更新:
以下代码展示了如何扩展标准弹出菜单,以显示您自己的弹出窗体而不是实际菜单。菜单项被呈现为带有DrawMenuItem
的列表框,还可以尊重项目的自定义绘制(如果有)。此外,还考虑了项目高度测量,因此项目高度应与使用标准菜单时相同。以下属性已引入到TPopupMenu
控件中:
- PopupForm - 在使用自定义模式时必须设置的属性,是弹出菜单时需要保持焦点的窗体
- PopupMode - 是正常模式和特殊模式之间的切换(默认为pmStandard)
- pmCustom - 将使用自定义表单而不是标准弹出菜单
- pmStandard - 将使用标准弹出菜单并忽略所有新属性
- PopupCount - 是要在菜单弹出时显示的项目计数,它具有与组合框中的DropDownCount类似的含义(默认值为5)
如何扩展弹出菜单控件:
创建一个空窗体并将其命名为TPopupForm
,该单元另存为PopupUnit
,然后复制、粘贴下面的代码并再次保存:
unit PopupUnit;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, Menus;
type
TPopupMode = (pmStandard, pmCustom);
TPopupMenu = class(Menus.TPopupMenu)
private
FPopupForm: TForm;
FPopupMode: TPopupMode;
FPopupCount: Integer;
public
constructor Create(AOwner: TComponent); override;
procedure Popup(X, Y: Integer); override;
property PopupForm: TForm read FPopupForm write FPopupForm;
property PopupMode: TPopupMode read FPopupMode write FPopupMode;
property PopupCount: Integer read FPopupCount write FPopupCount;
end;
type
TMenuItem = class(Menus.TMenuItem)
end;
TPopupForm = class(TForm)
private
FListBox: TListBox;
FPopupForm: TForm;
FPopupMenu: TPopupMenu;
FPopupCount: Integer;
procedure WMActivate(var AMessage: TWMActivate); message WM_ACTIVATE;
procedure ListBoxDrawItem(Control: TWinControl; Index: Integer;
Rect: TRect; State: TOwnerDrawState);
procedure ListBoxMeasureItem(Control: TWinControl; Index: Integer;
var Height: Integer);
procedure ListBoxMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
procedure ListBoxMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
procedure ListBoxMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
procedure ListBoxKeyDown(Sender: TObject; var Key: Word;
Shift: TShiftState);
protected
procedure Paint; override;
procedure CreateParams(var Params: TCreateParams); override;
public
constructor Create(AOwner: TComponent; APopupForm: TForm;
APopupMenu: TPopupMenu; APopupCount: Integer); reintroduce;
end;
var
PopupForm: TPopupForm;
implementation
{$R *.dfm}
constructor TPopupForm.Create(AOwner: TComponent; APopupForm: TForm;
APopupMenu: TPopupMenu; APopupCount: Integer);
var
I: Integer;
MaxWidth: Integer;
MaxHeight: Integer;
ItemWidth: Integer;
ItemHeight: Integer;
begin
inherited Create(AOwner);
BorderStyle := bsNone;
FPopupForm := APopupForm;
FPopupMenu := APopupMenu;
FPopupCount := APopupCount;
FListBox := TListBox.Create(Self);
FListBox.Parent := Self;
FListBox.BorderStyle := bsNone;
FListBox.Style := lbOwnerDrawVariable;
FListBox.Color := clMenu;
FListBox.Top := 2;
FListBox.Left := 2;
MaxWidth := 0;
MaxHeight := 0;
FListBox.Items.BeginUpdate;
try
FListBox.Items.Clear;
for I := 0 to FPopupMenu.Items.Count - 1 do
begin
TMenuItem(FPopupMenu.Items[I]).MeasureItem(FListBox.Canvas, ItemWidth,
ItemHeight);
if ItemWidth > MaxWidth then
MaxWidth := ItemWidth;
if I < FPopupCount then
MaxHeight := MaxHeight + ItemHeight;
FListBox.Items.Add('');
end;
finally
