Question

我正在探索iOS4.3 SDK＆amp;想要实现特定的动画效果。但不知道该怎么做。它是这样的 - 我在屏幕上有一个方框＆amp;当用户将手指放在盒子上时拖着他的手指，盒子应该跟着他。直到这里很容易。我能够像这样实现它 -

-(void)touchesEnded:(NSSet *)touches 
          withEvent:(UIEvent *)event
{
    UITouch *touch   = [touches anyObject];
    CGPoint location = [touch locationInView:self.view];
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationDuration:2];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseOut];
    CGAffineTransform scaleTrans  = CGAffineTransformMakeScale(scaleFactor, scaleFactor);
    CGAffineTransform rotateTrans = CGAffineTransformMakeRotation(angle * M_PI / 180);
    boxView.transform = CGAffineTransformConcat(scaleTrans, rotateTrans);
    angle             = (angle == 180 ? 360 : 180);
    scaleFactor       = (scaleFactor == 2 ? 1 : 2);
    boxView.center    = location;
    [UIView commitAnimations];
}

但是当用户抬起手指时，我希望盒子继续运动（好像有动量）。这就像苹果实施的相同橡皮筋滚动效果;即使你离开滚动，屏幕滚动＆amp;慢慢地停下来。我该如何实现？

Answer 1

if (recognizer.state == UIGestureRecognizerStateEnded) {

    CGPoint velocityPoint = [recognizer velocityInView:yourView];

    [UIView setAnimationDelegate:self];
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:0.5];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];



    [yourView setCenter:CGPointMake(yourView.center.x + (velocityPoint.x/4), yourView.center.y + (velocityPoint.y/4))];

    [recognizer setTranslation:CGPointZero inView:yourView];


   [UIView commitAnimations];

}

希望这会有所帮助：）

Answer 2

为什么不考虑使用UIPanGestureRecognizer。您可以使用translationInView:移动框，同时移动手指。当手势state为UIGestureRecognizerStateEnded时，您可以使用velocityInView:来获得所需的跟进效果。

iOS Touch，手势，动画

2 个答案: