XCode：要使图像与屏幕大小相同，需要哪些约束？

Question

在我的应用程序中有一个 UIViewController，其唯一工作是显示从服务器下载的图像。我希望此图像与默认屏幕大小相同；此外，由于此图像是一种食谱，我希望用户能够缩放图像 in/out 以便更好地阅读，这就是为什么我将 UIImageview 嵌入 UIScrollView.

UIScrollView有4个约束：UIScrollView和UIViewController之间的4个距离都设置为0。

UIImageView有4个约束：UIImageView和包含它的UIScrollView之间的4个距离都设置为0。

不管怎样，从下面的截图可以看出

结果与预期不符：UIScrollView 和 UIViewController 顶部之间的距离更大，图像更大。

你知道如何得到想要的结果吗？

<!--Recipe View Controller-->
    <scene sceneID="y5Y-bz-arP">
        <objects>
            <viewController id="VnP-A1-Srr" customClass="RecipeViewController" customModule="Fishmeter" customModuleProvider="target" sceneMemberID="viewController">
                <layoutGuides>
                    <viewControllerLayoutGuide type="top" id="J4Y-SW-LaP"/>
                    <viewControllerLayoutGuide type="bottom" id="Yuj-fl-Q0L"/>
                </layoutGuides>
                <view key="view" contentMode="scaleToFill" id="1xx-WP-lNU">
                    <rect key="frame" x="0.0" y="0.0" width="600" height="600"/>
                    <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                    <subviews>
                        <scrollView clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="scaleToFill" ambiguous="YES" misplaced="YES" translatesAutoresizingMaskIntoConstraints="NO" id="5rg-8n-qc9">
                            <rect key="frame" x="27" y="94" width="558" height="486"/>
                            <subviews>
                                <imageView userInteractionEnabled="NO" contentMode="scaleToFill" horizontalHuggingPriority="251" verticalHuggingPriority="251" ambiguous="YES" misplaced="YES" translatesAutoresizingMaskIntoConstraints="NO" id="Y0D-XM-XJ8">
                                    <rect key="frame" x="159" y="158" width="240" height="128"/>
                                </imageView>
                            </subviews>
                            <constraints>
                                <constraint firstAttribute="trailing" secondItem="Y0D-XM-XJ8" secondAttribute="trailing" id="P5c-2q-jZO"/>
                                <constraint firstItem="Y0D-XM-XJ8" firstAttribute="leading" secondItem="5rg-8n-qc9" secondAttribute="leading" id="VkK-Pa-vmE"/>
                                <constraint firstAttribute="bottom" secondItem="Y0D-XM-XJ8" secondAttribute="bottom" id="mzG-vW-1fV"/>
                                <constraint firstItem="Y0D-XM-XJ8" firstAttribute="top" secondItem="5rg-8n-qc9" secondAttribute="top" id="uoZ-V1-kxX"/>
                            </constraints>
                        </scrollView>
                    </subviews>
                    <color key="backgroundColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
                    <constraints>
                        <constraint firstAttribute="trailingMargin" secondItem="5rg-8n-qc9" secondAttribute="trailing" id="PbP-OD-eRM"/>
                        <constraint firstItem="Yuj-fl-Q0L" firstAttribute="top" secondItem="5rg-8n-qc9" secondAttribute="bottom" id="TQL-96-UgX"/>
                        <constraint firstItem="5rg-8n-qc9" firstAttribute="leading" secondItem="1xx-WP-lNU" secondAttribute="leadingMargin" id="XEX-ck-lZi"/>
                        <constraint firstItem="5rg-8n-qc9" firstAttribute="top" secondItem="J4Y-SW-LaP" secondAttribute="bottom" constant="-10" id="lL6-Dk-MZe"/>
                    </constraints>
                </view>
                <connections>
                    <outlet property="recipeImage" destination="Y0D-XM-XJ8" id="5pc-vd-Ak8"/>
                    <outlet property="scrollView" destination="5rg-8n-qc9" id="Ieo-Uk-HIB"/>
                </connections>
            </viewController>
            <placeholder placeholderIdentifier="IBFirstResponder" id="cUt-8l-j6r" userLabel="First Responder" sceneMemberID="firstResponder"/>
        </objects>
        <point key="canvasLocation" x="3265" y="-311"/>
    </scene>

Answer 1

为了使 UIScrollView 正确处理其内容，滚动视图内容的约束不能由滚动视图的大小定义。约束必须引用在滚动视图外定义的大小。

所以，去掉UIImageView的约束，设置约束到UIViewController主视图.[=10=的上下左右距离为0 ]

--T

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