ios - UIPanGestureRecognizer 状态结束后动画中的小问题

Question

我正在尝试实现 View 的拖动，当拖动停止时， View 滑到顶部并消失。我可以使用 UIPanGestureRecognizer 很好地拖动 View 。但在那之后，我用动画让它滑出。问题是在拖动之后，在 View 移动之前总是会有一点小问题......我四处搜索，无法弄清楚如何解决这个问题。这是代码:

- (void)moveView2:(UIPanGestureRecognizer *)pan {    
    CGPoint delta = [pan translationInView:self.view];
    CGPoint newCenter = CGPointMake(_view2.center.x, _view2.center.y + delta.y);
    _view2.center = newCenter;
    [pan setTranslation:CGPointZero inView:self.view];
    if (pan.state == UIGestureRecognizerStateEnded) {
        CGPoint velocity = [pan velocityInView:self.view];
        NSLog(@"Velocity is %f, %f", velocity.x, velocity.y);
        // Here is the delay
        [UIView animateWithDuration:0.5 delay:0.0 usingSpringWithDamping:0.5f   initialSpringVelocity:500 options:UIViewAnimationOptionCurveEaseInOut animations:^{
        _view2.center = CGPointMake(_view2.center.x, -600);
    } completion:nil];
}





#import "ViewController.h"

@interface ViewController ()

@property (weak, nonatomic) IBOutlet UIButton *fbButton;

@property (weak, nonatomic) IBOutlet UIButton *twitterButton;

@property UIView *view1;
@property UIView *view2;

@property CGPoint startPoint;
@property CGPoint endPoint;
@property CGPoint originCenter;

@property double startTime;
@property double endTime;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    CGRect frame = [UIScreen mainScreen].bounds;
    _view1 = [[UIView alloc] initWithFrame:frame];
    _view1.backgroundColor = [UIColor redColor];
    [self.view addSubview:_view1];
    _view2 = [[UIView alloc] initWithFrame:frame];
    _view2.backgroundColor = [UIColor greenColor];
    [self.view addSubview:_view2];
    UIPanGestureRecognizer *pan1 = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(moveView2:)];
    [_view2 addGestureRecognizer:pan1];
    /*
    UISwipeGestureRecognizer *swipe = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipeUpDown:)];
    [swipe setDirection:UISwipeGestureRecognizerDirectionUp];
    [_view2 addGestureRecognizer:swipe];
     */
}

/*
- (void)swipeUpDown:(UISwipeGestureRecognizer *)swipe {
    if (swipe.direction == UISwipeGestureRecognizerDirectionUp) {
        NSLog(@"Swipe up");
        [UIView animateWithDuration:0.5 animations:^{
            _view2.center = CGPointMake(_view2.center.x, -600);
        }];
    }
}*/

- (void)moveView2:(UIPanGestureRecognizer *)pan {
    CGPoint bigViewDelta = [pan translationInView:self.view];
    CGPoint newCenter = CGPointMake(_view2.center.x, _view2.center.y + bigViewDelta.y);
    _view2.center = newCenter;
    [pan setTranslation:CGPointZero inView:self.view];
    if (pan.state == UIGestureRecognizerStateEnded) {
        CGPoint velocityOfPan = [pan velocityInView:self.view];
        CGFloat velocityOfPanAbsolute = sqrt(velocityOfPan.x * velocityOfPan.x + velocityOfPan.y * velocityOfPan.y);
        // get simple points per second
        CGPoint currentPoint = _view2.center;
        CGPoint finalPoint = CGPointMake(_view2.center.x, -600);
        CGFloat distance = sqrt((finalPoint.x - currentPoint.x) * (finalPoint.x - currentPoint.x) + (finalPoint.y - currentPoint.y) * (finalPoint.y - currentPoint.y));
        // how far to travel
        CGFloat duration = 0.5;
        CGFloat animationVelocity = velocityOfPanAbsolute / (distance / duration);

        [UIView animateWithDuration:duration delay:0.0 usingSpringWithDamping:1.0 initialSpringVelocity:animationVelocity options:0 animations:^{
            _view2.center = CGPointMake(_view2.center.x, -600);
        } completion:nil];    }
}

