获取刷过的项目并设置其 BindingContext 空白 ListView

Question

我有一个运行良好的列表视图，直到我尝试通过其绑定上下文获取滑动的项目并且它使列表视图显示为空白。在这背后的代码中，我可以访问该项目的数据，但是当我运行我的应用程序时，它会使列表视图空白...

列表视图


<ListView
                        x:Name="MyList"
                        Grid.Row="1"
                        HasUnevenRows="True"
                        HeightRequest="10"
                        BackgroundColor="White"
                        IsGroupingEnabled="True"
                        IsPullToRefreshEnabled="false"
                        ItemsSource="{Binding LogItems}"
                        IsRefreshing="{Binding IsBusy, Mode=OneWay}"
                        RefreshCommand="{Binding LoadLogsCommand}"
                        SeparatorVisibility="None"                        
                        >
                        <ListView.ItemTemplate>
                            <DataTemplate >
                                <ViewCell Height="70">
                                    <StackLayout Orientation="Vertical"  VerticalOptions="Start"  >

                                        <SwipeView SwipeStarted="SwipeView_SwipeStarted" x:Name="mySwipeView" >                                            

                                            <Grid>
                                                <Grid.RowDefinitions>
                                                    <RowDefinition Height="5"/>
                                                    <RowDefinition Height="36"/>
                                                    <RowDefinition Height="36"/>
                                                    <RowDefinition Height="60"/>                                                
                                                </Grid.RowDefinitions>

                                                <Grid.ColumnDefinitions>
                                                    <ColumnDefinition Width="100"/>
                                                    <ColumnDefinition Width="20"/>
                                                    <ColumnDefinition Width="110"/>
                                                    <ColumnDefinition Width="20"/>
                                                    <ColumnDefinition Width="100"/>
                                                    <ColumnDefinition Width="36"/>
                                                
                                                </Grid.ColumnDefinitions>
                                                
                                                <Label
                                                       Grid.Row="1"
                                                       Grid.Column="0"
                                                       VerticalOptions="Center"
                                                       FontAttributes="None"                                       
                                                       Text="{Binding  .Name}"
                                                       TextColor="Black"
                                                       Margin="0, 0,0, 0"
                                                       Padding="20,10,0,0"
                                                       FontFamily="Hiragino Sans"
                                                       FontSize="14"
                                                       HeightRequest="53"                                      
                                                  />
...
                                                </Grid>
                                            </Grid>
                                            <SwipeView.RightItems>
                                                <SwipeItems Mode="Reveal" SwipeBehaviorOnInvoked="Close" >

                                                    <SwipeItemView Invoked="OnDeleteSwipeItemInvoked" >
                                                        <StackLayout Orientation="Vertical" WidthRequest="200" BackgroundColor="Red">
                                                            <StackLayout HorizontalOptions="Start">
                                                                <Image Source="deleteIcon3.png" HeightRequest="25" WidthRequest="25" Margin="70,15,0,0" />
                                                                <Label Text=" Delete" TextColor="White" FontSize="15" HorizontalOptions="CenterAndExpand" Margin="70,0,0,0"/>
                                                            </StackLayout>
                                                        </StackLayout>
                                                    </SwipeItemView>
                                                   </SwipeItems>
                                            </SwipeView.RightItems>
                                        </SwipeView>
                                    </StackLayout>
                                </ViewCell>
                            </DataTemplate>                              
                        </ListView.ItemTemplate>

代码隐藏


private void SwipeView_SwipeStarted(object sender, SwipeItemView e, SwipedEventArgs f, SwipeChangingEventArgs g) //SwipeStartedEventArgs e)
        {
            // var theItem = (myLogsModel)f.SelectedItem;
           var item = sender as SwipeItem;

           var model = item.BindingContext as myLogsModel;

var x = model.Name; ...

}

谁能帮我在不影响我的列表视图的情况下如何获取刷过的项目？

Answer 1

从Xamarin.Forms SwipeView，我们可以看到滑动开始时触发了SwipeStarted。伴随此事件的 SwipeStartedEventArgs 对象具有类型为 SwipeDirection 的 SwipeDirection 属性。

因此您可以从 OnDeleteSwipeItemInvoked 方法获取当前列表视图项。

我做了一个样例，你可以看看：

<ListView ItemsSource="{Binding items}">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <StackLayout>
                            <SwipeView>
                                <SwipeView.RightItems>
                                    <SwipeItems>
                                        <SwipeItemView Invoked="SwipeItemView_Invoked">
                                            <StackLayout
                                                BackgroundColor="Red"
                                                Orientation="Vertical"
                                                WidthRequest="200">
                                                <StackLayout HorizontalOptions="Start">
                                                    <Image
                                                        Margin="70,15,0,0"
                                                        HeightRequest="25"
                                                        Source="delete.png"
                                                        WidthRequest="25" />
                                                    <Label
                                                        Margin="70,0,0,0"
                                                        FontSize="15"
                                                        HorizontalOptions="CenterAndExpand"
                                                        Text=" Delete"
                                                        TextColor="White" />
                                                </StackLayout>
                                            </StackLayout>
                                        </SwipeItemView>
                                      
                                    </SwipeItems>
                                </SwipeView.RightItems>
                                <!--  Content  -->
                                <SwipeView.Content>
                                    <Grid
                                        BackgroundColor="LightGray"
                                        HeightRequest="60"
                                        WidthRequest="300">
                                        <Label
                                            HorizontalOptions="Center"
                                            Text="{Binding title}"
                                            VerticalOptions="Center" />
                                    </Grid>
                                </SwipeView.Content>

                            </SwipeView>
                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

public partial class Page4 : ContentPage
{
    public ObservableCollection<menuitem> items { get; set; }
    public Page4()
    {
        InitializeComponent();
        items = new ObservableCollection<menuitem>()
        {
            new menuitem(){title="title 1"},
            new menuitem(){title="title 2"},
            new menuitem(){title="title 3"},
            new menuitem(){title="title 4"},
            new menuitem(){title="title 5"},
            new menuitem(){title="title 6"}

        };
        this.BindingContext = this;
    }

   
    private void SwipeItemView_Invoked(object sender, EventArgs e)
    {
        SwipeItemView item = sender as SwipeItemView;
        menuitem model = item.BindingContext as menuitem;
      
    }
}

public class menuitem
{
    public string title { get; set; }
}

正如Jason所说，我们也建议您可以使用ListView上下文菜单来做，不需要使用SwipView。 Select 一项并长按以获取上下文菜单，如下面的屏幕截图。

 <ListView ItemsSource="{Binding items}">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <ViewCell.ContextActions>
                            <MenuItem Clicked="OnMore" Text="More" />
                            <MenuItem Clicked="OnDelete" Text="Delete" />
                        </ViewCell.ContextActions>
                        <StackLayout>
                            <Label Text="{Binding title}" />
                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

  private void OnMore(object sender, EventArgs e)
    {
        MenuItem item = sender as MenuItem;
        menuitem model = item.BindingContext as menuitem;
    }

关于ListView交互，请看：

https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/listview/interactivity

获取刷过的项目并设置其 BindingContext 空白 ListView

Getting the swiped item and setting its BindingContext blanks ListView

c#

binding

listview

swipe

xamarin