一、思维导图
二、当控制器一导航是隐藏的，控制器二导航是显示的，控制器一push控制器二，左滑手势返回时会出现黑框，
解决办法是：
1.在控制器一将要出现的方法设置为：[self.navigationController setNavigationBarHidden:YES animated:YES];
2.在控制器二将要出现的方法设置为：[self.navigationController setNavigationBarHidden:YES animated:YES];
三、刚开始导航是隐藏的，滚动一段距离后，显示导航。
解决思路是：
1.自定义一个和导航一样高的view,然后加到TableView的headView上。
2.当滑动的时候，通过偏移位置/滑动固定高度来设置view的alpha（透明度）。
3.当滑动到固定的高度后，view的alpha为1，那个view就会完全显示。
4.同时当没有滑动或没有滑动到固定的高度的时候，view不会显示或不能完全显示。
六.上代码。
#import "BSJMainNavViewController.h"
@interface BSJMainNavViewController ()<UIGestureRecognizerDelegate>
@end
@implementation BSJMainNavViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
UINavigationBar *navBar = [UINavigationBar appearance];
NSMutableDictionary *navInfo = [NSMutableDictionary dictionary];
navInfo[NSFontAttributeName] = [UIFont systemFontOfSize:16];
[navBar setBackgroundImage:[UIImage imageNamed:@"navigationbarBackgroundWhite"] forBarMetrics:UIBarMetricsDefault];
[navBar setTitleTextAttributes:navInfo];
//当重写导航的push方法时，导航的手势就失效了，可以这样写
self.interactivePopGestureRecognizer.delegate = self;
}
- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated{
if (self.childViewControllers.count >=1) {
UIButton *leftButton = [[UIButton alloc] init];
[leftButton setImage:[UIImage imageNamed:@"navigationButtonReturn"] forState:UIControlStateNormal];
[leftButton setImage:[UIImage imageNamed:@"navigationButtonReturnClick"] forState:UIControlStateHighlighted];
[leftButton setTitle:@"返回" forState:UIControlStateNormal];
[leftButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[leftButton setTitleColor:[UIColor redColor] forState:UIControlStateHighlighted];
[leftButton sizeToFit];
[leftButton addTarget:self action:@selector(backItemClick:) forControlEvents:UIControlEventTouchUpInside];
//按钮中有个imageView 和Label
//设置这个是设置imageView的内边距，如果设置它会imageView向内缩进
// leftButton setImageEdgeInsets:<#(UIEdgeInsets)#>
//设置这个是设置title的内边距，如果设置它会title向内缩进
// leftButton setTitleEdgeInsets:<#(UIEdgeInsets)#>
//设置整个按钮的内边距
[leftButton setContentEdgeInsets:UIEdgeInsetsMake(0,-20, 0, 0)];
viewController.hidesBottomBarWhenPushed = YES;
viewController.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:leftButton];
}
//最后再调这段代码，上面的代码是先改导航的左边按钮
[super pushViewController:viewController animated:animated];
}
#pragma mark --- delegate
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer{
//因为如果不设置>1，在主页面这个手势也会起作用，这样的话就不能push了就有bug
return self.childViewControllers.count > 1;
}
#pragma mark --- response methods
- (void)backItemClick:(UIButton *)sender{
[self popViewControllerAnimated:YES];
}
@end