Xamarin.Forms: How to access the collection used in ListView.ItemTemplate within ListView.GroupHeaderTemplate?

问题

I need to access the OnOff property in a Switch within the ListView.GroupHeaderTemplate this property is in the collection used by ListView.ItemTemplate, I have tried in many ways without success, has anyone ever had this problem?

> 
            <ListView            
            ItemsSource="{Binding ItemsGrouped}" 
            GroupShortNameBinding="{Binding Key}"
            IsGroupingEnabled="true"
            GroupDisplayBinding="{Binding Key}"
            x:Name="ListViewAllDevices">


            <ListView.ItemTemplate>
                <DataTemplate> 
                        <ViewCell.View>
                            <StackLayout>                               
                                        <Label Text="{Binding Title}"/>
                                        <Label Text="{Binding Description}"/>                                        
                            </StackLayout>
                        </ViewCell.View>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>


            <ListView.GroupHeaderTemplate>
                <DataTemplate>
                    <ViewCell>
                        <ViewCell.View>
                            <StackLayout>
                                    <Label Text="{Binding Key}" />                                
                                    <Switch IsToggled="{Binding OnOff, Source={x:Reference Name=ListViewAllDevices}}"/>
                            </StackLayout>
                        </ViewCell.View>
                    </ViewCell>
                </DataTemplate>
            </ListView.GroupHeaderTemplate>

回答1:

I think you may to change the viewModel .Each groupHeaderTemplate can bind one value. My code as below:

Model

 public class Person
{

    public string FullName
    {
        get;
        set;
    }

    public string Address
    {
        get;
        set;
    }
}

public class Group : ObservableCollection<Person>
{
    public Group(bool key)
    {
        Key = key;
    }

    public bool Key
    {
        get;
        private set;
    }
}

ItemSource

 listView.ItemsSource = new[] {
           new Group (true) {
               new Person { FullName = "Ass" ,Address = "cole house" }
           },

           new Group (false) {
               new Person { FullName = "Caprice Nave" }
           },

           new Group (false) {
               new Person { FullName = "James Smith", Address = "404 Nowhere Street"},
               new Person { FullName = "John Doe", Address = "404 Nowhere Ave" }
           }
       };

XMAL

 <ListView x:Name="listView" IsGroupingEnabled="true">

    <ListView.ItemTemplate>
        <DataTemplate>
            <ViewCell>
                <ViewCell.View>
                   <StackLayout>
                        <Label Text="{Binding FullName}"/>
                        <Label Text="{Binding Address}"/>
                   </StackLayout>
                </ViewCell.View>
            </ViewCell>
        </DataTemplate>
    </ListView.ItemTemplate>

    <ListView.GroupHeaderTemplate>

        <DataTemplate>
            <ViewCell>
                <ViewCell.View>
                    <StackLayout>
                        <Switch IsToggled="{Binding Key}"/>
                    </StackLayout>
                </ViewCell.View>
            </ViewCell>
        </DataTemplate>
    </ListView.GroupHeaderTemplate>

</ListView>

PS: Once you setListView.GroupHeaderTemplate ,ListView.GroupDisplayBinding will set to null automatically, so you don't need to set ListView.GroupDisplayBinding , but don't forget IsGroupingEnabled="true"

来源：https://stackoverflow.com/questions/45357041/xamarin-forms-how-to-access-the-collection-used-in-listview-itemtemplate-within