我在我的窗体上画一条线,语句如下,不行,为什么?该如何改?谢谢.
var a:tcanvas; //这样定义了a 与canvas 区别在哪?
begin
a:=tcanvas.Create;
a.Pen.Color:=clred;
a.MoveTo(10,100);
a.LineTo(100,100);
a.Brush.Color:=clbtnface;
a.Font.Name:='Arial';
a.textout(a.PenPos.X,a.PenPos.Y,'hello');
end;
var a:tcanvas; //这样定义了a 与canvas 区别在哪?
begin
a:=tcanvas.Create;
a.Pen.Color:=clred;
a.MoveTo(10,100);
a.LineTo(100,100);
a.Brush.Color:=clbtnface;
a.Font.Name:='Arial';
a.textout(a.PenPos.X,a.PenPos.Y,'hello');
end;
a.LineTo(100,100);
a.textout(a.PenPos.X,a.PenPos.Y,'hello');
这三条语句错,错误是 canvas dose not allow drawing
var
a:tcanvas; //ÕâÑù¶¨ÒåÁËa Óëcanvas Çø±ðÔÚÄÄ?
begin
// a:=tcanvas.Create;
a:=Form1.Canvas;
a.Pen.Color:=clred;
a.MoveTo(10,100);
a.LineTo(100,100);
a.Brush.Color:=clbtnface;
a.Font.Name:='Arial';
a.textout(a.PenPos.X,a.PenPos.Y,'hello');
procedure TForm1.Button1Click(Sender: TObject);
var
a:tcanvas;
begin
a:=Form1.Canvas;
a.Pen.Color:=clred;
a.MoveTo(10,100);
a.LineTo(100,100);
a.Brush.Color:=clbtnface;
a.Font.Name:='Arial';
a.textout(a.PenPos.X,a.PenPos.Y,'hello');
end;