ios - 自定义 Segue 中的 UIKit 动态

Question

我正在尝试使 View 作为自定义 segue 转换下降，但是当在 UIStoryboardSegue 实现中调用 perform 方法时，它不会下降。我曾尝试将 View 移动到源 View 中以查看它是否执行任何操作，但它没有执行任何操作。

-(void)perform {
    UIViewController *src  = (UIViewController *)self.sourceViewController;
    UIViewController *dest = (UIViewController *)self.destinationViewController;

    UIView *viewdrop = [dest.view snapshotViewAfterScreenUpdates:YES];
    viewdrop.frame = CGRectMake(0, -src.view.frame.size.height, dest.view.frame.size.width, dest.view.frame.size.height);
    [src.view addSubview:viewdrop];

    animator = [[UIDynamicAnimator alloc] initWithReferenceView:src.view];

    UIGravityBehavior* gravityBehavior = [[UIGravityBehavior alloc] initWithItems:@[viewdrop]];
    [animator addBehavior:gravityBehavior];
}

Answer 1

它没有下降的原因是重力行为需要时间，但是 segue 本身会在 perform 方法完成后立即释放。因此，您需要一种方法来至少在移动完成之前让 segue 保持事件状态。一种方法是在源 View Controller 中为 segue 创建一个强大的属性，并在 prepareForSegue 中设置它的值，

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    self.dropSegue = segue;
}

我对你的 segue 做了一个修改版本，它也添加了一个碰撞行为，并将源 View Controller 设置为碰撞行为的委托(delegate)，所以我可以使用委托(delegate)方法 collisionBehavior:endedContactForItem:withBoundaryIdentifier: 来设置dropSegue 属性为 nil(稍微延迟后)，这会导致 segue 被释放，

-(void)collisionBehavior:(UICollisionBehavior *)behavior endedContactForItem:(id<UIDynamicItem>)item withBoundaryIdentifier:(id<NSCopying>)identifier {
    NSLog(@"collision ended with %@", identifier);
    [self performSelector:@selector(setDropSegue:) withObject:nil afterDelay:1];
}

这是我的重力下降转场版本，

@interface RDSegue ()
@property (strong, nonatomic) UIDynamicAnimator *animator;
@end

@implementation RDSegue

-(id)initWithIdentifier:(NSString *)identifier source:(UIViewController *)source destination:(UIViewController *)destination {

    if (self = [super initWithIdentifier:identifier source:source destination:destination]) {
        UIViewController *src  = self.sourceViewController;
        UIViewController *dest = self.destinationViewController;
        self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:src.view];
        [src addChildViewController:dest];
        [dest didMoveToParentViewController:src];
        dest.view.frame = CGRectMake(0, -src.view.bounds.size.height, src.view.bounds.size.width, src.view.bounds.size.height);
        [src.view addSubview:dest.view];
    }
    return self;
}

-(void)perform {
    UIGravityBehavior* gravityBehavior = [[UIGravityBehavior alloc] initWithItems:@[[self.destinationViewController view]]];
    UICollisionBehavior *collide = [[UICollisionBehavior alloc] initWithItems:@[[self.destinationViewController view]]];
    CGPoint left = CGPointMake(self.animator.referenceView.bounds.origin.x, self.animator.referenceView.bounds.origin.y + self.animator.referenceView.bounds.size.height);
    CGPoint right = CGPointMake(self.animator.referenceView.bounds.origin.x + self.animator.referenceView.bounds.size.width, self.animator.referenceView.bounds.origin.y + self.animator.referenceView.bounds.size.height);
    [collide addBoundaryWithIdentifier:@"bottom" fromPoint:left toPoint:right];
    [collide setCollisionDelegate:self.sourceViewController];
    [self.animator addBehavior:gravityBehavior];
    [self.animator addBehavior:collide];
}

-(void)dealloc {
    NSLog(@"In dealloc");
}