Question

在我的视图控制器中，我有一个用于承载子视图的视图。我们称之为ViewA。控制器加载后，将从笔尖加载的视图设置为ViewA内的子视图。根据子视图中的内容，其高度可以是不同的大小。

因此，我创建了一个代理，当子视图的高度发生变化时，它将发出警报，通知其父视图更新其自身的高度：

UIViewController

class MyViewController: UIViewController, MyViewDelegate {

    @IBOutlet weak var myView: UIView!
    @IBOutlet weak var myViewHeightConstraint: NSLayoutConstraint!

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        let mySubView: MySubView = UINib(nibName: "MySubView", bundle: nil).instantiate(withOwner: MySubView(), options: nil)[0] as! MySubView
        mySubview.translatesAutoresizingMaskIntoConstraints = false
        mySubView.delegate = self
        myView.addSubView(mySubView)

        let leadingConstraint = NSLayoutConstraint(item: mySubView, attribute: .leading, relatedBy: .equal, toItem: myView, attribute: .leading, multiplier: 1, constant: 0)
        let trailingConstraint = NSLayoutConstraint(item: mySubView, attribute: .trailing, relatedBy: .equal, toItem: myView, attribute: .trailing, multiplier: 1, constant: 0)
        let topConstraint = NSLayoutConstraint(item: mySubView, attribute: .top, relatedBy: .equal, toItem: myView, attribute: .top, multiplier: 1, constant: 0)
        let bottomConstraint = NSLayoutConstraint(item: mySubView, attribute: .bottom, relatedBy: .equal, toItem: myView, attribute: .bottom, multiplier: 1, constant: 0)
        NSLayoutConstraint.activate([leadingConstraint, trailingConstraint, topConstraint, bottomConstraint])

    }

    override func viewDidLayoutSubviews() {
        addShadowToView()
    }

    func addShadowToView() {
        myView.layer.masksToBounds = false
        myView.layer.shadowColor = UIColor.black.cgColor
        myView.layer.shadowOpacity = 0.25
        myView.layer.shadowOffset = CGSize(width: 0, height: 0)
        myView.layer.shadowRadius = 5.0
        myView.layer.shadowPath = UIBezierPath(rect. myView.bounds).cgPath
    }


    MySubViewDelegate(_ mySubView: MySubView, didUpdateHeightTo height: CGFloat) {
        myViewHeightConstraint.constant = height
        myView.updateConstraints()
        addShadowToView()
    } 
}

MySubView

class MySubView: UIView {

    var delegate: MySubViewDelegate?

    @IBOutlet weak var aView: UIView!
    @IBOutlet weak var aViewHeghtConstraint: NSLayoutConstraint!\

    var isViewCollapsed = false

    @IBAction func toggleView() {

        aViewHeightConstraint.contant = isViewCollapsed ? 100 : 0
        isViewCollapsed = !isViewCollapsed

        updateConstraints()

        delegate.MSView(self, didUpdateHeightTo height: self.frame.height)
    }
}

protocol MySubViewDelegate {
    func MSView(_ MySubView: MySubView, didUpdateHeightTo height: CGFloat)
}

是否有更好的方法将展开和折叠的子视图放入父视图，从而能够更新其自身的框架以适应其子项的更改？

Answer 1

评论和发布代码后...

看起来您正在做很多不需要做的事情。

在适当的约束下，您需要的代码要少得多，并且根本不需要协议/委托。

首先-这只是一个提示-您可以以更简单，更易读的方式在代码中定义约束：

    myView.addSubview(mySubView)

    NSLayoutConstraint.activate([
        mySubView.topAnchor.constraint(equalTo: myView.topAnchor, constant: 0.0),
        mySubView.bottomAnchor.constraint(equalTo: myView.bottomAnchor, constant: 0.0),
        mySubView.leadingAnchor.constraint(equalTo: myView.leadingAnchor, constant: 0.0),
        mySubView.trailingAnchor.constraint(equalTo: myView.trailingAnchor, constant: 0.0),
        ])

第二个-也是一个技巧-如果创建“阴影”视图子类，则它可以自行处理阴影更新：

class MyShadowedView: UIView {

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

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }

    func commonInit() -> Void {
        // non-changing properties - set on init
        layer.masksToBounds = false
        layer.shadowColor = UIColor.black.cgColor
        layer.shadowOpacity = 0.25
        layer.shadowOffset = CGSize(width: 0, height: 0)
        layer.shadowRadius = 5.0
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        // update the shadowPath
        layer.shadowPath = UIBezierPath(rect: bounds).cgPath
    }

}

当您将myView作为UIView添加到情节提要中时，只需将其类分配给MyShadowedView，而无需进行任何调用来添加阴影-它会自己做。

第三-根据您发布的代码，您的myView似乎有高度限制，并且您将mySubView限制在其顶部和底部。这意味着mySubView将是myView的高度，并且永远不会改变。您的“委托”功能尝试进行更改，但它始终会超过其受限制的高度。

所以...

