Re: Custom controls in datagrid
From: CJ (cjohns_at_telkomsa.net)
Date: 06/02/04
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Date: Wed, 2 Jun 2004 09:47:52 +0200
In article <euVCX0BSEHA.2468@TK2MSFTNGP11.phx.gbl>, ernest@gesora.com
says...
> > 1) I lose the first character typed into the richtextbox: the user
> > clicks the cell and the richtextbox gets focus, but the first character
> > is swallowed and only the second character on is shown.
>
> Maybe you didn't take in consideration the parameter instantText of the
> method Edit.
This looked interesting, but doesn't seem to help. This is the sequence
of events:
click in cell:
Edit called, with instantText and cell value ""
Edit called, with instantText and cell value ""
type first char:
richtextboxtextchanged event is fired, and handler is called
Edit called, with instantText and cell value ""
richtextboxtextchanged, and handler is called
no character appears
type 2nd char:
richtextboxtextchanged, and handler is called
richtextboxtextchanged, and handler is called
and char appears
> > 2) There is some odd behaviour if the user first types in the second
> > column of the first row instead of the first column (there are only 2
> > columns). If you edit cell (2, 1) (row, column), then edit cell (1, 1),
> > and then go on to edit one of the cells in the newly created 2nd row,
> > the contents of (1,1) are lost. It appears that if cell (2,1) is edited
> > before cell (1,1), the commit event is not fired.
>
> Did you call the ColumnStartedEditing when the editing begins ?
> Does your control disapear when the cell loses the focus ?
> Are you sure your Commit executes every time the data in the cell is
> changed?
Yes I do call ColumnStartedEditing (in the richtextboxtextchanged
handler), and no, I'm not sure that the commit is executed when it needs
to be. But I can't control that - all I'm doing is inheriting from
DataGridTextBoxColumn and overriding the necessary methods (see code
below).
>
> > 3) Is there any way to allow text to be dropped onto the automatically
> > added bottom row without having to click on it first? I'm guessing not,
> > because the cells don't even contain the null text, so it seems as
> > though they haven't really been created yet (as such).
>
> You should know that the cells in a column(in the grid) are just
> pictures(rectangles with some text and/or picture inside), nothing else.
> A cell "gets alive" just in the moment it gets the focus. In that moment(and
> only in that moment), a control(a TextBox, CheckBox, DateTimePicker) becomes
> visible and occupies the space of the cell and sits over the grid.
> If a cell doesn't have the focus, then the surface of the cell is in fact
> the surface of the grid.
Okay, that makes sense.
Thanks for your help - I think that part of the problem is that I don't
really understand what goes on in a Datagrid (but I wouldn't think I'd
need to, just to do something this simple based on an msdn example!).
public class DataGridRichTextDragBoxColumn : DataGridTextBoxColumn
{
public RichTextDragBox rtdb = new RichTextDragBox();
// The isEditing field tracks whether or not the user is
// editing data with the hosted control.
private bool isEditing;
public DataGridRichTextDragBoxColumn() : base()
{
rtdb.Visible = false;
this.NullText = "";
}
protected override void Abort(int rowNum)
{
isEditing = false;
rtdb.TextChanged -= new EventHandler
(RichTextDragBoxChanged);
Invalidate();
}
protected override bool Commit(CurrencyManager dataSource,
int rowNum)
{
rtdb.Bounds = Rectangle.Empty;
rtdb.TextChanged -= new EventHandler
(RichTextDragBoxChanged);
if (!isEditing)
return true;
isEditing = false;
try
{
string val = rtdb.Text;
SetColumnValueAtRow(dataSource, rowNum, val);
}
catch (Exception)
{
Abort(rowNum);
return false;
}
Invalidate();
return true;
}
protected override void Edit(CurrencyManager source, int
rowNum, Rectangle bounds,
bool readOnly, string instantText, bool
cellIsVisible)
{
string val;
object o = GetColumnValueAtRow(source, rowNum);
if (Convert.IsDBNull(o))
val = this.NullText;
else
val = (string)o;
Console.WriteLine("IT: _" + instantText + "_ val: "
+ val);
if (cellIsVisible)
{
rtdb.Bounds = new Rectangle
(bounds.X + 2, bounds.Y + 2,
bounds.Width - 4, bounds.Height - 4);
rtdb.TextChanged += new EventHandler
(RichTextDragBoxChanged);
rtdb.Text = val;
rtdb.Visible = true;
rtdb.BringToFront();
rtdb.Focus();
}
else
{
rtdb.Text = val;
rtdb.Visible = false;
}
if (rtdb.Visible)
DataGridTableStyle.DataGrid.Invalidate
(bounds);
}
private void RichTextDragBoxChanged(object sender,
EventArgs e)
{
Console.WriteLine("DragBoxChanged");
this.isEditing = true;
base.ColumnStartedEditing(rtdb);
}
protected override Size GetPreferredSize(Graphics g, object
val)
{
return new Size(100, rtdb.PreferredHeight + 4);
}
protected override int GetMinimumHeight()
{
return rtdb.PreferredHeight + 4;
}
protected override int GetPreferredHeight(Graphics g,
object val)
{
return rtdb.PreferredHeight + 4;
}
protected override void Paint(Graphics g, Rectangle bounds,
CurrencyManager source, int rowNum)
{
Paint(g, bounds, source, rowNum, false);
}
protected override void Paint(Graphics g, Rectangle bounds,
CurrencyManager source,
int rowNum, bool alignToRight)
{
Paint(g,bounds, source, rowNum, Brushes.Red,
Brushes.Blue, alignToRight);
}
protected override void Paint(Graphics g, Rectangle bounds,
CurrencyManager source,
int rowNum, Brush backBrush, Brush foreBrush, bool
alignToRight)
{
string val;
object o = GetColumnValueAtRow(source, rowNum);
if (Convert.IsDBNull(o))
val = this.NullText;
else
val = (string)o;
Rectangle rect = bounds;
g.FillRectangle(backBrush,rect);
rect.Offset(0, 2);
rect.Height -= 2;
g.DrawString(val,
this.DataGridTableStyle.DataGrid.Font, foreBrush, rect);
}
protected override void SetDataGridInColumn(DataGrid val)
{
base.SetDataGridInColumn(val);
if (rtdb.Parent != null)
{
rtdb.Parent.Controls.Remove(rtdb);
}
if (val != null)
{
val.Controls.Add(rtdb);
}
}
}
-- CJ
- Next message: Volker Jobst: "Re: Combobox with empty or null values"
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