delphi - 如何制作带有滚动条的弹出菜单？

Question

我在程序中使用TPopupMenu，我想在其中添加一个垂直滚动条并能够设置其大小(例如10个可见项目)，并处理移动 slider 滚动条的事件(单击按钮后或滚动鼠标滚轮后)。我想知 Prop 有此功能的组件是否存在，或者我会对创建此组件的理论感到高兴。例如，我需要类似于 Vista/7 Explorer 地址栏中的弹出菜单的行为(包含当前文件夹中的子文件夹列表)

谢谢。

Answer 1

更新:

以下代码显示如何扩展标准弹出菜单以显示您自己的弹出表单而不是真正的菜单。菜单项使用 DrawMenuItem 渲染到列表框中，这也尊重项目的自定义绘制(如果有的话)。还考虑了项目高度测量，因此项目高度应该与使用标准菜单相同。 TPopupMenu 控件中引入了以下属性:

• PopupForm - 是使用自定义模式时必须设置的强制属性，它是弹出菜单时需要保持焦点的表单
• PopupMode - 在正常模式和特殊模式之间切换(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 - 弹出菜单时显示的项目数，与组合框的 DropDownCount 含义类似(默认为 5)

如何扩展弹出菜单控件:

创建一个空表单并将其命名为TPopupForm，单元另存为PopupUnit并复制、粘贴以下代码并再次保存:

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}

{ TPopupForm }

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;

{ TPopupMenu }

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.

如何使用扩展弹出菜单控件:

只需将 PopupUnit 添加到 uses 子句的末尾，弹出菜单控件就会获取新属性。

如果您想使用自定义表单而不是真实菜单的模式，请在菜单弹出之前使用以下内容:

// this will enable the custom mode
PopupMenu1.PopupMode := pmCustom;
// this will fake the currently focused form as active, it is mandatory to
// assign the currently focused form to this property (at least now); so Self
// used here is the representation of the currently focused form
PopupMenu1.PopupForm := Self;
// this will show 5 menu items and the rest will be accessible by scroll bars
PopupMenu1.PopupCount := 5;

如果您想使用经典弹出菜单，则保留设置不变，因为标准模式是默认模式，或者只需以这种方式设置模式，然后将显示标准弹出菜单(在这种情况下，将忽略其余新属性) :

PopupMenu1.PopupMode := pmStandard;

免责声明:

代码需要审查(至少缺少菜单快捷方式的实现)并且某些部分应该改进。