I have a ListBox with dates.
Each ListBoxItem (date) have another ListBox with that date's events.
When I select an event it gets highlighted (SelectedIndex/SelectedItem) and I navigate to another Pivot. This works fine.
My problem is that every ListBox has it's own SelectedItem. I want to clear the SelectedItem from each ListBox, but I cannot get it to work!
Here's my try:
//Store a reference to the latest selected ListBox
public ListBox SelectedListBox { get; set; }
private void SelectionChangedHandler(object sender, SelectionChangedEventArgs e)
{
ListBox lstBox = ((ListBox)sender);
//This row breaks the SECOND time!!
var episode = (Episode)lstBox.SelectedItem;
episodeShowName.Text = episode.Show; //Do some code
episodeTitle.Text = episode.Name; //Do some code
episodeNumber.Text = episode.Number; //Do some code
episodeSummary.Text = episode.Summary; //Do some code
resetListBox(lstBox); //Do the reset !
pivot1.SelectedIndex = 1;
}
private void resetListBox(ListBox lstBox)
{
if (SelectedListBox != null)
SelectedListBox.SelectedIndex = -1;
//If I remove this line, the code doesn't break anymore
SelectedListBox = lstBox; //Set the current ListBox as reference
}
var episode is null the second time. How come?
I found the problem!
private void resetListBox(ListBox lstBox)
{
if (SelectedListBox != null)
SelectedListBox.SelectedIndex = -1;
//If I remove this line, the code doesn't break anymore
SelectedListBox = lstBox; //Set the current ListBox as reference
}
When I set the previous selected ListBox's SelectedIndex to -1, the SelectionChangedHandler event gets triggered again (of course) and screws up ! :D
Easy fix:
private void SelectionChangedHandler(object sender, SelectionChangedEventArgs e)
{
ListBox lstBox = ((ListBox)sender);
if (lstBox.SelectedIndex < 0)
return;
Related
I'm trying to use a WPF listbox on a tablet.
In a dummy project I just made a listbox with a lot of items and when i select one this item will be showed in a textblock.
I have a selectionchanged event on the listBox
On my laptop everything works the way it should but when i run it on a tablet the selectionchanged event isn't triggered sporadically. On the screen the old selected item stays selected and the new selected one is highlighted but the item isn't shown in the textblock.
With remote debugging I have seen that the TouchDown, TouchMove and TouchUp event are all triggered, but some times the selectionChanged isn't triggered.
these things I've tried as well:
setting in Xaml inside the listbox:
ScrollViewer.PanningMode="None"
When I do this the selectionchanged event is always triggered but the user can't scroll down anymore with swiping (Which must be possible.
I think here lies the problem somewhere, but I don't have any solution yet.
Help Needed.
After a long time a solution for this problem was found.
first of we need some variables
private TouchPoint _movePoint;
private double _minimum = 0;
private double _maximum;
Me need to catch the TouchMove event of the listBox. This event triggers many times. We need get maximum and minimum Y-values of were the touch has been.
private void myListBox_TouchMove(object sender, TouchEventArgs e)
{
_movePoint := e.GetTouchPoint(myListBox);
if (_minimum.Equals(0))
{
_minimum := _movePoint.Position.Y;
_maximum := _movePoint.Position.Y;
return;
}
if (_movePoint.Position.Y < _minimum)
_minimum := _movePoint.Position.Y;
if (_movePoint.Position.Y > _maximum)
_maximum := _movePoint.Position.Y;
}
Now in the TouchUp event we look at the how far have been slided in the vertical direction. If this is not to big (in this example lower then 20), we gonna look at where the touchup event took place and look for the ListBoxItem that is on that place and set IsSelected=ture on this item.
private void myListBox_TouchUp(object sender, TouchEventArgs e)
{
var difference = _maximum - _minimum;
_maximum = 0;
_minimum=0;
if(difference < 20)
{
var touchPosition = e.GetTouchPoint(myListBox)
UIElement elem = myListBox.InputHitTest(touchPosition.Position) as UIElement;
while (elem != null)
{
if (elem == myListBox)
return;
ListBoxItem item = elem as ListBoxItem;
if (item != null)
{
item.IsSelected = true;
return;
}
elem = VisualTreeHelper.GetParent(elem) as UIElement;
}
}
}
This should work.
