IOS 修改UIAlertController的按钮标题的字体颜色，字号，内容
- (IBAction)buttonClick:(UIButton *)sender {
UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"提示" message:@"提示内容" preferredStyle:UIAlertControllerStyleAlert];
//修改标题的内容，字号，颜色。使用的key值是“attributedTitle”
NSMutableAttributedString *hogan = [[NSMutableAttributedString alloc] initWithString:@"heihei"];
[hogan addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:50] range:NSMakeRange(0, [[hogan string] length])];
[hogan addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0, [[hogan string] length])];
[alertController setValue:hogan forKey:@"attributedTitle"];
//修改按钮的颜色，同上可以使用同样的方法修改内容，样式
UIAlertAction *defaultAction = [UIAlertAction actionWithTitle:@"Default" style:UIAlertActionStyleDefault handler:nil];
[defaultAction setValue:[UIColor blueColor] forKey:@"_titleTextColor"];
UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:nil];
[cancelAction setValue:[UIColor greenColor] forKey:@"_titleTextColor"];
[alertController addAction:defaultAction];
[alertController addAction:cancelAction];
[self presentViewController:alertController animated:YES completion:nil];
}