无法在Swift中的自定义UIView上布置子视图 [英] Not able to lay out Subviews on a custom UIView in Swift

问题描述

因此，我创建了这个自定义容器视图，并使用自动布局约束对其进行了布局.

So I have created this custom container view which I am laying out using autolayout constraint.

    func configureSegmentContainerView() {
    segmentContainerView.topAnchor.constraint(equalTo: view.topAnchor, constant: 40).isActive = true
    segmentContainerView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 8).isActive = true
    segmentContainerView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -8).isActive = true
    segmentContainerView.heightAnchor.constraint(equalToConstant: 3).isActive = true 
    }

在视图控制器中，viewDidLoad()是这样的:

In the view controller, the viewDidLoad() is this:

    setupDataSource()
    segmentContainerView = ATCStorySegmentsView()
    view.addSubview(segmentContainerView)
    configureSegmentContainerView()
    segmentContainerView.translatesAutoresizingMaskIntoConstraints = false
    segmentContainerView.numberOfSegments = friendStory.count

现在，一旦设置了数据源并且我有了friendStory计数，就将其分配给segmentContainerView.numberofSegments

Now once the data source is setup and I have the friendStory count, I am assigning it to segmentContainerView.numberofSegments

在segmentContainerview类中，这是正在发生的事情:

In segmentContainerview class this is what is happening:

    var numberOfSegments: Int? {
    didSet {
        addSegments()
    } 
  }

在addSegments()中，我根据n umberOfSegments添加UIViews，这是该代码:

In addSegments(), I am adding UIViews depending upon the numberOfSegments this is the code for that:

 private func addSegments() {
    guard let numberOfSegments = numberOfSegments else { return }
    layoutIfNeeded()
    setNeedsLayout()
    for i in 0..<numberOfSegments {
        let segment = Segment()
        addSubview(segment.bottomSegment)
        addSubview(segment.topSegment)
        configureSegmentFrame(index: i, segmentView: segment)
        segmentsArray.append(segment)
    }
}

private func configureSegmentFrame(index: Int, segmentView: Segment) {
    guard let numberOfSegments = numberOfSegments else { return }
    let widthOfSegment : CGFloat = (self.frame.width - (padding * CGFloat(numberOfSegments - 1))) / CGFloat(numberOfSegments)

    let i = CGFloat(index)
    
    let segmentFrame = CGRect(x: i * (widthOfSegment + padding), y: 0, width: widthOfSegment, height: self.frame.height)
    segmentView.bottomSegment.frame = segmentFrame
    segmentView.topSegment.frame = segmentFrame
    segmentView.topSegment.frame.size.width = 0
}

**问题和问题:**我没有得到4个UIView，而是得到了3个，但是第三个没有正确放置，并且移出了父容器.我怎样才能使这些uiviews正确对齐.我猜想setNeedsLayout()和layoutIfNeeded()需要被调用存在一些问题.请帮忙.

**Question and Issue: ** Instead of getting 4 UIViews, I am getting 3, but the third one is not correctly placed and is going outside the parent container. How can I get these uiviews aligned correctly. I am guessing there is some issue with where setNeedsLayout() and layoutIfNeeded() needs to be called. Please help.

Segment是具有两个属性的结构-bottomSegment和topSegment.两者都是UIView

Segment is a struct with two properties - bottomSegment and topSegment. Both being UIView

您可以看到只有三个UIView段出现.我需要其中的4个(numberOfSegments = 4).我也给right and leftAnchor的父容器常数8和-8.因此所有4个细分都需要放置在此视图中.如您在上图中所看到的，最后一段在父容器之外.

You can see how just three UIView segments appear. I needs to 4 (numberOfSegments = 4) of these. Also I am giving the parent container constant of 8 and -8 for right and leftAnchor. so all 4 segments need to be placed within this view. As you can see in the picture above the last segment is going outside of the parent container.

推荐答案

问题是

let widthOfSegment : CGFloat = (self.frame.width ...

被称为太早了.在具有其实际框架之前，您不能执行任何依赖于self具有其框架的操作.

is being called too soon. You cannot do anything in that depends upon self having its frame until after it has its real frame.

对于UIView，该时刻是在第一次调用layoutSubviews之后.

For a UIView, that moment is after layoutSubviews has been called for the first time.

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