I have a ListBox with the following ItemTemplate:
<DataTemplate>
<StackPanel>
<TextBlock .... />
<ListBox .... />
</StackPanel>
</DataTemplate>
I would like to forbid the user to Select an item in a child ListBox, and that when user clicks on the child ListBox, a parent ListBox SelectedItem should be set respectively.
What I have tried is to set IsHitTestVisible of the child ListBox to false, and that prevents the user to select an item on it, but the problem is that if I click on the child ListBox, the mouse click is not passed to parent ListBoxItem, so it never gets selected.
So to summarize, I need:
prevent the user to select item on the child listbox.
item on the parent listbox should be selected when we click anywhere in the ItemTemplate area (even when clicked on Child listbox).
You could replace the inner ListBox with an ItemsControl. Based on your question, it sounds like you just need to display a collection, and prevent the user from interacting with it. A simple ItemsControl is well suited for that.
The ItemsControl does not support selection, so the click will get propagated up to your main ListBox.
EDIT
Based on your comment, I'd recommend trying one of two options. First, you could set IsHitTestVisible to false on the list box items, as in the following example
<!-- XAML for the inner list box -->
<ListBox>
<ListBox.Resources>
<Style TargetType="{x:Type ListBoxItem}">
<Setter Property="IsHitTestVisible" Value="False" />
</Style>
</ListBox.Resources>
</ListBox>
This will cause the click event to propagate up to your main list box, while still being able to use a list box.
Second, maybe it would be easier to just create two separate list boxes? Again, you haven't fully explained why this is required, but trying to load up one control with different modes of functionality sometimes overcomplicates things. Having two controls, and showing only one at a time based on some condition, can be an easy way to simplify the XAML.
Related
I have a WPF/MVVM app with a ListBox which displays data through a DataTemplate. I managed to change the selected item in the ListBox when pressing a button so the CommandParameter is linked to the ListBox's SelectedItem, but I cannot get the buttons to be enabled/disabled correctly in the same way. For example, if I have 2 items and the button should be enabled in one and disabled in the other, when I select an element BOTH buttons have the same state, and they BOTH change state when I select another item.
I am using a RelayCommand as used in many MVVM Frameworks.
Here is my XAML (removed "not interesting" parts):
<UserControl.Resources>
<DataTemplate x:Key="ItemTemplate">
<Grid>
<Button Content="Something" Name="EnabledDisabledButton" Click="Button_Click"
Command="{Binding RelativeSource={RelativeSource AncestorType={x:Type UserControl}}, Path=DataContext.SomeCommand}"
CommandParameter="{Binding RelativeSource={RelativeSource AncestorType={x:Type ListBox}}, Path=SelectedItem}"/>
</Grid>
</DataTemplate>
<Style TargetType="{x:Type ListBoxItem}" x:Key="ContainerStyle">
<Setter Property="ContentTemplate" Value="{StaticResource ItemTemplate}" />
</Style>
</UserControl.Resources>
<ListBox x:Name="myListBox" ItemsSource="{Binding ElementList}"
IsSynchronizedWithCurrentItem="True" ItemContainerStyle="{StaticResource ContainerStyle}"/>
I tried to pass the SelectedItem as a parameter to the RelayCommand's CanExecute method, but the result was the same as before.
Is there a way to pass the actual ListBoxItem in which the button "lives in" as a parameter to the command, so each one will be processed separately by the CanExecute method? Would it work if I got this? (right now I am handling the Click event to select the correct item in the list before executing the command).
In my CanExecute method I am evaluating some property of the SelectedItem in order to enable/disable the corresponding button. An alternative would be to evaluate this property for all elements, but I cannot think of a way to do it inside the ViewModel, and then communicate to the view the result (if it is even possible while using a DataTemplate for the items).
Thanks for your input, regards!
Converting My comment into an answer:
Why not just CommandParameter="{Binding}"?
You mention "MVVM" in the question, but it seems you use the MVVM way to your full advantage.
I would not have a Button_Click event in the style at all. That is because it is in fact a style, which per definition could be changed to another style which does not have the same event, which again will make the application stop working as wanted if you choose to have a style-based app in the future.
