iOS13 自定义返回键位置问题

iOS13 beta7已经出来了，为了提前适配应用，测试机升级看看应用是否有问题，幸好坑不算多，主要问题就是用系统导航栏的位置返回按钮向右偏移过多。主要与原有项目中的一些自定义导航返回键不统一。

之前项目已经对iOS11后导航栏的变化做过处理

iOS11以下通过UIBarButtonSystemItemFixedSpace进行处理，可以参考论坛的一篇文章，但是iOS13系统处理不了。
所以寻找新方法解决这个问题，让我们先删除原来项目代码，大刀阔斧的干，要有豁出去的精神。

因为是使用系统导航栏，况且项目很大，不容易去修改整个结构，遂就对系统导航进行修改

网上参考，在寻找一些解决方案。觉得这篇最合适 iOS11 导航栏按钮位置问题的解决——新，简洁流畅无冗余，结合自己项目做一些修改。最主要同时解决iOS13导航栏返回键偏移的问题。
使用layoutMargins这个属性

遍历图层大致可以看到时这样的结构

1	<_UINavigationBarContentView: 0x7fc141607250; frame = (0 0; 414 44); layer = <CALayer: 0x608000038cc0>>

这个UINavigationBarContentView平铺在导航栏中作为iOS11的各个按钮的父视图,该视图的所有的子视图都会有一个layoutMargins被占用,也就是系统调整的占位,我们只要把这个置空就行了.那样的话该视图下的所有的子视图的空间就会变成我们想要的那样,当然为了保险起见,该视图的父视图也就是bar的layoutMargins也置空,这样整个bar就会跟一个普通视图一样了左右的占位约束就不存在了

可以过代码处理

@implementation UINavigationBar (FixSpace)
+(void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        [self swizzleInstanceMethodWithOriginSel:@selector(layoutSubviews)
                                     swizzledSel:@selector(vst_layoutSubviews)];
    });
}

-(void)vst_layoutSubviews{
    [self vst_layoutSubviews];

    if (deviceVersion >= 11) {
        self.layoutMargins = UIEdgeInsetsZero;
        for (UIView *subview in self.subviews) {
            if ([NSStringFromClass(subview.class) containsString:@"ContentView"]) {
                subview.layoutMargins = UIEdgeInsetsZero;//可修正iOS11之后的偏移
            }
        }
    }
}
@end

最终代码

#import <UIKit/UIKit.h>

@interface UINavigationConfig : NSObject

@property (nonatomic, assign) CGFloat vst_defaultFixSpace; // item距离两端的间距,默认为0
@property (nonatomic, assign) BOOL vst_disableFixSpace;    // 是否禁止使用修正,默认为NO

+ (instancetype)shared;
- (instancetype)init NS_UNAVAILABLE;
+ (instancetype)new NS_UNAVAILABLE;

- (CGFloat)vst_systemSpace;

@end

@interface UINavigationItem (VSTFixSpace)

@end

@interface NSObject (VSTFixSpace)

@end

#import "UINavigationVSTFixSpace.h"
#import <objc/runtime.h>

void vst_swizzle(Class oldClass, NSString *oldSelector, Class newClass) {
    NSString *newSelector = [NSString stringWithFormat:@"vst_%@", oldSelector];
    Method old = class_getInstanceMethod(oldClass, NSSelectorFromString(oldSelector));
    Method new = class_getInstanceMethod(newClass, NSSelectorFromString(newSelector));
    method_exchangeImplementations(old, new);
}

@implementation UINavigationConfig

+ (instancetype)shared {
    static UINavigationConfig *config;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        config = [[self alloc] init];
    });
    return config;
}

-(instancetype)init {
    if (self = [super init]) {
        self.vst_defaultFixSpace = 0;
        self.vst_disableFixSpace = NO;
    }
    return self;
}

- (CGFloat)vst_systemSpace {
    return MIN([UIScreen mainScreen].bounds.size.width, [UIScreen mainScreen].bounds.size.height) > 375 ? 20 : 16;
}

