ios - 在 iOS 中使用手势导航 UIViewControllers

Question

我在 UINavigationController 中嵌入了几个 View Controller (一些是模态的，一些是推送的)，我使用滑动手势在它们之间导航:

// Gesture recognizers
UISwipeGestureRecognizer *downGesture = [[UISwipeGestureRecognizer alloc]initWithTarget:self action:@selector(dismissButton)];
downGesture.direction = UISwipeGestureRecognizerDirectionDown;
[downGesture setCancelsTouchesInView:NO];
[self.view addGestureRecognizer:downGesture];

这工作正常，但是我希望用户能够物理拖动模态呈现的 View Controller ，例如，向下和离开屏幕，而不是仅仅轻弹和动画完成其余的，或在屏幕上向右拖动并捕捉到上一个 View ，而不是点击后退按钮。

我已经尝试在 View 上使用平移手势来实现它，但当然之前的 View Controller 在它后面不可见，但它需要是可见的。这个效果是如何正确实现的？使用 View Controller 包含？如果是这样，那么在将几个 View Controller 推到堆栈上时它会如何工作？可以在 LetterPress 应用程序中找到我正在谈论的导航类型的示例。

谢谢。

Answer 1

是的，自定义容器 View 是可行的方法(iOS 5 及更高版本)。您基本上是编写自己的自定义容器，使用内置的 childViewControllers 属性来跟踪所有 subview Controller 。您可能希望自己的属性(例如 currentChildIndex)跟踪您当前所在的子 Controller :

@property (nonatomic) NSInteger currentChildIndex;

您的父 Controller 可能应该有一些用于非滑动相关导航的推送和弹出方法，例如:

- (void)pushChildViewController:(UIViewController *)newChildController
{
    // remove any other children that we've popped off, but are still lingering about

    for (NSInteger index = [self.childViewControllers count] - 1; index > self.currentChildIndex; index--)
    {
        UIViewController *childController = self.childViewControllers[index];
        [childController willMoveToParentViewController:nil];
        [childController.view removeFromSuperview];
        [childController removeFromParentViewController];
    }

    // get reference to the current child controller

    UIViewController *currentChildController = self.childViewControllers[self.currentChildIndex];

    // set new child to be off to the right

    CGRect frame = self.containerView.bounds;
    frame.origin.x += frame.size.width;
    newChildController.view.frame = frame;

    // add the new child

    [self addChildViewController:newChildController];
    [self.containerView addSubview:newChildController.view];
    [newChildController didMoveToParentViewController:self];

    [UIView animateWithDuration:0.5
                     animations:^{
                         CGRect frame = self.containerView.bounds;
                         newChildController.view.frame = frame;
                         frame.origin.x -= frame.size.width;
                         currentChildController.view.frame = frame;
                     }];

    self.currentChildIndex++;
}

- (void)popChildViewController
{
    if (self.currentChildIndex == 0)
        return;

    UIViewController *currentChildController = self.childViewControllers[self.currentChildIndex];
    self.currentChildIndex--;
    UIViewController *previousChildController = self.childViewControllers[self.currentChildIndex];

    CGRect onScreenFrame = self.containerView.bounds;

    CGRect offToTheRightFrame = self.containerView.bounds;
    offToTheRightFrame.origin.x += offToTheRightFrame.size.width;

    [UIView animateWithDuration:0.5
                     animations:^{
                         currentChildController.view.frame = offToTheRightFrame;
                         previousChildController.view.frame = onScreenFrame;
                     }];
}

就我个人而言，我为这两种方法定义了一个协议(protocol)，并确保我的父 Controller 配置为符合该协议(protocol):

@protocol ParentControllerDelegate <NSObject>

- (void)pushChildViewController:(UIViewController *)newChildController;
- (void)popChildViewController;

@end

@interface ParentViewController : UIViewController <ParentControllerDelegate>
...
@end

然后，当一个 child 想要插入一个新的 child 时，它可以这样做:

ChildViewController *controller = ... // instantiate and configure your next controller however you want to do that

id<ParentControllerDelegate> parent = (id)self.parentViewController;
NSAssert([parent conformsToProtocol:@protocol(ParentControllerDelegate)], @"Parent must conform to ParentControllerDelegate");

[parent pushChildViewController:controller];

当一个 child 想要弹出自己时，它可以这样做:

id<ParentControllerDelegate> parent = (id)self.parentViewController;
NSAssert([parent conformsToProtocol:@protocol(ParentControllerDelegate)], @"Parent must conform to ParentControllerDelegate");

[parent popChildViewController];

然后父 View Controller 设置了平移手势，以处理用户从一个 subview 平移到另一个 subview :

- (void)handlePan:(UIPanGestureRecognizer *)gesture
{
    static UIView *currentView;
    static UIView *previousView;
    static UIView *nextView;

    if (gesture.state == UIGestureRecognizerStateBegan)
    {
        // identify previous view (if any)

        if (self.currentChildIndex > 0)
        {
            UIViewController *previous = self.childViewControllers[self.currentChildIndex - 1];
            previousView = previous.view;
        }
        else
        {
            previousView = nil;
        }

        // identify next view (if any)

        if (self.currentChildIndex < ([self.childViewControllers count] - 1))
        {
            UIViewController *next = self.childViewControllers[self.currentChildIndex + 1];
            nextView = next.view;
        }
        else
        {
            nextView = nil;
        }

        // identify current view

        UIViewController *current = self.childViewControllers[self.currentChildIndex];
        currentView = current.view;
    }

    // if we're in the middle of a pan, let's adjust the center of the views accordingly