A rule I use is that a style is a style. A style has to do with the UI and "looks" of the app.
Functionality should be separate from the UI. The programmer can define the Command, and the designer can decide how the user will use that in the best way.
That's exactly where the code separation from the MVVM pattern cames into grip.
To separate the "looks" and user behavior and the app's logic.
Like...it should not matter to the model if a command fires from a button, a menu, a datacontext or a key stroke.
If this particular problem was handled to ME, I would solve it by having a HOLDER-class.
This is a class (DependencyObject which implements INotifyPropertyChanged) that holds a ICommand property as well as the "row" that will be displayed in the various rows in the ListBox.
The ICommand property will be bound to the Button, having the row (class) itself as CommandParameter to the call.
Then the actual row would be used in the ItemTemplate on the ListBox, with Bindings to different elements (proprty with or withouy Converters) to make whatever desired display available.
I hope I explained good enough...
Feel free to ask more if you want more details to my solution alternative.
I have a scenario where in I populate a listbox with a 1000 items. I set the ItemsSource property with a source of data.
I have a requirement where I need to strike out an item of the listbox based on certain criteria, when the UI loads. I am using styles + attached properties to achieve the same by setting ContentTemplate of ListBoxItem in the callback method of attached property.
My problem is when I try to generate a ListBoxItem using ItemContainerGenerator.ContainerFromItem, for an item which is at the end of the list, I get null. As a result, I cannot strike out items of the listbox which are at the bottom of the list.
Has it got something to do with virtualization. I want to obtain all those ListBoxItems on load.
Is there any workaround?
Thanks
This is definitely caused by virtualization. This is exactly what UI virtualization is supposed to do - only create ListBoxItem objects for items that are visible on the screen. You can easily see that this is indeed the cause by setting VirtualizingStackPanel.IsVirtualizing = false on your ListBox and see that ItemContainerGenerator.ContainerFromItem no longer returns null.
You can set a style for your ListBoxItems in your ListBox that will have the logic to strike out the items as needed. This should also work when virtualization is enabled. For example:
<ListBox>
<ListBox.Resources>
<Style TargetType=ListBoxItem>
...
</Style>
</ListBox.Resources>
</ListBox>
I have a list on my WPF xaml which contains two items. Below is the Style template for each item. Now on UI this shows like a group of radio buttons(No. of radio buttons depends on no. of items in my list).
<Style x:Key="RadioButtonListBoxItemStyle" TargetType="{x:Type ListBoxItem}" >
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<RadioButton FlowDirection="LeftToRight"
Margin="10 15"
Content="{Binding Value}"
GroupName="{Binding DisplayGroupName}"
IsChecked="{Binding IsSelected, Mode=TwoWay}" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Now I bind a list(having 2 items) using the above style template to get two radio buttons. What happens is everything works pretty fine i.e when I change the selection of radio button on UI the IsSelected property is getting updated properly to true or false depending on whether my radio is checked/un-checked. But if I try to set the list in the code manually, then from that point my binding of the radio button's with my list is lost and nothing happen's.
Any help on this would be great and based on my needs I have to set the list in the code manually. So is there any solution in a way that binding will not be lost even though I set the list in my code manually. Thanks.
-Ady.
This is a common problem with radio buttons in WPF, and it has to do an unusual aspect of binding, one that is marginally more feature than bug.
The design of binding assumes that the only two things that change the value of a binding's target property are a) actions in the UI and b) changes to the source property. If you set the target property of a binding in code - like, you explicitly set the Background of a Border, even though it has a binding - the binding decides that you know what you're doing, and that it should just get out of the way. So it turns itself off.
This is a pretty sensible design decision, for the most part. It's better than throwing an exception, for instance. Most of the time, you're not going to ever set IsEnabled in code anyway; you'll let the binding do it. Especially if you're using MVVM.
Okay, so what happens if you have radio buttons in a group?
When you check one button in the group, the WPF code that manages radio button groups unchecks all the other buttons in the group, by setting IsChecked to false in code. The binding disables itself. Oops.
Here's the solution: If you're using radio buttons and binding, don't use groups. Handle the mutual exclusion logic in your view model code. In your case, code your view models so that only one object in a collection can have IsSelected true at any given time. (Yes, this is a pain.)
