ios - UIAttachmentBehavior 不起作用。 UIDynamicAnimator

Question

我在使用 initWithItem:attachedToItem: 时遇到问题 初始化连接一个动态项的中心点到另一个动态项的中心点的附件行为。但是当我使用方法 pan 改变 topview 的中心点时，只有 topview 移动了，我无法让另一个 View 移动。它不应该一起移动吗？(顺便说一句，当我在顶部平移卡片时，我正在尝试实现一堆卡片并一起移动。)

-(void)pinch:(UIPinchGestureRecognizer *)gesture
{
    if(gesture.state ==  UIGestureRecognizerStateChanged){
        CGPoint pinchCen = [gesture locationInView:self.cardArea];
        if (gesture.scale <= 0.5 && !self.pileStat) {
            self.pileStat = !self.pileStat;
            NSUInteger number = [self.cardViews count];
            UIView *topView = [self.cardViews lastObject];
            [topView addGestureRecognizer:[[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(pan:)]];
            for (int i = 0; i < number;i++) {
                UIView *cardView = self.cardViews[i];
                [UIView animateWithDuration:0.5 animations:^{cardView.center = CGPointMake(pinchCen.x+i%10*0.5, pinchCen.y+i%10*0.5);} completion:^(BOOL finished){
                    if(i != number - 1){
                        UIAttachmentBehavior *attach = [[UIAttachmentBehavior alloc]initWithItem:cardView attachedToItem:topView];
                        [self.animator addBehavior:attach];
                    }
                }];
            }

        }
        else if(gesture.scale > 1.5 && self.pileStat)
        {
            self.pileStat = !self.pileStat;
        }
    }else if (gesture.state == UIGestureRecognizerStateEnded){
        gesture.scale = 1.0f;
    }
}
-(void)pan:(UIPanGestureRecognizer *)gesture
{
    if (gesture.state == UIGestureRecognizerStateChanged || UIGestureRecognizerStateEnded) {
    UIView *topView = [self.cardViews lastObject];
        CGPoint trans = [gesture translationInView:self.cardArea];
        topView.center = CGPointMake(trans.x+topView.center.x, trans.y+topView.center.y);
        [gesture setTranslation:CGPointMake(0, 0) inView:self.cardArea];
    }
}

Answer 1

setCenter 不能很好地与 UIDynamicAnimator 配合使用。您不应更改顶 View 的中心坐标，而应使用附加到触摸的另一个 UIAttachmentBehavior。使用此方法替换您的平移手势处理程序:

//Add a variable in your interface or header section called "touchAttachment" of type UIAttachmentBehavior
- (void) pan: (UIPanGestureRecognizer *) sender{
  UIView* topCard = [self.cardViews lastObject];
  if (sender.state == UIGestureRecognizerStateBegan){
    _touchAttachment = [[UIAttachmentBehavior alloc] initWithItem:topCard         
      attachedToAnchor: [sender locationInView:self.view]];
    [self.animator addBehavior:_touchAttachment];
  }
  else if (sender.state == UIGestureRecognizerStateChanged){
    [_touchAttachment setAnchorPoint: [sender locationInView: self.view]];
  }
  else if (sender.state == UIGestureRecognizerStateEnded){
    [self.animator removeBehavior: _touchAttachment];
    _touchAttachment = nil;
  }
}

确保添加“touchAttachment”变量。希望对您有所帮助:)