I have listbox bound to a collection of PhoneEntity. I also have a Remove button and it's command's CanExecute returns true if the listbox's SelectedItem != null. Pretty standard.
When I select a list item, the Remove button is enabled. But when I attempt to click the button, as soon as the button receives the focus on mouse down, the listbox's SelectedItem becomes null, so the button disables and cannot be clicked.
How do I keep the lisbox's selected item even if the list loses focus?
Thanks
It isn't pretty but... make a global variable to hold the selection index. Handle the on selection change and assign the selected index. Then handle the onFocusLost event and set the selection to that global variable.
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I have a listbox which uses the datatemplate to generate a list of checkboxes. The issue is when using the keyboard , the focus moves twice over the item. Once because of the list item and next for the checkbox. In order to change this in my code-behind, I set the checkbox IsChecked to True when Space is pressed for the list item. The issue is , the narrator reads the 'Space' instead of mentioning the 'checked' or 'unchecked' status of the checkbox. I understand this is because the foucs is on the list control and not the checkbox control. Is there a way for the narrator to read 'checked' without having the focus?
I have a ListView control which is bound to a ObservableCollection, I want to add a specific button at the end of the last item, so that when user click the button, clear up the colltions, then hide the button. Also, if the collection is empty, don't like the button display. After searching, I found many solutions on how to change the last item's style, but in my scenario, the button isn't the element of the ItemsSource. Anyone can help?
Thanks
Add the button to the template so it appears on every element in the ListView. Then use a trigger to show/hide the button based on whether the item is the last item in the list.
One way to do this is to expose the last item in your list via a property on your ViewModel. The trigger should compare the DataContext of the template, which is the current item, against the LastItem. Success should set the visibility of the button.
I hope this helps.
I have Listbox and some listboxitems. After selecting few items, if I click empty space between the listboxitems, selection changed event raised and previous selection gone.
How to prevent this behaviour?
In WPF I have a TreeView control where a particular item can be selected either by the user selecting the item directly in the tree view or by clicking on a screen control. The tree view is displaying a list of elements that are being displayed on a user defined form, basically a form designer application.
Here is my problem. When the user clicks on a screen control it calls a method that returns the TreeViewItem that represents the element. It then sets the IsSelected property to true for this element. It correctly changes the visual indicator in the TreeView and it raised the SelectedItemChanged event in the TreeView. This is all good.
However, it appears that somewhere behind the scenes the TreeView still thinks the previous item is selected. Here is why I have come to this conclusion. If I select ElementA by clicking on it in the TreeView is it correctly selected. If I then select ElementB by clicking on the screen control and programmatically setting the IsSelected property for the ElementB TreeViewItem it appears to have selected it correctly. Now if I select ElementA again by clicking on it in the TreeView it does nothing. The SelectedItemChanged event is not raised and the reverse selection box that indicates the selected item stays on ElementB. If I click on ElementB in the TreeView it also does not raise the SelectedItemChanged event, however it does not appear to update the internal flag since if I then click on ElementA on the TreeView it processes it correctly and raises the event.
The only workaround that I have found for this is in the SelectedItemChanged event handler to call the Focus method for the now selected TreeViewItem. If I do this I get the expected behaviour when I select screen controls and programmatically change the selected TreeViewItem.
This is not an acceptable solution though as it creates focus change flicker. When I select items on my form window the focus goes to the TreeView control and then back to the form, causing flicker and slight delay.
Anyone have any indeas.
Update
As requested here is some code. Here is my method of my Explorer window which is the manager of the TreeView in question.
public bool SelectItemByName(String controlName)
{
bool fReturn = false;
TreeViewItem tviToSelect = FindItemByName(_tviMaster, controlName);
if (tviToSelect != null && _tviSelectedItem != tviToSelect)
{
tviToSelect.IsSelected = true;
// Make sure the selected item is visible in the TreeView by expanding all of the parent nodes
ExpandAllParents(tviToSelect);
tviToSelect.BringIntoView();
fReturn = true;
}
return fReturn;
}
Every element has a unique identifier that I use as a cross reference between different areas of the interface. When you click a screen control it uses its identifier to find the cooresponding TreeViewItem in the TreeView. Then this code sets it as selected.
Then in my SelectedItemChanged event handler I had to include the following line.
_tviSelectedItem.Focus();
This fixes my initial issue but introducing the unwant screen flicker.
To recap, I select ElementA in the TreeView directly, then select one or more other elements in the form designer which in turn calls SelectItemByName to programatically set the selected item. All visual indicators show that this worked. In the TreeView the highlighted item changes to the new item that is selected. After selecting any number of elements through the form designer interface if you select ElementA by clicking on it directly in the TreeView it does nothing. It does not get highlighted and it does not fire the SelectedItemChanged event. If you inspect the SelectedItem and SelectedValue properties of the TreeView they all correctly coorespond to the item that was programmatically selected. However, the control somewhere appears to think that ElementA is still selected and doesn't recognize that the selection is changing.
I cannot believe that other people haven't run into this. It appears to be a significant flaw in the TreeView contol in WPF. Not sure if WinForms has the same issue or not.
Each TreeViewItem has an IsSelected property, and I suspect the old one isn't getting set to false. Try setting it to false whenever you set the new item to true.
var currentItem = treeView.ItemContainerGenerator
.ContainerFromItem(treeView.SelectedItem) as TreeViewItem;
currentItem.IsSelected = false;
If that doesn't work, try setting focus on the newly selected item at the same time as when you select it. Don't forget that WPF also has two focus scopes: Logical Focus and Keyboard Focus. You may need to set both.
treeViewItem.Focus(); // Sets Logical Focus
Keyboard.Focus(treeViewItem); // Sets Keyboard Focus
I have a C# .NET WinForm. In the form, I allow a user to add an item to a ListView by double-clicking in the ListView. This adds a TextBox control to the ListView and places the key cursor in the TextBox so a user can type.
I detect that a user is done with an item in a couple of ways (e.g. pressing Enter, Esc, Tab...), but also when they Leave (TextBox.Leave) the TextBox.
The problem is this set of steps:
User triggers TextBox.Leave by mousing down outside of the TextBox.
I add the new item to the ListView.
I select the the new item in the ListView.
Mouse up occurs and the new item that I just selected, loses focus and is unselected.
What I would like is for TextBox.Leave to be triggered by MouseUp, not MouseDown. How can I accomplish this?
Edit: Cody suggests using the ListView.LabelEdit property. Here are my results trying that:
listView_DoubleClick(...) {
listView.LabelEdit = true;
if(double clicked on existing listViewItem) {
listViewItem.BeginEdit(); //this works as expected
} else {
var newItem = listView.Items.Add("");
newItem.BeginEdit(); //this doesn't work, see below
}
}
The call to newItem.BeginEdit() only works when the user double clicks where the new item will show up. If they double click on any other blank area in the listview the new item is added, but it does not enter edit mode. What's going on here?
Pressing the mouse down on another control is causing that other control to request the focus and so the focus moving causes the TextBox.Leave event to occur. Preventing ever other possible control from requesting the focus is not a very viable option. But luckly you only need to prevent the ListView from using the MouseDown to shift focus. So you need to override the WndProc of your ListView and when the MouseDown windows message occurs and you are currently showing a TextBox you eat the message. In order words you do not allow the base class to process it.