UINavigationBar全透明

- (void)transparentNavigationBar {
  UINavigationBar*bar = self.navigationController.navigationBar;
  bar.translucent = YES;
  UIColor*color = [UIColor clearColor];
  CGRectrect = CGRectMake(0, 0,ScreenWidth, 64);
  UIGraphicsBeginImageContext(rect.size);
  CGContextRefcontext = UIGraphicsGetCurrentContext();
  CGContextSetFillColorWithColor(context, [colorCGColor]);
  CGContextFillRect(context, rect);
  UIImage*image = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  [bar setBackgroundImage:imageforBarMetrics:UIBarMetricsDefault];
}