c# - Xamarin:适用于 Android 和 Windows UWP 的 Xamarin 表单中分组列表的垂直字母索引(跳转列表)

Question

我为 ios、android 和 windows 平台设计了 Xamarin 表单中的分组 ListView 。当我在 ListView 中设置 GroupShortNameBinding 属性时，垂直索引(跳转列表)会自动出现在 IOS 中。但是跳转列表没有出现在android中。如何使用自定义渲染在 android 和 windows 中获得垂直索引的支持。如果谁能提供支持跨平台这个特性的自定义渲染源。

Answer 1

如果您不想要 CustomRenders，最简单的方法是使用 XAML hack。

您可以将 ListView 包装在高度和宽度等于父级(内容页面)的 RelativeLayout 中。

对于 ListView ，使用高度作为父级，宽度为父级的 90%。添加一个宽度为 10% 的堆栈布局，并从以高度为父级的相对布局的 90% 开始。使其方向垂直。将所有字母作为标签添加到堆栈布局并实现其 TapGesture至 ScrollTo特定的位置。

将 Android 的宽度设置为 90%，仅适用于 iOS，Windows 保持为 100%，堆栈布局宽度为 0%，并且 IsVisible=false。

View 模型:

public class JumpListViewModel : INotifyPropertyChanged
{
    private ObservableCollection<Item> _allItems;
    private List<string> _alphabetList;

    public event PropertyChangedEventHandler PropertyChanged;

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null) => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

    public JumpListViewModel()
    {
        AllItems = new ObservableCollection<Item>(new List<Item> { new Item { MyText = "1" }, new Item { MyText = "2" }, new Item { MyText = "3" } });

        AlphabetList = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray().Select(x => x.ToString()).ToList();
    }

    public ObservableCollection<Item> AllItems
    {
        get { return _allItems; }
        set
        {
            _allItems = value;
            OnPropertyChanged();
        }
    }

    public List<string> AlphabetList
    {
        get { return _alphabetList; }
        set
        {
            _alphabetList = value;
            OnPropertyChanged();
        }
    }
}

View :

<RelativeLayout VerticalOptions="FillAndExpand">

    <ListView VerticalOptions="FillAndExpand" HasUnevenRows="True" ItemsSource="{Binding AllItems}"
              SeparatorColor="Transparent" SeparatorVisibility="None" BackgroundColor="Transparent"
              RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=1}">
      <RelativeLayout.WidthConstraint>
        <OnPlatform x:TypeArguments="Constraint" Android="{ConstraintExpression Type=RelativeToParent, Property=Width,Factor=0.9}"
                    iOS="{ConstraintExpression Type=RelativeToParent, Property=Width,Factor=1}"
          WinPhone="{ConstraintExpression Type=RelativeToParent, Property=Width,Factor=1}" />
      </RelativeLayout.WidthConstraint>

      <ListView.ItemTemplate>
        <DataTemplate>
          <ViewCell>

            <StackLayout HorizontalOptions="FillAndExpand" BackgroundColor="Silver">

              <Label Text="{Binding MyText}" />
              <Button Text="button" />
              <BoxView HeightRequest="1" Color="Gray" BackgroundColor="Gray" HorizontalOptions="FillAndExpand" />

            </StackLayout>

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

    <ListView VerticalOptions="FillAndExpand" HasUnevenRows="True" ItemsSource="{Binding AlphabetList}"
              SeparatorColor="Transparent" SeparatorVisibility="None" BackgroundColor="Transparent"
              RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.9}"
      RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.05}"
      RelativeLayout.XConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=0.9}">
      <RelativeLayout.WidthConstraint>
        <OnPlatform x:TypeArguments="Constraint" Android="{ConstraintExpression Type=RelativeToParent, Property=Width,Factor=0.1}"
                    iOS="{ConstraintExpression Type=RelativeToParent, Property=Width,Factor=0, Constant=0}"
          WinPhone="{ConstraintExpression Type=RelativeToParent, Property=Width,Factor=0, Constant=0}" />
      </RelativeLayout.WidthConstraint>
      <ListView.IsVisible>
        <OnPlatform x:TypeArguments="x:Boolean" WinPhone="False" iOS="False" Android="True" />
      </ListView.IsVisible>
      <ListView.ItemTemplate>
        <DataTemplate>
          <ViewCell>
            <Label Text="{Binding .}" TextColor="Red" FontSize="Micro" />
          </ViewCell>
        </DataTemplate>
      </ListView.ItemTemplate>
    </ListView>

  </RelativeLayout>

Android 截图: