Question

嗨，
您能否让我知道如何在长按效果上显示上下文菜单。我添加了带有效果的ListView，但是长按listview后不会弹出上下文菜单。

MainPage.xaml

    <ContentView x:Name="Parent" BackgroundColor="White" Padding="20" >
    <dg:DataGrid ItemsSource="{Binding Data}" SelectionEnabled="True" RowHeight="70" HeaderHeight="50" BorderColor="#CCCCCC" HeaderBackground="#E0E6F8" ActiveRowColor="#8899AA">
        <dg:DataGrid.Columns>
            <dg:DataGridColumn Title="Logo" PropertyName="Logo" Width="50" SortingEnabled="False">
                <dg:DataGridColumn.CellTemplate>
                    <DataTemplate>


                        <ListView x:Name="MainListView" local:LongPressedEffect.Command="{Binding ShowAlertCommand}" local:LongPressedEffect.CommandParameter="{Binding .}">
                            <ListView.Effects>
                                <local:LongPressedEffect />
                            </ListView.Effects>
                            <ListView.ItemTemplate>
                                <DataTemplate>
                                    <ViewCell>                                            
                                        <ViewCell.ContextActions>
                                            <MenuItem Text="Add" ></MenuItem>
                                            <MenuItem Text="Delete" ></MenuItem>
                                            <MenuItem Text="Edit" ></MenuItem>
                                        </ViewCell.ContextActions>
                                    </ViewCell>
                                </DataTemplate>
                            </ListView.ItemTemplate>
                        </ListView>

                    </DataTemplate>
                </dg:DataGridColumn.CellTemplate>
            </dg:DataGridColumn>
            <dg:DataGridColumn Title="Team" PropertyName="Name" Width="2*" >                    
            </dg:DataGridColumn>
            <dg:DataGridColumn Title="Win" PropertyName="Win" Width="2*">
                <dg:DataGridColumn.CellTemplate>
                    <DataTemplate>
                        <Picker x:Name="Fruits" Title="Fruits" HorizontalOptions="FillAndExpand">
                            <Picker.Items>
                                <x:String>Apple</x:String>                       
                                <x:String>Orange</x:String>
                            </Picker.Items>
                        </Picker>
                    </DataTemplate>
                </dg:DataGridColumn.CellTemplate>
            </dg:DataGridColumn>
            <dg:DataGridColumn Title="Loose" PropertyName="Loose"  Width="1*">                    
            </dg:DataGridColumn>
            <dg:DataGridColumn PropertyName="Home">
                <dg:DataGridColumn.FormattedTitle>
                    <FormattedString>
                        <Span Text="Home" ForegroundColor="Black" FontSize="13" FontAttributes="Bold"/>
                        <Span Text=" (win-loose)" ForegroundColor="#333333" FontSize="11" />
                    </FormattedString>
                </dg:DataGridColumn.FormattedTitle>
            </dg:DataGridColumn>
            <dg:DataGridColumn Title="Percentage" PropertyName="Percentage"/>
            <dg:DataGridColumn Title="Streak" PropertyName="Streak" Width="0.7*"/>
        </dg:DataGrid.Columns>
</ContentView>

LongPressedEffect.cs

 public class LongPressedEffect : RoutingEffect
{

    public LongPressedEffect() : base("MyApp.LongPressedEffect")
    {

    }

    public static readonly BindableProperty CommandProperty = BindableProperty.CreateAttached("Command", typeof(ICommand), typeof(LongPressedEffect), (object)null);
    public static ICommand GetCommand(BindableObject view)
    {

        return (ICommand)view.GetValue(CommandProperty);

    }

    public static void SetCommand(BindableObject view, ICommand value)
    {
        view.SetValue(CommandProperty, value);
    }


    public static readonly BindableProperty CommandParameterProperty = BindableProperty.CreateAttached("CommandParameter", typeof(object), typeof(LongPressedEffect), (object)null);
    public static object GetCommandParameter(BindableObject view)
    {
        return view.GetValue(CommandParameterProperty);
    }

    public static void SetCommandParameter(BindableObject view, object value)
    {
        view.SetValue(CommandParameterProperty, value);
    }
}

AndroidLongPressedEffect.cs

public class AndroidLongPressedEffect : PlatformEffect
{
    private bool _attached;

    /// <summary>
    /// Initializer to avoid linking out
    /// </summary>
    public static void Initialize() { }
     /// <summary>
    /// Initializes a new instance of the
    /// <see cref="T:Yukon.Application.AndroidComponents.Effects.AndroidLongPressedEffect"/> class.
    /// Empty constructor required for the odd Xamarin.Forms reflection constructor search
    /// </summary>
    public AndroidLongPressedEffect()
    {
    }

    /// <summary>
    /// Apply the handler
    /// </summary>
    protected override void OnAttached()
    {
        //because an effect can be detached immediately after attached (happens in listview), only attach the handler one time.
        if (!_attached)
        {
            if (Control != null)
            {
                Control.LongClickable = true;
                Control.LongClick += Control_LongClick;
            }
            else
            {
                Container.LongClickable = true;
                Container.LongClick += Control_LongClick;

            }
            _attached = true;
        }
    }

    /// <summary>
    /// Invoke the command if there is one
    /// </summary>
    /// <param name="sender">Sender.</param>
    /// <param name="e">E.</param>
    private void Control_LongClick(object sender, Android.Views.View.LongClickEventArgs e)
    {
        Console.WriteLine("Invoking long click command");
        var command = LongPressedEffect.GetCommand(Element);
        command?.Execute(LongPressedEffect.GetCommandParameter(Element));            
    }

    /// <summary>
    /// Clean the event handler on detach
    /// </summary>
    protected override void OnDetached()
    {
        if (_attached)
        {
            if (Control != null)
            {
                Control.LongClickable = true;
                Control.LongClick -= Control_LongClick;
            }
            else
            {
                Container.LongClickable = true;
                Container.LongClick -= Control_LongClick;
            }
            _attached = false;
        }
    }
}

非常感谢您的帮助！
如果需要更多信息，请告诉我。

Answer 1

您可以将App.cs中的属性设置为currentPage。

public static ContentPage currentPage;

并将其设置在包含您的listView的contentPage中。

public xxxPage()
 {
    InitializeComponent();

    App.currentPage = this;

 }

在LongPressedEffect.cs

中

public static ICommand GetCommand(BindableObject view)
 {

   //do something you want
   App.currentPage.DisplayActionSheet("ActionSheet: Send to?", "Cancel", null, "Email", "Twitter", "Facebook");
   return (ICommand)view.GetValue(CommandProperty);
 }

在LongPress上显示ContextMenu以查看xamarin形式的视图

1 个答案: