如何在 Xamarin.Forms 中的 ListView 中绑定列表

Question

I have one ListView on my page having ItemSource as List<AssetModel> as shown below:

public class AssetModel
{
    public string AssetId { get; set; }
    public string Description { get; set; }

    public List<TaskDetail> TaskDetailList { get; set; }
}

public class TaskDetail
{
    public string Description { get; set; }
}

How can I bind TaskDetail list in my parent list?

Desired Layout:

Answer 1

It seems like a classic grouping listview use case. James Montemagno wrote an article about this kind of need that should help you a lot .

In summary, the grouping feature expects an object of type 'List of List' ( IEnumerable<IEnumerable<>> ), where each 'master item' is a list of 'detail item'.

To make it easy, you can use the class provided at the above mentioned article:

public class Grouping<K, T> : ObservableCollection<T>
{
    public K Key { get; private set; }

    public Grouping(K key, IEnumerable<T> items)
    {
        Key = key;
        foreach (var item in items)
            this.Items.Add(item);
    }
}

Then, the list property you must change its type to, for example, this:

ObservableCollection<Grouping<AssetModel, TaskDetail>> AssetsList { get; set; } = 
    new ObservableCollection<Grouping<AssetModel, TaskDetail>>();

This AssetsList is what you should bind to the ItemsSource of ListView

To fill this property, you'll need, for example, do this:

for (int i = 0; i < 5; i++)
{
    var asset = new AssetModel();
    asset.AssetId = new Guid().ToString();
    asset.Description = $"Asset { i + 1} ";
    asset.TaskDetailList = new List<TaskDetail>();

    for (int j = 0; j < 3; j++)
        asset.TaskDetailList.Add(new TaskDetail() { Description = $"Detail { (i + 1) } - { (j + 1) }" });

    var group = new Grouping<AssetModel, TaskDetail>(asset, asset.TaskDetailList);

    AssetsList.Add(group);
}

Then in your XAML you define your ListView Grouping properties:

<ListView ItemsSource="{Binding AssetsList}" 
          HasUnevenRows="True" 
          SeparatorVisibility="None"
          SeparatorColor="Transparent"
          IsGroupingEnabled="True">
    <ListView.GroupHeaderTemplate>
        <DataTemplate>
            <ViewCell>
                <StackLayout>
                    <StackLayout Orientation="Horizontal">
                        <Label Text="AssetId"
                               FontAttributes="Bold"/>
                        <Label Text={Binding Key.AssetId}/>
                    </StackLayout>
                    <StackLayout Orientation="Horizontal">
                        <Label Text="Description"
                               FontAttributes="Bold"/>
                        <Label Text={Binding Key.Description}/>
                    </StackLayout>
                </StackLayout>
            </ViewCell>
        </DataTemplate>
    </ListView.GroupHeaderTemplate>
    <ListView.ItemTemplate>
        <DataTemplate>
            <ViewCell>
                <StackLayout>
                    <Label Text={Binding Description}/>
                </StackLayout>
            </ViewCell>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>