    CGPoint translation = [gesture translationInView:gesture.view.superview];

    previousView.transform = CGAffineTransformMakeTranslation(translation.x, 0.0);
    currentView.transform = CGAffineTransformMakeTranslation(translation.x, 0.0);
    nextView.transform = CGAffineTransformMakeTranslation(translation.x, 0.0);

    // if we're all done, let's animate the completion (or if we didn't move far enough,
    // the reversal) of the pan gesture

    if (gesture.state == UIGestureRecognizerStateEnded ||
        gesture.state == UIGestureRecognizerStateCancelled ||
        gesture.state == UIGestureRecognizerStateFailed)
    {

        CGPoint center = currentView.center;
        CGPoint currentCenter = CGPointMake(center.x + translation.x, center.y);
        CGPoint offRight = CGPointMake(center.x + currentView.frame.size.width, center.y);
        CGPoint offLeft = CGPointMake(center.x - currentView.frame.size.width, center.y);

        CGPoint velocity = [gesture velocityInView:gesture.view.superview];

        if ((translation.x + velocity.x * 0.5) < (-self.containerView.frame.size.width / 2.0) && nextView)
        {
            // if we finished pan to left, reset transforms

            previousView.transform = CGAffineTransformIdentity;
            currentView.transform = CGAffineTransformIdentity;
            nextView.transform = CGAffineTransformIdentity;

            // set the starting point of the animation to pick up from where
            // we had previously transformed the views

            CGPoint nextCenter = CGPointMake(nextView.center.x + translation.x, nextView.center.y);
            currentView.center = currentCenter;
            nextView.center = nextCenter;

            // and animate the moving of the views to their final resting points,
            // adjusting the currentChildIndex appropriately

            [UIView animateWithDuration:0.25
                                  delay:0.0
                                options:UIViewAnimationOptionCurveEaseOut
                             animations:^{
                                 currentView.center = offLeft;
                                 nextView.center = center;
                                 self.currentChildIndex++;
                             }
                             completion:NULL];
        }
        else if ((translation.x + velocity.x * 0.5) > (self.containerView.frame.size.width / 2.0) && previousView)
        {
            // if we finished pan to right, reset transforms

            previousView.transform = CGAffineTransformIdentity;
            currentView.transform = CGAffineTransformIdentity;
            nextView.transform = CGAffineTransformIdentity;

            // set the starting point of the animation to pick up from where
            // we had previously transformed the views

            CGPoint previousCenter = CGPointMake(previousView.center.x + translation.x, previousView.center.y);
            currentView.center = currentCenter;
            previousView.center = previousCenter;

            // and animate the moving of the views to their final resting points,
            // adjusting the currentChildIndex appropriately

            [UIView animateWithDuration:0.25
                                  delay:0.0
                                options:UIViewAnimationOptionCurveEaseOut
                             animations:^{
                                 currentView.center = offRight;
                                 previousView.center = center;
                                 self.currentChildIndex--;
                             }
                             completion:NULL];
        }
        else
        {
            [UIView animateWithDuration:0.25
                                  delay:0.0
                                options:UIViewAnimationOptionCurveEaseInOut
                             animations:^{
                                 previousView.transform = CGAffineTransformIdentity;
                                 currentView.transform = CGAffineTransformIdentity;
                                 nextView.transform = CGAffineTransformIdentity;
                             }
                             completion:NULL];
        }
    }
}

看起来您是在进行上下平移，而不是我上面使用的左右平移，但希望您能理解基本概念。

---

顺便说一句，在 iOS 6 中，您所询问的用户界面(使用手势在 View 之间滑动)可能可以使用内置容器 Controller 更有效地完成，UIPageViewController .只需使用 UIPageViewControllerTransitionStyleScroll 的过渡样式和 UIPageViewControllerNavigationOrientationHorizo​​ntal 的导航方向。不幸的是，iOS 5 只允许页面 curl 过渡，而 Apple 只在 iOS 6 中引入了你想要的滚动过渡，但如果这就是你所需要的，UIPageViewController 可以比我更有效地完成工作'已经在上面列出(您不必执行任何自定义容器调用，无需编写手势识别器等)。

例如，您可以将“页面 View Controller ”拖到 Storyboard上，创建一个UIPageViewController 子类，然后在viewDidLoad 中，您需要配置第一个页面:

UIViewController *firstPage = [self.storyboard instantiateViewControllerWithIdentifier:@"1"]; // use whatever storyboard id your left page uses
self.viewControllerStack = [NSMutableArray arrayWithObject:firstPage];

[self setViewControllers:@[firstPage]
               direction:UIPageViewControllerNavigationDirectionForward
                animated:NO
              completion:NULL];

self.dataSource = self;

然后你需要定义下面的UIPageViewControllerDataSource方法:

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
    if ([viewController isKindOfClass:[LeftViewController class]])
        return [self.storyboard instantiateViewControllerWithIdentifier:@"2"];

    return nil;
}

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
    if ([viewController isKindOfClass:[RightViewController class]])
        return [self.storyboard instantiateViewControllerWithIdentifier:@"1"];

    return nil;
}

您的实现会有所不同(至少是不同的类名和不同的 Storyboard 标识符；我还让页面 View Controller 在用户请求时实例化下一页的 Controller ，因为我没有保留任何强引用对他们来说，当我完成转换到另一个页面时，它们将被释放......你也可以在启动时实例化它们，然后实例化这些 before 和 after 例程显然不会实例化，而是在数组中查找它们)，但希望你明白了。

但关键问题是我没有任何手势代码，没有自定义容器 View Controller 代码等。简单得多。