I need to add some decoration to the contents of a WPF TextBox control. That works fine basically, I can get the position of specified character indices and layout my other elements accordingly. But it all breaks when the TextBox is scrolled. My layout positions don't match with the displayed text anymore because it has moved elsewhere.
Now I'm pretty surprised that the TextBox class doesn't provide any information about its scrolling state, nor any events when the scrolling has changed. What can I do now?
I used Snoop to find out whether there is some scrolling sub-element that I could ask, but the ScrollContentPresenter also doesn't have any scrolling information available. I'd really like to put my decoration elements right into the scrolled area so that the scrolling can affect them, too, but there can only be a single content control and that's one of the TextBox internals already.
I'm not sure how to capture an event when the textbox has been scrolled (probably use narohi's answer for that), but there is a simple way to see what the current scroll position is:
// Gets or sets the vertical scroll position.
textBox.VerticalOffset
(From http://msdn.microsoft.com/en-us/library/system.windows.controls.primitives.textboxbase.verticaloffset(v=vs.100).aspx)
I'm using it to see if the textbox is scrolled to the end, like this:
public static bool IsScrolledToEnd(this TextBox textBox)
{
return textBox.VerticalOffset + textBox.ViewportHeight == textBox.ExtentHeight;
}
You can get the ScrollViewer with this method by passing in your textbox as the argument and the type ScrollView. Then you may subscribe to the ScrollChanged event.
public static T FindDescendant<T>(DependencyObject obj) where T : DependencyObject
{
if (obj == null) return default(T);
int numberChildren = VisualTreeHelper.GetChildrenCount(obj);
if (numberChildren == 0) return default(T);
for (int i = 0; i < numberChildren; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(obj, i);
if (child is T)
{
return (T)(object)child;
}
}
for (int i = 0; i < numberChildren; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(obj, i);
var potentialMatch = FindDescendant<T>(child);
if (potentialMatch != default(T))
{
return potentialMatch;
}
}
return default(T);
}
Example:
public MainWindow()
{
InitializeComponent();
Loaded += new RoutedEventHandler(MainWindow_Loaded);
}
void MainWindow_Loaded(object sender, RoutedEventArgs e)
{
ScrollViewer s = FindDescendant<ScrollViewer>(txtYourTextBox);
s.ScrollChanged += new ScrollChangedEventHandler(s_ScrollChanged);
}
void s_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
// check event args for information needed
}
I have a ListBox and a DockPanel. List box contains items that are supposed to be dragged onto the dock panel. I've implemented that by following this link.
There are a couple of things I do not understand though:
While dragging, all I see is a cursor. I'd like to literary see the list item I am
dragging to move around with my cursor. How do I do that?
Is the DragDropEffect property only for the different cursor design or it has a
higher purpose? :)
How do I make list item disappear from the ListBox once it is dropped onto the
DockPanel?
I'd like to enforce some animation on the items that I drag, like glow once it is
dropped. Which trigger/setter should I use for that?
