如何在 UIScrollView 中获取 contentview 以使用自动布局填充父级

Question

所以我有一个工作的 UIScrollView，它的内容视图可以水平滚动，没有问题。我已经关注了我能找到的所有在线资源以及与滚动相关的所有内容......我的问题是放在 contentview 中的内容没有填充到 UIScrollViews 底部。就像滚动条占据了底部的 5-10 像素，使得内容无法在那里拉伸。

在附加的示例图像中可以看出，文本并没有沿着整个栏对齐，所有项目都以相同的方式添加，唯一不同的是小滚动区域内的那些以 UIScrollView 作为父级。令人沮丧的是，如果我设置框架和内容区域而不是使用自动布局约束，这不是问题。

一切都在代码中（除了最外的父级，它的高度限制为 50，左右边距为 0）

滚动视图和内容视图的约束：

    //
    // scroll constraint
    //
    barScrollView.translatesAutoresizingMaskIntoConstraints = false

    // left constraint
    let leftSideConstraint = NSLayoutConstraint(item: barScrollView, attribute: .Left, relatedBy: .Equal, toItem: menuBtn, attribute: .Right, multiplier: 1.0, constant: 0)
    self.addConstraint(leftSideConstraint)

    // top constraint
    let topSideConstraint = NSLayoutConstraint(item: barScrollView, attribute: .Top, relatedBy: .Equal, toItem: self, attribute: .Top, multiplier: 1.0, constant: 0)
    self.addConstraint(topSideConstraint)

    // bottom constraint
    let botSideConstraint = NSLayoutConstraint(item: barScrollView, attribute: .Bottom, relatedBy: .Equal, toItem: self, attribute: .Bottom, multiplier: 1.0, constant: 0)
    self.addConstraint(botSideConstraint)

    // right side constraint
    let rightSideConstraint = NSLayoutConstraint(item: barScrollView, attribute: .Right, relatedBy: .Equal, toItem: collapseBtn, attribute: .Left, multiplier: 1.0, constant: 0)
    self.addConstraint(rightSideConstraint)


    //
    // scroll content constraint
    //
    barScrollContentView.translatesAutoresizingMaskIntoConstraints = false

    // left constraint
    let contentLeftSideConstraint = NSLayoutConstraint(item: barScrollContentView, attribute: .Left, relatedBy: .Equal, toItem: barScrollView, attribute: .Left, multiplier: 1.0, constant: 0)
    barScrollView.addConstraint(contentLeftSideConstraint)

    // top constraint
    let contentTopSideConstraint = NSLayoutConstraint(item: barScrollContentView, attribute: .Top, relatedBy: .Equal, toItem: barScrollView, attribute: .Top, multiplier: 1.0, constant: 0)
    barScrollView.addConstraint(contentTopSideConstraint)

    // bottom constraint
    let contentBotSideConstraint = NSLayoutConstraint(item: barScrollContentView, attribute: .Bottom, relatedBy: .Equal, toItem: barScrollView, attribute: .Bottom, multiplier: 1.0, constant: 0)
    barScrollView.addConstraint(contentBotSideConstraint)

    // right side constraint
    let contentRightSideConstraint = NSLayoutConstraint(item: barScrollContentView, attribute: .Right, relatedBy: .Equal, toItem: barScrollView, attribute: .Right, multiplier: 1.0, constant: 0)
    barScrollView.addConstraint(contentRightSideConstraint)

里面的所有项目都添加如下：

/**
 Add constraints to an item used in the bar

 - parameters:
   - newElement: The new element that is added
   - leftElement: The element to the left of the new element
   - parent: The parent view the constraint is added to
   - width: The size of the new element
   - isFirstItem: Boolean indicating if this item is the furtest item to the left side
 in the current container
 */
func addConstraintToItem(newElement: UIView, leftElement: UIView, parent: UIView, width: CGFloat, isFirstItem: Bool) {
    newElement.translatesAutoresizingMaskIntoConstraints = false

    // Width constraint
    let widthConstraint = NSLayoutConstraint(item: newElement, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: width)
    parent.addConstraint(widthConstraint)

    // Height constraint
    //let heightConstraint = NSLayoutConstraint(item: newElement, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: nil, attribute: NSLayoutAttribute.NotAnAttribute, multiplier: 1, constant: self.frame.height)
    //parent.addConstraint(heightConstraint)

    // left constraint
    var leftSideConstraint: NSLayoutConstraint

    if isFirstItem {
        leftSideConstraint = NSLayoutConstraint(item: newElement, attribute: .Left, relatedBy: .Equal, toItem: leftElement, attribute: .Left, multiplier: 1.0, constant: 0)

    } else {
        leftSideConstraint = NSLayoutConstraint(item: newElement, attribute: .Left, relatedBy: .Equal, toItem: leftElement, attribute: .Right, multiplier: 1.0, constant: 0)
    }
    parent.addConstraint(leftSideConstraint)

    // top constraint
    let topSideConstraint = NSLayoutConstraint(item: newElement, attribute: .Top, relatedBy: .Equal, toItem: parent, attribute: .Top, multiplier: 1.0, constant: 0)
    parent.addConstraint(topSideConstraint)

    // bot constraint
    let botSideConstraint = NSLayoutConstraint(item: newElement, attribute: .Bottom, relatedBy: .Equal, toItem: parent, attribute: .Bottom, multiplier: 1.0, constant: 0)
    parent.addConstraint(botSideConstraint)
}

Answer 1

尝试向barScrollContentView 添加两个约束：Center Y (Vertically in container) and fixed width。我认为这可能会解决您的问题。