traitCollectionDidChange奇怪的行为

override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
super.traitCollectionDidChange(previousTraitCollection)
if traitCollection.hasDifferentColorAppearance(comparedTo: previousTraitCollection) {
print("changed")
}
}


iOS 13应用程序只是在不更改模式（亮/暗）的情况下进入后台，但调用了“打印”功能。是否可以确定模式真正改变的时刻？

谢谢。

我自己也观察到了。
用户界面一切换到后台，就会立即切换-它会立即切换回去。
我想您应该简单地遵循更改并根据需要做出反应。
您可以通过选中add_filter( 'woocommerce_product_tax_class','wc_diff_rate_for_user',1,2 );
function wc_diff_rate_for_user( $tax_class,$product ) {
// not logged in users are not VIP,let's move on...
if (!is_user_logged_in()) {return $tax_class;}
// this user is not VIP,let's move on...
if (!current_user_can( 'VIP' ) ) {return $tax_class;}
// it's already Reduced Rate,let's move on..
if ($tax_class == 'Reduced Rate') {return $tax_class;}
// let's get all the product category for this product...
$terms = get_the_terms( $product->id,'product_cat' );
foreach ( $terms as $term ) { // checking each category
// if it's one of the category we'er looking for
if(in_array($term->term_id,array(81,82))) {
$tax_class = 'Reduced Rate';
// found it... no need to check other $term
break;
}
}
return $tax_class;
}
来找到当前的界面样式。
例如：
traitCollection.userInterfaceStyle