delphi - 创建一个接受 .PNG 图像作为 Glyph 的按钮

Question

我试图了解 SpeedButton 如何Glyph属性工作，我发现该字段声明为:

FGlyph: TObject;

而property如:

property Glyph: TBitmap read GetGlyph write SetGlyph stored HasCustomGlyph;

当我尝试创建自己的 SpeedButton 时，即使我逐行阅读代码，我也无法理解该代码。接受 .PNG图像也代替 .bmp仅图像。

我第一次考虑将该属性声明为 TPicture而不是TBitmap .

有没有办法用 Glyph : TPicture 创建 MySpeedButton ？

我尝试的方法如下:

TMyButton = class(TSpeedButton)
    private
     //
    FGlyph: TPicture;
    procedure SetGlyph(const Value: TPicture);
    protected
    //
    public
    //
    published
    //
      Property Glyph : TPicture read FGlyph write SetGlyph;
  end;

程序:

procedure TMyButton.SetGlyph(const Value: TPicture);
begin
  FGlyph := Value;
end;

Answer 1

您的SetGlyph()需要调用FGlyph.Assign(Value)而不是FGlyph := Value。请务必在构造函数中创建 FGlyph 并在析构函数中销毁它。然后，当 Graphic 不为空时，您可以在重写的 Paint() 中调用绘制图形。

type
  TMyButton = class(TGraphicControl)
  private
    FGlyph: TPicture;
    procedure GlyphChanged(Sender: TObject);
    procedure SetGlyph(const Value: TPicture);
    protected
      procedure Paint; override;
    public
      constructor Create(AOwner: TComponent); override;
      destructor Destroy; override;
    published
      property Glyph : TPicture read FGlyph write SetGlyph;
  end;

constructor TMyButton.Create(AOwner: TComponent);
begin
  inherited;
  FGlyph := TPicture.Create;
  FGlyph.OnChange := GlyphChanged;
end;

destructor TMyButton.Destroy;
begin
  FGlyph.Free;
  inherited;
end;

procedure TMyButton.GlyphChanged(Sender: TObject);
begin
  Invalidate;
end;

procedure TMyButton.SetGlyph(const Value: TPicture);
begin
  FGlyph.Assign(Value):
end;

procedure TMyButton.Paint;
begin
 ...
  if (FGlyph.Graphic <> nil) and (not FGlyph.Graphic.Empty) then
    Canvas.Draw(..., FGlyph.Graphic);
 ... 
end;