在 UIScrollView 中居中 UILabel答案

【问题标题】：Center UILabel inside UIScrollView在 UIScrollView 中居中 UILabel
【发布时间】：2018-07-12 08:03:54
【问题描述】：

我正在尝试显示具有可变文本长度的UILabel，因此我需要它位于UIScrollView 内。这是结果

问题是当文本很短时 UILabel 粘在顶部，当我删除顶部和底部约束并添加垂直中心约束时，我得到了这个错误

我该如何解决？

【问题讨论】：

ScrollView 需要 6 个（不是 4 个）约束。你也应该设置leading-trailing-top-bottom 和 width-height
我知道，如何在 ScrollView 中居中标签？我不知道高度，因为它是动态的，但宽度是固定的@QuocNguyen
对不起，我没有仔细阅读。您可以尝试将标签的约束设置为 centerX、centerY 和如下前导 imgur.com/a/DfxoSvq
你的问题解决了吗？
秘诀在于优先级。干得好！

标签： ios swift xcode uiscrollview

【解决方案1】：

我已经设法通过将垂直中心（优先级 750）添加到容器视图来做到这一点。在下面添加了故事板源，当您将较长的文本添加到标签时，它应该会滚动。

<?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="BYZ-38-t0r">
    <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>
        <!--View Controller-->
        <scene sceneID="tne-QT-ifu">
            <objects>
                <viewController id="BYZ-38-t0r" customClass="ViewController" sceneMemberID="viewController">
                    <view key="view" contentMode="scaleToFill" id="8bC-Xf-vdC">
                        <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                        <subviews>
                            <scrollView clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="gQl-vh-MlV">
                                <rect key="frame" x="0.0" y="20" width="375" height="647"/>
                                <subviews>
                                    <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="7JP-ij-rQ3">
                                        <rect key="frame" x="0.0" y="0.0" width="375" height="647"/>
                                        <subviews>
                                            <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" textAlignment="natural" lineBreakMode="tailTruncation" numberOfLines="0" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="hdc-ci-8Q2">
                                                <rect key="frame" x="20" y="20" width="335" height="607"/>
                                                <string key="text">Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum Lorem ipsum </string>
                                                <fontDescription key="fontDescription" type="system" pointSize="17"/>
                                                <nil key="textColor"/>
                                                <nil key="highlightedColor"/>
                                            </label>
                                        </subviews>
                                        <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
                                        <constraints>
                                            <constraint firstAttribute="bottom" secondItem="hdc-ci-8Q2" secondAttribute="bottom" constant="20" id="04P-f7-0B8"/>
                                            <constraint firstItem="hdc-ci-8Q2" firstAttribute="top" secondItem="7JP-ij-rQ3" secondAttribute="top" constant="20" id="AJ1-ka-NVH"/>
                                            <constraint firstAttribute="trailing" secondItem="hdc-ci-8Q2" secondAttribute="trailing" constant="20" id="Ihl-iD-MJL"/>
                                            <constraint firstItem="hdc-ci-8Q2" firstAttribute="leading" secondItem="7JP-ij-rQ3" secondAttribute="leading" constant="20" id="Mea-zN-gQ6"/>
                                        </constraints>
                                    </view>
                                </subviews>
                                <constraints>
                                    <constraint firstAttribute="bottom" secondItem="7JP-ij-rQ3" secondAttribute="bottom" priority="250" id="5Pl-Zc-jKy"/>
                                    <constraint firstItem="7JP-ij-rQ3" firstAttribute="leading" secondItem="gQl-vh-MlV" secondAttribute="leading" id="6wk-HX-XUh"/>
                                    <constraint firstItem="7JP-ij-rQ3" firstAttribute="centerY" secondItem="gQl-vh-MlV" secondAttribute="centerY" priority="750" id="a7o-hw-NRM"/>
                                    <constraint firstAttribute="trailing" secondItem="7JP-ij-rQ3" secondAttribute="trailing" id="hSU-wA-1v0"/>
                                    <constraint firstItem="7JP-ij-rQ3" firstAttribute="top" secondItem="gQl-vh-MlV" secondAttribute="top" id="o0p-fH-VhV"/>
                                    <constraint firstItem="7JP-ij-rQ3" firstAttribute="width" secondItem="gQl-vh-MlV" secondAttribute="width" id="wgf-e8-HLU"/>
                                </constraints>
                            </scrollView>
                        </subviews>
                        <color key="backgroundColor" red="1" green="1" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                        <constraints>
                            <constraint firstItem="6Tk-OE-BBY" firstAttribute="bottom" secondItem="gQl-vh-MlV" secondAttribute="bottom" id="Axy-dp-ZiJ"/>
                            <constraint firstItem="6Tk-OE-BBY" firstAttribute="trailing" secondItem="gQl-vh-MlV" secondAttribute="trailing" id="LED-nS-Ba6"/>
                            <constraint firstItem="gQl-vh-MlV" firstAttribute="top" secondItem="6Tk-OE-BBY" secondAttribute="top" id="RS2-MF-Aya"/>
                            <constraint firstItem="gQl-vh-MlV" firstAttribute="leading" secondItem="6Tk-OE-BBY" secondAttribute="leading" id="euc-Qn-E0q"/>
                        </constraints>
                        <viewLayoutGuide key="safeArea" id="6Tk-OE-BBY"/>
                    </view>
                </viewController>
                <placeholder placeholderIdentifier="IBFirstResponder" id="dkx-z0-nzr" sceneMemberID="firstResponder"/>
            </objects>
        </scene>
    </scenes>
</document>

【讨论】：

【解决方案2】：

您可以移除顶部约束并添加 vertical center 和 horizontal center 约束到您的标签，这样您的标签应该位于滚动视图的中心

【讨论】：