Question

我正在以Xamarin形式使用列表视图分组，但是有些数据是不绑定的。我正在使用Xamarin Forms 3.1最新版本。我的代码是：

<ListView ItemsSource="{Binding FacilityList}"
      IsGroupingEnabled="true" HasUnevenRows="True" ItemTapped="OnItemTapped">
            <ListView.GroupHeaderTemplate>
                <DataTemplate>
                    <ViewCell>
                        <Label Text="{Binding Heading}" TextColor="Black" FontSize="Medium" />
                    </ViewCell>
                </DataTemplate>
            </ListView.GroupHeaderTemplate>

            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <StackLayout>
                            <Image Source="{Binding ImageName}" HeightRequest="50" WidthRequest="50"/>
                            <Label Text="{Binding Name}" TextColor="Black" FontSize="Medium"/>
                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

我的视图模型是

 private ObservableCollection<FacilitiesGroup> facilityList;
    public ObservableCollection<FacilitiesGroup> FacilityList
    {
        get => facilityList;
        set => SetProperty(ref facilityList, value);
    }

    private Facility selectedItem;
    public Facility SelectedItem
    {
        get => selectedItem;
        set
        {
            SetProperty(ref selectedItem, value);
        }
    }

    public ICommand ItemTappedCommand { get; set; }

    public FacilityViewModel()
    {
        FacilityDataStore facilityDataStore = new FacilityDataStore();
        var items = facilityDataStore.GetList();
        var groupList = new List<FacilitiesGroup>();
        var group = new FacilitiesGroup()
        {
            Facilities = items.Where(x => x.IsSubscribed == true).ToList(),
            Heading = "Subscribed"
        };
        var group2 = new FacilitiesGroup()
        {
            Facilities = items.Where(x => x.IsSubscribed == false).ToList(),
            Heading = "Unsubscribed"
        };
        groupList.Add(group);
        groupList.Add(group2);
        FacilityList = new ObservableCollection<FacilitiesGroup>(groupList);
    }

FacilityGroup类代码为：

public class FacilitiesGroup
{
    public List<Facility> Facilities { get; set; }
    public string Heading { get; set; }
}

设施类是：

public class Facility
{
    [PrimaryKey, AutoIncrement]
    public int ID { get; set; }

    public string Name { get; set; }
    public bool IsSubscribed { get; set; }
    public string ImageName { get; set; }
}

我正在绑定数据：

public MainPage()
    {
        InitializeComponent();
        BindingContext = new FacilityViewModel();
    }

我不明白我的代码有什么问题。任何帮助将不胜感激。谢谢。

Answer 1

抱歉，响应延迟。我发现了这个sample，可能会有用

免责声明：我没有很好地观察ViewModel / Model的边界。我只是想弄清楚什么是行不通的。您需要根据需求和设计文档更新ViewModels / Models。

我不认为您正在寻找组头。这是指向Xamarin documentation的链接，其中讨论页眉/页脚并有图片

让我们从列表视图1开始。删除GroupHeaderTemplate并将GroupDisplayBinding属性添加到列表视图。

<ListView ItemsSource="{Binding FacilityList}"
      IsGroupingEnabled="true" 
      HasUnevenRows="True"           
      GroupDisplayBinding="{Binding Heading}" <---------
      ItemTapped="OnItemTapped">    
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <StackLayout>
                            <Image Source="{Binding ImageName}" HeightRequest="50" WidthRequest="50"/>
                            <Label Text="{Binding Name}" TextColor="Black" FontSize="Medium"/>
                        </StackLayout>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

进行更改后，如果您运行该应用程序。您应该在列表中看到两项。已订阅/未订阅。进展！

接下来，我们需要更改FacilitiesGroup模型。我们需要扩展ObservableCollection。

public class FacilitiesGroup : ObservableCollection<Facility>
{
    public string Heading { get; set; }
}

接下来，我们需要对FacilityViewModel进行更改

public FacilityViewModel()
{
    FacilityDataStore facilityDataStore = new FacilityDataStore();
    var items = facilityDataStore.GetList();
    var groupList = new List<FacilitiesGroup>();
    var group = new FacilitiesGroup()
    {
        Heading = "Subscribed"
    };

    foreach( Facility facility in items.Where(x => x.IsSubscribed == true ) )
    {
        group.Add(facility);
    }

    var group2 = new FacilitiesGroup()
    {
        Heading = "Unsubscribed"
    };

    foreach( Facility facility in items.Where(x => x.IsSubscribed == false ) )
    {
        group2.Add(facility);
    }

    groupList.Add(group);
    groupList.Add(group2);
    FacilityList = new ObservableCollection<FacilitiesGroup>(groupList);
}

希望有帮助！祝好运。

Answer 2

首先，您没有提到未绑定哪些特定数据。无论如何，请确保要绑定的列表不为空或为null。只需尝试下面的代码即可。

<ListView x:Name="FacilityListview"
  IsGroupingEnabled="true" HasUnevenRows="True" ItemTapped="OnItemTapped">
        <ListView.GroupHeaderTemplate>
            <DataTemplate>
                <ViewCell>
                    <Label Text="{Binding Heading}" TextColor="Black" FontSize="Medium" />
                </ViewCell>
            </DataTemplate>
        </ListView.GroupHeaderTemplate>

        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <StackLayout>
                        <Image Source="{Binding ImageName}" HeightRequest="50" WidthRequest="50"/>
                        <Label Text="{Binding Name}" TextColor="Black" FontSize="Medium"/>
                    </StackLayout>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

现在在控制器中将FacilityList分配为下面的itemsSource。

FacilityListview.ItemsSource = FacilityList;

Xamarin表单Listview组中的数据未绑定

2 个答案: