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 中。这是结果
问题是当文本很短时，UILabel 会粘在顶部，当我删除顶部和底部约束并添加垂直居中约束时，我得到了这个错误
我该如何解决？
最佳答案
我已经设法通过向容器 View 添加垂直中心(优先级 750)来做到这一点。在下面添加了 Storyboard源代码，当您向标签添加较长的文本时它应该滚动。
<?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>
关于ios - 在 UIScrollView 中居中 UILabel，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51300324/