The radio buttons will still work as expected, but since the only properties being set by code are the source properties, binding won't break.
you are setting the style for the listboxitem class, including the bindings. so, when you set the list from code behind it does not contain listboxitems, it contains the items from your list. so, the style does not apply. what you should do is make the <DataTemplate> for the type of item in your list--in effect telling WPF what you want each item to look like.
<DataTemplate TargetType="{x:Type MyCustomClass}" >
<DataTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox IsChecked="{Binding Deleteable, Mode=TwoWay}" />
<Label Content="{Binding Name}" />
</StackPanel>
</DataTemplate>
</DataTemplate>
(this is off the top of my head, so the xaml might not be exactly right)
I would like to prevent selection of ListBoxItems in my ListBox. My DataTemplate has a checkbox and this should be the only thing the user can click or select.
How can I do that?
Thanks!
This is almost a duplicate question. In fact, you're asking two questions here:
Either style your ListBoxItem so that it doesn't show selection (look elsewhere on SO for that answer), or replace ListBox with ItemsControl if you don't need the other features that ListBox provides.
Bind your checkbox's IsChecked property to the parent ListBoxItem.IsSelected property:
<CheckBox
IsChecked="{Binding
RelativeSource={RelativeSource Mode=FindAncestor,
AncestorType=ListBoxItem},
Path=IsSelected}"
/>
When your user will try to (un)check your checkboxes then item become 'active' in some way. And focused style will be applied. As far as i know there is no way to disable selection(because if you did your checkboxes will not work) but you can override focused(or selected) style of your listbox items
I'm developing a program in WPF (VB) that relies on keyboard navigation only.
In my program, I have a listbox that displays up to 20000 items.
What I want is that when the listbox has keyboard focus, and I move to the bottom item that is visible (using ArrowDown), I want the focus to move to the next item outside the listbox. I'm using PgUp and PgDown to scroll the listbox contents, and text search to jump to items.
Is there a way to detect if the focused/selected item is the last/first visible item in the listbox?
If so, I could just use:
ListBox1.MoveFocus(New TraversalRequest(FocusNavigationDirection.Down))
I'd suggest that you don't do this, the user interface should behave consitesntly with other user interfaces in the operating system.
Your users would be better off if you come up with an alternate user interface that's consistent with how user interfaces behave on your target operating system.
It is a little clear from your explanation but either your looking for:
navigation to move outside of the listbox when the last item is selected.
when navigation is attempted beyond the last item in the list that the navigation pops out of the listbox.
If (1) is your objective there is probably a reasonable solution using triggers and or some custom code handling for events based on the selected item and selected item changed. I would have to agree with Tom if this is the case though and suggest that you do not implement it this way since the last item will never be selectable without focus being programatically removed.
If your instead looking to do (2) then it is my experience that the natural behavior of a ListBox is to move to the next control when the Tab key is pressed and I've tested this for the down arrow key as well and it works the same. When I get to the last item in the list focus pops out of the listbox and to the next control according to it's parent.
UPDATE: I have to withdraw my original comments as the behavior I described above do not describe the default behavior in WPF for a ListBox however it is the behavior you will see the behavior I described above (which I believe is the behavior your looking for) when implementing an ItemsControl and specifying an ItemTemplate. Take a look at the following example.
<ItemsControl ItemsSource="{Binding ElementName=TheWindow, Path=ListOStrings}">
<ItemsControl.Template>
<ControlTemplate TargetType="{x:Type ItemsControl}">
<Border BorderBrush="Magenta"
BorderThickness="1">
<ScrollViewer>
<ItemsPresenter />
</ScrollViewer>
</Border>
</ControlTemplate>
</ItemsControl.Template>
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Content="{Binding}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
By chance, this just happens to have the behavior you described since each item in the list behaves almost like a control placed directly as a peer to all the other controls.
I use an easy trick to move the focus outside Listbox:
I disable the listbox so the focus moves automatically to the next control, then i enable the listbox again :)
Lst.IsEnabled = False
Lst.MoveFocus(New TraversalRequest(FocusNavigationDirection.Next))
Lst.IsEnabled = True