@end

@implementation UINavigationItem (VSTFixSpace)

+(void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        if (@available(iOS 11.0, *)) {} else {
            NSArray <NSString *>*oriSels = @[@"setLeftBarButtonItem:",
                                             @"setLeftBarButtonItem:animated:",
                                             @"setLeftBarButtonItems:",
                                             @"setLeftBarButtonItems:animated:",
                                             @"setRightBarButtonItem:",
                                             @"setRightBarButtonItem:animated:",
                                             @"setRightBarButtonItems:",
                                             @"setRightBarButtonItems:animated:"];
            
            [oriSels enumerateObjectsUsingBlock:^(NSString * _Nonnull oriSel, NSUInteger idx, BOOL * _Nonnull stop) {
                vst_swizzle(self, oriSel, self);
            }];
        }
    });
}

-(void)vst_setLeftBarButtonItem:(UIBarButtonItem *)leftBarButtonItem {
    [self setLeftBarButtonItem:leftBarButtonItem animated:NO];
}

-(void)vst_setLeftBarButtonItem:(UIBarButtonItem *)leftBarButtonItem animated:(BOOL)animated {
    if (!UINavigationConfig.shared.vst_disableFixSpace && leftBarButtonItem) {// 存在按钮且需要调节
        [self setLeftBarButtonItems:@[leftBarButtonItem] animated:animated];
    } else {// 不存在按钮,或者不需要调节
        [self vst_setLeftBarButtonItem:leftBarButtonItem animated:animated];
    }
}


-(void)vst_setLeftBarButtonItems:(NSArray<UIBarButtonItem *> *)leftBarButtonItems {
    [self setLeftBarButtonItems:leftBarButtonItems animated:NO];
}

-(void)vst_setLeftBarButtonItems:(NSArray<UIBarButtonItem *> *)leftBarButtonItems animated:(BOOL)animated {
    if (!UINavigationConfig.shared.vst_disableFixSpace && leftBarButtonItems.count) {// 存在按钮且需要调节
        UIBarButtonItem *firstItem = leftBarButtonItems.firstObject;
        CGFloat width = UINavigationConfig.shared.vst_defaultFixSpace - UINavigationConfig.shared.vst_systemSpace;
        if (firstItem.width == width) {// 已经存在space
            [self vst_setLeftBarButtonItems:leftBarButtonItems animated:animated];
        } else {
            NSMutableArray *items = [NSMutableArray arrayWithArray:leftBarButtonItems];
            [items insertObject:[self fixedSpaceWithWidth:width] atIndex:0];
            [self vst_setLeftBarButtonItems:items animated:animated];
        }
    } else {// 不存在按钮,或者不需要调节
        [self vst_setLeftBarButtonItems:leftBarButtonItems animated:animated];
    }
}

-(void)vst_setRightBarButtonItem:(UIBarButtonItem *)rightBarButtonItem{
    [self setRightBarButtonItem:rightBarButtonItem animated:NO];
}

- (void)vst_setRightBarButtonItem:(UIBarButtonItem *)rightBarButtonItem animated:(BOOL)animated {
    if (![UINavigationConfig shared].vst_disableFixSpace && rightBarButtonItem) {// 存在按钮且需要调节
        [self setRightBarButtonItems:@[rightBarButtonItem] animated:animated];
    } else {// 不存在按钮,或者不需要调节
        [self vst_setRightBarButtonItem:rightBarButtonItem animated:animated];
    }
}

- (void)vst_setRightBarButtonItems:(NSArray<UIBarButtonItem *> *)rightBarButtonItems{
    [self setRightBarButtonItems:rightBarButtonItems animated:NO];
}

