海神

代码： # UIUnderlinedButton.h   @interface UIUnderlinedButton : UIButton

+ (UIUnderlinedButton*) underlinedButton;

@end

# UIUnderlinedButton.m
 
@implementation UIUnderlinedButton
 
+ (UIUnderlinedButton*) underlinedButton {
  UIUnderlinedButton* button = [[UIUnderlinedButton alloc] init];
  return [button autorelease];
}

- (void) drawRect:(CGRect)rect {
  CGRect textRect = self.titleLabel.frame;
  // need to put the line at top of descenders (negative value)
  CGFloat descender = self.titleLabel.font.descender;
  CGContextRef contextRef = UIGraphicsGetCurrentContext();
  // set to same colour as text
  CGContextSetStrokeColorWithColor(contextRef, self.titleLabel.textColor.CGColor);
  CGContextMoveToPoint(contextRef, textRect.origin.x, textRect.origin.y + textRect.size.height + descender);
  CGContextAddLineToPoint(contextRef, textRect.origin.x + textRect.size.width, textRect.origin.y + textRect.size.height + descender);
  CGContextClosePath(contextRef);
  CGContextDrawPath(contextRef, kCGPathStroke);
}