Question

我正在尝试创建一个VCL组件，它允许您插入多个不同大小的TImages作为属性。我被告知最好使用TObjectList（Delphi component with a variable amount of TPictures），但现在我很难在属性编辑器中使单个TPictures 可分配。

我现在所拥有的:(编译）

unit ImageMultiStates; interface uses Vcl.Graphics, Vcl.StdCtrls, System.SysUtils, System.Classes, Vcl.Controls, Vcl.ExtCtrls, Forms, Generics.Collections; type TImageMultiStates = class(TImage) private FPictures: TObjectList<TPicture>; procedure SetPicture(Which: Integer; APicture: TPicture); function GetPicture(Which: Integer): TPicture; public Count: integer; constructor Create(AOwner: TComponent); override; destructor Destroy; override; procedure Activate(Which: Integer); published // property Pictures: TObjectList<TPicture> read GetPicture write SetPicture; // property Pictures[Index: Integer]: TObjectList<TPicture> read GetPicture write SetPicture; property Pictures: TObjectList<TPicture> read FPictures write FPictures; end; procedure Register; implementation constructor TImageMultiStates.Create(AOwner: TComponent); begin inherited Create(AOwner); FPictures := TObjectList<TPicture>.Create; end; destructor TImageMultiStates.Destroy; begin FPictures.Free; inherited Destroy; end; procedure TImageMultiStates.SetPicture(Which: Integer; APicture: TPicture); begin FPictures[Which] := APicture; if Which=0 then Picture.Assign(APicture); end; function TImageMultiStates.GetPicture(Which: Integer): TPicture; begin Result := FPictures[Which]; end; procedure TImageMultiStates.Activate(Which: Integer); begin Picture.Assign(FPictures[Which]); end; procedure Register; begin RegisterComponents('Standard', [TImageMultiStates]); end; end.

什么不起作用是PropertyEditor的最终结果。它显示了一个名为＆＃34; Pictures＆＃34;的单个项目，其值为＆＃34;（TObjectList）＆＃34;。点击它没有做任何事情，我没有得到一个合适的编辑器。有关该系列的其他想法已被注释掉，它们带来了其他错误：第一个抛出编译器错误＆＃34; E2008不兼容类型＆＃34;，第二个抛出＆＃34;发布属性＆＃39;图片＆＃39;不能是ARRAY＆＃34;。

Answer 1

IDE不知道如何在设计时编辑TObjectList，而DFM流媒体系统也不知道如何流式传输TObjectList。您必须实现自定义属性编辑器和自定义流逻辑。虽然这肯定是可能的，但这是很多工作。

使用System.Classes.TCollection可以更好地处理您尝试做的事情。 IDE和DFM流媒体系统都内置支持自动处理TCollection编辑和流媒体。

尝试更像这样的事情：

unit ImageMultiStates;

interface

uses
  System.Classes, Vcl.Controls, Vcl.ExtCtrls, Vcl.Graphics;

type
  TImagePictureItem = class(TCollectionItem)
  private
    FPicture: TPicture;
    procedure PictureChanged(Sender: TObject);
    procedure SetPicture(Value: TPicture);
  public
    constructor Create(Collection: TCollection); override;
    destructor Destroy; override;
  published
    property Picture: TPicture read FPicture write SetPicture;
  end;

  TImagePictureEvent = procedure(Sender: TObject; Index: Integer) of object; 

  TImagePictures = class(TOwnedCollection)
  private
    FOnPictureChange: TImagePictureEvent;
    function GetPicture(Index: Integer): TImagePictureItem;
    procedure SetPicture(Index: Integer; Value: TImagePictureItem);
  protected
    procedure Update(Item: TCollectionItem); override;
  public
    constructor Create(Owner: TComponent); reintroduce;
    property Pictures[Index: Integer]: TImagePictureItem read GetPicture write SetPicture; default;
    property OnPictureChange: TImagePictureEvent read FOnPictureChange write FOnPictureChange;
  end;

