正确设置CATextLayer的Font

iOS中，通常设置字体都是使用UIFont, 但是CATextLayer例外，详细阅读CATextLayer Class Reference，

May be either a CTFontRef, aCGFontRef, an instance ofNSFont (Mac OS X only), or a string naming the font. In iOS, you cannot assign aUIFont object to this property. Defaults to Helvetica.

The font property is only used when the string property is not an NSAttributedString.

Note: If the font property is a CTFontRef, a CGFontRef, or an instance of NSFont, the font size of the property is ignored.

设置CATextLayer字体：

错误：　textLayer.font = [UIFont fontWithName:@"HiraKakuProN-W3" size:12];
正确：　textLayer.font = @"HiraKakuProN-W3"; textLayer.fontSize = 12;