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iPhone有一个回退按钮在所有的导航条上.这是一个简单的没有文字箭头.

在一开始写项目的时候,就要做好一个准备,导航栏是自定义还是使用系统的,后期有什么改动,有什么比较特殊的需求、当然这些在更改需求的同时,很多东西都已经被改得面目全非了。

完全自定义导航栏,在实际开发中,并不能满足特殊需求,因此更多情况下,还是需要配合系统导航栏自定义,从而达到我们想要的效果。当我们自定义返回按钮之后,就会出现系统的右滑Pop功能就失效了,这是其中的一个小问题,下面就跟大家分享一下我所了解到的:

实现一个自定义按钮是简单的.类似这个设置controller 的navigationItem一个leftBarButtonItem.

- (void)viewDidLoad
{
  self.navigationItem.leftBarButtonItem = [self backButton];
}

- (UIBarButtonItem *)backButton
{
  UIImage *image = [UIImage imageNamed:@"back_button"];
  CGRect buttonFrame = CGRectMake(0, 0, image.size.width, image.size.height);

  UIButton *button = [[UIButton alloc] initWithFrame:buttonFrame];
  [button addTarget:self action:@selector(backButtonPressed) forControlEvents:UIControlEventTouchUpInside];
  [button setImage:[UIImage imageNamed:normalImage] forState:UIControlStateNormal];

  UIBarButtonItem *item; = [[UIBarButtonItem alloc] initWithCustomView:button];

  return item;
}

但是这样在iOS7上 pop手势交互就不好使了.我发现了一个轻松解决的办法.通过我的beta测试者,我收到了很多关于pop手势的崩溃日志.我发现在栈中推入一个controller后,快速向左平滑,将会引起崩溃.换句话说,如果用户在推入还在进行的时候立即去点击返回.那么导航控制器就秀逗了.我在调试日志里面发现这些:

nested pop animation can result in corrupted navigation bar

经过几个小时的奋斗和尝试,我发现可以缓解这个错误:设置手势的delegate为这个导航控制器就像Stuart Hall在他的帖子说的那样,分配了一个手势交互行为的委托在自定义按钮显示的时候.然后,当用户快速点击退出的时候,控制器因为手势发送了一个消息在本身已经被销毁的时候.我的解决方案是简单的让NavigationController自己成为响应的接受者.最好用一个UINavigationController的子类.

@interface CBNavigationController : UINavigationController <UIGestureRecognizerDelegate>
@end

@implementation CBNavigationController

- (void)viewDidLoad
{
  __weak CBNavigationController *weakSelf = self;

  if ([self respondsToSelector:@selector(interactivePopGestureRecognizer)])
  {
    self.interactivePopGestureRecognizer.delegate = weakSelf;
  }
}

@end

在转场/过渡的时候禁用 interactivePopGestureRecognizer当用户在转场的时候触发一个后退手势,则各种事件又凑一块了.导航栈内又成了混乱的.我的解决办法是,转场效果的过程中禁用手势识别,当新的视图控制器加载完成后再启用.再次建议使用UINavigationController的子类操作.

@interface CBNavigationController : UINavigationController <UINavigationControllerDelegate, UIGestureRecognizerDelegate>
@end

@implementation CBNavigationController

- (void)viewDidLoad
{
  __weak CBNavigationController *weakSelf = self;

  if ([self respondsToSelector:@selector(interactivePopGestureRecognizer)])
  {
    self.interactivePopGestureRecognizer.delegate = weakSelf;
    self.delegate = weakSelf;
  }
}

// Hijack the push method to disable the gesture

- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
  if ([self respondsToSelector:@selector(interactivePopGestureRecognizer)])
    self.interactivePopGestureRecognizer.enabled = NO;

  [super pushViewController:viewController animated:animated];
}

#pragma mark UINavigationControllerDelegate

- (void)navigationController:(UINavigationController *)navigationController
       didShowViewController:(UIViewController *)viewController
                    animated:(BOOL)animate
{
  // Enable the gesture again once the new controller is shown

  if ([self respondsToSelector:@selector(interactivePopGestureRecognizer)])
    self.interactivePopGestureRecognizer.enabled = YES;
}


@end

2015-07-21 更新 解决左滑手势冲突和不灵敏的问题

-(UIViewController *)popViewControllerAnimated:(BOOL)animated {

    return [super popViewControllerAnimated:YES];
}

#pragma mark UINavigationControllerDelegate
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {
    if ([self.childViewControllers count] == 1) {
        return NO;
    }
    return YES;
}

// 我们差不多能猜到是因为手势冲突导致的,那我们就先让 ViewController 同时接受多个手势吧。
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}
//运行试一试,两个问题同时解决,不过又发现了新问题,手指在滑动的时候,被 pop 的 ViewController 中的 UIScrollView 会跟着一起滚动,这个效果看起来就很怪(知乎日报现在就是这样的效果),而且也不是原始的滑动返回应有的效果,那么就让我们继续用代码来解决吧
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return [gestureRecognizer isKindOfClass:UIScreenEdgePanGestureRecognizer.class];
}

-(UIViewController *)popViewControllerAnimated:(BOOL)animated {

    return [super popViewControllerAnimated:YES];
}

#pragma mark UINavigationControllerDelegate
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {
    if ([self.childViewControllers count] == 1) {
        return NO;
    }
    return YES;
}

// 我们差不多能猜到是因为手势冲突导致的,那我们就先让 ViewController 同时接受多个手势吧。
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}
//运行试一试,两个问题同时解决,不过又发现了新问题,手指在滑动的时候,被 pop 的 ViewController 中的 UIScrollView 会跟着一起滚动,这个效果看起来就很怪(知乎日报现在就是这样的效果),而且也不是原始的滑动返回应有的效果,那么就让我们继续用代码来解决吧
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldBeRequiredToFailByGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return [gestureRecognizer isKindOfClass:UIScreenEdgePanGestureRecognizer.class];
}

在这里还是要感谢万能的Google!

文/煜寒了(简书作者)
原文链接:http://www.jianshu.com/p/349636eb3fca


本文出处程序员头条:http://www.iswifting.com/2016/03/16/ios-self-navigation/
转载请在开头注明本文出处。

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