Xamarin.Forms UWP应用中如何动态设置Picker控件内文本颜色

方案一：DataTemplate + 绑定 + 值转换器（推荐MVVM场景） #

1. 定义数据模型 #

创建包含名称和状态标记的实体类，若需要状态变化时自动更新UI，需实现INotifyPropertyChanged接口：

public class ItemModel : INotifyPropertyChanged
{
    private string _name;
    public string Name
    {
        get => _name;
        set
        {
            _name = value;
            OnPropertyChanged();
        }
    }

    private int _status;
    public int Status
    {
        get => _status;
        set
        {
            _status = value;
            OnPropertyChanged();
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

2. 实现值转换器 #

创建实现IValueConverter的类，将状态标记转换为对应的Brush：

public class StatusToColorConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, string language)
    {
        if (value is int status)
        {
            return status switch
            {
                0 => new SolidColorBrush(Colors.Red),
                1 => new SolidColorBrush(Colors.Green),
                // 可扩展更多状态对应的颜色
                _ => new SolidColorBrush(Colors.Black)
            };
        }
        return new SolidColorBrush(Colors.Black);
    }

    public object ConvertBack(object value, Type targetType, object parameter, string language)
    {
        throw new NotImplementedException();
    }
}

3. XAML配置 #

在页面资源中声明转换器，给Picker设置绑定数据的ItemTemplate：

<Page.Resources>
    <local:StatusToColorConverter x:Key="StatusToColorConverter"/>
</Page.Resources>

<Picker x:Name="ColorPicker" ItemsSource="{Binding ItemList}">
    <Picker.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Name}" Foreground="{Binding Status, Converter={StaticResource StatusToColorConverter}}"/>
        </DataTemplate>
    </Picker.ItemTemplate>
</Picker>

4. 绑定数据源 #

在页面ViewModel或后台代码中初始化数据源：

public ObservableCollection<ItemModel> ItemList { get; set; }

public MainPage()
{
    InitializeComponent();
    ItemList = new ObservableCollection<ItemModel>
    {
        new ItemModel { Name = "项目A", Status = 0 },
        new ItemModel { Name = "项目B", Status = 1 },
        new ItemModel { Name = "项目C", Status = 0 }
    };
    DataContext = this;
}

方案二：代码手动生成Picker项（适合简单场景） #

如果不需要MVVM模式，可直接在代码中创建ListPickerItem并设置颜色：

var picker = new Picker();
var items = new List<(string Name, int Status)>
{
    ("项目A", 0),
    ("项目B", 1),
    ("项目C", 0)
};

foreach (var item in items)
{
    var listItem = new ListPickerItem();
    listItem.Content = item.Name;
    listItem.Foreground = item.Status switch
    {
        0 => new SolidColorBrush(Colors.Red),
        1 => new SolidColorBrush(Colors.Green),
        _ => new SolidColorBrush(Colors.Black)
    };
    picker.Items.Add(listItem);
}
// 将picker添加到页面布局容器中

内容的提问来源于stack exchange，提问作者Kanmani Palani