FListBox.Items.EndUpdate;
end;
if FPopupMenu.Items.Count > FPopupCount then
MaxWidth := MaxWidth + GetSystemMetrics(SM_CXVSCROLL) + 16;
FListBox.Width := MaxWidth;
FListBox.Height := MaxHeight;
FListBox.ItemHeight := ItemHeight;
FListBox.OnMouseDown := ListBoxMouseDown;
FListBox.OnMouseUp := ListBoxMouseUp;
FListBox.OnDrawItem := ListBoxDrawItem;
FListBox.OnKeyDown := ListBoxKeyDown;
FListBox.OnMeasureItem := ListBoxMeasureItem;
FListBox.OnMouseMove := ListBoxMouseMove;
ClientWidth := FListBox.Width + 4;
ClientHeight := FListBox.Height + 4;
end;
procedure TPopupForm.CreateParams(var Params: TCreateParams);
begin
inherited;
Params.WindowClass.Style := Params.WindowClass.Style or CS_DROPSHADOW;
end;
procedure TPopupForm.ListBoxDrawItem(Control: TWinControl; Index: Integer;
Rect: TRect; State: TOwnerDrawState);
begin
DrawMenuItem(FPopupMenu.Items[Index], FListBox.Canvas, Rect, State);
end;
procedure TPopupForm.ListBoxKeyDown(Sender: TObject; var Key: Word;
Shift: TShiftState);
begin
case Key of
VK_ESCAPE: Close;
VK_RETURN:
begin
Close;
if FListBox.ItemIndex <> -1 then
FPopupMenu.Items[FListBox.ItemIndex].Click;
end;
end;
end;
procedure TPopupForm.ListBoxMeasureItem(Control: TWinControl; Index: Integer;
var Height: Integer);
var
ItemWidth: Integer;
begin
TMenuItem(FPopupMenu.Items[Index]).MeasureItem(FListBox.Canvas, ItemWidth,
Height);
end;
procedure TPopupForm.ListBoxMouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
SetCapture(FListBox.Handle);
end;
procedure TPopupForm.ListBoxMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
var
ItemIndex: Integer;
begin
ItemIndex := FListBox.ItemAtPos(Point(X, Y), True);
if ItemIndex <> FListBox.ItemIndex then
FListBox.ItemIndex := ItemIndex;
end;
procedure TPopupForm.ListBoxMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
Close;
if FListBox.ItemIndex <> -1 then
FPopupMenu.Items[FListBox.ItemIndex].Click;
end;
procedure TPopupForm.Paint;
begin
inherited;
Canvas.Pen.Color := clSilver;
Canvas.Rectangle(ClientRect);
end;
procedure TPopupForm.WMActivate(var AMessage: TWMActivate);
begin
SendMessage(FPopupForm.Handle, WM_NCACTIVATE, 1, 0);
inherited;
if AMessage.Active = WA_INACTIVE then
Release;
end;
constructor TPopupMenu.Create(AOwner: TComponent);
begin
inherited;
FPopupMode := pmStandard;
FPopupCount := 5;
end;
procedure TPopupMenu.Popup(X, Y: Integer);
begin
case FPopupMode of
pmCustom:
with TPopupForm.Create(nil, FPopupForm, Self, FPopupCount) do
begin
Top := Y;
Left := X;
Show;
end;
pmStandard: inherited;
end;
end;
end.
如何使用扩展的弹出式菜单控件:
只需将PopupUnit
添加到您的uses
从句的末尾,弹出式菜单控件就会获得新属性。
如果您想使用自定义表单而非真实菜单的模式,请在菜单弹出之前使用以下代码:
PopupMenu1.PopupMode := pmCustom;
PopupMenu1.PopupForm := Self;
PopupMenu1.PopupCount := 5;
如果您想使用经典的弹出式菜单,请将设置保持不变,因为标准模式是默认模式,或者只需这样设置即可显示标准的弹出式菜单(在这种情况下,忽略其他新属性):
PopupMenu1.PopupMode := pmStandard;
免责声明:
该代码需要进行审查(至少所有菜单快捷方式的实现都已经丢失),并且有些部分应该得到改进。