GridView loses SelectedIndex value when ItemsSource is refreshed - wpf

Microsoft I think this may be a bug. Have a ListView GridView to display a single record.
Naturally the down arrow key navigates through the ListViewItems. That is the behavior I expect. In XAML the ItemsSource and SelectedIndex is bound. The behavior I want is the right and left arrow keys to navigate to the next and prior record.
The way I achieved this is to handle ListView PreviewKeyDown Event. The problem I had is the SelectedIndex is reset to -1 when the ItemSource is refreshed and I want it to stay on the old SelectedIndex. So I had to manually reset the SelectedIndex as shown below.
Here is my problem: After AND ONLY DIRECTLY AFTER a left arrow or right arrow key the up and down keys do not pass the correct value for SelectedIndex.
For example SelectedIndex = 4 then right arrow and then down key the value passed to SelectedIndex is 0 and the value passed should be 4. The ListView is visually on SelectedIndex 4 so it is like it knows the SelectedIndex is 4 but it also does not know. If I do not change the ItemsSource the up and down arrow keys work correctly. I tried KeyDown and KeyUp events but in the case those events just don't fire at all in the fail condition described above.
WPF 4.0 Visual Studio 2010.
private void lvCurDocFields_PreviewKeyDown(object sender, KeyEventArgs e)
{
Debug.WriteLine("lvCurDocFields_PreviewKeyDown " + e.Key.ToString());
e.Handled = false;
Int32 lastIndex;
switch (e.Key) // e.KeyCode
{
case Key.Right:
lastIndex = lvCurDocFields.SelectedIndex;
App.StaticGabeLib.Search.SelectedDocIndex++;
if (lvCurDocFields.SelectedIndex != lastIndex)
{
lvCurDocFields.SelectedIndex = lastIndex;
}
e.Handled = true;
break;
case Key.Left:
lastIndex = lvCurDocFields.SelectedIndex;
App.StaticGabeLib.Search.SelectedDocIndex--;
if (lvCurDocFields.SelectedIndex != lastIndex)
{
lvCurDocFields.SelectedIndex = lastIndex;
}
e.Handled = true;
break;
}
base.OnPreviewKeyDown(e);
}

Normally, I store a reference to the item that was selected, update the list, and re-select it afterwards. ListIndex isn't a reliable way to maintain a selection if things are inserted or deleted from the list.
if(MyListControl.Items.Contains(PreviouslySelectedItem)) MyListControl.SelectedItem = PreviouslySelectedItem;

Related

Reset comboxbox selection after a selection is made

I have a combobox that is created with data from a dataset
foreach(var item in ds.MiDESValues)
{
string comboboxtext = ds.MiDESValues.Rows[k][1].ToString();
sFactorCB.Items.Add(comboboxtext);
k++;
}
On a selectionchanged event it will populate a listbox with that selection
private void sFactors_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
string add = sFactorCB.SelectedValue.ToString();
var svalue = ds.MiDESValues.Rows[0][2].ToString();
int Svalue = int.Parse(svalue);
SValue.Add(svalue);
SelectionListBox.Items.Add(add);
SelectionBox.Add(add);
// when a new item is added to Selection list box, select it and show it
// this will keep the last item highlighted and as the list grows beyond
// the view of the list box, the last item will always be shown
SelectionListBox.SelectedIndex = SelectionListBox.Items.Count - 1;
SelectionListBox.ScrollIntoView(SelectionListBox.SelectedItem);
}
That list box then used to populate a listbox used on the next page. If I navigate to the next page and then navigate back, the combobox is still showing the last selection I made therefor the listbox is being populated with that value.
I have tried setting the selectedindex of the combobox to sFactorCB.SelectedIndex = -1;, at the end of the sFactors_SelectionChanged event but i get System.NullReferenceException. How can I get the combobox to reset back to a non-selected item state? Thanks
Actually, you are doing it correctly. To clear the selection either set the SelectedIndex to -1 or the SelectedItem to null.
The problem is that once you do that your sFactors_SelectionChanged gets called again and since there is no current selection, the SelectedValue property is null thus causing the following to fail:
string add = sFactorCB.SelectedValue.ToString();
How to solve this sort of depends on your intended results when nothing is selected. The simplest thing to do would be to just check for nothing selected at the start of the handler and simply return.
private void sFactors_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (sFactorCB.SelectedIndex == -1 || sFactorCB.SelectedValue == null)
return;
string add = sFactorCB.SelectedValue.ToString();
...

