C# 将CollectionView滚动到ItemGroup

我有一个带有组的

CollectionView

。每个组都有一个带日期的字符串

随后，我创建了一个

CarouselView

，其中包含

CollectionView

组的所有日期

我试图创建一种方法来滚动

CarouselView

的元素，从而将

CollectionView

滚动到相应的组，但它不起作用

CollectionView

保持静止

<CollectionView x:Name="CollectionDiary"....../>

c#

公共类组：ObservableCollection
{
公共字符串名称{get；private set；}
公共组（字符串名称，ObservableCollection图标）：基（图标）
{
名称=名称；
}
}
public observetecollection tothumb{get；private set；}=new observetecollection（）；
幽默组=新幽默组（“月”+“”+年，新观察到的集合（））；
添加（组）；
组。添加（项目日志）；
私有无效ScrollCollectionView_已单击（对象发送者，事件参数e）
{
var current=CarouselView.CurrentItem作为组；
CollectionDiary.ScrollTo（当前，位置：ScrollToPosition.Start）；
}

我正在尝试创建一种方法来滚动CarouselView的元素，从而将CollectionView滚动到相应的组，但它不起作用

我同意Jason的观点，您可以让CollectionView滚动到CarouseView_滚动事件中当前组的第一项

 private void CarouselView_Scrolled(object sender, ItemsViewScrolledEventArgs e)
    {
        var current = CarouselView1.CurrentItem as HumorGroup;
        if(current!=null)
        {             
            CollectionDiary.ScrollTo(current.FirstOrDefault(),ScrollToPosition.Center);
        }
        
    }

我提供了一个示例，您可以查看：

<StackLayout>
        <CarouselView
            x:Name="CarouselView1"
            ItemsSource="{Binding humors}"
            Scrolled="CarouselView_Scrolled">
            <CarouselView.ItemTemplate>
                <DataTemplate>
                    <StackLayout>
                        <Label Text="{Binding Name}" />
                    </StackLayout>
                </DataTemplate>
            </CarouselView.ItemTemplate>

        </CarouselView>
        <CollectionView
            x:Name="CollectionDiary"
            HeightRequest="100"
            IsGrouped="True"
            ItemsSource="{Binding humors}"
            SelectionMode="Single">
            <CollectionView.ItemTemplate>
                <DataTemplate>
                    <StackLayout Orientation="Horizontal">
                        <Label Text="{Binding name}" />
                        <Label Text="{Binding count}" />
                    </StackLayout>
                </DataTemplate>
            </CollectionView.ItemTemplate>
            <CollectionView.GroupHeaderTemplate>
                <DataTemplate>
                    <Label
                        BackgroundColor="LightGray"
                        FontAttributes="Bold"
                        FontSize="Large"
                        Text="{Binding Name}" />
                </DataTemplate>
            </CollectionView.GroupHeaderTemplate>
        </CollectionView>
    </StackLayout>

 public partial class Page8 : ContentPage
{
    public GroupHumorViewmodel groups { get; set; }
    public Page8()
    {
        InitializeComponent();
        groups = new GroupHumorViewmodel();
        this.BindingContext =groups;
    }

    private void CarouselView_Scrolled(object sender, ItemsViewScrolledEventArgs e)
    {
        var current = CarouselView1.CurrentItem as HumorGroup;
        if(current!=null)
        {             
            CollectionDiary.ScrollTo(current.FirstOrDefault(),ScrollToPosition.Center);
        }
        
    }
}

public class HumorDiary
{
    public string name { get; set; }
    public int count { get; set; }
}

public class HumorGroup:ObservableCollection<HumorDiary>
{
    public string Name { get;  set; }
    public HumorGroup(string name, ObservableCollection<HumorDiary> humor) : base(humor)
    {
        Name = name;
    }
}

public class GroupHumorViewmodel
{
    public ObservableCollection<HumorGroup> humors { get; set; }

    public GroupHumorViewmodel()
    {          
        humors = new ObservableCollection<HumorGroup>();
        humors.Add(new HumorGroup("2021",new ObservableCollection<HumorDiary>() {
            new HumorDiary(){name="2021-day1",count=3},
            new HumorDiary(){name="2021-day2",count=3},
            new HumorDiary(){name="2021-day3",count=4},
            new HumorDiary(){name="2021-day4",count=2},
            new HumorDiary(){name="2021-day5",count=5},
            new HumorDiary(){name="2021-day6",count=4},
            new HumorDiary(){name="2021-day7",count=2},
            new HumorDiary(){name="2021-day8",count=5}


