如何通过 SnapKit 更新高度约束并更新单元格高度？

Question

我有一个 TableViewCell 和两个按钮来切换不同的约束。
我想更新它的高度约束和单元格高度。
就像
当我点击buttonB时跟随pic1一样，视图会像
pic2一样改变然后我点击buttonA，视图将回到pic1
我尝试修改约束，但我无法更新高度。
对我有什么想法或答案吗？
谢谢

图片1

图片2

这是代码：

class CellContainView: UIView {

let buttonA: UIButton = { () -> UIButton in
    let ui = UIButton()
    ui.titleLabel?.numberOfLines = 0
    ui.setTitle("Click\nA", for: .normal)
    ui.backgroundColor = UIColor.blue
    return ui
}()

let buttonB: UIButton = { () -> UIButton in
    let ui = UIButton()
    ui.titleLabel?.numberOfLines = 0
    ui.setTitle("Click\nB", for: .normal)
    ui.backgroundColor = UIColor.gray
    return ui
}()

let buttonC: UIButton = { () -> UIButton in
    let ui = UIButton()
    ui.titleLabel?.numberOfLines = 0
    ui.setTitle("Click\nC", for: .normal)
    ui.backgroundColor = UIColor.brown
    return ui
}()

let labelA: UILabel = { () -> UILabel in
    let ui = UILabel()
    ui.text = "Test"
    return ui
}()

let viewA: UIView = { () -> UIView in
    let ui = UIView()
    ui.backgroundColor = UIColor.red
    return ui
}()

override init(frame: CGRect) {
    super.init(frame: frame)

    addUI()
    addConstrain()
}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

func addUI() {

    self.addSubview(buttonA)
    self.addSubview(buttonB)
    self.addSubview(buttonC)
    self.addSubview(labelA)
    self.addSubview(viewA)

}

func addConstrain() {

    buttonA.snp.makeConstraints { (make) in
        make.left.top.equalToSuperview()
        make.height.equalTo(60)
    }

    buttonB.snp.makeConstraints { (make) in
        make.left.equalTo(buttonA.snp.right)
        make.top.right.equalToSuperview()
        make.width.equalTo(buttonA.snp.width)
        make.height.equalTo(buttonA.snp.height)
    }

    buttonC.snp.makeConstraints { (make) in
        make.left.equalTo(15)
        make.right.equalTo(-15)
        make.bottom.equalTo(-15)
        make.height.equalTo(50)
    }

    labelA.snp.makeConstraints { (make) in
        make.left.equalTo(15)
        make.top.equalTo(buttonA.snp.bottom).offset(15)
        make.width.equalTo(195)
        make.height.equalTo(50)
    }

    viewA.snp.makeConstraints { (make) in
        make.left.equalTo(labelA.snp.right)
        make.top.equalTo(buttonA.snp.bottom).offset(15)
        make.right.equalTo(-15)
        make.height.equalTo(50)
        make.bottom.equalTo(buttonC.snp.top).offset(-10)
    }
}

func updateConstrain(sender: UIButton) {

    switch sender {
    case buttonA:

        viewA.snp.updateConstraints { (make) in
            make.height.equalTo(50)
        }

    case buttonB:

        viewA.snp.updateConstraints { (make) in
            make.height.equalTo(150)
        }

    default:
        break
    }

}

}

class TestTableViewCell: UITableViewCell {

let cellContainView: CellContainView = { () -> CellContainView in
    let ui = CellContainView()
    ui.backgroundColor = UIColor.orange
    return ui
}()

override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
    super.init(style: style, reuseIdentifier: reuseIdentifier)

    self.addSubview(cellContainView)

    cellContainView.snp.makeConstraints { (make) in
        make.left.top.equalTo(15)
        make.bottom.right.equalTo(-15)
    }

}

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

}

class ViewController: UIViewController, UITableViewDelegate, UITableViewDataSource {

let tableView: UITableView = { () -> UITableView in
    let ui = UITableView()
    return ui
}()

override func viewDidLoad() {
    super.viewDidLoad()

    tableView.delegate = self
    tableView.dataSource = self
    tableView.rowHeight = UITableViewAutomaticDimension
    tableView.estimatedRowHeight = 44
    tableView.register(TestTableViewCell.self, forCellReuseIdentifier: "TestTableViewCell")
    tableView.tableFooterView = UIView()

    self.view.addSubview(tableView)
    tableView.snp.makeConstraints { (make) in
        make.top.left.right.bottom.equalToSuperview()
    }
}

@objc func buttonAClicked(sender: UIButton) {

    let index = IndexPath(row: 0, section: 0)
    let cell = tableView.cellForRow(at: index) as! TestTableViewCell
    cell.cellContainView.updateConstrain(sender: sender)
    tableview.reloadData()
}

