FMX 的 Canvas 在不同的系统上会分别使用:
WinVista、Win7: D2D (FMX.Canvas.D2D.pas)
WinXP: GDI+ (FMX.Canvas.GDIP.pas)
Mac 系列: Core Graphics (FMX.Canvas.Mac.pas)

和 HTML5 中的 Canvas 非常类似, 现在的 Canvas 模糊了 Pen 的概念:
之前的 Canvas.Pen 对应: Canvas.Stroke;
之前的 Canvas.Brush 对应: Canvas.Fill.

在 FMX 中, Canvas 无处不在, 其 Canvas.Stroke、Canvas.Fill 的状态也各不相同, 一般要先初始化它们.

测试: 窗体上放 Button1、Panel1, 激活 Panel1 的 OnPaint 事件:

procedure TForm1.FormCreate(Sender: TObject);

begin

Self.OnPaint := Panel1.OnPaint;

Button1.OnPaint := Panel1.OnPaint;

Panel1.Opacity := 0.75;

end;

 

procedure TForm1.Panel1Paint(Sender: TObject; Canvas: TCanvas; const ARect: TRectF);

begin

{画直线}

Canvas.Stroke.Kind := TBrushKind.bkSolid;

// Canvas.Stroke.Color := claBlack;

Canvas.DrawLine(ARect.Location, ARect.BottomRight, 1);

 

{填充椭圆}

// Canvas.Fill.Kind := TBrushKind.bkSolid;

Canvas.Fill.Color := claGreen;

Canvas.FillEllipse(RectF(ARect.Width/5, ARect.Height/5, ARect.Width/5*4, ARect.Height/5*4), 1);

end;




效果图:

绘图命令:



Canvas.DrawLine(); //

Canvas.DrawRect(); //画矩形; 集合 TCorners: 四个角是否使用指定的样式类型; 枚举 TCornerType: 角样式类型

Canvas.DrawRectSides(); //画矩形边; 集合 TSides 指定要画的边

Canvas.DrawEllipse(); //

Canvas.DrawArc(); //

Canvas.DrawPath(); //

Canvas.DrawBitmap(); //

Canvas.DrawThumbnail(); //画略缩图

Canvas.DrawPolygon(); //

Canvas.FillRect(); //

Canvas.FillEllipse(); //

Canvas.FillArc(); //

Canvas.FillPath(); //

Canvas.FillPolygon(); //

Canvas.FillText(); //

 

{测试文本输出}

procedure TForm1.Panel1Paint(Sender: TObject; Canvas: TCanvas; const ARect: TRectF);

begin

Canvas.Fill.Color := claRed;

Canvas.Font.Size := 30;

Canvas.FillText(ARect, 'TEST 测试字符串', True, 1, [], TTextAlign.taLeading, TTextAlign.taCenter);

end;