Xamarin.Forms ListView：设置选中项的高亮颜色

public class CustomListViewRenderer : ListViewRenderer
    {
        protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged(sender, e);

            if (Control == null)
            {
                return;
            }

            if (e.PropertyName == "ItemsSource")
            {
                foreach (var cell in Control.VisibleCells)
                {
                    cell.SelectionStyle = UITableViewCellSelectionStyle.None;
                }
            }
        }
    }

对于Android，您可以在values/styles.xml中添加此样式。

<style name="ListViewStyle.Light" parent="android:style/Widget.ListView">
    <item name="android:listSelector">@android:color/transparent</item>
    <item name="android:cacheColorHint">@android:color/transparent</item>
  </style>

namespace MyProject
{
    public class ListView2 : ListView
    {
        public ListView2(ListViewCachingStrategy cachingStrategy) : base(cachingStrategy)
        {
        }
    }
}

    <ListView2 x:Name="myListView" ListViewCachingStrategy="RecycleElement" ItemsSource="{Binding ListSource}" RowHeight="50">
        <ListView.ItemTemplate>
          <DataTemplate>
            <ViewCell>
              <ViewCell.View>
                  <Label Text="{Binding Name}" HorizontalOptions="Center" TextColor="White" />
                </ContentView>
              </ViewCell.View>
            </ViewCell>
          </DataTemplate>
        </ListView.ItemTemplate>
    </ListView2>

[assembly: ExportRenderer(typeof(ListView2), typeof(ListView2Renderer))]
namespace MyProject.iOS
{
    public partial class ListView2Renderer : ListViewRenderer
    {
        protected override void OnElementChanged(ElementChangedEventArgs<ListView> e)
        {
            base.OnElementChanged(e);
            if (Control != null && e != null)
            {
                //oldDelegate = (UITableViewSource)Control.Delegate;
                Control.Delegate = new ListView2Delegate(e.NewElement);
            }
        }
    }


    class ListView2Delegate : UITableViewDelegate
    {
        private ListView _listView;

        internal ListView2Delegate(ListView listView)
        {
            _listView = listView;
        }

        public override void WillDisplay(UITableView tableView, UITableViewCell cell, Foundation.NSIndexPath indexPath)
        {
            cell.SelectedBackgroundView = new UIView()
            {
                BackgroundColor = Color.Red.ToUIColor()
            };
        }

        protected override void Dispose(bool disposing)
        {
            if (disposing)
            {
                _listView = null;
            }
            base.Dispose(disposing);
        }
    }
}

• 对于使用默认缓存策略ListViewCachingStrategy.RetainElement的ListViews，请使用普通的ListView和此线程中提供的ListItemViewCellRenderer代码。

• 对于使用非默认缓存策略（即ListViewCachingStrategy.RecycleElement或ListViewCachingStrategy.RecycleElementAndDataTemplate）的ListViews，请使用此ListView2。

我还向Xamarin提交了一个功能请求，请投票支持它，如果您认为应将其添加到标准ListView中：ListView迫切需要SelectedItemBackgroundColor属性

@android:color/transparent

改变选择颜色的最简单方法是将以下内容添加到您的Android.Resources.values.styles中

  <item name="android:colorPressedHighlight">@android:color/holo_blue_bright</item>
  <item name="android:colorFocusedHighlight">@android:color/holo_blue_bright</item>
  <item name="android:colorActivatedHighlight">@android:color/holo_blue_bright</item>

public partial class SelectableCell : ViewCell {

  public static readonly BindableProperty IsSelectedProperty = BindableProperty.Create(nameof(IsSelected), typeof(bool), typeof(SelectableCell), false, propertyChanged: OnIsSelectedPropertyChanged);
  public bool IsSelected {
    get => (bool)GetValue(IsSelectedProperty);
    set => SetValue(IsSelectedProperty, value);
  }

  // You can omit this if you only want to use IsSelected via binding in XAML
  private static void OnIsSelectedPropertyChanged(BindableObject bindable, object oldValue, object newValue) {
    var cell = ((SelectableCell)bindable);
    // change color, visibility, whatever depending on (bool)newValue
  }

  // ...
}

public class IsSelectedConverter : IValueConverter {
  public object Convert(object value, Type targetType, object parameter, CultureInfo culture) =>
    value != null && value == ((ViewCell)parameter).View.BindingContext;

  public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) =>
    throw new NotImplementedException();
}

<ListView x:Name="ListViewName">
  <ListView.ItemTemplate>
    <DataTemplate>
      <local:SelectableCell x:Name="ListViewCell"
        IsSelected="{Binding SelectedItem, Source={x:Reference ListViewName}, Converter={StaticResource IsSelectedConverter}, ConverterParameter={x:Reference ListViewCell}}" />
    </DataTemplate>
  </ListView.ItemTemplate>
</ListView>

这个相对复杂的绑定用于检查当前选中的实际项。它将列表视图的SelectedItem属性与单元格中视图的BindingContext进行比较。该绑定上下文是我们实际绑定到的数据对象。换句话说，它检查SelectedItem指向的数据对象是否实际上是单元格中的数据对象。如果它们相同，我们就有了选定的单元格。我们将其绑定到IsSelected属性中，然后可以在XAML或代码后台中使用它来查看视图单元格是否处于选定状态。

只有一个注意点：如果您想在页面显示时设置默认选定项，您需要聪明一些。不幸的是，Xamarin Forms没有页面显示事件，我们只有出现事件，这对于设置默认值来说太早了：绑定不会被执行。所以，使用一点延迟：

protected override async void OnAppearing() {
  base.OnAppearing();

  Device.BeginInvokeOnMainThread(async () => {
    await Task.Delay(100);
    ListViewName.SelectedItem = ...;
  });
}

public class ListViewRenderer : Xamarin.Forms.Platform.iOS.ListViewRenderer
{
    public ListViewRenderer()
    {
    }

    public override void LayoutSubviews()
    {
        base.LayoutSubviews();

        var controller = this.ViewController as UITableViewController;
        if (controller != null)
        {
            var tableView = controller.TableView;
            if (tableView != null && tableView.Subviews != null)
            {
                //For lower iOS version, this line must add, otherwise it can not find any UITableViewCell
                tableView.LayoutSubviews();

                var backgroundColor = Color.Red.ToUIColor();
                foreach (var subview in tableView.Subviews)
                {
                    if (subview is UITableViewCell tableViewCell)
                    {
                        tableViewCell.SelectedBackgroundView = new UIView
                        {
                            BackgroundColor = backgroundColor
                        };
                        tableViewCell.MultipleSelectionBackgroundView = new UIView
                        {
                            BackgroundColor = backgroundColor
                        };
                    }
                }
            }
        }
    }
}