- (void)vst_setRightBarButtonItems:(NSArray<UIBarButtonItem *> *)rightBarButtonItems animated:(BOOL)animated {
    if (!UINavigationConfig.shared.vst_disableFixSpace && rightBarButtonItems.count) {// 存在按钮且需要调节
        UIBarButtonItem *firstItem = rightBarButtonItems.firstObject;
        CGFloat width = UINavigationConfig.shared.vst_defaultFixSpace - UINavigationConfig.shared.vst_systemSpace;
        if (firstItem.width == width) {// 已经存在space
            [self vst_setRightBarButtonItems:rightBarButtonItems animated:animated];
        } else {
            NSMutableArray *items = [NSMutableArray arrayWithArray:rightBarButtonItems];
            [items insertObject:[self fixedSpaceWithWidth:width] atIndex:0];
            [self vst_setRightBarButtonItems:items animated:animated];
        }
    } else {// 不存在按钮,或者不需要调节
        [self vst_setRightBarButtonItems:rightBarButtonItems animated:animated];
    }
}

- (UIBarButtonItem *)fixedSpaceWithWidth:(CGFloat)width {
    UIBarButtonItem *fixedSpace = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace target:nil action:nil];
    fixedSpace.width = width;
    return fixedSpace;
}

@end

@implementation NSObject (VSTFixSpace)

+ (void)load {
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        if (@available(iOS 13.0, *)) {
            NSDictionary <NSString *, NSString *>*oriSels = @{@"_UINavigationBarContentView": @"layoutSubviews",
                                                              @"_UINavigationBarContentViewLayout": @"_updateMarginConstraints"};
            [oriSels enumerateKeysAndObjectsUsingBlock:^(NSString * _Nonnull cls, NSString * _Nonnull oriSel, BOOL * _Nonnull stop) {
                vst_swizzle(NSClassFromString(cls), oriSel, NSObject.class);
            }];
        }
    });
}

- (void)vst_layoutSubviews {
    [self vst_layoutSubviews];
    if (UINavigationConfig.shared.vst_disableFixSpace) return;
    if (![self isMemberOfClass:NSClassFromString(@"_UINavigationBarContentView")]) return;
    id layout = [self valueForKey:@"_layout"];
    if (!layout) return;
    SEL selector = NSSelectorFromString(@"_updateMarginConstraints");
    IMP imp = [layout methodForSelector:selector];
    void (*func)(id, SEL) = (void *)imp;
    func(layout, selector);
}

- (void)vst__updateMarginConstraints {
    [self vst__updateMarginConstraints];
    if (UINavigationConfig.shared.vst_disableFixSpace) return;
    if (![self isMemberOfClass:NSClassFromString(@"_UINavigationBarContentViewLayout")]) return;
    [self vst_adjustLeadingBarConstraints];
    [self vst_adjustTrailingBarConstraints];
}

- (void)vst_adjustLeadingBarConstraints {
    if (UINavigationConfig.shared.vst_disableFixSpace) return;
    NSArray<NSLayoutConstraint *> *leadingBarConstraints = [self valueForKey:@"_leadingBarConstraints"];
    if (!leadingBarConstraints) return;
    CGFloat constant = UINavigationConfig.shared.vst_defaultFixSpace - UINavigationConfig.shared.vst_systemSpace;
    for (NSLayoutConstraint *constraint in leadingBarConstraints) {
        if (constraint.firstAttribute == NSLayoutAttributeLeading &&
            constraint.secondAttribute == NSLayoutAttributeLeading) {
            constraint.constant = constant;
        }
    }
}

- (void)vst_adjustTrailingBarConstraints {
    if (UINavigationConfig.shared.vst_disableFixSpace) return;
    NSArray<NSLayoutConstraint *> *trailingBarConstraints = [self valueForKey:@"_trailingBarConstraints"];
    if (!trailingBarConstraints) return;
    CGFloat constant = UINavigationConfig.shared.vst_systemSpace - UINavigationConfig.shared.vst_defaultFixSpace;
    for (NSLayoutConstraint *constraint in trailingBarConstraints) {
        if (constraint.firstAttribute == NSLayoutAttributeTrailing &&
            constraint.secondAttribute == NSLayoutAttributeTrailing) {
            constraint.constant = constant;
        }
    }
}

@end

原文demo地址