfOperationContext.Current != null)
{
WcfOperationContext.Current.Items.Remove(key);
}
}
public override void SetValue(object newValue)
{
if (WcfOperationContext.Current != null)
{
WcfOperationContext.Current.Items.Add(key, newValue);
}
}
}
My solution for this was to use this nuget package: UnityWCF
The Service should be instantiated by Unity and new instance per call.
For this use this settings on the service:
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall, ...
Inject DbContext where you need. And register in Unity like this:
container.RegisterType<DbContext, YourDbContext>(new HierarchicalLifetimeManager(), ...);
I'm upgrading AutoMapper in a project, converting from the static Mapper.CreateMap to the new way and injecting a IMapper where I need to map.
This is going great except for one use case. I have several ITypeConverters for complex mapping which are using the Mapper.Map function. How can I fix this? Below is the code I'm using at the moment.
The static Mapper.Map can't find my defined mappings because the're not being created using the static method.
public partial class ApplicationMappingsProfile
{
private void RegisterMappings()
{
CreateMap<Application, AppDto>()
.ConvertUsing<ApplicationTypeConverter>();
}
}
private class ApplicationTypeConverter : ITypeConverter<App, AppDto>
{
public AppDto Convert(ResolutionContext context)
{
var src = context.SourceValue as App;
if (src == null)
{
return null;
}
var dto = Mapper.Map<App, AppDto>(src);
dto.property = Mapper.Map<Property>(src.SomeProperty);
return result;
}
}
The ResolutionContext contains a reference to the current Mapping engine. Switch the Mapper.Map with context.Engine.Mapper.Map and you're good to go.
public partial class ApplicationMappingsProfile
{
private void RegisterMappings()
{
CreateMap<Application, AppDto>()
.ConvertUsing<ApplicationTypeConverter>();
}
}
private class ApplicationTypeConverter : ITypeConverter<App, AppDto>
{
public AppDto Convert(ResolutionContext context)
{
var src = context.SourceValue as App;
if (src == null)
{
return null;
}
var dto = Mapper.Map<App, AppDto>(src);
dto.property = context.Engine.Mapper.Map.Map<Property>(src.SomeProperty);
return result;
}
}