使用iOS 7.0淡出自定义navbaritem

Question

我一直在使用iOS 7和我的导航控制器之一，出于某种原因，我不得不使用自定义后退按钮（后面有箭头图像和文本）作为leftBarButtonItem。现在，在iOS 7中，当屏幕上显示操作表或警报时，它会淡出左右栏项目按钮。但是使用我的自定义按钮，只有文本淡出，对于后退箭头按钮，我必须进行特殊处理。是否有直接的方法：

这是我的代码：

添加自定义按钮（PS：由于某些原因，我必须通过自定义按钮）：

- (void)showCustomBackButton {
    UIButton *aCustomBackButton = [UIButton buttonWithType:101];
    [aCustomBackButton addTarget:self action:@selector(backAction) forControlEvents:UIControlEventTouchUpInside];
    [aCustomBackButton setTitle:@"Back" forState:UIControlStateNormal];


    UIImage *backArrow = [UIImage imageNamed:@"backArrowImage"];
    UIImageView *imageView = [[UIImageView alloc]initWithImage:@"backArrow"];
    [imageView setFrame:CGRectMake(kScreenOrigin, topMargin, backArrow.size.width, backArrow.size.height)];
    [aCustomBackButton addSubview:imageView];
    UIBarButtonItem *aNegativeSpacer = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil];
    aNegativeSpacer.width = -8.0;
    UIBarButtonItem *aLeftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:aCustomBackButton];
    aLeftBarButtonItem.tag = 100;
    self.navigationItem.leftBarButtonItems = @[aNegativeSpacer, aLeftBarButtonItem];
}

- (void)showCustomBackButtonFaded {
    UIBarButtonItem *aBarButtonItem = [self.navigationItem.leftBarButtonItems lastObject];

    if (aBarButtonItem && aBarButtonItem.tag == 100) {
        UIButton *aCustomBackButton = [UIButton buttonWithType:101];
        [aCustomBackButton addTarget:self action:@selector(backAction) forControlEvents:UIControlEventTouchUpInside];
        [aCustomBackButton setTitle:@"Back" forState:UIControlStateNormal];

        UIImage *backArrow = [UIImage imageNamed:@"fadedBackArrow"];
        UIImageView *imageView = [[UIImageView alloc]initWithImage:backArrow];
        [imageView setFrame:CGRectMake(kScreenOrigin, topMargin, backArrow.size.width, backArrow.size.height)];
        [aCustomBackButton addSubview:imageView];
        UIBarButtonItem *aNegativeSpacer = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil];
        aNegativeSpacer.width = -8;
        UIBarButtonItem *aLeftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:aCustomBackButton];
        self.navigationItem.leftBarButtonItems = @[aNegativeSpacer, aLeftBarButtonItem];
    }
}