iOS基于 UILabel实现文字添加描边功能

- (void)drawTextInRect:(CGRect)rect 
{  
 CGSize shadowOffset = self.shadowOffset; 
 UIColor *textColor = self.textColor;  
 
 CGContextRef c = UIGraphicsGetCurrentContext();  
 CGContextSetLineWidth(c, 1);  
 CGContextSetLineJoin(c, kCGLineJoinRound);  
 
 CGContextSetTextDrawingMode(c, kCGTextStroke);  
 self.textColor = [UIColor whiteColor];  
 [super drawTextInRect:rect]; 
 
 CGContextSetTextDrawingMode(c, kCGTextFill);  
 self.textColor = textColor;  
 self.shadowOffset = CGSizeMake(0, 0);  
 [super drawTextInRect:rect];  
 
 self.shadowOffset = shadowOffset; 
}