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[英]What is a good way to reset a UIPanGestureRecognizer's view to its original frame once the pan gesture is done?
[英]Reset UIView's frame with a pan gesture without hardcoding start values
我有一个附加到UIView的UIPanGestureRecognizer。 我要做的基本上是拖放到存储桶中。 如果用户放开了UIView并且它不在存储桶中,则我希望它动画返回其原始开始位置。 我的UIPanGestureRecognizer被调用的选择器是:
- (void)handleDragDescriptionView:(UIPanGestureRecognizer *)gestureRecognizer {
UIView *panViewPiece = [gestureRecognizer view];
CGRect originalFrame = CGRectMake(946, 20, 58, 30);
CGPoint translation = [gestureRecognizer translationInView:panViewPiece];
if (gestureRecognizer.state == UIGestureRecognizerStateBegan || gestureRecognizer.state == UIGestureRecognizerStateChanged) {
panViewPiece.center = CGPointMake(panViewPiece.center.x + translation.x, panViewPiece.center.y + translation.y);
[gestureRecognizer setTranslation:CGPointZero inView:panViewPiece.superview];
}
else if (gestureRecognizer.state == UIGestureRecognizerStateCancelled) {
[UIView animateWithDuration:0.25 animations:^{
self.dragDescriptionView.frame = originalFrame;
}];
}
else {
[UIView animateWithDuration:0.25 animations:^{
self.dragDescriptionView.frame = originalFrame;
}];
}
}
我想知道如果没有方法顶部的originalFrame
我是否可以做到这一点。 我原来有
CGRect originalFrame = _dragDescriptionView.frame;
而不是硬编码,但不会返回。 可能是因为我在拖动时正在更新该值。 我不特别喜欢对值进行硬编码,但是我不确定是否有解决方法。 谢谢!
您实际上只需要跟踪视图的原始中心。 将originalCenter
为实例变量,并仅在手势开始时进行设置:
@implementation MyViewController {
CGPoint _originalCenter;
}
- (void)handleDragDescriptionView:(UIPanGestureRecognizer *)gestureRecognizer {
UIView *panViewPiece = [gestureRecognizer view];
switch (gestureRecognizer.state) {
case UIGestureRecognizerStateBegan:
_originalCenter = panViewPiece.center;
break;
case UIGestureRecognizerStateChanged: {
CGPoint translation = [gestureRecognizer translationInView:panViewPiece.superview];
panViewPiece.center = CGPointMake(panViewPiece.center.x + translation.x, panViewPiece.center.y + translation.y);
[gestureRecognizer setTranslation:CGPointZero inView:panViewPiece.superview];
break;
}
case UIGestureRecognizerStateEnded:
case UIGestureRecognizerStateCancelled: {
[UIView animateWithDuration:0.25 animations:^{
panViewPiece.center = _originalCenter;
}];
break;
}
default:
break;
}
}
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