@objc func buttonBClicked(sender: UIButton) {

    let index = IndexPath(row: 0, section: 0)
    let cell = tableView.cellForRow(at: index) as! TestTableViewCell
    cell.cellContainView.updateConstrain(sender: sender)
    tableview.reloadData()
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return 1
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCell(withIdentifier: "TestTableViewCell", for: indexPath) as! TestTableViewCell

    cell.cellContainView.buttonA.addTarget(self, action: #selector(buttonAClicked), for: .touchUpInside)
    cell.cellContainView.buttonB.addTarget(self, action: #selector(buttonBClicked), for: .touchUpInside)

    return cell
}

}

单击 buttonB 时更新约束问题（添加更新 viewA heightConstrain & tableview.reloadData()）：

TestCellUpdateHeight[29975:5195310] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want. 
Try this: 
    (1) look at each constraint and try to figure out which you don't expect; 
    (2) find the code that added the unwanted constraint or constraints and fix it. 
(
"<SnapKit.LayoutConstraint:0x6040000a4320@CellContainView.swift#75 UIButton:0x7fa1d0d0d680.height == 60.0>",
"<SnapKit.LayoutConstraint:0x6040000a49e0@CellContainView.swift#89 UIButton:0x7fa1d0d10610.height == 50.0>",
"<SnapKit.LayoutConstraint:0x6040000a51c0@CellContainView.swift#104 UIView:0x7fa1d0d11130.height == 150.0>",
"<SnapKit.LayoutConstraint:0x6040000a4800@CellContainView.swift#80 UIButton:0x7fa1d0d0f7b0.top == TestCellUpdateHeight.CellContainView:0x7fa1d0d0d470.top>",
"<SnapKit.LayoutConstraint:0x6040000a4a40@CellContainView.swift#82 UIButton:0x7fa1d0d0f7b0.height == UIButton:0x7fa1d0d0d680.height>",
"<SnapKit.LayoutConstraint:0x6040000a4ec0@CellContainView.swift#88 UIButton:0x7fa1d0d10610.bottom == TestCellUpdateHeight.CellContainView:0x7fa1d0d0d470.bottom - 15.0>",
"<SnapKit.LayoutConstraint:0x6040000a5100@CellContainView.swift#102 UIView:0x7fa1d0d11130.top == UIButton:0x7fa1d0d0f7b0.bottom + 15.0>",
"<SnapKit.LayoutConstraint:0x6040000a5220@CellContainView.swift#105 UIView:0x7fa1d0d11130.bottom == UIButton:0x7fa1d0d10610.top - 10.0>",
"<SnapKit.LayoutConstraint:0x6040000a52e0@TestTableViewCell.swift#26 TestCellUpdateHeight.CellContainView:0x7fa1d0d0d470.top == TestCellUpdateHeight.TestTableViewCell:0x7fa1d208a000.top + 15.0>",
"<SnapKit.LayoutConstraint:0x6040000a53a0@TestTableViewCell.swift#27 TestCellUpdateHeight.CellContainView:0x7fa1d0d0d470.bottom == TestCellUpdateHeight.TestTableViewCell:0x7fa1d208a000.bottom - 15.0>",
"<NSLayoutConstraint:0x6080002819f0 'UIView-Encapsulated-Layout-Height' TestCellUpdateHeight.TestTableViewCell:0x7fa1d208a000'TestTableViewCell'.height == 230   (active)>"
)

Will attempt to recover by breaking constraint 

Answer 1

一般来说，要更新 a 的高度约束，uiview:UIView您应该先保存它：

var viewHeightConstraint: Constraint!
uiview.snp.makeConstraints { (make) in
    viewHeightConstraint = make.height.equalTo(50).constraint
}

如果您只是使用updateConstraints函数，它将添加导致问题的新高度约束Unable to simultaneously satisfy constraints。所以你必须删除最后一个：

viewHeightConstraint.deactivate()

然后再次进行约束：

uiview.snp.makeConstraints { (make) in
    viewHeightConstraint = make.height.equalTo(100).constraint
}

Answer 2

你目前在做什么

labelA.snp.updateConstraints { (make) in
   make.bottom.equalTo(buttonC.snp.top).offset(-100)
}

将增加 labelA 的底部距离，但会使其顶部常数与您需要的相同

1-更新高度labelA

或者

2-更新前面的redView的高度

也不要忘记打电话

cell.cellContainView.updateConstrain(sender: sender)
cell.layoutIfNeeded()

另请注意，由于单元格重用，您可能会发现其他单元格被拉伸，因此您需要跟踪拉伸的单元格索引并将其应用到内部cellForRowAt

你也可以这样做

func tableView(_ tableView: UITableView, 
     heightForRowAt indexPath: IndexPath) -> CGFloat
   return expandArr[indexPath.row] ? 300 : 100
}

在哪里

var expandArr = [Bool]()

指示单元格是否展开，如果您有一个模型，您可以向其中添加一个 bool 值，而不是这个单独的 arr （用于说明）