delphi – 拖放时移动图像

我在TPanel上有一个T Image,另一个(空)TPanels.我想拖
图像从第一个到第二个面板使用拖放.

我真的想看到图像从一个面板移动到
其他(半透明).

我想我应该使用TDragObject.GetDragImages,但我不知道如何构建整个魔术.

procedure TForm1.Image1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X,Y: Integer);
begin
  Image1.ControlStyle := Image1.ControlStyle + [csdisplayDragImage]; // ???
  timage(Sender).BeginDrag(False);
end;

procedure TForm1.Image1StartDrag(Sender: TObject; var DragObject: TDragObject);
begin
  // ???
end;

procedure TForm1.Panel1DragOver(Sender,Source: TObject; X,Y: Integer;
  State: TDragState; var Accept: Boolean);
begin
  if (Source is timage) then
    Accept := timage(Source).Parent <> Sender;
end;

procedure TForm1.Panel1DragDrop(Sender,Y: Integer);
begin
  if (Source is timage) then
  begin
    timage(Source).Parent := TPanel(Sender);
    timage(Source).Align := alClient;
  end;
end;

更新 – 我发现一个有用的文章：Implementing Professional Drag & Drop In VCL/CLX Applications

解决方法

unit Unit3;

interface
// 2012 Thomas Wassermann - demo
uses
  Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,Dialogs,ExtCtrls;

type


  TMyDragObject = class(TDragControlObject)
  private
    FImageList:timageList;
    fdragSource:TControl;
  protected
    function GetDragImages: TDragImageList; override;
  public
    Procedure StartDrag(G:TGraphic;p:TPoint;DragSource:TControl);
    Constructor Create(AControl: TControl); override;
    Destructor Destroy;override;
    Property DragSource:TControl read fdragSource;
  end;



  TForm3 = class(TForm)
    Panel1: TPanel;
    Panel2: TPanel;
    Image1: timage;
    procedure Image1StartDrag(Sender: TObject; var DragObject: TDragObject);
    procedure FormCreate(Sender: TObject);
    procedure Panel1DragOver(Sender,Y: Integer; State: TDragState; var Accept: Boolean);
    procedure FormDestroy(Sender: TObject);
    procedure Panel1DragDrop(Sender,Y: Integer);
  private
    { Private-Deklarationen }
    fdragObject:TMyDragObject;
  public
    { Public-Deklarationen }
  end;

var
  Form3: TForm3;

implementation

constructor TMyDragObject.Create(AControl: TControl);
begin
  inherited;
  FImageList:=timageList.Create(nil);
end;

destructor TMyDragObject.Destroy;
begin
  FImageList.Free;
  inherited;
end;

function TMyDragObject.GetDragImages: TDragImageList;
begin
   Result := FImageList;
end;

{$R *.dfm}

procedure TMyDragObject.StartDrag(G: TGraphic;p:TPoint;DragSource:TControl);
var
 bmp:TBitMap;
begin
   fdragSource := DragSource;
   bmp:=TBitMap.Create;
   try
   FImageList.Width := g.Width;
   FImageList.Height := g.Height;
   bmp.Width := g.Width;
   bmp.Height := g.Height;
   bmp.Canvas.Draw(0,g);
   FImageList.Add(bmp,nil);
   finally
     bmp.Free;
   end;
    FImageList.SetDragImage(0,p.x,p.y)
end;

procedure TForm3.FormCreate(Sender: TObject);
var
 i:Integer;
begin
  ControlStyle := ControlStyle + [csdisplayDragImage];
  for I := 0 to ControlCount -1  do
      if Controls[i] is TPanel then
         TPanel(Controls[i]).ControlStyle := TPanel(Controls[i]).ControlStyle + [csdisplayDragImage];
  ReportMemoryLeaksOnShutDown := True;
end;

procedure TForm3.FormDestroy(Sender: TObject);
begin
  if Assigned(fdragObject) then fdragObject.Free;
end;

procedure TForm3.Image1StartDrag(Sender: TObject; var DragObject: TDragObject);
var
 p:TPoint;

begin
    p:=timage(Sender).ScreenToClient(mouse.cursorpos);
    if Assigned(fdragObject) then fdragObject.Free;
    fdragObject := TMyDragObject.Create(timage(Sender));
    fdragObject.StartDrag(timage(Sender).Picture.Graphic,p,timage(Sender));
    DragObject := fdragObject;
end;

procedure TForm3.Panel1DragDrop(Sender,Y: Integer);
begin
  if fdragObject.DragSource is timage then
    timage(fdragObject.DragSource).Parent := TPanel(Sender);
end;

procedure TForm3.Panel1DragOver(Sender,Y: Integer; State: TDragState; var Accept: Boolean);
begin
    Accept := Source is TMyDragObject;
end;

end.