学习 TTreeView [9] - OnDragDrop、OnDragOver

本例效果图:

---

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, ComCtrls, StdCtrls;



type

  TForm1 = class(TForm)

    TreeView1: TTreeView;

    procedure FormCreate(Sender: TObject);

    procedure TreeView1DragOver(Sender, Source: TObject; X, Y: Integer;

      State: TDragState; var Accept: Boolean);

    procedure TreeView1DragDrop(Sender, Source: TObject; X, Y: Integer);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.FormCreate(Sender: TObject);

var

  stream: TStream;

begin

  TreeView1.Align := alLeft;

  stream := TMemoryStream.Create;

  with TStringList.Create do begin

    Add('一连长');

    Add(' 一排长');

    Add('  一班长');

    Add('   战士1');

    Add('   战士2');

    Add('   战士3');

    Add('   战士4');

    Add('  二班长');

    Add('  三班长');

    Add(' 二排长');

    Add(' 三排长');

    Add('二连长');

    Add('三连长');

    SaveToStream(stream);

    Free;

  end;

  stream.Position := 0;

  TreeView1.LoadFromStream(stream);

  stream.Free;

  TreeView1.DragMode := dmAutomatic; {允许自动拖放}

end;



{只允许拖动子节点}

procedure TForm1.TreeView1DragOver(Sender, Source: TObject; X, Y: Integer;

  State: TDragState; var Accept: Boolean);

begin

  Accept := not TTreeView(Source).Selected.HasChildren;

end;



procedure TForm1.TreeView1DragDrop(Sender, Source: TObject; X, Y: Integer);

var

  n1,n2: TTreeNode;

begin

  if Sender=Source then

  begin

    n1 := TTreeView(Sender).Selected;    {源}

    n2 := TTreeView(Sender).DropTarget;  {目标}

    TreeView1.Items.Insert(n2, n1.Text); {目标前插入}

    n1.Delete;                           {删除源}

  end;

end;



end.