iOS - 在关闭和滚动手势之间切换

Question

我正在尝试模仿 Line Messenger 应用程序(日本事实上的 Messenger 应用程序)中的一种行为。

基本上，它们有一个模态视图 Controller ，里面有一个 ScrollView 。当滚动 Action 到达其内容的顶部时， View Controller 会无缝切换到交互式关闭动画。此外，当手势将 View 返回到屏幕顶部时，控制将返回到 ScrollView 。

这是它的外观的 gif。

对于我的生活，我无法弄清楚他们是如何做到的。我尝试了几种不同的方法，但都失败了，而且我没有想法。谁能指出我正确的方向？

EDIT2

澄清一下，我要模拟的行为不仅仅是向下拖动窗口。我可以做到，没问题。

我想知道相同的滚动手势(不抬起手指)如何触发关闭过渡，然后在 View 被拖回原始位置后将控制权转移回 ScrollView 。

这是我想不通的部分。

结束EDIT2

编辑1

这是我目前所拥有的。我能够使用 ScrollView 委托(delegate)方法来添加处理常规关闭动画的目标选择器，但它仍然无法按预期工作。

我创建一个 UIViewController 并将 UIWebView 作为属性。然后，我将其放入模态呈现的 UINavigationController 中。

导航 Controller 使用动画/过渡 Controller 进行常规交互式解雇(这可以通过在导航栏上打手势来完成)。

从这里开始，一切正常，但无法从 ScrollView 触发解雇。

NavigationController.h

@interface NavigationController : UINavigationController <UIViewControllerTransitioningDelegate>

@property (nonatomic, strong) UIPanGestureRecognizer *gestureRecog;

- (void)handleGesture:(UIPanGestureRecognizer*)gestureRecognizer;

@end

NavigationController.m

#import "NavigationController.h"
#import "AnimationController.h"
#import "TransitionController.h"

@implementation NavigationController {
    AnimationController *_animator;
    TransitionController *_interactor;
}

- (instancetype)init {
    self = [super init];

    self.transitioningDelegate = self;

    _animator = [[AnimationController alloc] init];
    _interactor = [[TransitionController alloc] init];

    return self;
}

- (void)viewDidLoad {
    [super viewDidLoad];

    // Set the gesture recognizer
    self.gestureRecog = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleGesture:)];
    [self.view addGestureRecognizer:_gestureRecog];
}

- (id<UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id<UIViewControllerAnimatedTransitioning>)animator {
    if (animator == _animator && _interactor.hasStarted) {
        return _interactor;
    }
    return nil;
}

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed {
    if (dismissed == self || [self.viewControllers indexOfObject:dismissed] != NSNotFound) {
        return _animator;
    }
    return nil;
}

- (void)handleGesture:(UIPanGestureRecognizer *)gestureRecog {
    CGFloat threshold = 0.3f;

    CGPoint translation = [gestureRecog translationInView:self.view];
    CGFloat verticalMovement = translation.y / self.view.bounds.size.height;
    CGFloat downwardMovement = fmaxf(verticalMovement, 0.0f);
    CGFloat downwardMovementPercent = fminf(downwardMovement, 1.0f);

    switch (gestureRecog.state) {
        case UIGestureRecognizerStateBegan: {
            _interactor.hasStarted = YES;
            [self dismissViewControllerAnimated:YES completion:nil];
            break;
        }
        case UIGestureRecognizerStateChanged: {
            if (!_interactor.hasStarted) {
                _interactor.hasStarted = YES;
                [self dismissViewControllerAnimated:YES completion:nil];
            }
            _interactor.shouldFinish = downwardMovementPercent > threshold;
            [_interactor updateInteractiveTransition:downwardMovementPercent];
            break;
        }
        case UIGestureRecognizerStateCancelled: {
            _interactor.hasStarted = NO;
            [_interactor cancelInteractiveTransition];
            break;
        }
        case UIGestureRecognizerStateEnded: {
            _interactor.hasStarted = NO;
            if (_interactor.shouldFinish) {
                [_interactor finishInteractiveTransition];
            } else {
                [_interactor cancelInteractiveTransition];
            }
            break;
        }
        default: {
            break;
        }
    }
}

@end

现在，我必须让手势处理在 ScrollView 到达顶部时触发。所以，这就是我在 View Controller 中所做的。

WebViewController.m

#import "WebViewController.h"
#import "NavigationController.h"

@interface WebViewController ()

@property (weak, nonatomic) IBOutlet UIWebView *webView;
@end

@implementation WebViewController {
    BOOL _isHandlingPan;
    CGPoint _topContentOffset;
}

- (void)viewDidLoad {
    [super viewDidLoad];

    [self.webView.scrollView setDelegate:self];
}    

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    if ((scrollView.panGestureRecognizer.state == UIGestureRecognizerStateBegan ||
         scrollView.panGestureRecognizer.state == UIGestureRecognizerStateChanged) &&
        ! _isHandlingPan &&
        scrollView.contentOffset.y < self.navigationController.navigationBar.translucent ? -64.0f : 0) {

        NSLog(@"Adding scroll target");

        _topContentOffset = CGPointMake(scrollView.contentOffset.x, self.navigationController.navigationBar.translucent ? -64.0f : 0);
        _isHandlingPan = YES;
        [scrollView.panGestureRecognizer addTarget:self action:@selector(handleGesture:)];
    }
}
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    NSLog(@"Did End Dragging");
    if (_isHandlingPan) {
        NSLog(@"Removing action");
        _isHandlingPan = NO;
        [scrollView.panGestureRecognizer removeTarget:self action:@selector(handleGesture:)];
    }
}
- (void)handleGesture:(UIPanGestureRecognizer*)gestureRecognizer {
    [(NavigationController*)self.navigationController handleGesture:gestureRecognizer];
}

这仍然不能正常工作。即使在关闭动画期间， ScrollView 仍会随着手势滚动。

结束EDIT1

Answer 1

这是一个自定义的交互式过渡。

首先，你需要设置UIViewController的transitioningDelegate

id<UIViewControllerTransitioningDelegate> transitioningDelegate;

然后实现这两个方法

 //Asks your delegate for the transition animator object to use when dismissing a view controller.
 - animationControllerForDismissedController:
 //Asks your delegate for the interactive animator object to use when dismissing a view controller.
 - interactionControllerForDismissal:

当拖动到顶部时，开始过渡，您可以使用 UIPercentDrivenInteractiveTransition 来控制滚动过程中的进度。

也可以引用ZFDragableModalTransition的源码

ZFDragableModalTransition 的图像