我无法在 Xamarin Studio 上使用 C# 更改 CollectionViewCell 的 UILabel 字体

Question

我在 ViewController 上有一个 CollectionView，它是 RootTabController 的一个选项卡。此 CollectionView 的 Cell 设计为 .xib:

西伯 UI:

<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="11762" systemVersion="16D32" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" colorMatched="YES">
<device id="retina4_7" orientation="portrait">
    <adaptation id="fullscreen"/>
</device>
<dependencies>
    <deployment identifier="iOS"/>
    <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="11757"/>
    <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"/>
    <collectionViewCell opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center" reuseIdentifier="GridBoxCell" id="cZE-iV-UFb" customClass="GridBoxViewCell">
        <rect key="frame" x="0.0" y="0.0" width="50" height="50"/>
        <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
        <view key="contentView" opaque="NO" clipsSubviews="YES" multipleTouchEnabled="YES" contentMode="center">
            <rect key="frame" x="0.0" y="0.0" width="50" height="50"/>
            <autoresizingMask key="autoresizingMask"/>
            <subviews>
                <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Label" textAlignment="center" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="4">
                    <rect key="frame" x="0.0" y="0.0" width="50" height="50"/>
                    <fontDescription key="fontDescription" type="system" pointSize="12"/>
                    <color key="textColor" white="1" alpha="1" colorSpace="calibratedWhite"/>
                    <nil key="highlightedColor"/>
                </label>
            </subviews>
        </view>
        <color key="backgroundColor" red="0.20000000000000001" green="0.031372549019607843" blue="0.38039215686274508" alpha="1" colorSpace="calibratedRGB"/>
        <constraints>
            <constraint firstItem="4" firstAttribute="top" secondItem="cZE-iV-UFb" secondAttribute="top" id="10"/>
            <constraint firstItem="4" firstAttribute="leading" secondItem="cZE-iV-UFb" secondAttribute="leading" id="11"/>
            <constraint firstAttribute="bottom" secondItem="4" secondAttribute="bottom" id="12"/>
            <constraint firstAttribute="trailing" secondItem="4" secondAttribute="trailing" id="13"/>
        </constraints>
        <userDefinedRuntimeAttributes>
            <userDefinedRuntimeAttribute type="number" keyPath="layer.cornerRadius">
                <real key="value" value="5"/>
            </userDefinedRuntimeAttribute>
        </userDefinedRuntimeAttributes>
        <connections>
            <outlet property="Value_Label" destination="4" id="name-outlet-4"/>
        </connections>
    </collectionViewCell>
</objects>

我正在尝试通过基于设备屏幕大小的代码在构造阶段更改 UıLabel 的字体，同时在添加到 CollectionView 之前加载 Xib：

Xib代码：

        protected GridBoxViewCell(IntPtr handle) : base(handle)
        {
            // Note: this .ctor should not contain any initialization logic.

            var selectback_view = new UIView(); // Selectedbackground UIview.

            selectback_view.BackgroundColor = UIColor.FromRGB(117, 24, 73); // pink Color

            SelectedBackgroundView = selectback_view;  // Selected background assigned.

            if (UIDevice.CurrentDevice.Model.Contains("iPad")) // If a iPad
            {
                Value_Label.Font = UIFont.FromName(".SFUIText", 20f); // Increse font width.
            }

            else // If a iPhone or iPod Touch
            {
                if (UIScreen.MainScreen.Bounds.Width == 414 && UIScreen.MainScreen.Bounds.Height == 736) // a iPhone Plus 5.5 in point
                {
                    Value_Label.Font = UIFont.FromName(".SFUIText", 16f); // Increse font width.
                }

                if (UIScreen.MainScreen.Bounds.Width == 375 && UIScreen.MainScreen.Bounds.Height == 667) // a iPhone 4.7 in point
                {
                    Value_Label.Font = UIFont.FromName(".SFUIText", 14f); // Increse font width.
                }

            }
}

但是，这一行给出了 NullReferenceException:

Value_Label.Font = UIFont.FromName(".SFUIText", 14f); // Increse font width.

位于键盘顶部的 UIBarButton "Done" 将在 UITextBox 上输入的值添加到基于 LinkedList 的 GridViewDataSource。 CollectionView的刷新数据显示方块。

一开始是可以的，现在不行了。我无法弄清楚为什么它不起作用 now.Also 请注意，xib 运行没有问题 4" iPhones like SE 因为我没有为它编写任何约束，它使用默认字体。如果你我会很高兴可以帮助我。谢谢。

Answer 1

您应该覆盖 awakeFromNib 方法并在该方法中分配字体。

我无法在 Xamarin Studio 上使用 C# 更改 CollectionViewCell 的 UILabel 字体

I Cannot Change CollectionViewCell's UILabel Font with C# on Xamarin Studio

c#

uilabel

xamarin.ios

uicollectionview

uicollectionviewcell