This article was first published in German an
Delphi-PRAXiS
The default methods
Usually you can bring any control on a form to front or send it to the back using the methods supplied with the TControl class.
AnyControl.BringToFront;
AnyControl.SendToBack; |
However, often these methods will not suffice. If you want to move the control just one position, there are no public methods to acompolish just this. In the private section of the TControl-class you find the method
SetZOrderPosition which you cannot use. Looking at the source code, you'll notice, you cannot even cut-n-copy that, as it is accessing some private variables/objects, which are not made public either.
A simple solution
The solution, to work around this limitation, is to move the control either to the top or the back and move the others, that should remain in front (or behind), too. The following procedure will do just this.
The first parameter
Sender takes the control to be moved. The second paramter points the direction.
True will bring it to front,
False will move it to the back.
procedure ChangeControlZOrder(Sender: TObject; MoveUp: Boolean = True);
var
I, Curr: Integer;
Control: TControl;
List: TList;
begin
if Sender is TControl then
begin
// sender is an control
Control := Sender as TControl;
// check for parent control, managing the z-order
if Control.Parent = nil then
// not available
Exit;
// get position of the sender
Curr := -1;
for I := 0 to Pred(Control.Parent.ControlCount) do
if Control.Parent.Controls[I] = Sender then
begin
Curr := I;
Break;
end;
if Curr < 0 then
// hm, position not found
Exit;
List := TList.Create;
try
if MoveUp then
begin
for I := Curr + 2 to Pred(Control.Parent.ControlCount) do
// get the other controls, to be moved, too
List.Add(Control.Parent.Controls[I]);
// bring sender to front
Control.BringToFront;
for I := 0 to Pred(List.Count) do
// move the remaining controls
TControl(List[I]).BringToFront;
end else begin
for I := 0 to Curr - 2 do
// get the other controls, to be moved, too
List.Add(Control.Parent.Controls[I]);
// send sender to back
Control.SendToBack;
for I := Pred(List.Count) downto 0 do
// move the remaining controls
TControl(List[I]).SendToBack;
end;
finally
List.Free;
end;
end;
end;
|
Have fun,
Daniel Wischnewski
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