我有一个CarouselView,它绑定到图像的ItemsSource。
但是我想通过更改CarouselView的索引来更改当前显示的图像。

我尝试使用CarouselView.Position来选择元素的索引。但不幸的是,这不起作用。

我该如何实现?
谢谢

最佳答案

我尝试使用CarouselView.Position来选择元素的索引。但不幸的是,这不起作用。

由于您要对ItemsSourceCarouselView使用数据绑定,因此可以为图像模型实现INotifyPropertyChanged接口。

例如:

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:cv="clr-namespace:Xamarin.Forms;assembly=Xamarin.Forms.CarouselView"
             x:Class="FormsIssue2.Page1">
    <Grid>
        <cv:CarouselView ItemsSource="{Binding Zoos, Mode=OneWay}" x:Name="CarouselZoos">
            <cv:CarouselView.ItemTemplate>
                <DataTemplate>
                    <Grid>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="*" />
                            <RowDefinition Height="Auto" />
                        </Grid.RowDefinitions>
                        <Image Grid.RowSpan="2" Aspect="AspectFill" Source="{Binding ImageUrl, Mode=OneWay}" />
                        <StackLayout Grid.Row="1" BackgroundColor="#80000000" Padding="12">
                            <Label TextColor="White" Text="{Binding Name, Mode=OneWay}" FontSize="16" HorizontalOptions="Center" VerticalOptions="CenterAndExpand" />
                        </StackLayout>
                    </Grid>
                </DataTemplate>
            </cv:CarouselView.ItemTemplate>
        </cv:CarouselView>
    </Grid>
</ContentPage>

后面的代码:
public partial class Page1 : ContentPage
{
    public Page1()
    {
        InitializeComponent();

        Zoos = new ObservableCollection<Zoo>
      {
        new Zoo
        {
            ImageUrl = "http://wallpaper-gallery.net/images/image/image-13.jpg",
            Name = "Woodland Park Zoo"
        },
            new Zoo
        {
            ImageUrl =  "https://s3-us-west-1.amazonaws.com/powr/defaults/image-slider2.jpg",
            Name = "Cleveland Zoo"
            },
        new Zoo
        {
            ImageUrl = "http://i.stack.imgur.com/WCveg.jpg",
            Name = "Phoenix Zoo"
        }
    };

        //CarouselZoos.ItemsSource = Zoos;
        this.BindingContext = this;
        CarouselZoos.ItemSelected += CarouselZoos_ItemSelected;
    }

    private void CarouselZoos_ItemSelected(object sender, SelectedItemChangedEventArgs e)
    {
        var item = e.SelectedItem as Zoo;
        if (item == null)
            return;
        item.ImageUrl = "https://3.bp.blogspot.com/-W__wiaHUjwI/Vt3Grd8df0I/AAAAAAAAA78/7xqUNj8ujtY/s1600/image02.png";
    }

    public ObservableCollection<Zoo> Zoos { get; set; }
}

public class Zoo : INotifyPropertyChanged
{
    private string _ImageUrl;

    public string ImageUrl
    {
        get { return _ImageUrl; }
        set
        {
            if (value != _ImageUrl)
            {
                _ImageUrl = value;
                OnPropertyChanged("ImageUrl");
            }
        }
    }

    private string _Name;

    public string Name
    {
        get { return _Name; }
        set
        {
            if (value != _Name)
            {
                _Name = value;
                OnPropertyChanged("Name");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string propertyName)
    {
        var handler = PropertyChanged;
        if (handler != null)
            handler(this, new PropertyChangedEventArgs(propertyName));
    }
}

选择一个项目后,您可以在SelectedItemChangedEventArgs中找到该项目的实例,然后可以更改该项目的图像源。

更新:

根据我们的讨论,我认为缩略图的CarouselView和较大图像的CarouselView的项目来源按相同的顺序排列,然后在缩略图中选择该项目时,您可以获取缩略图的位置并滚动CarouselView对于像这样的大图像:
var postion = CarouselThunbnails.Position;
CarouselImages.Position = postion;

09-25 15:54