在ViewController中，您想要添加一个UIView，将其类分配给MyShadowedView，并按照通常的方式为其赋予Top，Leading和Trailing约束（或Top，Width和CenterX，如果您需要的。）

对于其高度，给它一个关于高度限制的高度限制，但是将其设置为占位符，该占位符将在运行时删除。这使您可以在设计过程中看到它（并避免IB抱怨缺少约束），但是在运行时，您添加的子视图将控制其高度：

您的xib看起来像这样（简化了-我确定您有更多元素）

注意：为aView的底部约束赋予999的优先级也有助于避免IB约束警告。

点击按钮时，您的代码将在aView和100之间切换0的高度约束的常数。这将扩展/折叠其超级视图的高度，如果其超级视图（视图控制器中的myView），它将控制其高度。

您的完整代码最终为：

//
//  TannerViewController.swift
//
//  Created by Don Mag on 12/12/18.
//

import UIKit

class MySubView: UIView {

    @IBOutlet weak var aView: UIView!
    @IBOutlet weak var aViewHeightConstraint: NSLayoutConstraint!

    var isViewCollapsed = false

    @IBAction func toggleView(_ sender: Any) {
        aViewHeightConstraint.constant = isViewCollapsed ? 100 : 0
        isViewCollapsed = !isViewCollapsed
    }

}

class TannerViewController: UIViewController {

    @IBOutlet weak var myView: MyShadowedView!

    override func viewDidLoad() {
        super.viewDidLoad()

        let mySubView: MySubView = UINib(nibName: "MySubView", bundle: nil).instantiate(withOwner: MySubView(), options: nil)[0] as! MySubView
        mySubView.translatesAutoresizingMaskIntoConstraints = false
        myView.addSubview(mySubView)

        NSLayoutConstraint.activate([
            mySubView.topAnchor.constraint(equalTo: myView.topAnchor, constant: 0.0),
            mySubView.bottomAnchor.constraint(equalTo: myView.bottomAnchor, constant: 0.0),
            mySubView.leadingAnchor.constraint(equalTo: myView.leadingAnchor, constant: 0.0),
            mySubView.trailingAnchor.constraint(equalTo: myView.trailingAnchor, constant: 0.0),
            ])

    }

}

class MyShadowedView: UIView {

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

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        commonInit()
    }

    func commonInit() -> Void {
        // non-changing properties - set on init
        layer.masksToBounds = false
        layer.shadowColor = UIColor.black.cgColor
        layer.shadowOpacity = 0.25
        layer.shadowOffset = CGSize(width: 0, height: 0)
        layer.shadowRadius = 5.0
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        // update the shadowPath
        layer.shadowPath = UIBezierPath(rect: bounds).cgPath
    }

}

结果：

为方便地对此进行测试，这是情节提要的源代码：

<?xml version="1.0" encoding="UTF-8"?>
<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="14109" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES" initialViewController="jPc-3G-hfP">
    <device id="retina4_7" orientation="portrait">
        <adaptation id="fullscreen"/>
    </device>
    <dependencies>
        <deployment identifier="iOS"/>
        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14088"/>
        <capability name="Safe area layout guides" minToolsVersion="9.0"/>
        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
    </dependencies>
    <scenes>
        <!--Tanner View Controller-->
        <scene sceneID="f8L-af-3cE">
            <objects>
                <viewController id="jPc-3G-hfP" customClass="TannerViewController" customModule="SW4Temp" customModuleProvider="target" sceneMemberID="viewController">
                    <view key="view" contentMode="scaleToFill" id="0I2-oK-Mx2">
                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                        <subviews>
                            <view clipsSubviews="YES" contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="uKj-M5-owl" customClass="MyShadowedView" customModule="SW4Temp" customModuleProvider="target">
                                <rect key="frame" x="40" y="120" width="295" height="100"/>
                                <color key="backgroundColor" red="1" green="0.83234566450000003" blue="0.47320586440000001" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                <constraints>
                                    <constraint firstAttribute="height" constant="100" placeholder="YES" id="qvT-aM-Weq" userLabel="Placeholder Height = 100"/>
                                </constraints>
                            </view>
                        </subviews>
                        <color key="backgroundColor" red="0.99953407049999998" green="0.98835557699999999" blue="0.47265523669999998" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                        <constraints>
                            <constraint firstItem="uKj-M5-owl" firstAttribute="top" secondItem="twx-NV-wpY" secondAttribute="top" constant="100" id="141-8C-ZNl"/>
                            <constraint firstItem="twx-NV-wpY" firstAttribute="trailing" secondItem="uKj-M5-owl" secondAttribute="trailing" constant="40" id="5Zs-Or-GhR"/>
                            <constraint firstItem="uKj-M5-owl" firstAttribute="leading" secondItem="twx-NV-wpY" secondAttribute="leading" constant="40" id="R95-i1-Xb2"/>
                        </constraints>
                        <viewLayoutGuide key="safeArea" id="twx-NV-wpY"/>
                    </view>
                    <connections>
                        <outlet property="myView" destination="uKj-M5-owl" id="uCY-bV-QJd"/>
                    </connections>
                </viewController>
                <placeholder placeholderIdentifier="IBFirstResponder" id="q6f-6s-ke9" userLabel="First Responder" sceneMemberID="firstResponder"/>
            </objects>
            <point key="canvasLocation" x="53.600000000000001" y="101.19940029985008"/>
        </scene>
    </scenes>
</document>

