• iOS左滑手势失效


    iOS7之后,苹果优化了一个小功能,就是对于UINavagationController堆栈里的UIViewController,只要轻轻在视图控制器的左边缘右滑一下,该视图控制器就会pop出栈(前提当然是对于非根视图控制器而言)。实现方法很简单,一句话搞定:

    self.navigationController.interactivePopGestureRecognizer.enabled = YES;
    

    事实上对于一个视图控制器而言,该属性的默认值即为YES,因此不设置也能实现右滑pop的功能。

    然而这个功能很有局限性,因为它不允许当前视图控制器自定义了leftBarButtonItem,一旦自定义,右滑功能就会失效。这里有一个方法:

    self.navigationController.interactivePopGestureRecognizer.delegate = nil;
    

    设置代理为nil之后即便自定义了leftBarButtonItem也可以右滑pop。

    或者,把手势的许可打开 也可:

    self.navigationController.interactivePopGestureRecognizer.enabled = YES ;
    

    事实上如果自定义了leftBarButtonItem,常用的做法是重新设置代理:

    - (void)viewDidAppear:(BOOL)animated{
         self.navigationController.interactivePopGestureRecognizer.delegate = (id)self;
    }
    

    然后实现手势协议即可:

    #pragma mark - UIGestureRecognizerDelegate
    - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer*)gestureRecognizer{
        //判断是否为rootViewController
        if (self.navigationController && self.navigationController.viewControllers.count == 1) {
            return NO;
        }
        return YES;
    }
    

    不过呢,如果我们自定义的返回button只是文字或图片的话,这样设置就可以,不会失效

        UIBarButtonItem *item = [[UIBarButtonItem alloc]init];
        item.title = @"";
        self.navigationItem.backBarButtonItem = item;
    

    如果是要自定义view的当作button的话,就要用leftBarButtonItem设置,并用上述讲的防止手势失效的方案.

    有朋友提出以上方式在多次滑动之后会导致界面假死,这里再给出一种解决方案:

    在所有除一级页面之外的页面的viewDidAppear和viewWillDisappear中加入以下代码:

    - (void)viewWillDisappear:(BOOL)animated {
        [super viewWillDisappear:animated];
        //代理置空,否则会闪退
        if ([self.navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {
            self.navigationController.interactivePopGestureRecognizer.delegate = nil;
        }
    }
    
    - (void)viewDidAppear:(BOOL)animated {  
        [super viewDidAppear:animated];  
        //开启iOS7的滑动返回效果  
        if ([self.navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {  
            //只有在二级页面生效  
            if ([self.navigationController.viewControllers count] == 2) {  
                self.navigationController.interactivePopGestureRecognizer.delegate = self;  
            }  
        }  
    } 
    

    在UINavigationController的delegate中实现以下方法:

    - (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated {  
    //开启滑动手势
        if ([navigationController respondsToSelector:@selector(interactivePopGestureRecognizer)]) {
            navigationController.interactivePopGestureRecognizer.enabled = YES;
        }
    }  
    

    在pushviewcontroller之前加入以下代码:

    //在切换界面的过程中禁止滑动手势,避免界面卡死
    if ([_currentNav respondsToSelector:@selector(interactivePopGestureRecognizer)]) {
        _currentNav.interactivePopGestureRecognizer.enabled = NO;
    }
    [_currentNav pushViewController:viewController animated:YES];
    

    即可在实现滑动返回的同时,避免界面卡死的问题。

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  • 原文地址:https://www.cnblogs.com/dongliu/p/6856398.html
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