iOS11 适配UIscrollView以及UItableView

前两天Xcode版本更新到了GM Seed版本。正好有需要适配iOS11,就下载了下来试试看。
然后发现用到了下拉刷新的地方奇丑无比，下拉刷新漏了一半在外面。
如图：

wrongRefresh.png

透视发现这个TableView的contentInset为(20,0,0,0),经过一番查找，在UIScrollView的.h文件中发现了一个新增的属性：

/* Configure the behavior of adjustedContentInset.
 Default is UIScrollViewContentInsetAdjustmentAutomatic.
 */
@property(nonatomic) UIScrollViewContentInsetAdjustmentBehavior contentInsetAdjustmentBehavior API_AVAILABLE(ios(11.0),tvos(11.0));

这个属性的默认值是UIScrollViewContentInsetAdjustmentAutomatic，
再看看这个iOS11新增的枚举：

typedef NS_ENUM(NSInteger, UIScrollViewContentInsetAdjustmentBehavior) {
    UIScrollViewContentInsetAdjustmentAutomatic, // Similar to .scrollableAxes, but for backward compatibility will also adjust the top & bottom contentInset when the scroll view is owned by a view controller with automaticallyAdjustsScrollViewInsets = YES inside a navigation controller, regardless of whether the scroll view is scrollable
    UIScrollViewContentInsetAdjustmentScrollableAxes, // Edges for scrollable axes are adjusted (i.e., contentSize.width/height > frame.size.width/height or alwaysBounceHorizontal/Vertical = YES)
    UIScrollViewContentInsetAdjustmentNever, // contentInset is not adjusted
    UIScrollViewContentInsetAdjustmentAlways, // contentInset is always adjusted by the scroll view's safeAreaInsets
} API_AVAILABLE(ios(11.0),tvos(11.0));

UIScrollViewContentInsetAdjustmentAutomatic的注释说明:

but for backward compatibility will also adjust the top & bottom 
contentInset when the scroll view is owned by a view controller with 
automaticallyAdjustsScrollViewInsets = YES inside a navigation 
controller, regardless of whether the scroll view is scrollable

大概意思是说当一个ScrollView是一个控制器的View的子View并且navigation controller中automaticallyAdjustsScrollViewInsets = YES的时候，会自动调整contentInset的top和Bottom。

根据这些资料首先尝试了修改UIScrollView的UIScrollViewContentInsetAdjustmentBehavior这个属性的默认值，因为项目中很多地方都用到了UITableView以及UIScrollView,一个一个改太麻烦了，所以想到了runtime，直接上代码吧：

#import "UIScrollView+contentInset.h"

@implementation UIScrollView (contentInset)

+ (void)load {
    [super load];
    //因为是为了适配iOS11 所以只有在系统是iOS11的时候用过运行时修改这个值
    if (iOS11) {
        Method originalM = class_getInstanceMethod([self class], @selector(initWithFrame:));
        Method exchangeM = class_getInstanceMethod([self class], @selector(cl_initWithFrame:));
        method_exchangeImplementations(originalM, exchangeM);
    }
}

- (instancetype)cl_initWithFrame:(CGRect)frame {
    
    if (@available(iOS 11.0, *)) {
        self.contentInsetAdjustmentBehavior = UIScrollViewContentInsetAdjustmentNever;
    } else {
        // Fallback on earlier versions
    }
    return [self cl_initWithFrame:frame];
}

@end

ps:附上修改之后的图片：

correct.png