如何在组件中添加对操作的支持

Question

我需要做什么才能向我的组件添加操作支持。它是一个按钮组件，但我想无论它是什么组件类型，它都是相同的。任何信息或如何操作都会有帮助。

Answer 1

这取决于您如何定义行动支持。有两种类型：

• 组件的可能自定义的 Action 属性，可由 Action 组件分配
• Action 组件本身。

动作属性

每个 TControl 后代都有一个 Action 属性，默认情况下该属性的执行链接到鼠标左键单击。此链接由 ActionLink 管理。默认的 ActionLink 是 TControlActionLink 类型，它负责 Action 和 Control 的标题、提示、启用状态等的同步。如果这个基本功能就是您想要的，那么只需在组件类型声明中发布 Action 属性，Delphi 框架就会处理所有事情，例如 Serg 和 LU RD 已回答。

如果您希望自己的 Action 属性链接到某些其他条件或事件（即，除了 Click 之外），或者如果您想为组件的特定子元素（不是 TControl 后代）实现 Action 属性，那么您可以通过定义和实现自定义 ActionLink 类来实现您自己的自定义 Action 属性。

假设您的组件是某种具有列的网格，并且您希望每个列都有一个操作属性，当用户单击列的标题时应该调用该属性。由于此类列可能是 TCollectionItem 类型，因此默认情况下列类型没有操作属性。所以你必须自己实现一个。考虑下一个示例，它将操作的标题链接到列的标题，将操作的启用状态反向链接到列的只读属性等等...：

unit Unit1;

interface

uses
  Classes, ActnList, SysUtils;

type
  TColumn = class;

  TColumnActionLink = class(TActionLink)
  protected
    FClient: TColumn;
    procedure AssignClient(AClient: TObject); override;
    function IsCaptionLinked: Boolean; override;
    function IsEnabledLinked: Boolean; override;
    function IsOnExecuteLinked: Boolean; override;
    function IsVisibleLinked: Boolean; override;
    procedure SetCaption(const Value: String); override;
    procedure SetEnabled(Value: Boolean); override;
    procedure SetOnExecute(Value: TNotifyEvent); override;
    procedure SetVisible(Value: Boolean); override;
  end;

  TColumnActionLinkClass = class of TColumnActionLink;

  TColumn = class(TCollectionItem)
  private
    FActionLink: TColumnActionLink;
    FGrid: TComponent;
    FOnTitleClick: TNotifyEvent;
    FReadOnly: Boolean;
    FTitle: String;
    FVisible: Boolean;
    function DefaultTitleCaption: String;
    procedure DoActionChange(Sender: TObject);
    function GetAction: TBasicAction;
    function IsOnTitleClickStored: Boolean;
    function IsReadOnlyStored: Boolean;
    function IsVisibleStored: Boolean;
    procedure SetAction(Value: TBasicAction);
  protected
    procedure ActionChanged(Sender: TObject; CheckDefaults: Boolean); dynamic;
    procedure DoTitleClick; virtual;
    function GetActionLinkClass: TColumnActionLinkClass; virtual;
    property ActionLink: TColumnActionLink read FActionLink write FActionLink;
  public
    destructor Destroy; override;
    procedure InitiateAction; virtual;
  published
    property Action: TBasicAction read GetAction write SetAction;
    property OnTitleClick: TNotifyEvent read FOnTitleClick write FOnTitleClick
      stored IsOnTitleClickStored;
    property ReadOnly: Boolean read FReadOnly write FReadOnly
      stored IsReadOnlyStored;
    property Title: String read FTitle write FTitle;
    property Visible: Boolean read FVisible write FVisible
      stored IsVisibleStored;
  end;

implementation

{ TColumnActionLink }

procedure TColumnActionLink.AssignClient(AClient: TObject);
begin
  FClient := TColumn(AClient);
end;

function TColumnActionLink.IsCaptionLinked: Boolean;
begin
  Result := inherited IsCaptionLinked and (Action is TCustomAction) and
    (FClient.Title = TCustomAction(Action).Caption);
end;

function TColumnActionLink.IsEnabledLinked: Boolean;
begin
  Result := inherited IsEnabledLinked and (Action is TCustomAction) and
    (FClient.ReadOnly <> TCustomAction(Action).Enabled);
end;

function TColumnActionLink.IsOnExecuteLinked: Boolean;
begin
  Result := inherited IsOnExecuteLinked and
    (@FClient.OnTitleClick = @Action.OnExecute);
end;

function TColumnActionLink.IsVisibleLinked: Boolean;
begin
  Result := inherited IsVisibleLinked and (Action is TCustomAction) and
    (FClient.Visible = TCustomAction(Action).Visible);
end;

procedure TColumnActionLink.SetCaption(const Value: string);
begin
  if IsCaptionLinked then
    FClient.Title := Value;
end;

procedure TColumnActionLink.SetEnabled(Value: Boolean);
begin
  if IsEnabledLinked then
    FClient.ReadOnly := not Value;
end;

procedure TColumnActionLink.SetOnExecute(Value: TNotifyEvent);
begin
  if IsOnExecuteLinked then
    FClient.OnTitleClick := Value;
end;

procedure TColumnActionLink.SetVisible(Value: Boolean);
begin
  if IsVisibleLinked then
    FClient.Visible := Value;
end;

