导航之偷梁换柱-pop到指定控制器

这里要达到的效果是A.Nav - push -> B B - push -> C C-pop- >A
以及 如果C不popA 则 能 C -push - >B B和C相互都能push出来 最后他们pop 都能pop 到A 的效果.而且系统自带的手势也能滑到A控制器.

通常情况下，我们的控制器之间的跳转是这样的：

A -present-> B         B -dismiss-> A```
相互之间都是有层级关系和顺序的

首先导航控制器push和pop 是栈先进后出原理
A-push->B B-push->C 之后 控制器的子控制器数组为(A, B, C)
C- pop->A 则要将数组中的B移除, 达到想要的效果

直接上代码
AppDelegate.m中

import "AppDelegate.h"

import "ViewController.h"

import "qqViewController.h"

@interface AppDelegate ()

@end

@implementation AppDelegate

• (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
  self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
  self.window.backgroundColor = [UIColor whiteColor];
  [self.window makeKeyAndVisible];

  qqViewController *view = [qqViewController new];
  UINavigationController *navi = [[UINavigationController alloc] initWithRootViewController:view];
  self.window.rootViewController = navi;
  return YES;
  }

A控制器qqViewController.m中

import "qqViewController.h"

import "hhViewController.h"

@interface qqViewController ()

@end

@implementation qqViewController

• (void)viewDidLoad {
  [super viewDidLoad];
  self.navigationItem.title = @"首页";
  self.view.backgroundColor = [UIColor blackColor];
  [self.view addSubview:[self createButton]];
  }
• (UIButton *)createButton {
  UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
  button.backgroundColor = [UIColor redColor];
  button.frame = CGRectMake(140, 100, 100, 30);
  [button setTitle:@"点击" forState:UIControlStateNormal];
  [button addTarget:self action:@selector(push) forControlEvents:UIControlEventTouchUpInside];
  return button;
  }
• (void)push {
  hhViewController *v = [hhViewController new];
  [self.navigationController pushViewController:v animated:YES];
  }

B控制器hhViewController.m中

import "hhViewController.h"

import "ccViewController.h"

@interface hhViewController ()
@end

@implementation hhViewController

• (void)viewWillAppear:(BOOL)animated {
  [self.navigationController setViewControllers:@[self.navigationController.childViewControllers.firstObject, self]];
  // 在B控制器将要出现的时候 偷梁换柱 将导航控制器的ViewControllers中的元素修改掉 达到C-pop 回去的是A控制器
  }
• (void)viewDidLoad {
  [super viewDidLoad];
  self.navigationItem.title = @"第二";
  self.view.backgroundColor = [UIColor redColor];
  [self.view addSubview:[self createButton]];
  }
• (void)push {
  ccViewController *v = [ccViewController new];
  v.view.backgroundColor = [UIColor grayColor];
  [self.navigationController pushViewController:v animated:YES];
  }
• (UIButton *)createButton {
  UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
  button.backgroundColor = [UIColor greenColor];
  button.frame = CGRectMake(140, 200, 100, 30);
  [button setTitle:@"点击" forState:UIControlStateNormal];
  [button addTarget:self action:@selector(push) forControlEvents:UIControlEventTouchUpInside];
  return button;
  }

C控制器ccViewController.m中

import "ccViewController.h"

import "hhViewController.h"

@interface ccViewController ()

@end

@implementation ccViewController

• (void)viewWillAppear:(BOOL)animated {
  [self.navigationController setViewControllers:@[self.navigationController.childViewControllers.firstObject, self]];
  // 在C控制器将要出现的时候 偷梁换柱 将导航控制器的ViewControllers中的元素修改掉 达到C-push->B B-pop->A
  }
• (void)viewDidLoad {
  [super viewDidLoad];
  self.navigationItem.title = @"第三";
  [self.view addSubview:[self createButton]];
  }
• (void)push {
  hhViewController *v = [hhViewController new];
  v.view.backgroundColor = [UIColor redColor];
  [self.navigationController pushViewController:v animated:YES];
  }
• (UIButton *)createButton {
  UIButton *button = [UIButton buttonWithType:UIButtonTypeSystem];
  button.backgroundColor = [UIColor greenColor];
  button.frame = CGRectMake(100, 200, 100, 30);
  [button setTitle:@"点击" forState:UIControlStateNormal];
  [button addTarget:self action:@selector(push) forControlEvents:UIControlEventTouchUpInside];
  return button;
  }

看看运行效果吧


![qh_1.gif](http://upload-images.jianshu.io/upload_images/1788484-a951085ecd4413ea.gif?imageMogr2/auto-orient/strip)


![qh_2.gif](http://upload-images.jianshu.io/upload_images/1788484-4fc594dfdbff77ff.gif?imageMogr2/auto-orient/strip)

以下可以选择性适当忽略:
禁止pop后，**< Back**中的**<**会置灰，文字**Back**却不会(可能又是Apple Inc.的小Bug)。解决方法很简单：在vc中调用以下两句代码。 

[self.navigationController setNavigationBarHidden:YES animated:YES];
[self.navigationController setNavigationBarHidden:NO animated:YES];

比如，用户点击backBarButtonItem
时，我提示用户是否继续离开，如果用户选择**OK**则**POP**离开，如果用户选择**NO**则留在本页并执行上面两句，使**

import "NavigationController.h"

@interface NavigationController ()

@end

@implementation NavigationController

• (void)viewDidLoad {
  [super viewDidLoad];

// 如果想把导航系统手势改成全屏滑的时候 则是注释的部分
// // 设置代理
// id target = self.interactivePopGestureRecognizer.delegate;
// // 创建手势
// UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:target action:@selector(handleNavigationTransition:)];
// // 设置pan手势的代理
// pan.delegate = self;
// // 添加手势
// [self.view addGestureRecognizer:pan];
// // 将系统自带的手势覆盖掉
// self.interactivePopGestureRecognizer.enabled = NO;

// 在这里我们还是保留系统自带滑动UIScreenEdgePanGestureRecognizer
// 设置代理
self.interactivePopGestureRecognizer.delegate = self;

}
// 表示的意思是:当前控制器是根控制器,那么就不接收触摸事件,只有当不是根控制器时才需要接收事件.

pragma mark - UIGestureRecognizerDelegate

// 是否触发手势

• (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
  {
  return self.childViewControllers.count > 1;
  }

建好之后 回到AppDelegate.m

import "NavigationController.h"

将NavigationController设置成根视图的导航

在B控制器hhViewController.m中
添加自定义item

在viewDidLoad方法中添加
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(pop)];
方法实现

• (void)pop {
  [self.navigationController popViewControllerAnimated:YES];
  }

在C控制器ccViewController.m中
添加自定义item

在viewDidLoad方法中添加
self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemStop target:self action:@selector(pop)];
方法实现

• (void)pop {
  [self.navigationController popViewControllerAnimated:YES];
  }

可以看效果啦

![qh_3.gif](http://upload-images.jianshu.io/upload_images/1788484-f54b01514fb4bc02.gif?imageMogr2/auto-orient/strip)


代码如果想简化 直接创建基类继承UIViewController的BaseViewController
将相同的代码都放到里面 在创建A\B\C控制器的时候继承BaseViewController，直接调用父类的方法就行.这里就不演示啦.

附上Demo:https://github.com/catcups/pop