Here's my code for basic dragging and dropping:
Code-behind for the ListBox part
private Point startPosition;
private void ListBox_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
startPosition = e.GetPosition(null);
}
private void ListBox_PreviewMouseMove(object sender, MouseEventArgs e)
{
Point currentPosition;
Vector offset;
ListBox listBox;
ListBoxItem item;
Match match;
DataObject dragData;
currentPosition = e.GetPosition(null);
offset = startPosition - currentPosition;
if (e.LeftButton == MouseButtonState.Pressed &&
(Math.Abs(offset.X) > SystemParameters.MinimumHorizontalDragDistance ||
Math.Abs(offset.Y) > SystemParameters.MinimumVerticalDragDistance))
{
// Get the data binded to ListBoxItem object, which is "match"
listBox = sender as ListBox;
item = FindAnchestor<ListBoxItem>((DependencyObject)e.OriginalSource);
match = (Match)listBox.ItemContainerGenerator.ItemFromContainer(item);
dragData = new DataObject("match", match);
DragDrop.DoDragDrop(item, dragData, DragDropEffects.Move);
}
}
Code-behind for the DockPanel part
private void DockPanel_DragEnter(object sender, DragEventArgs e)
{
if (!e.Data.GetDataPresent("match") ||
sender == e.Source)
{
e.Effects = DragDropEffects.None;
}
}
private void DockPanel_Drop(object sender, DragEventArgs e)
{
Match match;
DockPanel matchSlot;
ContentPresenter contentPresenter;
Binding binding;
if (e.Data.GetDataPresent("match"))
{
match = e.Data.GetData("match") as Match;
matchSlot = sender as DockPanel;
contentPresenter = new ContentPresenter();
contentPresenter.ContentTemplate = this.FindResource("MatchTemplate") as DataTemplate;
binding = new Binding();
binding.Source = match;
contentPresenter.SetBinding(ContentPresenter.ContentProperty, binding);
matchSlot.Children.Clear();
matchSlot.Children.Add(contentPresenter);
}
}
Thanks for all the help.
Ok, after a while I found some answers and discovered a few things on my own.
As for the DragDropEffect enum, it should be used for two reasons:
To distinguish if the item is moved or copied in the code. It serves like a flag and should be used most commonly like this:
if (e.DragDropEffect == DragDropEffect.Move)
{
...
}
else ...
To decorate the mouse cursor based on the enum value. This way it tells the user if he or she is moving or copying the item.
As for the drag and drop visualization here's a link to the post containing the reference which is an excellent starting point for drag and drop to build on: WPF Drag & Drop: How to literally drag an element?
Is there a way to make some of the items in a ListBox readonly/disabled so they can't be selected? Or are there any similar controls to ListBox to provide this functionality?
ListBox doesn't have support for that. You can bolt something on, you could deselect a selected item. Here's a silly example that prevents even-numbered items from being selected:
private void listBox1_SelectedIndexChanged(object sender, EventArgs e) {
for (int ix = listBox1.SelectedIndices.Count - 1; ix >= 0; ix--) {
if (listBox1.SelectedIndices[ix] % 2 != 0)
listBox1.SelectedIndices.Remove(listBox1.SelectedIndices[ix]);
}
}
But the flicker is quite noticeable and it messes up keyboard navigation. You can get better results by using CheckedListBox, you can prevent the user from checking the box for an item:
private void checkedListBox1_ItemCheck(object sender, ItemCheckEventArgs e) {
if (e.Index % 2 != 0) e.NewValue = CheckState.Unchecked;
}
But now you cannot override drawing to make it look obvious to the user that the item isn't selectable. No great solutions here, it is far simpler to just not display items in the box that shouldn't be selectable.
#Hans solution causing that the item id selected for a short time and then selection disappearing. I don't like that - this can be confusing for the enduser.
I prefer to hide some edit option buttons for the item that should be disabled:
if (lbSystemUsers.Items.Count > 0 && lbSystemUsers.SelectedIndices.Count > 0)
if (((RemoteSystemUserListEntity)lbSystemUsers.SelectedItem).Value == appLogin)
{
bSystemUsersDelete.Visible = false;
bSystemUsersEdit.Visible = false;
}
else
{
bSystemUsersDelete.Visible = true;
bSystemUsersEdit.Visible = true;
}
Here is the list that lists the users and disallow to edit user that is actually logged in to the edit panel.
ListBox doesn't have a ReadOnly (or similar) property, but you can make a custom ListBox control. Here's a solution that worked pretty well for me:
https://ajeethtechnotes.blogspot.com/2009/02/readonly-listbox.html
public class ReadOnlyListBox : ListBox
{
private bool _readOnly = false;
public bool ReadOnly
{
get { return _readOnly; }
set { _readOnly = value; }
}
protected override void DefWndProc(ref Message m)
{
// If ReadOnly is set to true, then block any messages
// to the selection area from the mouse or keyboard.