{ TColumn }

procedure TColumn.ActionChanged(Sender: TObject; CheckDefaults: Boolean);
begin
  if Sender is TCustomAction then
    with TCustomAction(Sender) do
    begin
      if not CheckDefaults or (Caption = DefaultTitleCaption) then
        FTitle := Caption;
      if not CheckDefaults or (not ReadOnly) then
        ReadOnly := not Enabled;
      if not CheckDefaults or not Assigned(FOnTitleClick) then
        FOnTitleClick := OnExecute;
      if not CheckDefaults or (Self.Visible = True) then
        Self.Visible := Visible;
      Changed(False);
    end;
end;

function TColumn.DefaultTitleCaption: String;
begin
  Result := 'Column' + IntToStr(Index);
end;

destructor TColumn.Destroy;
begin
  FreeAndNil(FActionLink);
  inherited Destroy;
end;

procedure TColumn.DoActionChange(Sender: TObject);
begin
  if Sender = Action then
    ActionChanged(Sender, False);
end;

procedure TColumn.DoTitleClick;
begin
  if Assigned(FOnTitleClick) then
    if (Action <> nil) and (@FOnTitleClick <> @Action.OnExecute) then
      FOnTitleClick(Self)
    else if FActionLink = nil then
      FOnTitleClick(Self)
    else if FActionLink <> nil then
      if (FGrid <> nil) and not (csDesigning in FGrid.ComponentState) then
      begin
        if not FActionLink.Execute(FGrid) then
          FOnTitleClick(Self);
      end
      else
        if not FActionLink.Execute(nil) then
          FOnTitleClick(Self);
end;

function TColumn.GetAction: TBasicAction;
begin
  if FActionLink <> nil then
    Result := FActionLink.Action
  else
    Result := nil;
end;

function TColumn.GetActionLinkClass: TColumnActionLinkClass;
begin
  Result := TColumnActionLink;
end;

procedure TColumn.InitiateAction;
begin
  if FActionLink <> nil then
    FActionLink.Update;
end;

function TColumn.IsOnTitleClickStored: Boolean;
begin
  Result := (FActionLink = nil) or not ActionLink.IsOnExecuteLinked;
end;

function TColumn.IsReadOnlyStored: Boolean;
begin
  Result := (FActionLink = nil) or not FActionLink.IsEnabledLinked;
  if Result then
    Result := FReadOnly;
end;

function TColumn.IsVisibleStored: Boolean;
begin
  Result := (FActionLink = nil) or not FActionLink.IsVisibleLinked;
  if Result then
    Result := not Visible;
end;

procedure TColumn.SetAction(Value: TBasicAction);
begin
  if Value = nil then
    FreeAndNil(FActionLink)
  else
  begin
    if FActionLink = nil then
      FActionLink := GetActionLinkClass.Create(Self);
    FActionLink.Action := Value;
    FActionLink.OnChange := DoActionChange;
    ActionChanged(Value, csLoading in Value.ComponentState);
    if FGrid <> nil then
      Value.FreeNotification(FGrid);
  end;
  Changed(False);
end;

end.

请注意，此代码仅被剥离到适用的操作部分。

^{来源：www.nldelphi.com。}

动作组件

动作组件可分配给任意组件的动作属性。但由于编写这样一个操作组件所涉及的所有内容的解释都非常全面，因此我将通过提供下面的示例来让自己变得容易。

假设您想要创建一个提供缩放功能的控件，并且还想要可以分配给工具栏按钮的相应 ZoomIn 和 ZoomOut 操作。

unit Zoomer;

interface

uses
  Classes, Controls, ActnList, Forms, Menus, Windows;

type
  TZoomer = class;

  TZoomAction = class(TCustomAction)
  private
    FZoomer: TZoomer;
    procedure SetZoomer(Value: TZoomer);
  protected
    function GetZoomer(Target: TObject): TZoomer;
    procedure Notification(AComponent: TComponent; Operation: TOperation);
      override;
  public
    destructor Destroy; override;
    function HandlesTarget(Target: TObject): Boolean; override;
    procedure UpdateTarget(Target: TObject); override;
  published
    property Caption;
    property Enabled;
    property HelpContext;
    property HelpKeyword;
    property HelpType;
    property Hint;
    property ImageIndex;
    property ShortCut;
    property SecondaryShortCuts;
    property Visible;
    property OnExecute; { This property could be omitted. But if you want to be
                          able to override the default behavior of this action
                          (zooming in on a TZoomer component), then you need to
                          assign this event. From within the event handler
                          you could invoke the default behavior manually. }
    property OnHint;
    property OnUpdate;
    property Zoomer: TZoomer read FZoomer write SetZoomer;
  end;

