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Drag and Drop со списками



Оформил: DeeCo

{ 
 This example shows how to drag&drop within a TListBox. 
 The Demo Program also shows how to implement an autoscroll-feature. 

 Dieses Beispiel zeigt, wie man drag & drop in einer TListBox realisiert. 
 Im Demo-Programm wird auch eine Autoscroll-Funktion gezeigt. 
}

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

 procedure TForm1.ListBox1DragDrop(Sender, Source: TObject; X, Y: Integer);
 var
   iTemp: Integer;
   ptTemp: TPoint;
   szTemp: string;
 begin
   { change the x,y coordinates into a TPoint record }
   ptTemp.x := x;
   ptTemp.y := y;

   { Use a while loop instead of a for loop due to items possible being removed 
   from listboxes this prevents an out of bounds exception }
   iTemp := 0;
    while iTemp <= TListBox(Source).Items.Count-1 do
   begin
     { look for the selected items as these are the ones we wish to move }
     if TListBox(Source).selected[iTemp] then
     begin
       { use a with as to make code easier to read }
       with Sender as TListBox do
       begin
       { need to use a temporary variable as when the item is deleted the 
        indexing will change }
         szTemp := TListBox(Source).Items[iTemp];

         { delete the item that is being dragged  }
         TListBox(Source).Items.Delete(iTemp);

       { insert the item into the correct position in the listbox that it 
       was dropped on }
         Items.Insert(itemAtPos(ptTemp, True), szTemp);
       end;
     end;
     Inc(iTemp);
   end;
 end;





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