转换新的父视图:
CGPoint newCenter = [self.view convertPoint:oldCenter toView:self.leftView];
CGPoint oldCenter = self.dragIV.center;
//转换成相对于新的 leftView的中心点
CGPoint newCenter = [self.view convertPoint:oldCenter toView:self.leftView];
[self.leftView addSubview:self.dragIV];
//添加到leftView之后 需要 设置转换完之后的新的中心点
self.dragIV.center = newCenter;