        }));

        humors.Add(new HumorGroup("2020", new ObservableCollection<HumorDiary>() {
            new HumorDiary(){name="2020-day1",count=3},
            new HumorDiary(){name="2020-day2",count=3},
            new HumorDiary(){name="2020-day3",count=4},
            new HumorDiary(){name="2020-day4",count=2},
            new HumorDiary(){name="2020-day5",count=5},
            new HumorDiary(){name="2020-day6",count=4},
            new HumorDiary(){name="2020-day7",count=2},
            new HumorDiary(){name="2020-day8",count=5}


        }));

        humors.Add(new HumorGroup("2019", new ObservableCollection<HumorDiary>() {
            new HumorDiary(){name="2019-day1",count=3},
            new HumorDiary(){name="2019-day2",count=3},
            new HumorDiary(){name="2019-day3",count=4},
            new HumorDiary(){name="2019-day4",count=2},
            new HumorDiary(){name="2019-day5",count=5},
            new HumorDiary(){name="2019-day6",count=4},
            new HumorDiary(){name="2019-day7",count=2},
            new HumorDiary(){name="2019-day8",count=5}


        }));
      
    }
}

公共部分类第8页：内容页
{
公共组模型组{get；set；}
公共页8（）
{
初始化组件（）；
groups=新的groupViewModel（）；
this.BindingContext=组；
}
私有void CarouselView_滚动（对象发送者，ItemsViewScrolledEventArgs e）
{
var current=CarouselView1.CurrentItem作为组；
如果（当前！=null）
{             
CollectionDiary.ScrollTo（current.FirstOrDefault（），ScrollToPosition.Center）；
}
}
}
公开课幽默日记
{
公共字符串名称{get；set；}
公共整数计数{get；set；}
}
公共类幽默组：ObservableCollection
{
公共字符串名称{get；set；}
公共幽默组（字符串名称，ObservableCollection幽默）：基础（幽默）
{
名称=名称；
}
}
公共类组视图模型
{
公共可观察收集幽默{get；set；}
公共组视图模型（）
{          
体液=新观察到的集合（）；
添加（新的体液组（“2021”，新的可观察集合）（）{
new HumorDiary（）{name=“2021-day1”，count=3}，
new HumorDiary（）{name=“2021-day2”，count=3}，
new HumorDiary（）{name=“2021-day3”，count=4}，
new HumorDiary（）{name=“2021-day4”，count=2}，
new HumorDiary（）{name=“2021-day5”，count=5}，
new HumorDiary（）{name=“2021-day6”，count=4}，
new HumorDiary（）{name=“2021-day7”，count=2}，
新建日志（）{name=“2021-day8”，计数=5}
}));
humors.添加（新的HumorGroup（“2020”，新的ObservableCollection）（）{
new HumorDiary（）{name=“2020-day1”，count=3}，
new HumorDiary（）{name=“2020-day2”，count=3}，
new HumorDiary（）{name=“2020-day3”，count=4}，
new HumorDiary（）{name=“2020-day4”，count=2}，
new HumorDiary（）{name=“2020-day5”，count=5}，
new HumorDiary（）{name=“2020-day6”，count=4}，
new HumorDiary（）{name=“2020-day7”，count=2}，
新建日志（）{name=“2020-day8”，计数=5}
}));
体液补充（新体液组（“2019”，新可观察集合）（）{
新建日期（{name=“2019-day1”，count=3}，
新建日期（{name=“2019-day2”，计数=3}，
新建日期（{name=“2019-day3”，计数=4}，
新建日期（{name=“2019-day4”，计数=2}，
新建日期（{name=“2019-day5”，count=5}，
新建日期（{name=“2019-day6”，count=4}，
新建日期（{name=“2019-day7”，计数=2}，
新建日志（）{name=“2019-day8”，计数=5}
}));
}
}

