相关疑难解决方法(0)

我在UIView中有一个元素,其约束条件是它应该始终距离视图底部10个像素.然后我尝试为此视图的高度设置动画,使其看起来在屏幕上滑动.根据约束,元素应始终距视图底部10个像素.当我像这样添加视图时,这是正确的...

printView *vc = [self.storyboard instantiateViewControllerWithIdentifier:@"printView"];
    [self addChildViewController:vc];
    vc.view.frame = CGRectMake(0, 60, vc.view.frame.size.width, HEIGHT);
    vc.view.layer.masksToBounds = FALSE;
    [vc.view.layer setShadowOffset:CGSizeMake(0.0, 5.0)];
    [vc.view.layer setShadowOpacity:0.8];
    vc.view.layer.shadowColor = [[UIColor blackColor] CGColor];
    vc.view.layer.shadowRadius = 8;
    vc.view.clipsToBounds = TRUE;
    [self.view insertSubview:vc.view aboveSubview:docWebView];

我可以将HEIGHT更改为我想要的任何内容,并且元素总是距离视图底部10个像素.当我尝试设置高度动画时出现问题

printView *vc = [self.storyboard instantiateViewControllerWithIdentifier:@"printView"];
    [self addChildViewController:vc];
    vc.view.frame = CGRectMake(0, 60, vc.view.frame.size.width, 0);
    vc.view.layer.masksToBounds = FALSE;
    [vc.view.layer setShadowOffset:CGSizeMake(0.0, 5.0)];
    [vc.view.layer setShadowOpacity:0.8];
    vc.view.layer.shadowColor = [[UIColor blackColor] CGColor];
    vc.view.layer.shadowRadius = 8;
    vc.view.clipsToBounds = TRUE;
    [self.view insertSubview:vc.view aboveSubview:docWebView];
    [UIView animateWithDuration:5.0 animations:^{
        vc.view.frame = CGRectMake(0, 60, vc.view.frame.size.width, …