procedure TForm1.FormCreate(Sender: TObject);
begin
with Application do
SetWindowLong(Handle, GWL_EXSTYLE, GetWindowLong(Handle, GWL_EXSTYLE) and
not WS_EX_APPWINDOW or WS_EX_TOOLWINDOW);
SetWindowPos(Handle, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE or SWP_NOSIZE);
end;
type
TfrmDropBin = class(TForm, IDropTarget)
private
procedure WMNCHitTest(var Msg:TWMNCHitTest); message WM_NCHITTEST;
protected
procedure CreateParams(var Params: TCreateParams); override;
procedure CreateWnd; override;
procedure DestroyWnd; override;
procedure DoClose(var Action: TCloseAction); override;
// DragDrop 支持
function DragEnter(const dataObj: IDataObject; grfKeyState: Longint; pt: TPoint; var dwEffect: Longint): HResult; stdcall;
function IDropTarget_DragOver(grfKeyState: Longint; pt: TPoint; var dwEffect: Longint): HResult; stdcall;
function IDropTarget.DragOver = IDropTarget_DragOver; // 解决 IDropTarget.DragOver 与 TForm.DragOver 冲突问题
function DragLeave: HResult; stdcall;
function Drop(const dataObj: IDataObject; grfKeyState: Longint; pt: TPoint; var dwEffect: Longint): HResult; stdcall;
public
constructor Create(AOwner: TComponent); override;
end;
var
frmDropBin: TfrmDropBin;
procedure ShowDropBin(Sender: TMenuItem);
implementation
{$R *.dfm}
type
// 虽然 Delphi 的 Windows 单元定义了 SetLayeredWindowAttributes(); ( external 'User32.dll' )
// 但为了兼容 Win9x, 不能直接调用。
TSetLayeredWindowAttributes = function (Hwnd: THandle; crKey: COLORREF; bAlpha: Byte; dwFlags: DWORD): Boolean; stdcall;
var
User32ModH: HMODULE;
SetLayeredWindowAttributes: TSetLayeredWindowAttributes = nil;
procedure ShowDropBin(Sender: TMenuItem);
begin
if Assigned(frmDropBin) then frmDropBin.Close
else begin
frmDropBin := TfrmDropBin.CreateParented(GetDesktopWindow);
end;
end;
procedure TfrmDropBin.CreateParams(var Params: TCreateParams);
begin
inherited CreateParams(Params);
with Params do begin
Style := WS_POPUP or WS_CLIPSIBLINGS {or WS_BORDER};
ExStyle := WS_EX_TOOLWINDOW or WS_EX_TOPMOST;
end;
end;
procedure TfrmDropBin.CreateWnd;
begin
inherited CreateWnd;
Visible := True;
// 为 2000/XP 创建半透明、穿透效果
if Assigned(SetLayeredWindowAttributes) then begin
SetWindowLong(Handle, GWL_EXSTYLE, GetWindowLong(Handle, GWL_EXSTYLE) or WS_EX_LAYERED);
SetLayeredWindowAttributes(Handle, clWhite, 128, LWA_ALPHA or LWA_COLORKEY);
end;
// 设置为接受拖拽
OleCheck(RegisterDragDrop(Handle, Self));
end;
procedure TfrmDropBin.DestroyWnd;
begin
if HandleAllocated then RevokeDragDrop(Handle);
inherited DestroyWnd;
end;
function TfrmDropBin.DragEnter(const dataObj: IDataObject; grfKeyState: Longint; pt: TPoint; var dwEffect: Longint): HResult; stdcall;
begin
//
// 也可以在此判断是否接受拖拽,修改 dwEffect 可以得到不同的效果 ...
//
dwEffect := DROPEFFECT_COPY;
Result := S_OK;
end;
function TfrmDropBin.IDropTarget_DragOver(grfKeyState: Longint; pt: TPoint; var dwEffect: Longint): HResult; stdcall;
begin
dwEffect := DROPEFFECT_COPY;
Result := S_OK;
end;
function TfrmDropBin.DragLeave: HResult; stdcall;
begin
Result := S_OK;
end;
function TfrmDropBin.Drop(const dataObj: IDataObject; grfKeyState: Longint; pt: TPoint; var dwEffect: Longint): HResult; stdcall;
begin
//
// 处理 dataObj 中包含的拖拽内容 ...
//
dwEffect := DROPEFFECT_NONE;
Result := S_OK;
end;