  TImageMultiStates = class(TImage)
  private
    FActivePicture: Integer;
    FPictures: TImagePictures;
    function GetPicture(Index: Integer): TPicture;
    procedure PictureChanged(Sender: TObject; Index: Integer);
    procedure SetActivePicture(Index: Integer);
    procedure SetPicture(Index: Integer; Value: TPicture);
    procedure SetPictures(Value: TImagePictures);
  protected
    procedure Loaded; override;
  public
    constructor Create(Owner: TComponent); override;
    function Count: integer;
    property Pictures[Index: Integer]: TPicture read GetPicture write SetPicture;
  published
    property ActivePicture: Integer read FActivePicture write SetActivePicture default -1;
    property Picture stored False;
    property Pictures: TImagePictures read FPictures write SetPictures;
  end;

procedure Register;

implementation

{ TImagePictureItem }

constructor TImagePictureItem.Create(Collection: TCollection);
begin
  inherited Create(Collection);
  FPicture := TPicture.Create;
  FPicture.OnChange := PictureChanged;
end;

destructor TImagePictureItem.Destroy;
begin
  FPicture.Free;
  inherited;
end;

procedure TImagePictureItem.PictureChanged(Sender: TObject);
begin
  Changed(False);
end;

procedure TImagePictureItem.SetPicture(Value: TPicture);
begin
  FPicture.Assign(Value);
end;

{ TImagePictures }

constructor TImagePictures.Create(Owner: TComponent);
begin
  inherited Create(Owner, TImagePictureItem);
end;

function TImagePictures.GetPicture(Index: Integer): TImagePictureItem;
begin
  Result := TImagePictureItem(inherited GetItem(Index));
end;

procedure TImagePictures.SetPicture(Index: Integer; Value: TImagePictureItem);
begin
  inherited SetItem(Index, Value);
end;

procedure TImagePictures.Update(Item: TCollectionItem);
begin
  if Assigned(FOnPictureChange) then
  begin
    if Item <> nil then
      FOnPictureChange(Self, Item.Index)
    else
      FOnPictureChange(Self, -1);
  end;
end;

{ TImageMultiStates }

constructor TImageMultiStates.Create(Owner: TComponent);
begin
  inherited Create(Owner);
  FPictures := TImagePictures.Create(Self);
  FPictures.OnPictureChange := PictureChanged;
  FActivePicture := -1;
end;

procedure TImageMultiStates.Loaded;
begin
  inherited;
  PictureChanged(nil, FActivePicture);
end;

function TImageMultiStates.Count: Integer;
begin
  Result := FPictures.Count;
end;

procedure TImageMultiStates.PictureChanged(Sender: TObject; Index: Integer);
begin
  if (FActivePicture <> -1) and ((Index = -1) or (Index = FActivePicture)) then
    Picture.Assign(GetPicture(FActivePicture));
end;

function TImageMultiStates.GetPicture(Index: Integer): TPicture;
begin
  Result := FPictures[Index].Picture;
end;

procedure TImageMultiStates.SetPicture(Index: Integer; Value: TPicture);
begin
  FPictures[Index].Picture.Assign(Value);
end;

procedure TImageMultiStates.SetActivatePicture(Value: Integer);
begin
  if FActivePicture <> Value then
  begin
    if ComponentState * [csLoading, csReading] = [] then
      Picture.Assign(GetPicture(Value));
    FActivePicture := Value;
  end;
end;

procedure Register;
begin
  RegisterComponents('Standard', [TImageMultiStates]);

  // the inherited TImage.Picture property is published, and you cannot
  // decrease the visibility of an existing property.  However, if you move
  // this procedure into a separate design-time package, you can then use
  // DesignIntf.UnlistPublishedProperty() to hide the inherited
  // Picture property at design-time, at least:
  //
  // UnlistPublishedProperty(TImageMultiStates, 'Picture');
  //
  // Thus, users are forced to use the TImageMultiStates.Pictures and
  // TImageMultiStates.ActivePicture at design-time.  The inherited
  // Picture property will still be accessible in code at runtime, though...
end;

end.

delphi组件属性：TObjectList <tpicture>

1 个答案: