Hi,
I'm new to both Prism and WPF, and I have a question regarding sharing data between views.
Application I'm working on resembles SQL Server Development Studio. Demo contains two regions. First region contains tree (like Object explorer in SQL Server DS). Tree nodes are bound to different view models. Example would be DatabaseA->Tables->dbo.TableA->Columns etc.
Second region is initially empty. When I double click on tree node I would like to open view that displays data I clicked in tree.
In detail:
1. double click on tree node
2. node data and display it in second region
3. if second region isn't empty, check if clicked node data is already displayed in one of existing tab pages
4. if not, create new tab page with clicked node data, otherwise focus existing tab page
Until now, I managed to created tree. When tree node is clicked app calls:
UriQuery uriQuery = new UriQuery {{"ID", unit.Id.ToString()}};
uriQuery.Add("TypeName", "Unit");
var uri = new Uri("DebugTreeItemView" + uriQuery, UriKind.Relative);
RegionManager.RequestNavigate("SECOND_REGION", uri);
This will open view with tab control and I can fetch uri parameters. But I'm not satisfied with this solution. I need a way to:
1. intercept this RegionManager.RequestNavigate call in order to check if tab control is alread created. Also, I need to check that clicked node data isn't already displayed in one of existing tab pages.
2. I would like to send Unit object directly to tab control view instead of sending ID and typename. What is the best way to achieve this?
Thanks.
I would have a ShellViewModel controlling my overall application. It would contain the TreeNode collection for the left side, and the OpenTabs collection for the right side. It would also contain the SelectedTabIndex for the right side, and perhaps the SelectedTreeNode for the left side if it made sense to do so.
When you want to open a new Tab, I would use the EventAggregator to publish an OpenTab event and pass it the selected TreeNode item. The ShellViewModel would subscribe to those events, and would determine if that object already existed in the OpenTabs collection. If it exists, it simply sets the SelectedTabIndex. If not, it adds the item to the OpenTabs collection before setting the SelectedTabIndex
A while back I posted something here on this sort of navigation with MVVM if you're interested
Related
I'm using 3 levels tree VO's. All three VO's has bind variables. The VO's are connected via View link. I'm using createViewLinkAccessorRS in order to pass the variables from parent to child VO.. i defined Target Data Source (EL_expression) for second and third level.The tree works fine, and the nodes filled correctly (all the way down). The Problem is that the second and the third tree level attributes are only shown in the tree component. anywhere else in the page it looks like they are empty ({bindings.(attname).inputValue} = null) (E.g - after dragging the third tree level "FlowOrder" from the AppModuleDataControl and create a form out of it, and selecting the second node of the tree will update all the third level tree node (please see attached image), but will leave the entire form which was just created empty)
Any idea why the FlowOrder bindings are empty? i assume that maybe it has to do with the bind variable of the VO .. i even thought i would change the tree selection listener so on the second level click it will perform a full query of "FlowOrder" via executewithparams, but it does not make any sense because the data was fetched already after clicking level 2 tree)
(Jdeveloper : 12.2.1.2.0)
attached image: Details
Check out my explanation on trees and example application in another post: ADF filter table based on tree selection The tree shows data from view link accessors. The form shows data from view instance. They are in different state.
I have just started using visual studio c++ (2010) with windows forms, but have cannot for the life of me find out how to create new UI items in response to events. What I would want to happen is click a button, and have a new row, with a couple of text boxes and buttons appear, with onebutton to delete the row if I keep clicking, more rows will appear, named row0, row1 etcv. I looked at this page, (http://msdn.microsoft.com/en-us/library/aa984255(v=vs.71).aspx), about adding controls programmatically, but when I add a new text box inside a click event, the text box is only created inside the scope of the event (as expected!), but I want to be able to create it insde the newRow click event, but access it and . I thought of making a 'row' class, with row.text and row.deleteButton properties, and at each creation of a row, respective events will be created for button clicks and text edits.
Is there anyway to do this, ie a function that can be created that creates new objects by passing the required name?
The trick for this to work is that you need to have declarations outside of the event handler to keep track of the newly added UI components. In the link you've given the added TextBox is locally scoped within the event function, and this will be removed from the heap (i.e. memory) when the event is finished.
So one solution would be to add a list of UI components to your form, and then have the events add to or remove from this list of components. To get this solution working you possibly need to read up on lists of objects (or possibly dictionaries) and how to handle these.
Sorry for a rather general answer, but the question is also very broad... :)
How can I reset my viewmodel when the user clicks new button on the view that has the viewmodel as it's datacontext?
For example:
If I have a view NewCustomer and upon save, the data is saved to the DB and the newly created account number is displayed. But when the user clicks the New button in the screen, I want the view (viewmodel) to be reinitialized. Or if the user clicked cancel in the screen to clear all changes.
How can I achieve this? I am using Prism 5.0 and Unity as my container.
If I used IRegionMemberLifetime, I can clear the viewmodel data when I navigate away and navigate again to the view (by setting the KeepAlive as false on clicking New button before navigating away). But I want the form to be cleared without navigating. Can this be done?
You could have a screen/workspaceViewModel, and another ViewModel wrapping your data.
So two classes: CarScreenViewModel and CarViewModel.
The CarScreenViewModel would have a property, say CurrentCar, which reflects what is currently selected in the screen. Then, when clicking the Create button, you simply set:
CurrentCar = new CarViewModel();
Resetting partially loaded data will only lead to behaviour that is hard to reproduce. It is better to start with a fresh instance.
Your standard approach will be something like below
ViewModels
CustomersContainerViewModel which contains
a collection of CustomerViewModel s
and ICommands like
CreateNewCustomer
DeleteExistingCustomer
UpdateExistingCustomer
Your View will contain
the CustomersContainerView which will contain
a collection of Customer Objects in your required UI element
a button to Create new customer (which will launch a new screen which contains the newCustomer fields it can also contain cancel, which will just close the form)
a button to delete (can also be a ContextMenu)
a button to update (can also be a ContextMenu) which will launch a customer form filled with details from DB.
Hopefully this makes some sense... Let me know if you have problem with any of the above
Update - Forgot to add. NewCustomer Command will add a new Customer object to your CustomerCollection and that should open a NewCustomer form (or whatever you chose) for user to input the customer details. Cancel/Delete will just remove that record from the collection. Delete will update the DB as well in addition
In my case
yourViewName.variableName.postValue("")
I have a series of views that are to be displayed depending on the currently selected item in a tree within a parent view. These views are created and registered with the region during the initialization method of the parent view and are being correctly deactivated/activated, therefore giving the effect of swapping in/out the correct view. These views have a single underlying viewmodel as their datacontext, which contains data objects supporting INotifyPropertyChanged.
This solution works if there are no currently outstanding edits in progress within the child view but if there is a edit in progress in a view (i.e. the user has changed the contents of a description but hasn't clicked out of the text box) and that view is deactivated (i.e. the a different tree item is clicked within the parent view, thus causing a de-activation to occur) a NullReferenceException is being thrown in the NotifyPropertyChanged() of the underlying data object attached to the now deactivated view.
What seems to be happening is this:
An edit is started by the user in the child view
The user clicks an item in the tree in the parent view
The controller picks up the change in the selected item in the tree
The current child view is deactivated
The new view is activated
The change from the edit happens to the underlying data object (the set method is getting called)
A change notification event is generated by the data object as a result of this change
A null reference exception is thrown.
Presumably, this change notification event is being sent to the now de-activated view, but the view is not null.
I have not tried this myself, but I believe one solution was to listen for the deactivate event of the view using IActiveAware and cancel any editing.
See if this link helps.
I have a combobox that goes out to the database to load it's content on clicking the dropdown arrow. if after the dropdown box is shown with data and I don't select anything, than the current value of the combobox is blown away. Inside my routine to load data, I tried saving the current value and restoring it back after the loading is done. doesn't work.
[Edit] Added the code from the comment here for legibility
MyUltraCombo myultracombo = new MyUltraCombo();
//MyUltraCombo inherits from UltraCombo inside MyUltraCombo, I keep the table name to load from
MyUltraCombo.BeforeDropDown += new System.ComponentModel.CancelEventHandler(cb_BeforeDropDown);
//inside the eventhandler
myultracombo.Load();
//inside the Load method
datatable = DataUtility.GetAllRecords(tablename);
combobox.datasource = datatable;
If you store "the current value" as just the SelectedItem property, then it will probably not be an object that is present in the new list, since it will consist of completely new objects. What you will have to do is store an ID of the current value (if you're lucky to have a unique id) and then search the newly created list for an object with the same id (or whatever you use to uniquely identify an item, maybe just ToString()...).