前言：
维护别人写的代码，增加的新需求，所有界面都要添加返回的手势，当我看到上个大师写的控制器代码，无话可说... 本身没有公共类，添加实在是特别费劲，网上也看了很多帖子，都说用Runtime 比较容易，找了篇写不的错的，给大家分享一下。
正文：
#import "UINavigationController+ZWPanBack.h"
#import <objc/runtime.h>
@interface ZWFullScreenPopGestureRecognizerDelegate: NSObject <UIGestureRecognizerDelegate>
@property (nonatomic, weak) UINavigationController *navigationController;
@end
@implementation ZWFullScreenPopGestureRecognizerDelegate
//代理方法的实现
//在这里做手势识别判断
- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)gestureRecognizer {
//判断是否是根控制器，如果是直接取消手势
if (self.navigationController.viewControllers.count <= 1) {
return NO;
}
//如果正在转场动画，取消手势
if ([[self.navigationController valueForKey:@"_isTransitioning"] boolValue]) {
return NO;
}
//判断手势方向，如果是从左往右拖动才开启手势
CGPoint translation = [gestureRecognizer translationInView:gestureRecognizer.view];
if (translation.x <= 0) {
return NO;
}
return YES;
}
@end
@implementation UINavigationController (ZWPanBack)
//系统方法，加载时调用
+ (void)load {
Method originalMethod = class_getInstanceMethod([self class], @selector(pushViewController:animated:));
Method swizzledMethod = class_getInstanceMethod([self class], @selector(zw_pushViewController:animated:));
//系统方法和自定义方法交换
method_exchangeImplementations(originalMethod, swizzledMethod);
}
//自定义方法和系统方法做交换
- (void)zw_pushViewController:(UIViewController *)viewController animated:(BOOL)animated {
//寻找交互手势，如果交互手势没有被添加就添加交互手势。
if (![self.interactivePopGestureRecognizer.view.gestureRecognizers containsObject:self.zw_popGestureRecognizer]) {
[self.interactivePopGestureRecognizer.view addGestureRecognizer:self.zw_popGestureRecognizer];
NSArray *targets = [self.interactivePopGestureRecognizer valueForKey:@"targets"];
id internalTarget = [targets.firstObject valueForKey:@"target"];
SEL internalAction = NSSelectorFromString(@"handleNavigationTransition:");
self.zw_popGestureRecognizer.delegate = [self zw_fullScreenPopGestureRecognizerDelegate];
[self.zw_popGestureRecognizer addTarget:internalTarget action:internalAction];
// 禁用系统的交互手势
self.interactivePopGestureRecognizer.enabled = NO;
}
if (![self.viewControllers containsObject:viewController]) {
[self zw_pushViewController:viewController animated:animated];
}
}
//自定义的交互手势
- (ZWFullScreenPopGestureRecognizerDelegate *)zw_fullScreenPopGestureRecognizerDelegate {
//通过关联对象，直接将属性delegate添加到navigationController中
ZWFullScreenPopGestureRecognizerDelegate *delegate = objc_getAssociatedObject(self, _cmd);
if (!delegate) {
delegate = [[ZWFullScreenPopGestureRecognizerDelegate alloc] init];
delegate.navigationController = self;
objc_setAssociatedObject(self, _cmd, delegate, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
return delegate;
}
//通过关联对象添加属性 zw_popGestureRecognizer
- (UIPanGestureRecognizer *)zw_popGestureRecognizer {
UIPanGestureRecognizer *panGestureRecognizer = objc_getAssociatedObject(self, _cmd);
if (panGestureRecognizer == nil) {
panGestureRecognizer = [[UIPanGestureRecognizer alloc] init];
panGestureRecognizer.maximumNumberOfTouches = 1;
objc_setAssociatedObject(self, _cmd, panGestureRecognizer, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
return panGestureRecognizer;
} 当然这个写的是用Push跳转，使用pop道理其实也是一样的。到这里其实手势已经可以正常使用了.
但是在A界面需要隐藏UINavigationController，B界面需要显示的时候，你会发现当你在B界面手势触发之后，A界面的viewWillAppear会直接调用。这时你写的self.navigationController.navigationBarHidden = YES ;就会触发，造成滑动时UINavigationController隐藏了。看图
这时 ，我们就不能使用self.navigationController.navigationBarHidden = YES;
这是因为导航条是属于导航控制器的而并不是导航控制器的每个子VC都有一个属于自己的导航条。
而我实际想要的效果却是在手势滑动返回A界面途中导航条随着B界面一起偏移，如图
那就是在A的viewWillAppear方法中不要使用self.navigationController.navigationBar.hidden = YES;这个方法而应该使用[self.navigationControllersetNavigationBarHidden:YESanimated:YES]这个方法，相应的在B的viewWillAppear方法中也不要使用self.navigationController.navigationBar.hidden = NO这个方法而应该使用[self.navigationControllersetNavigationBarHidden:NOanimated:YES]这个方法。注意：animated这个参数一定要设置为YES，因为使用[self.navigationController setNavigationBarHidden:YES animated:YES]之所以能达到上图这种我们想要的效果就是因为有这个动画，而这个动画效果就是导航条随着导航控制器的子VC的界面一起偏移。
