1 建立导航控制器 

2.导航控制器添加如下代码

- (void)viewDidLoad {    [super viewDidLoad];      id target = self.interactivePopGestureRecognizer.delegate;   UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:target action:NSSelectorFromString(@"handleNavigationTransition:")];    pan.delegate = self;    [self.view addGestureRecognizer:pan];    self.interactivePopGestureRecognizer.enabled = NO;}- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer{    if (self.childViewControllers.count == 1) {        return NO;    }    return YES;}