I had a quick question on working with listboxes in WP7 using MVVM Light. Basically before I was using MVVM all I had to do was set the SelectedIndex to -1 inside of the OnNavigatedTo event when the page was navigated to. Then inside of the SelectionChanged event I would check if the SelectedIndex was equal to -1 and if so I would ignore it. The reason I did this was just in case the user wanted to select the same item again when they came back to the page.
Now with MVVM (MVVM Light) I'm binding the event to a command, which takes care of the first part. But now I'm stuck because I don't know how to set the SelectedIndex to -1 from the ViewModel which prevents the user from selecting the same item again. Any ideas?
An even better solution is to not use the selection event to trigger a navigation. Use the tap event of the indivdual item instead.
This also avoids issues of accidental navigation when scrolling.
Try creating a SelectedItem property on your viewmodel, then do a two-way between the SelectedItem viewmodel property and the SelectedItem property on your ListBox. Then you can update it with whatever value you want when your Command fires and the result will propagate back to your ListBox.
Related
Using MVVM Light I have a listbox databound to a collection of several items.
One of the items is the selected one.
With this code it works perfectly and ViewModel structures are updated correctly:
<Name="listBox1"
ItemsSource="{Binding Path=Models}"
SelectedItem="{Binding Path=csProfile.Model, Mode=TwoWay}">
My problem is that when I enter the page if the selected Item is not in the first items it is not visible and the user does not know what was the previous selection.
How could I force the Listbox to always show the Selected Item?
Possibly via properties or Binding.
M
There's no property you can bind to to set what's visible. Instead call ScrollToVerticalOffset() on the ScrollViewer inside the ListBox.
I think you are looking for the ScrollIntoView method. A similar topic was discussed here:
Automatic Scrolling in a Silverlight List Box
The API reference is here: http://msdn.microsoft.com/en-us/library/system.windows.controls.listbox.scrollintoview(VS.95).aspx
Calling UpdateLayout() before calling ScrollIntoView on the selected item seems to be necessary.
I am using a listbox in a data template - and from an earlier post I cannot reference the listbox directly in the code behind.
As a result I am capturing the last selected object in the selectionchanged event for the listbox and using this when I want to navigate.
I now need to also clear the selected object in the listbox -can I do this in the selectionchanged event (after storing it away).
Alternatively I could use the MouseLeftButtonDown event on the listbox (which I understand is the equivalent of a 'click') but can I get the selected object in the listbox in this event.
thanks
In the selection changed event set <ListboxName>.SelectedIndex = -1;
Also, do not use the MouseLeftButtonDown event. This will fire whenever the user touches the ListBox, even if they're just trying to scroll up / down and not actually selecting an item.
If you can't change the SelectedIndex in code behind then, instead of detecting the SelectionChanged event you could detect a Tap event on the ListBoxItem.
I have a Listbox with Button and Textblock as ItemTemplate. Button has an onClick event.
All i want is to get the index of the clicked item, but SelectedIndex property in my ListBox is always -1!
How can I get the index of the clicked item?
The problem is that the Button control is swallowing the mouse events to provide the Click behavior, so the ListBox never receives any events to tell it that the selection has changed.
As #Alexander suggests, you could use an MVVM-style approach with commands to handle the action in a view model and pass the data context as the parameter.
Alternatively, you could replace the Button with any other layout control and either use the gesture service from the Silverlight Toolkit or use the regular MouseLeftButtonUp event. In either instance, the mouse events will bubble up and enable the ListBox to handle selection.
You might want to actually select something in your listbox then :p
If you want to get data object associated with current ListItem use RouteCommand. Here is example
<ListView.ItemTemplate>
<DataTemplate>
<Button Margin="5,0" Command="{StaticResource ButtonCommand}"
CommandParameter="{Binding}">
</DataTemplate>
<ListView.ItemTemplate>
You need also define Command at least in ListView.Resources
<RoutedCommand x:Key="ButtonCommand"/>
And then setup CommandBinding like this
<ListView.CommandBindings>
<CommandBinding Command="{StaticResource ButtonCommand}" Executed="Button_Click"/>
</ListView.CommandBindings>
In the end write handler
Button_Click(object sender, ExecutedRoutedEventArgs e)
{
e.Parameter// object that you Specified in CommandParameter
}
In advance you can use any MVVM framework, define all command and commands logic in model and then just bind this commands to corresponding elements.
I have a list of panorama Items.
I want to know when the user has reached a particular panorama item and then take necessary action.
I tried using the eventhandler GotFocus on the panorama item but it doesn't get invoked when the user reaches the item
The Panorama control has a SelectionChanged event which is fired when the user pans from one item to the next. You can then use the SelectedItem or SelectedIndex properties to find the item which is currently in view.
I have binded RadCombo on LoadonDemand Event. when i change page of radgrid, RadCombo looses its selected item.
How to maintain RadCombo selected item.
Please Help
Have you tried using the RadComboBox's trackChanges() and commitChanges() methods to preserve the selected item across post-backs?
http://www.telerik.com/help/aspnet-ajax/combobox-client-side-radcombobox.html
I'm assuming the RadGrid is not contained in a RadAjaxPanel because if it were this would be taken care of automatically through partial page rendering (i.e. only the RadGrid would be re-rendered when paging occurs). It would probably be helpful if you could post you page's markup.
When you page the grid is rebound and the controls inside it are recreated. To keep the combobox selection, save it Cache of Session object and then recover it from there wiring the PageIndexChanged event of the grid.