如果要在按钮里的字体加下划线

可以新建一个类继承UIButton 再重写(void)drawRect:(CGRect)rect方法

- (void)drawRect:(CGRect)rect     {            // Get the Render Context        CGContextRef ctx = UIGraphicsGetCurrentContext();        // Measure the font size, so the line fits the text.        // Could be that "titleLabel" is something else in other classes like UILable, dont know.        // So make sure you fix it here if you are enhancing UILabel or something else..        CGSize fontSize =[self.titleLabel.text sizeWithFont:self.titleLabel.font                                                    forWidth:self.bounds.size.width                                              lineBreakMode:UILineBreakModeTailTruncation];        // Get the fonts color.         const float * colors = CGColorGetComponents(self.titleLabel.textColor.CGColor);        // Sets the color to draw the line        CGContextSetRGBStrokeColor(ctx, colors[0], colors[1], colors[2], 1.0f); // Format : RGBA        // Line Width : make thinner or bigger if you want        CGContextSetLineWidth(ctx, 1.0f);        // Calculate the starting point (left) and target (right)           float fontLeft = self.titleLabel.center.x - fontSize.width/2.0;        float fontRight = self.titleLabel.center.x + fontSize.width/2.0;        // Add Move Command to point the draw cursor to the starting point        CGContextMoveToPoint(ctx, fontLeft, self.bounds.size.height - 1);        // Add Command to draw a Line        CGContextAddLineToPoint(ctx, fontRight, self.bounds.size.height - 1);        // Actually draw the line.        CGContextStrokePath(ctx);        // should be nothing, but who knows...        [super drawRect:rect];       }