iOS navigationBar.hidden和navigationBarHidden调用关系

背景

启动页是搞了一个UIWindow，在window上搞了一个UINavigationController

UINavigationController *nav = [[UINavigationController alloc] init];
window.rootViewController = nav;

启动页先执行，启动页下面的VC后执行，但是发现启动页上突然多了一个导航条，导航条已经提前通过navigationController.navigationBarHidden = YES;隐藏了；

原因是因为在执行后面程序的时候，有个地方搞了一个runtime，里面将当前所有的UINavigationController获取了一遍，然后navigationController.navigationBarHidden = NO;

解决办法：

直接设置

navigationController.navigationBar.hidden = YES;

具体原因

设置navigationController.navigationBar.hidden = YES;后，再设置
navigationController.navigationBarHidden = NO就不起作用了

流程分析

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    self.navigationController.navigationBar.backgroundColor = [UIColor redColor];
    self.navigationController.navigationBar.hidden = YES;
    // Do any additional setup after loading the view.
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(clickTap:)];
    [self.view addGestureRecognizer:tap];
    
    [self.navigationController addObserver:self forKeyPath:@"navigationBar.hidden" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];
    [self.navigationController addObserver:self forKeyPath:@"navigationBarHidden" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];
}

- (void)clickTap:(UITapGestureRecognizer *)sender {
    self.navigationController.navigationBarHidden = NO;
    NSLog(@"%d --- %d",self.navigationController.navigationBar.hidden, self.navigationController.navigationBarHidden);
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
    NSLog(@"keyPath --- %@ --- %@",keyPath,change);
}

为了研究navigationBar.hidden和navigationBarHidden的关系，对navigationController添加KVO监听。

[self.navigationController addObserver:self forKeyPath:@"navigationBar.hidden" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];
[self.navigationController addObserver:self forKeyPath:@"navigationBarHidden" options:NSKeyValueObservingOptionOld|NSKeyValueObservingOptionNew context:nil];

当self.navigationController.navigationBar.hidden = YES
点击屏幕触发
self.navigationController.navigationBarHidden = NO;

触发KVO
navigationBarHidden

keyPath --- navigationBarHidden --- {
kind = 1;
new = 0;
old = 0;
}

最终

self.navigationController.navigationBar.hidden == 1
self.navigationController.navigationBarHidden == 0

导航条没有出现

当self.navigationController.navigationBar.hidden = YES
点击屏幕触发
self.navigationController.navigationBarHidden = YES;

触发KVO
navigationBar.hidden
navigationBarHidden

keyPath --- navigationBar.hidden --- {
kind = 1;
new = 1;
old = 1;
}

keyPath --- navigationBarHidden --- {
kind = 1;
new = 1;
old = 0;
}

最终

self.navigationController.navigationBar.hidden == 1
self.navigationController.navigationBarHidden == 1

导航条没有出现

当self.navigationController.navigationBar.hidden = NO
点击屏幕触发
self.navigationController.navigationBarHidden = YES;

触发KVO
navigationBar.hidden
navigationBarHidden

keyPath --- navigationBar.hidden --- {
kind = 1;
new = 1;
old = 0;
}

keyPath --- navigationBarHidden --- {
kind = 1;
new = 1;
old = 0;
}

最终

self.navigationController.navigationBar.hidden == 1
self.navigationController.navigationBarHidden == 1

导航条初始为显示，点击屏幕后隐藏

当self.navigationController.navigationBar.hidden = NO
点击屏幕触发
self.navigationController.navigationBarHidden = NO;

触发KVO
navigationBarHidden

keyPath --- navigationBarHidden --- {
kind = 1;
new = 0;
old = 0;

}

最终

self.navigationController.navigationBar.hidden == 1
self.navigationController.navigationBarHidden == 1

导航条初始为显示，点击屏幕为显示

总结

当
navigationController.navigationBar.hidden =YES的时候，调用
self.navigationController.navigationBarHidden =NO/YES导航条始终是隐藏的；

当
navigationController.navigationBar.hidden =NO的时候，调用
self.navigationController.navigationBarHidden =YES是通过调用navigationController.navigationBar.hidden=YES达到修改导航条隐藏的目的；