iphone - 当前的 ChildView Controller

Question

我正在尝试在我的 View Controller 上实现 SwipeGesture。

我目前面临的问题是我无法确定当前显示的 subview Controller 是什么。

swipeGesture 被添加到容器 View Controller 。然后必须判断当前显示的VC在父子关系中是什么，然后向右或向左移动。

Answer 1

如果您在谈论自定义容器 View Controller ，容器 Controller 的工作就是跟踪它。因此，您可能拥有自己的 @property 来跟踪您所处的位置，并在 transitionFromController 滑动时调整它。因此，您可能有一个数字属性，当您向右移动时递增，向左移动时递减。

一般来说(如果您只是想跟踪您传递给 transitionFromViewController 的是哪个“来自” Controller )，有两种方法。 Adding a child controller 中的 list 14-3 暗示了一种方法View Controller 编程指南。

在这种情况下，在 viewDidLoad 中，您为第一个 View Controller 执行 addChildViewController。不过，在这种情况下，此时您不会通过 addChildViewController 加载其他 subview Controller ，而是让执行转换的方法来处理它(如 list 14-3 所示) ).

如果您这样做，您只需获取 [self.childViewControllers lastObject]，这将是您的“当前”子 Controller 。所以，这可能看起来像:

@interface ViewController ()

@property (nonatomic) NSInteger currentIndex;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    UIViewController *initialController = ... // set your initial controller

    [self addChildViewController:initialController];
    initialController.view.frame = self.containerView.bounds;
    [self.containerView addSubview:initialController.view];
    [initialController didMoveToParentViewController:self];

    UISwipeGestureRecognizer *gesture;

    gesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipe:)];
    gesture.direction = UISwipeGestureRecognizerDirectionRight;
    [self.containerView addGestureRecognizer:gesture];

    gesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipe:)];
    gesture.direction = UISwipeGestureRecognizerDirectionLeft;
    [self.containerView addGestureRecognizer:gesture];

}

- (void) handleSwipe:(UISwipeGestureRecognizer *)gesture
{
    if (gesture.direction == UISwipeGestureRecognizerDirectionLeft && self.currentIndex < (kMaxIndex - 1))
    {
        self.currentIndex++;

        UIViewController *newController = ... // set your new controller
        UIViewController *oldController = [self.childViewControllers lastObject];

        [self cycleFromViewController:oldController
                     toViewController:newController
                            direction:gesture.direction];

    }
    else if (gesture.direction == UISwipeGestureRecognizerDirectionRight && self.currentIndex > 0)
    {
        self.currentIndex--;

        UIViewController *newController = ... // set your new controller
        UIViewController *oldController = [self.childViewControllers lastObject];

        [self cycleFromViewController:oldController
                     toViewController:newController
                            direction:gesture.direction];
    }
}

- (void) cycleFromViewController:(UIViewController*) oldController
                toViewController:(UIViewController*) newController
                       direction:(UISwipeGestureRecognizerDirection)direction
{
    [oldController willMoveToParentViewController:nil];
    [self addChildViewController:newController];

    newController.view.frame = oldController.view.frame;

    UIViewAnimationOptions options;

    if (direction == UISwipeGestureRecognizerDirectionRight)
        options = UIViewAnimationOptionTransitionFlipFromLeft;
    else if (direction == UISwipeGestureRecognizerDirectionLeft)
        options = UIViewAnimationOptionTransitionFlipFromRight;

    [self transitionFromViewController:oldController
                      toViewController:newController
                              duration:0.33
                               options:options
                            animations:^{
                                [oldController removeFromParentViewController];
                            }
                            completion:^(BOOL finished) {
                                [newController didMoveToParentViewController:self];
                            }];
}

我看到有人做的另一种模型是通过 viewDidLoad 中的 addChildViewController 加载所有潜在的子 Controller 。我个人不喜欢这种方法，但我知道人们这样做并且效果很好。

但是如果你这样做，你就不能再依赖 childViewControllers 来知道哪个 Controller 是当前 Controller 。在这种情况下，您必须为 currentChildController 定义自己的类属性。所以它可能看起来像:

@interface ViewController ()

@property (nonatomic, strong) UIViewController *currentChildController;
@property (nonatomic) NSInteger currentIndex;

@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self addChildViewController:[self.storyboard instantiateViewControllerWithIdentifier:@"ChildOne"]];
    [self addChildViewController:[self.storyboard instantiateViewControllerWithIdentifier:@"ChildTwo"]];
    [self addChildViewController:[self.storyboard instantiateViewControllerWithIdentifier:@"ChildThree"]];

    self.currentChildController = self.childViewControllers[0];

    self.currentChildController.view.frame = self.containerView.bounds;
    [self.containerView addSubview:self.currentChildController.view];

    for (UIViewController *controller in self.childViewControllers)
        [controller didMoveToParentViewController:self];

    UISwipeGestureRecognizer *gesture;

    gesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipe:)];
    gesture.direction = UISwipeGestureRecognizerDirectionRight;
    [self.containerView addGestureRecognizer:gesture];

    gesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipe:)];
    gesture.direction = UISwipeGestureRecognizerDirectionLeft;
    [self.containerView addGestureRecognizer:gesture];
}

- (void) cycleFromViewController:(UIViewController*) oldController
                toViewController:(UIViewController*) newController
                       direction:(UISwipeGestureRecognizerDirection) direction
{
    self.currentChildController = newController;

    newController.view.frame = oldController.view.frame;

    UIViewAnimationOptions options;

    if (direction == UISwipeGestureRecognizerDirectionRight)
        options = UIViewAnimationOptionTransitionFlipFromLeft;
    else if (direction == UISwipeGestureRecognizerDirectionLeft)
        options = UIViewAnimationOptionTransitionFlipFromRight;

    [self transitionFromViewController:oldController
                      toViewController:newController
                              duration:0.33
                               options:options
                            animations:^{
                            }
                            completion:nil];
}

- (void) handleSwipe:(UISwipeGestureRecognizer *)gesture
{
    if (gesture.direction == UISwipeGestureRecognizerDirectionLeft && self.currentIndex < (kMaxIndex - 1))
    {
        self.currentIndex++;

        UIViewController *oldController = self.currentChildController;
        UIViewController *newController = self.childViewControllers[self.currentIndex];

        [self cycleFromViewController:oldController
                     toViewController:newController
                            direction:gesture.direction];

    }
    else if (gesture.direction == UISwipeGestureRecognizerDirectionRight && self.currentIndex > 0)
    {
        self.currentIndex--;

        UIViewController *oldController = self.currentChildController;
        UIViewController *newController = self.childViewControllers[self.currentIndex];

        [self cycleFromViewController:oldController
                     toViewController:newController
                            direction:gesture.direction];
    }
}

这是两种合乎逻辑的方法。

顺便说一下，第一种方法并不排除让您自己的类属性知道您在哪个 Controller 上，有时这很有用(例如，如果您使用的动画类型取决于您是否要“右”或“左”)，但除非是这种情况，否则您只需查看 [self.childViewControllers lastObject] 即可。