iOS12 好像获取不到self.navigationBar.subviews

[shengxiaolei]

• (void)setNavigationBackgroundAlpha:(CGFloat)navAlpha {
  CGFloat alpha = MAX(MIN(navAlpha, 1), 0);
  UIView *barBackground = self.navigationBar.subviews[0];
  UIView *colorView = [self getColorViewOnView:barBackground];
  colorView.alpha = alpha;
  if ([barBackground valueForKey:@"_shadowView"]) {
  UIView *shadowView = [barBackground valueForKey:@"_shadowView"];
  shadowView.alpha = alpha;
  shadowView.hidden = alpha == 0 ? YES : NO;
  }
  }

这个方法报错在iOS 12下

[koalahl]

改成 [[self.navigationBar subViews] firstObject] . 可以

[yimao009]

• (void)setNavigationBackgroundAlpha:(CGFloat)navAlpha {
  CGFloat alpha = MAX(MIN(navAlpha, 1), 0);
  UIView *barBackground = self.navigationBar.subviews[0];
  UIView *colorView = [self getColorViewOnView:barBackground];
  colorView.alpha = alpha;
  if ([barBackground valueForKey:@"_shadowView"]) {
  UIView *shadowView = [barBackground valueForKey:@"_shadowView"];
  shadowView.alpha = alpha;
  shadowView.hidden = alpha == 0 ? YES : NO;
  }
  }

这个方法报错在iOS 12下

[0如果数组为空， 会发生奔溃， 使用firstObject会返回nil， oc里可以给nil发消息

[yimao009]

改成 [[self.navigationBar subViews] firstObject] . 可以

您好， iOS12和之前的系统在navgationbar上有什么更新变化吗， 为什么会导致这个bug呢？往指点