Firemonkey：Image.Bitmap.DrawLine在ipad上不可见

Question

我正在为IOS的DelphiXE2 firemonkey构建一个应用程序。如果我在Xcode IPAD Simulator的Mac上进行测试，我看到了按钮。但是当我点击按钮时，没有线条可见。为什么？

代码：（在窗体一个按钮和一个图片）

unit Unit3; 

interface 

uses 
    SysUtils, Types, UITypes, Classes, Variants, FMX_Types, FMX_Controls, FMX_Forms, 
    FMX_Dialogs, FMX_Objects; 

type 
    TForm3 = class(TForm) 
    Image1: TImage; 
    Button1: TButton; 
    procedure Button1Click(Sender: TObject); 
    procedure FormCreate(Sender: TObject); 
    private 
    { Private-Deklarationen } 
    public 
    { Public-Deklarationen } 
    end; 

var 
    Form3: TForm3; 

implementation 

{$R *.lfm} 

procedure TForm3.Button1Click(Sender: TObject); 
var pt0,pt1 : TPointF; 
begin 
    pt0.Create(0,0); 
    pt1.Create(200,200); 
    with Image1.Bitmap do begin 
    Canvas.Stroke.Color := $ffff0000 ; // Red 
    Canvas.BeginScene; 

    Canvas.DrawLine(pt0,pt1,1); 
    BitmapChanged; // without this, no output 
    Canvas.EndScene; 
    end; 

end; 


procedure TForm3.FormCreate(Sender: TObject); 
begin 
    Image1.Bitmap := TBitmap.Create(200,200); 
end; 
end. 

Answer 1

我觉得应该是：

pt0 := TPointF.Create(0, 0); 

Answer 2

试试这个

pt0.X:=X; 
    pt0.Y:=Y; 
    pt1.X:=X+4; 
    pt1.Y:=Y+4; 
    with Image1.Bitmap do begin 
    Canvas.Stroke.Color := $ffff0000 ; // Red 
    Canvas.Stroke.Kind := TBrushKind.bkSolid; 
    Canvas.StrokeThickness:= 10; 
    Canvas.BeginScene; 
    Canvas.DrawLine(pt0,pt1,100); 
    Canvas.EndScene; 
    end;