delphi – 有没有办法在使用Frames时具有类似KeyPreview的功能？

简而言之：所有关键消息都输入到活动控件的TWinControl.CNKeyDwon中.该方法调用TWinControl.IsMenuKey,它在确定消息是否为ShortCut时遍历所有父节点.是通过调用其GetPopupMenu.IsShortCut方法来实现的.我已经覆盖了Frame的GetPopupMenu方法,如果它不存在则创建一个.请注意,您始终可以自己向框架添加PopupMenu.通过继承TPopupMenu并重写IsShortCut方法,调用Frame的KeyDown方法,该方法用作您需要的KeyPreview功能. (我也可以分配OnKeyDdown事件处理程序).

unit Unit2;

interface

uses
  Winapi.Messages,System.Classes,Vcl.Controls,Vcl.Forms,Vcl.Menus,Vcl.StdCtrls;

type
  TPopupMenu = class(Vcl.Menus.TPopupMenu)
  public
    function IsShortCut(var Message: TWMKey): Boolean; override;
  end;

  TFrame2 = class(TFrame)
    Label1: TLabel;
    Edit1: TEdit;
  private
    FPreviewPopup: TPopupMenu;
  protected
    function GetPopupMenu: Vcl.Menus.TPopupMenu; override;
    procedure KeyDown(var Key: Word; Shift: TShiftState); override;
  end;

implementation

{$R *.dfm}

{ TPopupMenu }

function TPopupMenu.IsShortCut(var Message: TWMKey): Boolean;
var
  ShiftState: TShiftState;
begin
  ShiftState := KeyDataToShiftState(Message.KeyData);
  TFrame2(Owner).KeyDown(Message.CharCode,ShiftState);
  Result := Message.CharCode = 0;
  if not Result then
    Result := inherited IsShortCut(Message);
end;

{ TFrame2 }

function TFrame2.GetPopupMenu: Vcl.Menus.TPopupMenu;
begin
  Result := inherited GetPopUpMenu;
  if Result = nil then
  begin
    if FPreviewPopup = nil then
      FPreviewPopup := TPopupMenu.Create(Self);
    Result := FPreviewPopup;
  end;
end;

procedure TFrame2.KeyDown(var Key: Word; Shift: TShiftState);
begin
  if (Key = Ord('X')) and (ssCtrl in Shift) then
  begin
    Label1.Caption := 'OH NO,DON''T DO THAT!';
    Key := 0;
  end;
end;

end.