iOS 切换状态栏StatusBar

1.先写 [self setNeedsStatusBarAppearanceUpdate];
2.重写 [self preferredStatusBarStyle];

• (UIStatusBarStyle)preferredStatusBarStyle {
  if (self.view.backgroundColor == kWhiteColor) {
  return UIStatusBarStyleDefault;
  }
  return UIStatusBarStyleLightContent;
  }
  3.即可控制切换