How to retain Focus of the first row after sorting and searching in the datagrid?

When my datagrid loads up I am able to get the focus of the first row by providing selected index=0 in the xaml but when I perform searching the focus gets lost so I want focus to be retain at the first row no matter I do sorting and searching on the datagrid.
Here is my code that searches particular thing in the datagrid.
private void TextBox_TextChanged(object sender, RoutedEventArgs e)
{
TextBox STB = (TextBox)sender;
this.SearchValue = STB.Text;
//ContentPresenter CP = (ContentPresenter)STB.TemplatedParent;
//DataGridColumnHeader DGCH = (DataGridColumnHeader)CP.TemplatedParent;
//DataGridColumn DGC = DGCH.Column;
//this.ColumnName = DGC.Header.ToString();
this.Datalist.Filter = this.CustomeFilter;
DataGrid dataGrid = this as DataGrid;
dataGrid.CurrentCell = new DataGridCellInfo(
dataGrid.Items[0], dataGrid.Columns[0]);
dataGrid.BeginEdit();
}
In above code I am trying to get the focus of the current cell but all in vain.
private bool CustomeFilter(object item)
{
SymbolData ltpObj = item as SymbolData;
//WpfApplication1.Model.LtpMessage ltpObj = item as WpfApplication1.Model.LtpMessage;
string values = (string)ltpObj.Symbol.ToString();
values = values.ToUpper();
//return values.StartsWith(this.SearchValue.ToString().ToUpper());
if (values.StartsWith(this.SearchValue.ToString().ToUpper()))
{ return true; }
else
return false;
}
You should read this:
How to programmatically select and focus a row or cell in a DataGrid in WPF: https://blog.magnusmontin.net/2013/11/08/how-to-programmatically-select-and-focus-a-row-or-cell-in-a-datagrid-in-wpf/
You can select and focus a row or cell of a DataGrid programmatically and get the same behaviour as when using the mouse by accessing the visual user interface elements of the DataGrid control and calling the UIElement.Focus() method on a particular DataGridCell object as described in the blog post above. There are code samples included.
You cannot simply set the SelectedItem or SelectedIndex property of the DataGrid to focus the row or cell though.

WPF Datagrid Selection Issue

In my WPF application I have one datagrid and one textbox. In the textChanged event of the textbox, I put this:
myDatagrid.ItemsSource =
myListOfObjects.Where(item => item.Name.Contains(MyTextBox.Text)); //Filter
if (myDatagrid.Items.Count > 0) // If no itens, then do nothing
{
myDatagrid.SelectedIndex = 0; // If has at least one item, select the first
}
myDatagrid.Items.Refresh();
Note that I force the selection when the text changes, in the first row of the DataGrid.
But unfortunately, the color of the row does not change to blue, making it hard to see the selection.
I realy need this, because in the PreviewKeyDown event of the textbox I have this:
private void myTextBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
if (e.Key == Key.Up)
{
if (!(myDataGrid.SelectedIndex <= 0))
{
myDataGrid.SelectedIndex--; // Go one position Up
}
}
if (e.Key == Key.Down)
{
if (!(myDataGrid.SelectedIndex == myDataGrid.Items.Count - 1))
{
myDataGrid.SelectedIndex++; // Go one position Down
}
}
}
So, when the textbox is focused and the user press the Up or the Down key, the selection does not appear to change.
Any idea of how I can make the selected item on the datagrid change it's color to blue?
Other thing: in my virtual machine, it works!! With the same code! How it's possible?
I think that is the aeroglass, but I change the theme to the Windows 7 Basic (same in the virtual machine) and still don't work.
Thanks, and sorry for my english.
Could you try using SelectedItem? you could always create a new property and bind to this and then set this item directly rather than using the selected index. Hopefully this would trigger any additional logic in the DataGrid control :)
//Declare property outside of method
public ObjectType SelectedItem { get; set; }
//Set datacontext on load
DataContext = this;
myDatagrid.ItemsSource = myListOfObjects.Where(item => item.Name.Contains(MyTextBox.Text)); //Filter
if (myDatagrid.Items.Count > 0) // If no itens, then do nothing
{
SelectedItem = myDatagrid.ItemSource[0]; // If has at least one item, select the first
}
myDatagrid.Items.Refresh();
Also don't forget to set your binding!
SelectedItem="{Binding SelectedItem}"
hope that helps!

