Xamarin中TextCell绑定文本不显示问题排查及解决

问题现象 #

ListView绑定ViewModel中Model的Guests属性（该属性为Newtonsoft反序列化生成的ObservableCollection<string>，已添加JsonProperty特性保证setter被调用，测试数据共12条），使用TextCell并通过{Binding .}绑定文本时，首次加载单元格已渲染但无文本显示。通过热重载移除绑定中的“.”再保存，文本会正常显示；重新添加“.”后文本也能正常更新，修改TextColor属性也存在类似首次不生效的情况，疑似首次加载时绑定逻辑异常。

相关代码 #

初始视图代码 #

<ListView ItemsSource="{Binding Guests}"
          Margin="0" HeightRequest="300"
          VerticalOptions="FillAndExpand"
          RowHeight="28"
          SelectionMode="None">
    <ListView.ItemTemplate>
        <DataTemplate>
            <TextCell Text="{Binding .}" TextColor="{StaticResource BT-DarkGray}"/>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

Model代码 #

private ObservableCollection<string> _guest;

[JsonProperty("guests")]
public ObservableCollection<string> Guests
{
    get => _guest; 
    set => SetProperty(ref _guest, value); 
}

private ObservableCollection<LocalShowFlight> _flights;
[JsonProperty("flights")]
public ObservableCollection<LocalShowFlight> Flights
{
    get => _flights; 
    set => SetProperty(ref _flights, value); 
}
private ObservableCollection<LocalShowTiming> _timings;
[JsonProperty("timings")]
public ObservableCollection<LocalShowTiming> Timings
{
    get => _timings; 
    set => SetProperty(ref _timings, value); 
}

public void RaisCollectionChanged()
{
    OnPropertyChanged(nameof(Guests));
    OnPropertyChanged(nameof(Flights));
    OnPropertyChanged(nameof(TimingOther));
}

ViewModel代码 #

public ShowBandAppModelV2 Model
{
    get { return _model; }
    set
    {
        SetProperty(ref _model, value);
        Model?.RaisCollectionChanged();
    }
}

解决方法 #

将TextCell替换为包含Label的ViewCell，并为DataTemplate指定x:DataType="x:String"，修改后的视图代码如下：

<ListView.ItemTemplate>
    <DataTemplate x:DataType="x:String">
        <ViewCell>
            <Label Text="{Binding .}" TextColor="{StaticResource BT-DarkGray}" VerticalTextAlignment="Start"
                   LineBreakMode="TailTruncation"/>
        </ViewCell>
    </DataTemplate>
</ListView.ItemTemplate>

内容的提问来源于stack exchange，提问作者Bart Peirens