ListView 没有取消选择 [英] ListView not unselecting

问题描述

我正在使用 ListView 处理 Xamarin.Forms 项目.

I am working on a Xamarin.Forms project with a ListView.

ListView 的 XAML 是

The XAML for the ListView is

<render:CustomListView x:Name="listview" ItemSelected="ItemSelected" ItemTapped="ItemTapped"></render:CustomListView>

C# 是

public void ItemTapped(object sender, ItemTappedEventArgs e)
    {
        var Selected = e.Item as Classes.NavigationItem;
        //Handle clicked
        }
       ((ListView)sender).SelectedItem = null;

    }

    private void ItemSelected(object sender, SelectedItemChangedEventArgs e)
    {
        ((ListView)sender).SelectedItem = null;
    }

我的自定义渲染器是

Android(自定义列表视图):

Android (Custom ListView):

public class NavigationListViewAndroid : ListViewRenderer
{
    #pragma warning disable CS0618 // Type or member is obsolete
    public NavigationListViewAndroid() { }
    #pragma warning restore CS0618 // Type or member is obsolete

    public NavigationListViewAndroid(Context context) : base(context)
    {

    }

    protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.ListView> e)
    {
        base.OnElementChanged(e);
        Control.SetSelector(Android.Resource.Color.DarkerGray);
    }

}

iOS(ViewCell):

iOS (ViewCell):

public class NavigationViewCelliOS : ViewCellRenderer
{
    public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell, UITableView tv)
    {
        var cell = base.GetCell(item, reusableCell, tv);
        cell.SelectionStyle = UITableViewCellSelectionStyle.Gray;

        return cell;
    }
}

我的问题是:

Android:它选择了该行，但保持选中状态，直到您单击另一个(对于两者)，我希望它在您放手时取消选择

Android: It selected the row but stays selected until you click another one (for both), I want it to deselect when you let go

iOS:即使按住也不会突出显示灰色

iOS: Never highlights gray at all even if held down

推荐答案

要将背景颜色应用于列表视图所选项目，请按照下列步骤操作:

To apply background color to list view selected item follow these steps:

制作自定义控件:

using Xamarin.Forms;

namespace xamformsdemo.CustomControls
{
  public class ExtendedViewCell : ViewCell
  {
    public static readonly BindableProperty SelectedBackgroundColorProperty =
    BindableProperty.Create("SelectedBackgroundColor", 
                            typeof(Color), 
                            typeof(ExtendedViewCell), 
                            Color.Default);

    public Color SelectedBackgroundColor
    {
       get { return (Color)GetValue(SelectedBackgroundColorProperty); }
       set { SetValue(SelectedBackgroundColorProperty, value); }
    }
  }
}

Android 渲染器:

Android Renderer:

[assembly: ExportRenderer(typeof(ExtendedViewCell), typeof(ExtendedViewCellRenderer))]
namespace xamformsdemo.Droid.CustomRenderers
{
  public class ExtendedViewCellRenderer : ViewCellRenderer
  {

private Android.Views.View _cellCore;
private Drawable _unselectedBackground;
private bool _selected;

protected override Android.Views.View GetCellCore(Cell item, 
                                                  Android.Views.View convertView, 
                                                  ViewGroup parent, 
                                                  Context context)
{
  _cellCore = base.GetCellCore(item, convertView, parent, context);

  _selected = false;
  _unselectedBackground = _cellCore.Background;

  return _cellCore;
}

protected override void OnCellPropertyChanged(object sender, PropertyChangedEventArgs args)
{
  base.OnCellPropertyChanged(sender, args);

  if (args.PropertyName == "IsSelected")
  {
    _selected = !_selected;

    if (_selected)
    {
      var extendedViewCell = sender as ExtendedViewCell;
      _cellCore.SetBackgroundColor(extendedViewCell.SelectedBackgroundColor.ToAndroid());
    }
    else
    {
      _cellCore.SetBackground(_unselectedBackground);
    }
  }
}
  }

}

iOS 渲染器:

[assembly: ExportRenderer(typeof(ExtendedViewCell), typeof(ExtendedViewCellRenderer))]
namespace xamformsdemo.iOS.CustomRenderers
{
  public class ExtendedViewCellRenderer : ViewCellRenderer
  {
    public override UITableViewCell GetCell(Cell item, UITableViewCell reusableCell, UITableView tv)
   {
      var cell = base.GetCell(item, reusableCell, tv);
      var view = item as ExtendedViewCell;
      cell.SelectedBackgroundView = new UIView
       {
         BackgroundColor = view.SelectedBackgroundColor.ToUIColor(),
       };

      return cell;
    }

  }
}

在 XAML 中使用:

Use in XAML:

<ListView.ItemTemplate>
  <DataTemplate>
    <customControls:ExtendedViewCell SelectedBackgroundColor="Teal">
      <ViewCell.View>
        <StackLayout HorizontalOptions="FillAndExpand" 
                     VerticalOptions="FillAndExpand" Orientation="Vertical" 
                     Padding="4" Spacing="8">
          <Label TextColor="White" Text="{Binding .ItemName}"/>
          <Label TextColor="Yellow" Text="{Binding .LastUpdated, StringFormat='Last seen: {0:HH:mm:ss}'}"/>
        </StackLayout>
      </ViewCell.View>
    </customControls:ExtendedViewCell>
  </DataTemplate>
</ListView.ItemTemplate>

您可以参考以下链接解决问题:https://blog.wislon.io/posts/2017/04/11/xamforms-listview-selected-colour

You can refer this link below to solve problem: https://blog.wislon.io/posts/2017/04/11/xamforms-listview-selected-colour

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