学习笔记-NavigationBar透明

    self.navigationController.navigationBar.translucent = YES;
    UIColor *color = [UIColor clearColor];
    CGRect rect = CGRectMake(0, 0, ScreenWidth, 64);
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [color CGColor]);
    CGContextFillRect(context, rect);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    [self.navigationController.navigationBar setBackgroundImage:image forBarMetrics:UIBarMetricsDefault];
    self.navigationController.navigationBar.clipsToBounds = YES;