Delphi 怎样才能清空PaintBox里的图形

刷新一下 PaintBox1.Refresh;

procedure TForm1.Button2Click(Sender: TObject);
begin
PaintBox1.Canvas.MoveTo(0,0);
PaintBox1.Canvas.LineTo(100,100);
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
PaintBox1.Canvas.Brush.Color := clBtnFace;
PaintBox1.Canvas.FillRect(PaintBox1.ClientRect);