I am making an application where there is a history and I want the history to be updated automatically when there is a change in my list.
Thank you
Assuming you're using view models, just bind your ListView to an ObservableCollection<T> in the view model via the ItemsSource dependency property - when the collection changes, the view will update as well. (And if you're not already using MVVM, I'd suggest moving to it ASAP.)
Related
I have an abstract base view model (IBaseViewModel) and two classes that implement it (Base1ViewModel, Base2ViewModel). I also have a Xaml user control, and I want in one page to use Base1ViewModel as view model and in another page Base2ViewModel as view model.
Prism best practice is to bind to view model by name, so what I ended up doing is duplicating the xaml file into Base1View and Base2View so each view gets the right view model, but this is obviously not ideal because then changes to the xaml should be duplicated as well.
Is there a solution/design in which I can reuse the same xaml user control with two different view models?
Thanks,
Noam
I've a hard time getting my Cocoa application to work as expected. It consists of a toolbar in the main.nib and a custom view in a details.nib file. Now I want the user to select an entry in a NSPopupButton in the toolbar and the content of the custom view should be changed accordingly.
To achive this I've added an ArrayController to my main.nib, showing the following configuration:
Furthermore the Managed Object Context is bound to the Model Key Path delegate.managedObjectContext (it is no document based application).
With this configuration the NSPopupButton works just fine and if I add a Label to the toolbar (also in the main.nib) and bind it's value to the selection (Controller Key), name (Key Value Path) the content is refreshed whenever I change the selection.
The Bindings of the NSPopupButton look like shown in the following screenshot:
So in my details.nib I tried the following to achieve the same effect. I've added an ArrayController, whichs Managed Object Context is also bound to the Model Key Path delegate.managedObjectContext. Also the configuration is exactly the same as shown in the above pictures. I've then added a label and bound it's value to the selection (Controller Key), name (Key Value Path) of this ArrayController.
The problem is that the Label only displays the the initial selection after the application did launched correctly. Afterwards, when I change the selection of my NSPopupButton, the label does not change accordingly.
What are my options to get the ArrayController working accross multiple NIB files?
BTW: I've tried to follow this blog post to get it working but it seems I'm missing something here.
Update:
If I replace the Label in the details.nib by a NSTextField and change the text of it, the changes are reflected in the related NSPopupButton entry. So I guess I made something right, but the main problem remains: I can only edit the entry which was loaded during application startup. Switching to another NSPopupButton entry does not change the text in the NSTextField.
Update 2:
I've created a small sample project with exactly the same configuration and uploaded it on GitHub. So feel free to check it out or create a pull request with a solution approach.
It seems you're missing the fact that, when you create the second array controller on the Details.xib it has no relation to the array controller on the MainMenu.xib. They are two separate instances.
When you change the selection on the PopUp the only array controller affected is the one on MainMenu.xib.
You have several options here:
When you create your DetailViewController pass a reference to the array controller on the Controller and bind to that (don't create a new one on the details.xib)
Just use simple KVO to observe the selection on Controller, and programatically change your label value.
Just use simple KVO to observe the selection on Controller and update the array controller on the DetailsViewController to keep them in sync.
your solution here...
As long as you understand what's going on I'm sure you'll find the best solution to your original problem.
I have NSCollectionView with full of items, have one scenario where after deletion of one item the collection view should be refresh and it should display update items.
I am able to delete item, but collection view is not refreshing,
googled a lot, but got nothing,
NSCollectionView is a subclass of NSView. And you must be knowing MVC design pattern. View is intended only to show the data/values from the model.
In your case you must have some array. You need to update the array and set the content of NSCollectionView programmatically or using Cocoa Bindings.
- (void)setContent:(NSArray *)content;
Also you may need to refresh the view :
[yourCollectionView setNeedsDisplay:YES]
Anoop's suggestion didn't work for, but following did, copied from here
Turns out that the NSCollectionView item views can be refreshed by setting the ItemPrototype, e.g.,
ItemPrototype = new SomeViewController()
This causes all the existing views to be recreated.
Is it possible to use two ViewModels for a single View at MvvmCross?
The reason is an existing Core library which already has navigation in place and a working app on top of it. Now I need to create another app and leverage the only View for two ViewModels (in core lib there is one view navigated to another using ShowViewModel and I just want to stay at the same view and change my datacontext).
Thank you for any suggestions.
Yes
you can continue to use ShowViewModel and change the way navigation happens by overriding the presenter - see Custom Presenters in the wiki
or you can use a different navigation mechanism entirely - there's nothing forcing you to use ShowViewModel
I am trying to get my head around MVVM and the Navigation-based project template in SL4. At the moment I am trying to move the ContentFrame_Navigated event handler into the ViewModel. Basically this event handler checks each hyperlink button in the menu bar against the current page and adjusts the style accordingly. To do this it seems I need to pass the EventArgs as well as another object. I see MVVM Light has the PassEventArgsToCommand bit, but what about passing another object/control? In this case it's the StackPanel hosting the list of menu item hyperlinks. I'm just getting my head around the MVVM concept, what's the best practice in this case?
Cheers,
Dany.
With MVVM you have to think more abstract. You are not daling with a list of HyperLink elements, but with a list of Navigation Targets. I.e. you should separate the presentation (HyperLink elemen) from the data (the URL, the Title, whether the item is selected or not, etc.). You now hold the data in a list on your ViewModel (normally you would see this data as the ViewModel of your Hyperlinks, and name it accordingly). The items are held in a ObservableCollection so that you can track changes if a item is added etc.
To display this list you can use a class inheriting from ItemsPresnter (e.g. a ListBox) and use binding to set the properties. Now you navigate to a page you can set the IsSelected property of the relevant item in the list, resetting all other IsSelected properties.
As the navigation targets can be seen as a global collection, you can also hold it in a property on the ViewLocator, so that all Views and ViewModel can access this list, and setting the IsSelectedProperty is applicable to all Views. This global collection represent you navigation state.
And, BTW, the EventToCommand, the RelayCommand, and the Command attribute ony support one parameter. Furthermore, from experience I can advise you that it is not good practice (although you obviously can do it) to mix View objects, such as EventArgs, or elements and your ViewModel.
one solution is to put the menu items the ViewModel, and the View can bind this list.
then the View wouldn't need to send the menu items to the ViewModel