How to Move ListBox Items with the Mouse-蒲公英云

How to Move ListBox Items with the Mouse

The TListBox Delphi component displays a collection of items in a scrollable list. Delphi makes it easy to program dragging and dropping into your applications.

Here’s how to allow a user to rearrange (change item’s position) the items of a ListBox using drag and drop:

Drop a TListBox (named ListBox1) on a form
Add several strings using the Items property
Set ListBox1’s DragMode to dmAutomatic (in Form’s OnCreate or using Object Inspector at design-time).
Handle LisBox-es MouseDown, DragOver and DragDrop events

var // form level
StartingPoint : TPoint;

implementation

…

procedure TForm1.FormCreate(Sender: TObject) ;
begin
ListBox1.DragMode := dmAutomatic;
end;

procedure TForm1.ListBox1DragDrop(Sender, Source: TObject; X, Y: Integer) ;
var
DropPosition, StartPosition: Integer;
DropPoint: TPoint;
begin
DropPoint.X := X;
DropPoint.Y := Y;
with Source as TListBox do
begin
StartPosition := ItemAtPos(StartingPoint,True) ;
DropPosition := ItemAtPos(DropPoint,True) ;

Items.Move(StartPosition, DropPosition) ;
end;
end;

procedure TForm1.ListBox1DragOver(Sender, Source: TObject; X, Y: Integer; State: TDragState; var Accept: Boolean) ;
begin
Accept := Source = ListBox1;
end;

procedure TForm1.ListBox1MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer) ;
begin
StartingPoint.X := X;
StartingPoint.Y := Y;
end;