使用 MonoTouch.CoreText 在特定坐标处绘制文本片段

我正在尝试通过示例应用程序了解 CoreTexthttp://docs.xamarin.com/recipes/ios/graphics_and_drawing/core_text/draw_unicode_text_with_coretext/

I am trying to get a grasp of CoreText, working from the example app at http://docs.xamarin.com/recipes/ios/graphics_and_drawing/core_text/draw_unicode_text_with_coretext/

作为测试，我想在视图中的视图上写入N"、E"、S"和W"各自的职位.但只有第一个('N')被绘制.

As a test I want to write to write 'N', 'E', 'S' and 'W' on the view in the respective positions. But only the first one (the 'N') gets drawn.

这是我的 TextDrawingView.cs 版本:

Here's my version of TextDrawingView.cs:

using System;
using System.Drawing;
using MonoTouch.UIKit;
using MonoTouch.Foundation;
using MonoTouch.CoreText;
using MonoTouch.CoreGraphics;

namespace CoreTextDrawing
{
    public class TextDrawingView : UIView
    {
        public TextDrawingView ()
        {
        }

        //based upon docs.xamarin.com/recipes/ios/graphics_and_drawing/\
        //    core_text/draw_unicode_text_with_coretext/

        public override void Draw (RectangleF rect)
        {
            base.Draw (rect);

            var gctx = UIGraphics.GetCurrentContext ();
            gctx.SetFillColor (UIColor.Green.CGColor);

            DrawText ("N", Bounds.Width / 2, Bounds.Height / 4, gctx);
            DrawText ("W", Bounds.Width / 4, Bounds.Height / 2, gctx);
            DrawText ("E", Bounds.Width / 4 * 3, Bounds.Height / 2, gctx);
            DrawText ("S", Bounds.Width / 2, Bounds.Height / 4 * 3, gctx);
        }

        private void DrawText (string t, float x, float y, CGContext gctx)
        {
            gctx.TranslateCTM (x, y);
            gctx.ScaleCTM (1, -1);
            var attributedString = new NSAttributedString (t,
                                       new CTStringAttributes {
                    ForegroundColorFromContext = true,
                    Font = new CTFont ("Arial", 24)
                }); 

            using (var textLine = new CTLine (attributedString)) { 
                textLine.Draw (gctx);
            }
        }
    }
}

我不知道为什么只画了N".4个DrawText中的每一个如果它们是唯一的调用，则调用工作正常.

I have no idea why only the 'N' gets drawn. Each of the 4 DrawText invocations work fine if they are the only invocation.

我似乎缺乏一些基本的了解.

I seem to lack some basic understanding.

基本上我想在特定坐标上绘制一些字母屏幕，但未能理解如何实现这一点.

Basically I want to draw some letters at specific coordinates on the screen, but failed to understand how to achieve this.

有人帮忙吗?

TIA，

圭多