delphi - 如何修改TComponentProperty以仅显示下拉列表中的特定项目？

请考虑以下场景：

我有一个名为TMenuItemSelector的组件，该组件具有两个已发布的属性：PopupMenu-允许从表单中选择TPopupMenu的实例，而MenuItem允许从表单中选择TMenuItem的任何实例。

我想以MenuItem属性修改属性编辑器的方式，当分配了PopupMenu时，在下拉列表中仅可见该PopupMenu中的菜单项。

我知道我需要编写自己的TComponentProperty后代并覆盖GetValues方法。问题是我不知道如何访问TMenuItemSelector所在的表单。

原始TComponentProperty使用此方法来迭代所有可用实例：

procedure TComponentProperty.GetValues(Proc: TGetStrProc);
begin
  Designer.GetComponentNames(GetTypeData(GetPropType), Proc);
end;

但是，Designer似乎是预编译的，所以我不知道GetComponentNames是如何工作的。

到目前为止，这是我所拥有的，我想我唯一缺少的是GetValues的实现：

unit uMenuItemSelector;

interface

uses
  Classes, Menus, DesignIntf, DesignEditors;

type
  TMenuItemSelector = class(TComponent)
  private
    FPopupMenu: TPopUpMenu;
    FMenuItem: TMenuItem;
    procedure SetPopupMenu(const Value: TPopUpMenu);
    procedure SetMenuItem(const Value: TMenuItem);
  published
    property PopupMenu: TPopUpMenu read FPopupMenu write SetPopupMenu;
    property MenuItem: TMenuItem read FMenuItem write SetMenuItem;
  end;

type
  TMenuItemProp = class(TComponentProperty)
  public
    function GetAttributes: TPropertyAttributes; override;
    procedure GetValues(Proc: TGetStrProc); override;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterPropertyEditor(TypeInfo(TMenuItem), TMenuItemSelector, 'MenuItem', TMenuItemProp);
  RegisterComponents('Test', [TMenuItemSelector]);
end;

{ TMenuItemSelector }

procedure TMenuItemSelector.SetMenuItem(const Value: TMenuItem);
begin
  FMenuItem := Value;
end;

procedure TMenuItemSelector.SetPopupMenu(const Value: TPopUpMenu);
begin
  FPopupMenu := Value;
end;

{ TMenuItemProperty }

function TMenuItemProp.GetAttributes: TPropertyAttributes;
begin
  Result := inherited GetAttributes + [paValueList, paSortList];
end;

procedure TMenuItemProp.GetValues(Proc: TGetStrProc);
begin
  //How to filter MenuItems from the form in a way that only
  //MenuItems which belong to TMenuItemSelector.PopupMenu are displayed? \
  //And how to get to that form?
  //inherited;

end;

end.

有人可以帮忙吗？

谢谢。

最佳答案

调用TMenuItemProp.GetValues()时，您需要查看当前正在编辑其TMenuItemSelector属性的MenuItem对象，查看该对象是否分配了PopupMenu，如果是，则按需要遍历其项，例如：

procedure TMenuItemProp.GetValues(Proc: TGetStrProc);
var
  Selector: TMenuItemSelector;
  I: Integer;
begin
  Selector := GetComponent(0) as TMenuItemSelector;
  if Selector.PopupMenu <> nil then
  begin
    with Selector.PopupMenu.Items do
    begin
      for I := 0 to Count-1 do
        Proc(Designer.GetComponentName(Items[I]));
    end;
  end else
    inherited GetValues(Proc);
end;

顺便说一句，您需要在单独的程序包中实现TMenuItemSelector和TMenuItemProp。除RegisterComponents()函数（在运行时程序包中实现）外，不允许将设计时代码编译为运行时可执行文件。这违反了EULA，并且不允许分发Embarcadero的设计时数据。您需要在仅运行时程序包中实现TMenuItemSelector，然后在仅设计时程序包中实现TMenuItemProp和Register()，该程序包中仅Requires仅运行时程序包，而uses是TMenuItemSelector所在的单元声明，例如：

unit uMenuItemSelector;

interface

uses
  Classes, Menus;

type
  TMenuItemSelector = class(TComponent)
  private
    FPopupMenu: TPopUpMenu;
    FMenuItem: TMenuItem;
    procedure SetPopupMenu(const Value: TPopUpMenu);
    procedure SetMenuItem(const Value: TMenuItem);
  protected
    procedure Notification(AComponent: TComponent; Operation: TOperation); override;
  published
    property PopupMenu: TPopUpMenu read FPopupMenu write SetPopupMenu;
    property MenuItem: TMenuItem read FMenuItem write SetMenuItem;
  end;

implementation

{ TMenuItemSelector }

procedure TMenuItemSelector.Notification(AComponent: TComponent; Operation: TOperation);
begin
  inherited;
  if Operation = opRemove then
  begin
    if AComponent = FPopupMenu then
    begin
      FPopupMenu := nil;
      FMenuItem := nil;
    end
    else if AComponent = FMenuItem then
    begin
      FMenuItem := nil;
    end;
  end;
end;

procedure TMenuItemSelector.SetMenuItem(const Value: TMenuItem);
begin
  if FMenuItem <> Value then
  begin
    if FMenuItem <> nil then FMenuItem.RemoveFreeNotification(Self);
    FMenuItem := Value;
    if FMenuItem <> nil then FMenuItem.FreeNotification(Self);
  end;
end;

procedure TMenuItemSelector.SetPopupMenu(const Value: TPopUpMenu);
begin
  if FPopupMenu <> Value then
  begin
    if FPopupMenu <> nil then FPopupMenu.RemoveFreeNotification(Self);
    FPopupMenu := Value;
    if FPopupMenu <> nil then FPopupMenu.FreeNotification(Self);
    SetMenuItem(nil);
  end;
end;

end.

。

unit uMenuItemSelectorEditor;

interface

uses
  Classes, DesignIntf, DesignEditors;

type
  TMenuItemSelectorMenuItemProp = class(TComponentProperty)
  public
    function GetAttributes: TPropertyAttributes; override;
    procedure GetValues(Proc: TGetStrProc); override;
  end;

procedure Register;

implementation

uses
  Menus, uMenuItemSelector;

procedure Register;
begin
  RegisterComponents('Test', [TMenuItemSelector]);
  RegisterPropertyEditor(TypeInfo(TMenuItem), TMenuItemSelector, 'MenuItem', TMenuItemSelectorMenuItemProp);
end;

{ TMenuItemSelectorMenuItemProp }

function TMenuItemSelectorMenuItemProp.GetAttributes: TPropertyAttributes;
begin
  Result := inherited GetAttributes + [paValueList, paSortList] - [paMultiSelect];
end;

procedure TMenuItemSelectorMenuItemProp.GetValues(Proc: TGetStrProc);
var
  Selector: TMenuItemSelector;
  I: Integer;
begin
  Selector := GetComponent(0) as TMenuItemSelector;
  if Selector.PopupMenu <> nil then
  begin
    with Selector.PopupMenu.Items do
    begin
      for I := 0 to Count-1 do
        Proc(Designer.GetComponentName(Items[I]));
    end;
  end else
    inherited GetValues(Proc);
end;

end.