// Let all other messages pass through to the
// Windows default implementation of DefWndProc.
if (!_readOnly || ((m.Msg <= 0x0200 || m.Msg >= 0x020E)
&& (m.Msg <= 0x0100 || m.Msg >= 0x0109)
&& m.Msg != 0x2111
&& m.Msg != 0x87))
{
base.DefWndProc(ref m);
}
}
}
I know this is old thread, but i'll post a workaround for other readers in future.
listBox.Enabled = false;
listBox.BackColor = Color.LightGray;
This will change background color of list box to Light Gray. So this is not builtin "native way" to do it, but at least gives user some feedback that he is not supposed to / can't edit that field.
To get read-only behaviour I have MyCBLLocked, a boolean associated with the MyCBL checkbox list control, and on the CheckItem event I do:
private void MyCBL_ItemCheck(object sender, ItemCheckEventArgs e)
{
if (MyCBLLocked)
e.NewValue = e.CurrentValue;
}
So instead of
MyCBL.Enabled = false;
I use
MyCBLLocked = true;
and the user can scroll through the many selections but not mess things up with changes.
Within an event, I'd like to put the focus on a specific TextBox within the ListViewItem's template. The XAML looks like this:
<ListView x:Name="myList" ItemsSource="{Binding SomeList}">
<ListView.View>
<GridView>
<GridViewColumn>
<GridViewColumn.CellTemplate>
<DataTemplate>
<!-- Focus this! -->
<TextBox x:Name="myBox"/>
I've tried the following in the code behind:
(myList.FindName("myBox") as TextBox).Focus();
but I seem to have misunderstood the FindName() docs, because it returns null.
Also the ListView.Items doesn't help, because that (of course) contains my bound business objects and no ListViewItems.
Neither does myList.ItemContainerGenerator.ContainerFromItem(item), which also returns null.
To understand why ContainerFromItem didn't work for me, here some background. The event handler where I needed this functionality looks like this:
var item = new SomeListItem();
SomeList.Add(item);
ListViewItem = SomeList.ItemContainerGenerator.ContainerFromItem(item); // returns null
After the Add() the ItemContainerGenerator doesn't immediately create the container, because the CollectionChanged event could be handled on a non-UI-thread. Instead it starts an asynchronous call and waits for the UI thread to callback and execute the actual ListViewItem control generation.
To be notified when this happens, the ItemContainerGenerator exposes a StatusChanged event which is fired after all Containers are generated.
Now I have to listen to this event and decide whether the control currently want's to set focus or not.
As others have noted, The myBox TextBox can not be found by calling FindName on the ListView. However, you can get the ListViewItem that is currently selected, and use the VisualTreeHelper class to get the TextBox from the ListViewItem. To do so looks something like this:
private void myList_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (myList.SelectedItem != null)
{
object o = myList.SelectedItem;
ListViewItem lvi = (ListViewItem)myList.ItemContainerGenerator.ContainerFromItem(o);
TextBox tb = FindByName("myBox", lvi) as TextBox;
if (tb != null)
tb.Dispatcher.BeginInvoke(new Func<bool>(tb.Focus));
}
}
private FrameworkElement FindByName(string name, FrameworkElement root)
{
Stack<FrameworkElement> tree = new Stack<FrameworkElement>();
tree.Push(root);
while (tree.Count > 0)
{
FrameworkElement current = tree.Pop();
if (current.Name == name)
return current;
int count = VisualTreeHelper.GetChildrenCount(current);
for (int i = 0; i < count; ++i)
{
DependencyObject child = VisualTreeHelper.GetChild(current, i);
if (child is FrameworkElement)
tree.Push((FrameworkElement)child);
}
}
return null;
}
I noticed that the question title does not directly relate to the content of the question, and neither does the accepted answer answer it. I have been able to "access the ListViewItems of a WPF ListView" by using this:
public static IEnumerable<ListViewItem> GetListViewItemsFromList(ListView lv)
{
return FindChildrenOfType<ListViewItem>(lv);
}
public static IEnumerable<T> FindChildrenOfType<T>(this DependencyObject ob)
where T : class
{
foreach (var child in GetChildren(ob))
{
T castedChild = child as T;
if (castedChild != null)
{
yield return castedChild;
}
else
{
foreach (var internalChild in FindChildrenOfType<T>(child))
{
yield return internalChild;
}
}
}
}
public static IEnumerable<DependencyObject> GetChildren(this DependencyObject ob)
{
int childCount = VisualTreeHelper.GetChildrenCount(ob);
for (int i = 0; i < childCount; i++)
{
yield return VisualTreeHelper.GetChild(ob, i);
}
}
I'm not sure how hectic the recursion gets, but it seemed to work fine in my case. And no, I have not used yield return in a recursive context before.
