ios - 如何动画旋转和移动 UIView 到其原始位置？

Question

我有一个带有平移手势识别器的 UIImageView，我可以根据用户操作移动和旋转它。当用户抬起手指时，我希望它动画回到原来的位置，这是我的代码:

- (IBAction)handlePan:(UIPanGestureRecognizer *)recognizer {

    if (recognizer.state == UIGestureRecognizerStateBegan) {
        startX = recognizer.view.center.x;
        startY = recognizer.view.center.y;
        startRotation = atan2(recognizer.view.transform.b, recognizer.view.transform.a);
        NSLog(@"Start Position %f %f %f", startX, startY, startRotation);
    } else if (recognizer.state == UIGestureRecognizerStateEnded) {

        float distance = (startX - recognizer.view.center.x) / DISTANCE_TO_ACCEPT;
        CGPoint center = recognizer.view.center;


            // animate back
            [UIView animateWithDuration:0.5 animations:^{
                NSLog(@"Position %f %f %f", recognizer.view.center.x, recognizer.view.center.y, atan2(recognizer.view.transform.b, recognizer.view.transform.a));
                NSLog(@"Destination %f %f %f", startX, startY, startRotation);
                NSLog(@"Translation %f %f %f", startX - center.x, startY - center.y, (startRotation - atan2(recognizer.view.transform.b, recognizer.view.transform.a)));

                recognizer.view.transform = CGAffineTransformRotate(CGAffineTransformTranslate(recognizer.view.transform, startX - center.x, startY - center.y), (CGFloat) (startRotation - atan2(recognizer.view.transform.b, recognizer.view.transform.a)));
            }];


    } else if (recognizer.state == UIGestureRecognizerStateChanged) {
        // move image
        CGPoint translation = [recognizer translationInView:self.view];
        recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y);
        [recognizer setTranslation:CGPointMake(0, 0) inView:self.view];

        // rotate image
        float distance = (startX - recognizer.view.center.x) / DISTANCE_TO_ACCEPT;

        // cap distance
        if (distance > 1) {
            distance = 1;
        } else if (distance < -1) {
            distance = -1;
        }

        double rotation = 15 - startRotation;
        rotation = rotation * distance;
        recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, (CGFloat) ((rotation * M_PI / 180) - atan2(recognizer.view.transform.b, recognizer.view.transform.a)));

    }

}

但它永远不会回到原来的位置。它总是有某种偏移量。 ImageView 的进一步移动只会使情况变得更糟。看起来位置在后退动画期间没有修改，因为当我再次平移图像时，开始位置和旋转等于它在上一次移动结束时的位置和旋转[即使在屏幕上图像位置和轮换已更改]。

我在这里做错了什么？

谢谢

Answer 1

在 UIGestureRecognizerStateEnded 状态下尝试这样的事情:

recognizer.view.transform = CGAffineTransformIdentity;
recognizer.view.center = CGPointMake(startX,startY);