Question

我有一个TableCellView，其中包含以下视图：

class MyCell: UITableViewCell {

    var headerStackView: UIStackView = {
        var stackView = UIStackView()
        stackView.axis = .horizontal
        stackView.distribution = .fillEqually
        stackView.spacing = 0
        stackView.contentMode = .scaleToFill
        stackView.translatesAutoresizingMaskIntoConstraints = false
        return stackView
    }()

    var pointsStackView: UIStackView = {
        var stackView = UIStackView()
        stackView.axis = .horizontal
        stackView.distribution = .fillEqually
        stackView.spacing = 10
        stackView.contentMode = .scaleToFill
        stackView.translatesAutoresizingMaskIntoConstraints = false
        return stackView
    }()

    var webContainerView: UIView = {
        var webCont = UIView()
        webCont.translatesAutoresizingMaskIntoConstraints = false
        return webCont
    }()

    var contentWKWebView: WKWebView = {
        let preferences = WKPreferences()
        preferences.javaScriptEnabled = true

        let configuration = WKWebViewConfiguration()
        configuration.preferences = preferences
        let jsPath = Bundle.main.path(forResource: "web_assets/jqmath-0.4.0", ofType: "css")!
        let baseUrl = URL(fileURLWithPath: jsPath)
        let html_loading = "<html><body><h1>Loading ...</h1></body></html>"

        var wkwv = WKWebView(frame: .zero, configuration: configuration)
        wkwv.loadHTMLString(html_loading, baseURL: baseUrl)
        wkwv.scrollView.isScrollEnabled = false
        wkwv.scrollView.bounces = false
        wkwv.translatesAutoresizingMaskIntoConstraints = false
        return wkwv
    }()

    var webViewHeightConstraint: NSLayoutConstraint?

然后，init包含以下几行：

override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
    print ("Inside INIT")
    super.init(style: style, reuseIdentifier: reuseIdentifier)

    self.addSubview(self.headerStackView)
    self.addSubview(self.pointsStackView)
    self.addSubview(self.webContainerView)
    self.webContainerView.addSubview(self.contentWKWebView)

    headerStackView.leftAnchor.constraint(equalTo: self.leftAnchor, constant: 0).isActive = true
    headerStackView.rightAnchor.constraint(equalTo: self.rightAnchor, constant: 0).isActive = true
    headerStackView.topAnchor.constraint(equalTo: self.topAnchor, constant: 10).isActive = true
    headerStackView.bottomAnchor.constraint(equalTo: self.pointsStackView.topAnchor, constant: -10).isActive = true

    pointsStackView.leftAnchor.constraint(equalTo: self.leftAnchor, constant: 10).isActive = true
    pointsStackView.bottomAnchor.constraint(equalTo: self.webContainerView.topAnchor, constant: -10).isActive = true

    webContainerView.leftAnchor.constraint(equalTo: self.leftAnchor, constant: 0).isActive = true
    webContainerView.rightAnchor.constraint(equalTo: self.rightAnchor, constant: 0).isActive = true
    webContainerView.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -10).isActive = true

    contentWKWebView.navigationDelegate = self
    contentWKWebView.leftAnchor.constraint(equalTo: self.webContainerView.leftAnchor, constant: 2).isActive = true
    contentWKWebView.rightAnchor.constraint(equalTo: self.webContainerView.rightAnchor, constant: -2).isActive = true
    contentWKWebView.topAnchor.constraint(equalTo: self.webContainerView.topAnchor, constant: 2).isActive = true
    contentWKWebView.bottomAnchor.constraint(equalTo: self.webContainerView.bottomAnchor, constant: -2).isActive = true
    webViewHeightConstraint = contentWKWebView.heightAnchor.constraint(equalToConstant: 100)
    webViewHeightConstraint?.isActive = true

func layoutSubviews只是将一些值设置到各个视图中。

我正在使用以下代码根据HTML内容调整WKWebView的高度：

extension MyCell: WKNavigationDelegate {
    func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
        webView.evaluateJavaScript("document.documentElement.scrollHeight", completionHandler: { (height, error) in
            self.webViewHeightConstraint?.constant = height as! CGFloat
        })
    }
}

两行：

webViewHeightConstraint = contentWKWebView.heightAnchor.constraint(equalToConstant: 100)
webViewHeightConstraint?.isActive = true

克服所有其他限制，我得到：

无法同时满足约束条件

其中有大量冲突约束。

如果我将它们注释掉，则不会有约束冲突，但是WKWebView不会显示任何内容（可能是因为它没有初始化的高度约束。

我想念什么？

WKWebView高度限制原因：无法同时满足约束

0 个答案: