视图和超级视图之间的自动布局标准空间不起作用

Question

我使用Auto Layout Visual Format Lanugage使子视图的框架适合其超视图的框架，减去标准的空间量（约8px）（a＆＃34;标准空间＆＃34;用可视格式语言表示为-。

这是我的代码：

class ViewController: UIViewController {

    var imageView: UIImageView = UIImageView()

    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.backgroundColor = UIColor.redColor()

        imageView.backgroundColor = UIColor.greenColor()
        imageView.setTranslatesAutoresizingMaskIntoConstraints(false)
        self.view.addSubview(imageView)

        let viewsDict = ["imageView": imageView]

        let imageViewConstraintsH = NSLayoutConstraint.constraintsWithVisualFormat("H:|-[imageView]-|",
            options: NSLayoutFormatOptions.allZeros,
            metrics: nil,
            views: viewsDict)
        self.view.addConstraints(imageViewConstraintsH)

        let constraintsV = NSLayoutConstraint.constraintsWithVisualFormat("V:|-[imageView]-|",
            options: NSLayoutFormatOptions.allZeros,
            metrics: nil,
            views: viewsDict)
        self.view.addConstraints(constraintsV)
    }
}

正如您在下面的屏幕截图中看到的那样，标准间距是水平的，但不是垂直的：

Answer 1

我无法解答为什么它不起作用（Apple DTS也不能），但您可以使用superview中的内置布局指南来完成同样的事情，如下所示：

- (void)viewDidLoad {
    [super viewDidLoad];

    id  topLayoutGuide = self.topLayoutGuide;
    id  bottomLayoutGuide = self.bottomLayoutGuide;

    UIImageView *imageView = [[UIImageView alloc]init];
    [imageView setTranslatesAutoresizingMaskIntoConstraints:false];

    NSDictionary *views = NSDictionaryOfVariableBindings(imageView, topLayoutGuide, bottomLayoutGuide);


    self.view.backgroundColor = [UIColor grayColor];
    imageView.backgroundColor = [UIColor whiteColor];

    [self.view addSubview:imageView];

    [self.view addConstraints:
    [NSLayoutConstraint constraintsWithVisualFormat:@"H:|-[imageView]-|"
                                            options:0
                                            metrics:nil
                                              views:NSDictionaryOfVariableBindings(imageView)]
     ];
    [self.view addConstraints:
    [NSLayoutConstraint constraintsWithVisualFormat:@"V:[topLayoutGuide]-[imageView]-[bottomLayoutGuide]"
                                            options:0
                                            metrics:nil
                                              views:views]
     ];

}

感谢T. Cooper