如何更改 UITableViewCell 高度？

Question

我已经在单元格内实现了带有滚动视图的表格视图。该单元格由两个视图组成，第二个视图（以绿色显示）在滑动后出现：

我现在想要实现的是，当单元格向右滑动时，单元格高度逐渐扩大。因此，当我开始向右滑动单元格并且绿色子视图在主屏幕上变得可见时，我希望单元格的高度增加，直到绿色子视图完全可见。然后当我向左滑动时，一切都恢复正常。

由于 UITableViewCell 符合滚动视图委托，我怀疑我在单元格子类中编写了一些代码 - 也许使用contentOffset.y滚动视图的scrollViewDidScroll。

Answer 1

这是使用自动布局和自动调整单元格大小的示例（Swift 3）。不确定您打算如何“开始”绿色视图，因此此演示将其初始化为 40 磅宽（高度包含在宽度的 50% 内）。

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您只需创建一个新的 .swift 文件并将其粘贴进去，然后在 Storyboard 中添加一个 UITableViewController 并将其类分配给StretchCellTableViewController。其他一切都是在代码中创建的...不需要 IBOutlet。

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//\n//  StretchCellTableViewController.swift\n//  SWTemp2\n//\n//  Created by Don Mag on 6/22/17.\n//  Copyright \xc2\xa9 2017 DonMag. All rights reserved.\n//\n\nimport UIKit\n\nclass NonStretchCell: UITableViewCell {\n\n    // pretty standard one-label cell\n\n    var theLabel: UILabel!\n\n    override init(style: UITableViewCellStyle, reuseIdentifier: String?) {\n        super.init(style: style, reuseIdentifier: reuseIdentifier)\n        setupCell()\n    }\n\n    required init?(coder aDecoder: NSCoder) {\n        super.init(coder: aDecoder)\n        setupCell()\n    }\n\n    func setupCell() {\n\n        theLabel = UILabel()\n        theLabel.font = UIFont.systemFont(ofSize: 16.0, weight: UIFontWeightLight)\n        theLabel.numberOfLines = 0\n        theLabel.translatesAutoresizingMaskIntoConstraints = false\n\n        self.addSubview(theLabel)\n\n        theLabel.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 8.0).isActive = true\n        theLabel.topAnchor.constraint(equalTo: self.topAnchor, constant: 6.0).isActive = true\n        theLabel.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: -6.0).isActive = true\n        theLabel.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -8.0).isActive = true\n\n    }\n\n}\n\nclass StretchCell: UITableViewCell {\n\n    var stretchView: UIView!\n\n    var widthConstraint: NSLayoutConstraint!\n\n    var scaleAction : ((CGFloat)->())?\n\n    override init(style: UITableViewCellStyle, reuseIdentifier: String?) {\n        super.init(style: style, reuseIdentifier: reuseIdentifier)\n        setupCell()\n    }\n\n    required init?(coder aDecoder: NSCoder) {\n        super.init(coder: aDecoder)\n        setupCell()\n    }\n\n    func setBarWidth(_ w: CGFloat) -> Void {\n        widthConstraint.constant = w\n    }\n\n    func setupCell() {\n\n        // instantiate the view\n        stretchView = UIView()\n        stretchView.translatesAutoresizingMaskIntoConstraints = false\n        stretchView.backgroundColor = .green\n\n        // add it to self (the cell)\n        self.addSubview(stretchView)\n\n        // "pin" it to top, bottom and left\n        stretchView.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 0.0).isActive = true\n        stretchView.topAnchor.constraint(equalTo: self.topAnchor, constant: 0.0).isActive = true\n        stretchView.bottomAnchor.constraint(equalTo: self.bottomAnchor, constant: 0.0).isActive = true\n\n        // set height constraint to be 50% of the width\n        stretchView.heightAnchor.constraint(equalTo: stretchView.widthAnchor, multiplier: 0.5).isActive = true\n\n        // instantiate the width constraint\n        widthConstraint = NSLayoutConstraint(item: stretchView, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 40)\n\n        // needs priority of 999 so auto-layout doesn\'t complain\n        widthConstraint.priority = 999\n\n        // activate the width constraint\n        NSLayoutConstraint.activate([widthConstraint])\n\n        // create a UIPanGestureRecognizer and add it to the stretch view\n        let panGesture = UIPanGestureRecognizer(target: self, action: #selector(didPan(sender:)))\n\n        stretchView.addGestureRecognizer(panGesture)\n\n    }\n\n    func didPan(sender: UIPanGestureRecognizer) {\n\n        let loc = sender.location(in: self)\n\n        if sender.state == .began {\n\n            // if you want to do something on drag start...