I have a ListView binding to grouped data. What I would like is to be able to bind the background of each group based on the content of the item. GroupStyle.ContainerStyle was deprecated in 8.1 without changing the ItemsPanel of the ListView. This unfortunately comes with a performance hit though.
Is there a way for me to define a background for the entirety of a Group without changing the ItemsPanel of the ListView?
Unfortunately, I can't change the template of the items and header together (though I've tried) because some of the items are duplicated and do not know which group they are in.
There are two different approaches to solve this problem:
add the responsible Property to your ItemTemplate and connect it with a converter, which converts it to a type you need (in your case a BackgroundColor). The problem is, as already mentioned, that this is very costly and in my opinion a converter is not made for such a huge operation. Don't forget that in MVVM the ViewModel should provide all the information which is needed by the one who designs the view.
the better way is to add a Property which is called something like “ItemBackground” and which you bind to the ItemTemplate. I prefer this approach, because there is no logic which background to use in the View.
Related
I have a UWP app that I am working on, and using absolute position creates problems when using the app on screen sizes different than the one it was designed for.
I'm not sure how exactly i should place elements at distances from each other without using margin and absolute position. How should I be doing this?
Edit: I am using XAML to design the UI.
Well, it depends on what UI you want to build up.
There are various panels and, usually, there is NO need to use absolute position in most cases.
Usually, the Grid panel is used to create flexible layouts, by adding rows and columns: for example, if you want to create a page with some content and a bottom app bar with buttons on it, you usually create a Grid with as many rows as you need for your content controls, plus one for the bottom appbar itself.
Years ago, I also started building UIs by using absolute position for every element, but then times passes and you start having a flexible mind in order to build flexible layouts.
Sorry to not answer any further, but your question is just TOO broad to give any precise answer.
Best regards
How do you properly position elements in XAML without using absolute position?
You should use an appropriate layout panel:
Layout panels are containers that allow you to arrange and group UI elements in your app. The built-in XAML layout panels include RelativePanel, StackPanel, Grid, VariableSizedWrapGrid, and Canvas.
I have a couple of ListViews on different pages in my UWP application. For some reason, one of them seems to have Padding along the bottom below the last ListViewItem, while the other does not.
Neither of them has bottom Padding specified, so I'm wondering if this could be inherited from a parent control? I searched the entire XAML of the one with Padding, and it is not set anywhere else either. It isn't a huge problem, but I would prefer my controls to be consistent throughout my application, and I think adding the bottom Padding to the ListView without it to make them match seems silly, especially when I am unsure of why the first one has Padding in the first place.
Is there somewhere to determine where properties are set in the hierarchy, similar to the way CSS works?
Here is what they look like:
No padding:
Padding:
I added a Background to the ListView control to verify that there is no Padding there..
So it would seem it would have to come from the ListViewItem itself, but it does not have the Padding property set.
The issue turned out to be that one of the parent controls of the ListView that was displaying correctly (how I wanted it to) had a VerticalAlignment="Top" set, while all the parents of the other ListView were set to VerticalAlignment="Stretch".
I was finally able to get XAML Spy working properly, and it was helpful in previewing the changes while the application was running so that I could determine which element I needed to set the VerticalAlignment on without recompiling over and over again. Thanks to #ChrisW for the recommendation.
I'd like to get the effect visible on the picture:
I don't think it is. A GridView already has a ScrollViewer in itself, so multiple of them does not make sense. I would try to use a single GridView with GroupStyleSelector/ItemContainerStyleSelector/ItemTemplateSelector implementations and DataTemplates to define each item. A less dynamic version might just be a ScrollViewer with Style set to HorizontalScrollViewerStyle, a horizontal StackPanel and a few VariableSizedWrapGrids - if you bind the GridView to some groups or other panels to define the content.
This looks like a good sample based on the description (though the images seem to be missing for me).
I'm facing the following problems:
We have meta data for items, each item can be a different type of NSControl, currently NSTokenField and NSTextField, but we might need NSCombo or other types.
I need to build a form in which each entry will have a label and an editable control.
this form has to be built dynamically since the items are retrieved from the server.
I've implemented it with NSMatrix, and apart from it looking pretty shabby, I'm faced with some visual issues I don't know how to solve.
The visual issue is every time I move the mouse over the NSTextFieldCell the tokens get drawn on the top left corner of the NSMatrix form.
now, I'm considering moving to another type of control,
I've googled for few hours, and found the following controls:
NSForm,
NSMatirx (parent of NSForm),
NSCollectionView,
NSTableView
which one of these is the most appropriate for this task?
I hope I am clear since I wanted to add pictures, but it wouldn't let me due to lack of "reputation points".
Thanks for your help,
Eyal.
NSTokenField is a subclass of NSTextField so you could use an NSTableView to display them.
You could also draw a custom NSCell with all elements in it. When each "item" has a different number of elements then this becomes a bit more complicated though.
I have seen that in Cocoa I can create a custom view using drawing primitives which allows me to draw what I like but at a very low level.
Instead I'd like to create custom widgets using a combination of existing controls. For example:
I'd like to create a table with images and combobox in cells
I'd like to create a custom widget wich is a combination of several (for example a list, a button and combobox)
How can I approach this problem ?
Secondly a typical cocoa developer uses external controls? Is there a repository or a list of interesting external custom controls (commercial or free) ?
I'd like to create a table with images and combobox in cells
There already exists NSImageCell and NSComboBoxCell. Are you sure you need to do anything different?
If the problem is that you want an image and a combo box in the same cell, you will have to subclass NSCell. Currently table views can only contain cells, not views, which makes your life harder (as understanding how cell drawing works is more difficult). That will change in Lion, however, so if you can wait until then, this will become easier!
I'd like to create a custom widget wich is a combination of several (for example a list, a button and combobox)
How is your custom widget different to just placing those three things in the same view?
You could write your own NSView subclass. When it's created, it should create a list, a button and a combobox and add them as subviews to itself. Your NSView subclass should handle the logic of keeping them in sync or doing whatever it is you want them to do. Then, to use this combination control in Interface Builder, you place a Custom View and set its class (rightmost tab of the inspector) to your NSView subclass.
BTW, on a tangent, are you sure you mean combobox? Loads of people coming from Windows get this one wrong. A combobox is a combination of a menu and a text field: it allows the user to enter custom text that is not in the menu. If you just want a dropdown menu of choices (and the user can't enter a custom one), you use an NSPopupButton.
Secondly a typical cocoa developer uses external controls?
Yes, sometimes. Things like BWToolkit can be very useful. There's a lot more that are just floating around mailing lists as code snippets, rather than being cleaned up and put in a library. Search for what you need to do!