Question

我在我的应用程序中以模态方式呈现视图控制器。我希望用户能够轻弹＆＃34;用手势远离视线。我为此写了下面的代码：

- (void)handlePan:(UIPanGestureRecognizer *)recognizer {
    CGFloat elasticThreshold = 100;
    CGFloat dismissThreshold = 200;
    CGPoint translation = [recognizer translationInView:self.view];
    CGFloat newY = 0;
    CGFloat translationFactor = 0.5;

    if (recognizer.state == UIGestureRecognizerStateEnded) {
        if (translation.y < dismissThreshold) {
            newY = 0;
        }
    } else {
        if (translation.y > elasticThreshold) {
            CGFloat frictionLength = translation.y - elasticThreshold;
            CGFloat frictionTranslation = 30 * atan(frictionLength/120) + frictionLength/10;
            newY = frictionTranslation + (elasticThreshold * translationFactor);
        } else {
            newY = translation.y*translationFactor;
        }
    }

    if (translation.y > dismissThreshold) {
        [UIView animateKeyframesWithDuration:0.5 delay:0.0 options:0 animations:^{
            [UIView addKeyframeWithRelativeStartTime:0.0 relativeDuration:0.5 animations:^{
                self.overlay.effect = nil;
                self.collectionView.transform = CGAffineTransformMakeTranslation(0, self.view.frame.size.height);
            }];
            [UIView addKeyframeWithRelativeStartTime:0.1 relativeDuration:0.1 animations:^{
                self.pageControl.frame = CGRectMake((self.view.frame.size.width-200)/2, self.view.frame.size.height, 200, 20);
            }];
        } completion:^(BOOL finished) {
            if (finished) {
                [self dismissViewControllerAnimated:YES completion:nil];
            }
        }];
    } else {
        self.collectionView.transform = CGAffineTransformMakeTranslation(0, newY);
        self.pageControl.transform = CGAffineTransformMakeTranslation(0, (newY+self.collectionView.frame.size.height)-20);
    }
}

这与UIGestureRecognizer：

相关联

self.pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
self.pan.delegate = self;
self.pan.maximumNumberOfTouches = 1;
[self.view addGestureRecognizer:self.pan];

然而，发生的是完成块立即执行。因此，您会看到视图向下移动（因为dismissViewControllerAnimated），同时看到overlay.effect消失。但是，我想要的是让我的动画发生，然后让视图控制器静静地解散它。

任何想法在这里出了什么问题？

Answer 1

这是因为您嵌套 UIView动画块。您应该使用dispatch_after：

double delayInSeconds = 0.5;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
    [self dismissViewControllerAnimated:YES completion:nil];
});

Answer 2

如果没有工作要做，UIView关键帧（或标准）动画将立即执行其完成块。如果没有任何动画效果，它将不会等待动画的持续时间。

似乎在您开始关闭动画的情况下，视图已经处于最终状态，因此没有动画并且立即运行完成块。

动画无法正常工作

2 个答案: