ios - 如何在 UIScrollView 中获取内容 View 以使用自动布局填充父级

Question

所以我有一个工作的 UIScrollView 和一个可以水平滚动的内容 View ，那里没有问题。我已经关注了我能找到的所有在线资源，并且与滚动相关的所有内容都有效...我的问题是放在 contentview 内的内容没有填充到 UIScrollViews 底部。这就像滚动条占据了底部的 5-10 个像素，使得内容无法延伸到那里。

在所附的示例图像中，可以看到文本并未沿着整个栏对齐，所有项目都以相同的方式添加，唯一的不同是小滚动区域内的项目将 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(除了最外面的父级，它具有固定的高度约束 50 和左右边距 0)

ScrollView 和内容 View 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)

并且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:居中 Y(在容器中垂直)和固定宽度。我认为这可能会解决您的问题。