Which CheckedListBox type control (in devexpress) allows color change for individual items?

I am using CheckedListBox , but I need to highlight individual items with different colors/fonts or some other highlighting method.
But it allows to change visual properties for the whole control only and not for individual items.
Additional Info:
I am using 2 such lists (because need checkboxes for easier selection) and 2 buttons (>> <<) for include/exclude type functionality. Is there any other better way to implement such whereby my requirement as above also gets fulfilled ?
I've only dabbled with DevExpress controls, but I think you have to subscribe to the DrawItem event and set the e.Handled property to true.
Something like this (CheckedListBox items with different colors):
private void checkedListBoxControl1_DrawItem(object sender, ListBoxDrawItemEventArgs e) {
CheckedListBoxControl clbControl = sender as CheckedListBoxControl;
ButtonState state = ButtonState.Normal;
if (clbControl.GetItemChecked(e.Index))
state = ButtonState.Checked;
ControlPaint.DrawCheckBox(e.Graphics, new Rectangle(e.Bounds.X, e.Bounds.Y, 15, 15), state);
string itemText = e.Item.ToString();
Rectangle textRect = new Rectangle(e.Bounds.X + 15, e.Bounds.Y, e.Bounds.Width - 15, e.Bounds.Height);
if ((e.State & DrawItemState.Selected) != 0) {
e.Graphics.FillRectangle(SystemBrushes.Highlight, textRect);
}
if (state== ButtonState.Checked)
e.Graphics.DrawString(itemText, e.Appearance.Font, new SolidBrush(Color.Red), textRect, e.Appearance.GetStringFormat());
else
e.Graphics.DrawString(itemText, e.Appearance.Font, new SolidBrush(Color.Black), textRect, e.Appearance.GetStringFormat());
e.Handled = true;
}

Is ScrollIntoView synchronized in virtualstackpannel (Especially in WPF DataGrid)?

We have a problem for focus a cell of DataGrid after Its data of bounded collection has Refreshed.
for example we set a filter for its collection and then we want to refocus a stored cell of stored column.
Is it true that we think a call to ScrollIntoView is synchronized it means after call it our desired row and cell are created and we can set focus? (again it means after we call to ScrollIntoView , Is it true we think that Itemsgenerator finished its work and we can surly find our desired cell)
$
//set filter of DataGrid Collection
DataGrid_Standard.ScrollIntoView(rowNumber,cellNumber);
//we sure our desired cell are created now
DataGridRow row = (DataGridRow)DataGrid_Standard.ItemContainerGenerator.ContainerFromIndex(index);
if (row == null)
{
// may be virtualized, bring into view and try again
DataGrid_Standard.ScrollIntoView(DataGrid_Standard.Items[index]);
row = (DataGridRow)DataGrid_Standard.ItemContainerGenerator.ContainerFromIndex(index);
}
DataGridCellsPresenter presenter = GetVisualChild<DataGridCellsPresenter>(rowContainer);
// try to get the cell but it may possibly be virtualized
DataGridCell cell = (DataGridCell)presenter.ItemContainerGenerator.ContainerFromIndex(column);
// now try to bring into view and retreive the cell
DataGrid_Standard.ScrollIntoView(rowContainer, DataGrid_Standard.Columns[column]);
cell = (DataGridCell)presenter.ItemContainerGenerator.ContainerFromIndex(column); cell.focus();
Related
Here's a datagrid Selection changed event handler that moves a virtualized row into view and then sets the focus to that row. This works for me:
private void DataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
DataGrid dg = (DataGrid)sender;
if (dg.SelectedItem == null) return;
dg.ScrollIntoView(dg.SelectedItem);
DataGridRow dg_row = (DataGridRow)dg.ItemContainerGenerator.ContainerFromItem(dg.SelectedItem);
if (dg_row == null) return;
dg_row.MoveFocus(new TraversalRequest(FocusNavigationDirection.Next));
}
EDIT: Using the dg_row.MoveFocus method had an undesriable effect (a checkbox column required two clicks to set instead of one) and it worked better for me to just use
dg_row.Focus();
Action action = () =>
{
dg .ScrollIntoView(dg .SelectedItem);
var item = dg.ItemContainerGenerator.ContainerFromIndex(index) as DataGridRow;
if (item == null) return;
item.Focus();
};
Dispatcher.BeginInvoke(DispatcherPriority.Background, action);
This should work fine for your case.

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