和mySubView.xib：

<?xml version="1.0" encoding="UTF-8"?>
<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="14109" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES">
    <device id="retina4_7" orientation="portrait">
        <adaptation id="fullscreen"/>
    </device>
    <dependencies>
        <deployment identifier="iOS"/>
        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14088"/>
        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
    </dependencies>
    <objects>
        <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner"/>
        <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
        <view contentMode="scaleToFill" id="iN0-l3-epB" customClass="MySubView" customModule="SW4Temp" customModuleProvider="target">
            <rect key="frame" x="0.0" y="0.0" width="332" height="202"/>
            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
            <subviews>
                <button opaque="NO" contentMode="scaleToFill" verticalHuggingPriority="1000" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="T7q-1U-5iM">
                    <rect key="frame" x="106" y="20" width="120" height="30"/>
                    <color key="backgroundColor" red="0.92143100499999997" green="0.92145264149999995" blue="0.92144101860000005" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                    <constraints>
                        <constraint firstAttribute="width" constant="120" id="WJn-fl-dH1"/>
                    </constraints>
                    <state key="normal" title="Button"/>
                    <connections>
                        <action selector="toggleView:" destination="iN0-l3-epB" eventType="touchUpInside" id="LSR-3h-g1f"/>
                    </connections>
                </button>
                <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="Vtd-O9-gRZ">
                    <rect key="frame" x="40" y="70" width="252" height="100"/>
                    <color key="backgroundColor" red="0.46202266219999999" green="0.83828371759999998" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                    <constraints>
                        <constraint firstAttribute="height" constant="100" id="e3B-MV-NZK"/>
                    </constraints>
                </view>
            </subviews>
            <color key="backgroundColor" red="0.83216959239999999" green="0.98548370600000001" blue="0.47333085539999997" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
            <constraints>
                <constraint firstAttribute="bottom" secondItem="Vtd-O9-gRZ" secondAttribute="bottom" priority="999" constant="20" id="0aE-RM-0AZ"/>
                <constraint firstItem="T7q-1U-5iM" firstAttribute="top" secondItem="iN0-l3-epB" secondAttribute="top" constant="20" id="Acg-yV-bn2"/>
                <constraint firstItem="Vtd-O9-gRZ" firstAttribute="top" secondItem="T7q-1U-5iM" secondAttribute="bottom" constant="20" id="KVh-lw-Sst"/>
                <constraint firstItem="T7q-1U-5iM" firstAttribute="centerX" secondItem="iN0-l3-epB" secondAttribute="centerX" id="NUj-4y-fDg"/>
                <constraint firstItem="Vtd-O9-gRZ" firstAttribute="leading" secondItem="iN0-l3-epB" secondAttribute="leading" constant="40" id="cS4-7R-wW7"/>
                <constraint firstAttribute="trailing" secondItem="Vtd-O9-gRZ" secondAttribute="trailing" constant="40" id="kkG-9K-cEP"/>
            </constraints>
            <freeformSimulatedSizeMetrics key="simulatedDestinationMetrics"/>
            <connections>
                <outlet property="aView" destination="Vtd-O9-gRZ" id="SNl-ng-33p"/>
                <outlet property="aViewHeightConstraint" destination="e3B-MV-NZK" id="S4R-ct-gzE"/>
            </connections>
            <point key="canvasLocation" x="12" y="-179"/>
        </view>
    </objects>
</document>

Answer 2

在更新约束的常量之后，应调用layoutIfNeeded来强制布局更新，然后再获取新的高度：

print("Before:", self.frame.height)
heightConstraint.constant += 10
layoutIfNeeded()
print("After:", self.frame.height)

结果：

Before: 132.0
After: 142.0
Before: 142.0
After: 152.0
Before: 152.0
After: 162.0

处理包含能够折叠和展开的子视图的视图

2 个答案: