Solution: Navbar title or back button disappears after pushing/popping about ltnavigationbar HOT 6 CLOSED

- (UIView *)overlay
{
    return objc_getAssociatedObject(self, &overlayKey);
}

- (void)setOverlay:(UIView *)overlay
{
    objc_setAssociatedObject(self, &overlayKey, overlay, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (void)lt_setBackgroundColor:(UIColor *)backgroundColor
{
    if (!self.overlay) {
        [self setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
        self.overlay = [[UIView alloc] initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.bounds), CGRectGetHeight(self.bounds) + 20)];
        self.overlay.userInteractionEnabled = NO;
        self.overlay.autoresizingMask = UIViewAutoresizingFlexibleWidth;    // Should not set `UIViewAutoresizingFlexibleHeight`
        
        [[self.subviews firstObject] insertSubview:self.overlay atIndex:self.subviews.count -1];
    }
    self.overlay.backgroundColor = backgroundColor;
}

- (void)lt_setTranslationY:(CGFloat)translationY
{
    self.transform = CGAffineTransformMakeTranslation(0, translationY);
}

- (void)lt_setElementsAlpha:(CGFloat)alpha
{
    [[self valueForKey:@"_leftViews"] enumerateObjectsUsingBlock:^(UIView *view, NSUInteger i, BOOL *stop) {
        view.alpha = alpha;
    }];
    
    [[self valueForKey:@"_rightViews"] enumerateObjectsUsingBlock:^(UIView *view, NSUInteger i, BOOL *stop) {
        view.alpha = alpha;
    }];
    
    UIView *titleView = [self valueForKey:@"_titleView"];
    titleView.alpha = alpha;
    //    when viewController first load, the titleView maybe nil
    [[self subviews] enumerateObjectsUsingBlock:^(UIView *obj, NSUInteger idx, BOOL *stop) {
        if ([obj isKindOfClass:NSClassFromString(@"UINavigationItemView")]) {
            obj.alpha = alpha;
            *stop = YES;
        }
    }];
}

- (void)lt_reset
{
    [self setBackgroundImage:nil forBarMetrics:UIBarMetricsDefault];
    [self.overlay removeFromSuperview];
    self.overlay = nil;
}