- (void)viewDidAppear:(BOOL)animated {
/*
    [UIView transitionFromView:_view2 toView:_view1 duration:2 options:UIViewAnimationOptionCurveEaseInOut completion:^(BOOL finished) {
    }];
*/

    /*
    // get the view that's currently showing
    UIView *currentView = _view2;
    // get the the underlying UIWindow, or the view containing the current view view
    UIView *theWindow = [currentView superview];
    // remove the current view and replace with myView1
    [currentView removeFromSuperview];
    //[theWindow addSubview:newView];
    // set up an animation for the transition between the views
    CATransition *animation = [CATransition animation];
    [animation setDuration:0.5];
    [animation setType:kCATransitionPush];
    [animation setSubtype:kCATransitionFromLeft];
    [animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];
    [[theWindow layer] addAnimation:animation forKey:@"SwitchToView1"];
     */
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

Answer 1

你的意思是动画发生之前的延迟？嗯，我没有看到任何会导致这种情况的东西，但是 animateWithDuration 的参数非常非常好奇。

一、UIViewAnimationOptionCurveEaseInOut对我来说没有意义，因为这常用于说“慢慢开始，加快速度，也慢慢停止”。这对于一个标准动画来说很好，您不希望动画的开始过于刺耳。但这在这种情况下没有意义，因为您可能希望它不要缓慢启动，而是使用您最初提供的任何速度。如果我使用任何 option , 我会使用 UIViewAnimationOptionCurveEaseOut .即使这样也没有意义，因为它是 usingSpringWithDamping指示在此动画结束时发生的情况的参数。 (而且，最重要的是，您将其拖出屏幕，所以我不清楚您为什么关心退出曲线。)

二、initialSpringVelocity对我来说似乎也不对。正如此参数的文档所述:

The initial spring velocity. For smooth start to the animation, match this value to the view’s velocity as it was prior to attachment.

A value of 1 corresponds to the total animation distance traversed in one second. For example, if the total animation distance is 200 points and you want the start of the animation to match a view velocity of 100 pt/s, use a value of 0.5.

所以，500表示您想在一秒钟内从当前位置到最终位置的距离旅行 500 倍。这快得离谱。

我会尝试将初始速度与手势的最终速度相匹配。因此，计算手势的绝对速度，然后将其除以要经过的距离除以动画的持续时间。

第三，如果您将其拖出屏幕，我不确定您为什么要使用 usingSpringWithDamping的 0.5 .那是有弹性的。为什么你要让它在你正在使用的所有东西中弹出，因为它会停止在屏幕上并且你无论如何都看不到它？令我震惊的是，任何小于 1.0 的值在一个或多个初始弹跳期间， View 可能会弹回可见屏幕。我不会使用低于 1.0 的任何东西如果在屏幕外设置动画。

把所有这些放在一起，我得到了类似的东西:

CGPoint velocityOfPan = [pan velocityInView:self.view];
CGFloat velocityOfPanAbsolute = hypof(velocityOfPan.x, velocityOfPan.y);                // get simple points per second
CGPoint currentPoint = _view2.center.x;
CGPoint finalPoint = CGPointMake(_view2.center.x, -600);
CGFloat distance = hypof(finalPoint.x - currentPoint.x, finalPoint.y - currentPoint.y); // how far to travel
CGFloat duration = 0.5;
CGFloat animationVelocity = velocityOfPanAbsolute / (distance / duration);

[UIView animateWithDuration:duration delay:0.0 usingSpringWithDamping:1.0 initialSpringVelocity:animationVelocity options:0 animations:^{
    _view2.center = CGPointMake(_view2.center.x, -600);
} completion:nil];

说了这么多，虽然有可能 animateWithDuration被“缓入缓出”和戏剧性的 initialSpringVelocity组合弄糊涂了，我实际上不明白为什么会导致“打嗝”。

你在这个动画之后立即做其他事情吗？任何可能阻塞主队列的东西？

你的意思是手势被第一次识别之前的一点延迟？是的，这是平移手势识别器的一个功能。 (我认为它试图确定它是否真的是平底锅 vs 长按 vs 等)。

你可以通过使用 UILongPressGestureRecognizee 来解决这个问题。与 minimumPressDuration为零(尽管您必须自己计算 translationInView)。