  TZoomInAction = class(TZoomAction)
  public
    constructor Create(AOwner: TComponent); override;
    procedure ExecuteTarget(Target: TObject); override;
  end;

  TZoomer = class(TCustomControl)
  public
    procedure ZoomIn;
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('RoyMKlever', [TZoomer]);
  RegisterActions('Zoomer', [TZoomInAction], nil);
end;

{ TZoomAction }

destructor TZoomAction.Destroy;
begin
  if FZoomer <> nil then
    FZoomer.RemoveFreeNotification(Self);
  inherited Destroy;
end;

function TZoomAction.GetZoomer(Target: TObject): TZoomer;
begin
  if FZoomer <> nil then
    Result := FZoomer
  else if (Target is TZoomer) and TZoomer(Target).Focused then
    Result := TZoomer(Target)
  else if Screen.ActiveControl is TZoomer then
    Result := TZoomer(Screen.ActiveControl)
  else
    { This should not happen! HandlesTarget is called before ExecuteTarget,
      or the action is disabled }
    Result := nil;
end;

function TZoomAction.HandlesTarget(Target: TObject): Boolean;
begin
  Result := ((FZoomer <> nil) and FZoomer.Enabled) or
    ((FZoomer = nil) and (Target is TZoomer) and TZoomer(Target).Focused) or
    ((Screen.ActiveControl is TZoomer) and Screen.ActiveControl.Enabled);
end;

procedure TZoomAction.Notification(AComponent: TComponent;
  Operation: TOperation);
begin
  inherited Notification(AComponent, Operation);
  if (Operation = opRemove) and (AComponent = FZoomer) then
    FZoomer := nil;
end;

procedure TZoomAction.SetZoomer(Value: TZoomer);
begin
  if FZoomer <> Value then
  begin
    if FZoomer <> nil then
      FZoomer.RemoveFreeNotification(Self);
    FZoomer := Value;
    if FZoomer <> nil then
      FZoomer.FreeNotification(Self);
  end;
end;

procedure TZoomAction.UpdateTarget(Target: TObject);
begin
  Enabled := HandlesTarget(Target);
end;

{ TZoomInAction }

constructor TZoomInAction.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  Caption := 'Zoom in';
  Hint := 'Zoom in|Zooms in on the selected zoomer control';
  ShortCut := Menus.ShortCut(VK_ADD, [ssCtrl]);
end;

procedure TZoomInAction.ExecuteTarget(Target: TObject);
begin
  GetZoomer(Target).ZoomIn;
  { For safety, you cóuld check if GetZoomer <> nil. See remark in GetZoomer. }
end;

{ TZoomer }

procedure TZoomer.ZoomIn;
begin
  { implementation of zooming in }
end;

end.

激活此操作（通过单击工具栏按钮或选择菜单项）会按以下优先级调用 ZoomIn 例程：

1. 您在操作的相关属性中手动设置的 Zoomer 控件（如果这样做），并且如果操作已启用，否则：
2. 应用程序请求的目标，但仅当该目标是聚焦的 Zoomer 控件时，否则：
3. 整个应用程序中的活动控件，但仅当该目标是启用时变焦控制。

随后，只需添加 ZoomOut 操作：

type
  TZoomOutAction = class(TZoomAction)
  public
    constructor Create(AOwner: TComponent); override;
    procedure ExecuteTarget(Target: TObject); override;
  end;

{ TZoomOutAction }

constructor TZoomOutAction.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  Caption := 'Zoom out';
  Hint := 'Zoom out|Zooms out on the selected zoomer control';
  ShortCut := Menus.ShortCut(VK_SUBTRACT, [ssCtrl]);
end;

procedure TZoomOutAction.ExecuteTarget(Target: TObject);
begin
  GetZoomer(Target).ZoomOut;
end;

请注意，操作组件需要在 IDE 中注册才能在设计时使用它们。

Delphi 帮助中适用的阅读内容：

• 编写操作组件、
• 操作如何查找他们的目标，
• 注册操作，
• 操作触发时会发生什么，
• 更新操作，
• 设置操作列表。

^{来源：www.nldelphi.com。}

Answer 2

基本操作支持是在 TControl 类中实现的，因此在最简单的情况下，您所要做的就是从 TControl 后代继承您的组件并将 Action 属性声明为已发布，例如：

type
  TMyGraphicControl = class(TGraphicControl)
  published
    property Action;
  end;

如果您的组件有其他属性应该链接到 TAction 属性，您还应该重写 ActionChange 方法。

Answer 3

如果您的组件已经是 TButton 的后代，那么操作支持将被继承。
您所需要做的就是将操作属性声明为已发布。