我会尝试查找组中的第一个项目并滚动到该项目，我需要CollectionView向上滚动到组名，而不是第一个元素，因为某些组可能是empty@trecchino从中，我们可以发现我们需要指定要跳转到该位置的特定项。有关于github的功能请求。

<StackLayout>
        <CarouselView
            x:Name="CarouselView1"
            ItemsSource="{Binding humors}"
            Scrolled="CarouselView_Scrolled">
            <CarouselView.ItemTemplate>
                <DataTemplate>
                    <StackLayout>
                        <Label Text="{Binding Name}" />
                    </StackLayout>
                </DataTemplate>
            </CarouselView.ItemTemplate>

        </CarouselView>
        <CollectionView
            x:Name="CollectionDiary"
            HeightRequest="100"
            IsGrouped="True"
            ItemsSource="{Binding humors}"
            SelectionMode="Single">
            <CollectionView.ItemTemplate>
                <DataTemplate>
                    <StackLayout Orientation="Horizontal">
                        <Label Text="{Binding name}" />
                        <Label Text="{Binding count}" />
                    </StackLayout>
                </DataTemplate>
            </CollectionView.ItemTemplate>
            <CollectionView.GroupHeaderTemplate>
                <DataTemplate>
                    <Label
                        BackgroundColor="LightGray"
                        FontAttributes="Bold"
                        FontSize="Large"
                        Text="{Binding Name}" />
                </DataTemplate>
            </CollectionView.GroupHeaderTemplate>
        </CollectionView>
    </StackLayout>

 public partial class Page8 : ContentPage
{
    public GroupHumorViewmodel groups { get; set; }
    public Page8()
    {
        InitializeComponent();
        groups = new GroupHumorViewmodel();
        this.BindingContext =groups;
    }

    private void CarouselView_Scrolled(object sender, ItemsViewScrolledEventArgs e)
    {
        var current = CarouselView1.CurrentItem as HumorGroup;
        if(current!=null)
        {             
            CollectionDiary.ScrollTo(current.FirstOrDefault(),ScrollToPosition.Center);
        }
        
    }
}

public class HumorDiary
{
    public string name { get; set; }
    public int count { get; set; }
}

public class HumorGroup:ObservableCollection<HumorDiary>
{
    public string Name { get;  set; }
    public HumorGroup(string name, ObservableCollection<HumorDiary> humor) : base(humor)
    {
        Name = name;
    }
}

public class GroupHumorViewmodel
{
    public ObservableCollection<HumorGroup> humors { get; set; }

    public GroupHumorViewmodel()
    {          
        humors = new ObservableCollection<HumorGroup>();
        humors.Add(new HumorGroup("2021",new ObservableCollection<HumorDiary>() {
            new HumorDiary(){name="2021-day1",count=3},
            new HumorDiary(){name="2021-day2",count=3},
            new HumorDiary(){name="2021-day3",count=4},
            new HumorDiary(){name="2021-day4",count=2},
            new HumorDiary(){name="2021-day5",count=5},
            new HumorDiary(){name="2021-day6",count=4},
            new HumorDiary(){name="2021-day7",count=2},
            new HumorDiary(){name="2021-day8",count=5}


        }));

        humors.Add(new HumorGroup("2020", new ObservableCollection<HumorDiary>() {
            new HumorDiary(){name="2020-day1",count=3},
            new HumorDiary(){name="2020-day2",count=3},
            new HumorDiary(){name="2020-day3",count=4},
            new HumorDiary(){name="2020-day4",count=2},
            new HumorDiary(){name="2020-day5",count=5},
            new HumorDiary(){name="2020-day6",count=4},
            new HumorDiary(){name="2020-day7",count=2},
            new HumorDiary(){name="2020-day8",count=5}


        }));

        humors.Add(new HumorGroup("2019", new ObservableCollection<HumorDiary>() {
            new HumorDiary(){name="2019-day1",count=3},
            new HumorDiary(){name="2019-day2",count=3},
            new HumorDiary(){name="2019-day3",count=4},
            new HumorDiary(){name="2019-day4",count=2},
            new HumorDiary(){name="2019-day5",count=5},
            new HumorDiary(){name="2019-day6",count=4},
            new HumorDiary(){name="2019-day7",count=2},
            new HumorDiary(){name="2019-day8",count=5}


        }));
      
    }
}