You can traverse up the ViewTree to find the item 'ListViewItem' record set that corresponds to the cell triggered from hit test.
Similarly, you can get the column headers from the parent view to compare and match the cell's column. You may want to bind the cell name to the column header name as your key for your comparator delegate/filter.
For example: HitResult is on TextBlock shown in green. You wish to obtain the handle to the 'ListViewItem'.
/// <summary>
/// ListView1_MouseMove
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void ListView1_MouseMove(object sender, System.Windows.Input.MouseEventArgs e) {
if (ListView1.Items.Count <= 0)
return;
// Retrieve the coordinate of the mouse position.
var pt = e.GetPosition((UIElement) sender);
// Callback to return the result of the hit test.
HitTestResultCallback myHitTestResult = result => {
var obj = result.VisualHit;
// Add additional DependancyObject types to ignore triggered by the cell's parent object container contexts here.
//-----------
if (obj is Border)
return HitTestResultBehavior.Stop;
//-----------
var parent = VisualTreeHelper.GetParent(obj) as GridViewRowPresenter;
if (parent == null)
return HitTestResultBehavior.Stop;
var headers = parent.Columns.ToDictionary(column => column.Header.ToString());
// Traverse up the VisualTree and find the record set.
DependencyObject d = parent;
do {
d = VisualTreeHelper.GetParent(d);
} while (d != null && !(d is ListViewItem));
// Reached the end of element set as root's scope.
if (d == null)
return HitTestResultBehavior.Stop;
var item = d as ListViewItem;
var index = ListView1.ItemContainerGenerator.IndexFromContainer(item);
Debug.WriteLine(index);
lblCursorPosition.Text = $"Over {item.Name} at ({index})";
// Set the behavior to return visuals at all z-order levels.
return HitTestResultBehavior.Continue;
};
// Set up a callback to receive the hit test result enumeration.
VisualTreeHelper.HitTest((Visual)sender, null, myHitTestResult, new PointHitTestParameters(pt));
}
We use a similar technique with WPF's new datagrid:
Private Sub SelectAllText(ByVal cell As DataGridCell)
If cell IsNot Nothing Then
Dim txtBox As TextBox= GetVisualChild(Of TextBox)(cell)
If txtBox IsNot Nothing Then
txtBox.Focus()
txtBox.SelectAll()
End If
End If
End Sub
Public Shared Function GetVisualChild(Of T As {Visual, New})(ByVal parent As Visual) As T
Dim child As T = Nothing
Dim numVisuals As Integer = VisualTreeHelper.GetChildrenCount(parent)
For i As Integer = 0 To numVisuals - 1
Dim v As Visual = TryCast(VisualTreeHelper.GetChild(parent, i), Visual)
If v IsNot Nothing Then
child = TryCast(v, T)
If child Is Nothing Then
child = GetVisualChild(Of T)(v)
Else
Exit For
End If
End If
Next
Return child
End Function
The technique should be fairly applicable for you, just pass your listviewitem once it's generated.
Or it can be simply done by
private void yourtextboxinWPFGrid_LostFocus(object sender, RoutedEventArgs e)
{
//textbox can be catched like this.
var textBox = ((TextBox)sender);
EmailValidation(textBox.Text);
}