\n            //print("Gesture began")\n\n        } else if sender.state == .changed {\n\n            //print("Gesture is changing", loc)\n\n            // update the width of the stretch view (but keep it at least 20-pts wide, so it doesn\'t disappear)\n            // height is set to 1:1 so it updates automatically\n            widthConstraint.constant = max(loc.x, 20)\n\n            // call back to the view controller\n            scaleAction?(widthConstraint.constant)\n\n        } else if sender.state == .ended {\n\n            // if you want to do something on drag end...\n            //print("Gesture ended")\n\n        }\n\n    }\n\n}\n\n\nclass StretchCellTableViewController: UITableViewController {\n\n    // array to track the bar widths, assuming we have more than one row with a bar\n    // only a few rows will have the "stretch bar" - but for this example we\'ll just track a barWidth for *every* row\n    var barWidths = [CGFloat]()\n\n    override func viewDidLoad() {\n        super.viewDidLoad()\n\n        tableView.rowHeight = UITableViewAutomaticDimension\n        tableView.estimatedRowHeight = 80\n\n        tableView.register(StretchCell.self, forCellReuseIdentifier: "StretchCell")\n        tableView.register(NonStretchCell.self, forCellReuseIdentifier: "NonStretchCell")\n\n        // init array for barWidths... initial value: 40, 30 slots\n        barWidths = Array(repeating: 40, count: 30)\n    }\n\n    override func numberOfSections(in tableView: UITableView) -> Int {\n        return 1\n    }\n\n    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {\n        return barWidths.count\n    }\n\n    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {\n\n        // just make every 5th row a "Stretch" cell (starting at #3)\n        if indexPath.row % 5 == 3 {\n            let cell = tableView.dequeueReusableCell(withIdentifier: "StretchCell", for: indexPath) as! StretchCell\n            cell.selectionStyle = .none\n\n            // cells are reused, so set the bar width to our saved value\n            cell.setBarWidth(barWidths[indexPath.row])\n\n            // "call-back" function\n            cell.scaleAction = {\n                (newWidth) in\n                // update the bar width in our tracking array\n                self.barWidths[indexPath.row] = newWidth\n\n                // disable Animations, because we\'re changing the size repeatedly\n                UIView.setAnimationsEnabled(false)\n\n                // wrap begin/end updates() to force row-height re-calc\n                self.tableView.beginUpdates()\n                self.tableView.endUpdates()\n\n                // re-enable Animations\n                UIView.setAnimationsEnabled(true)\n            }\n\n            cell.preservesSuperviewLayoutMargins = false\n            cell.separatorInset = UIEdgeInsets.zero\n            cell.layoutMargins = UIEdgeInsets.zero\n\n            return cell\n        }\n\n        let cell = tableView.dequeueReusableCell(withIdentifier: "NonStretchCell", for: indexPath) as! NonStretchCell\n\n        // just for demonstration\'s sake\n\n        if indexPath.row % 7 == 5 {\n            cell.theLabel.text = "Row: \\(indexPath.row) - This is just to show the text wrapping onto multiple lines. Pretty standard for auto-sizing UITableView cells."\n        } else {\n            cell.theLabel.text = "Row: \\(indexPath.row)"\n        }\n\n        cell.preservesSuperviewLayoutMargins = false\n        cell.separatorInset = UIEdgeInsets.zero\n        cell.layoutMargins = UIEdgeInsets.zero\n\n        return cell\n    }\n\n}\n

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结果是：

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