iOS 15 适配和新特性

1、苹果对导航栏的性能做了优化，默认情况下，如果导航栏与视图没有折叠，导航栏的背景透明，如果系统检测到有重叠的话，会变成毛玻璃的效果

if (@available(iOS 15.0, *)) {
NSDictionary *textAttr = @{
                                   NSForegroundColorAttributeName : [UIColor whiteColor],
                                   NSFontAttributeName: [UIFont systemFontOfSize:17],
                                   };
    UINavigationBarAppearance *appearance = [[UINavigationBarAppearance alloc] init];
    [appearance setShadowImage:[[UIImage alloc] init]];
appearance.titleTextAttributes = textAttr;
    [appearance setBackgroundColor:TAD_THM.navigationBackgroundColor];
    // 隐藏分割线 设置一个透明或者纯色的图片 设置nil 或者 [UIImage new]无效
    [appearance setBackgroundImage:[UIImage zt_imageWithPureColor:[UIColor whiteColor]]];
    [appearance setShadowImage:[UIImage zt_imageWithPureColor:[UIColor whiteColor]]];

    [[UINavigationBar appearance] setScrollEdgeAppearance: appearance];
// 滚动页面 防止导航栏会变白色
[[UINavigationBar appearance] setStandardAppearance:appearance];

        [[UINavigationBar appearance] setCompactAppearance:appearance];

// 隐藏导航栏底部一个线条
            [self.navigationController.navigationBar.subviews.firstObject.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
                if ([obj isKindOfClass:NSClassFromString(@"_UIBarBackgroundShadowContentImageView")] || [obj isKindOfClass:NSClassFromString(@"_UIBarBackgroundShadowView")]) {
                    obj.hidden=YES;
                }
            }];
}

颜色转图片

+ (UIImage *)zt_imageWithPureColor:(UIColor *)color {
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(3, 3), NO, [UIScreen mainScreen].scale);
    UIBezierPath* p = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, 3, 3)];
    [color setFill];
    [p fill];
    UIImage* img = UIGraphicsGetImageFromCurrentImageContext();
    return img;
}
+ (UIImage *)zt_imageWithPureColor:(UIColor *)color size:(CGSize )size{
    UIGraphicsBeginImageContextWithOptions(size, NO, [UIScreen mainScreen].scale);
    UIBezierPath* p = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, size.width, size.height)];
    [color setFill];
    [p fill];
    UIImage* img = UIGraphicsGetImageFromCurrentImageContext();
    return img;
}

UINavigationBar默认是透明的，有滑动时会逐渐变为模糊效果，可以通过改变scrollEdgeAppearance属性直接变为模糊效果

if (@available(iOS 15.0, *)){
    UINavigationBarAppearance *appearance = [[UINavigationBarAppearance alloc] init];
    appearance.backgroundEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleRegular];
    navBar.scrollEdgeAppearance = appearance;
}

2、UITableView新增了一条新属性：sectionHeaderTopPadding， 默认会给每一个section header 增加一个高度，当我们使用 UITableViewStylePlain 初始化UITableView的时候，能发现sectionHeader增高了22px。解决办法就是手动去除这个高度

if (@available(iOS 15.0, *)) {
    table.sectionHeaderTopPadding = 0;
}

全局适配设置

if (@available(iOS 15.0, *)) {
    //设置默认的分组头部间隙为0
    [UITableView appearance].sectionHeaderTopPadding = CGFLOAT_MIN;
}

3、UIImageWriteToSavedPhotosAlbum存储图片之后的回调不再返回图片了，会返回nil，如果在回调方法里面操作image有可能会直接Crash，目前的解决办法声明一个全局image去记录，后面再去操作

self.image = image;
UIImageWriteToSavedPhotosAlbum(image,self,@selector(image:didFinishSavingWithError:contextInfo:), NULL);
            
- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo{
    // self.image doing...
}