问题描述
当我更新绑定到 ListView 的 ObservableCollection 时,它会自动滚动到顶部。
我获取数据的代码目前看起来像这样,记录是 ObsevableCollection:
public async Task getData()
{
var client = new HttpClient();
HttpResponseMessage response = await client.GetAsync(new Uri("https://api.nomics.com/v1/currencies/ticker?key=<api key>&limit=10"));
var jsonString = await response.Content.ReadAsstringAsync();
JsonArray root = JsonValue.Parse(jsonString).GetArray();
records.Clear();
for (uint i = 0; i < root.Count; i++)
{
string id = root.GetobjectAt(i).GetNamedString("id");
string name = root.GetobjectAt(i).GetNamedString("name");
decimal price = decimal.Parse(root.GetobjectAt(i).GetNamedString("price"));
records.Add(new Coin {
id = id,name = name,price = Math.Round(price,4),logo = "https://cryptoicon-api.vercel.app/api/icon/" + id.ToLower()
});
};
}
我的 XAML 布局:
<ListView x:Name="CoinsLV" Grid.Row="1" IsItemClickEnabled="True" ItemClick="listView_ItemClick" ScrollViewer.VerticalScrollMode="Auto">
<ListView.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" Padding="5">
<Image Width="50" Height="50">
<Image.source>
<BitmapImage UriSource="{Binding logo}" />
</Image.source>
</Image>
<StackPanel>
<TextBlock Text="{Binding name}"
Margin="20,0"
FontSize="18"
FontWeight="SemiBold"
Foreground="DarkGray" />
<TextBlock Text="{Binding price}"
Margin="20,0"
FontSize="20"
Foreground="White"
Opacity="1" />
</StackPanel>
</StackPanel>
</DataTemplate>
</ListView.ItemTemplate>
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<ItemsstackPanel ItemsUpdatingScrollMode="KeepItemsInView" />
</ItemsPanelTemplate>
</ListView.ItemsPanel>
</ListView>
有什么办法可以禁用这种行为,因为它会导致非常糟糕的用户体验。 我试过单独更新每个项目,但无法使其正常工作。 谢谢。
解决方法
我可以重现您的问题。原因是你在添加item之前使用了Books.Clear()
清除了datasource,导致ListView的ItemsSource为null,导致listView滚动到顶部。
要解决这个问题,您需要创建一个集合来记录以前的项目,然后您可以从总集合中删除这些以前的项目。
如下:
XML 代码:
<ListView IsItemClickEnabled="True" ScrollViewer.VerticalScrollMode="Auto" ItemsSource="{x:Bind Books}" Height="600">
…
</ListView>
背后的代码:
public sealed partial class MainPage : Page
{
public ObservableCollection<Book> Books;
public ObservableCollection<Book> OldBooks;
public MainPage()
{
this.InitializeComponent();
Books =new ObservableCollection<Book>()
{
new Book(){logo=new Uri("ms-appx:///Assets/2.JPG"),name="Chinese",price=25},new Book(){logo=new Uri("ms-appx:///Assets/2.JPG"),name="English",price=26},……
};
OldBooks = new ObservableCollection<Book>();
foreach (var book in Books)
{
OldBooks.Add(book);
}
}
private void Button_Click(object sender,RoutedEventArgs e) //update button
{
Books.Add(new Book() { logo = new Uri("ms-appx:///Assets/1.JPG"),name = "Math",price = 20 });
……
Books.Add(new Book() { logo = new Uri("ms-appx:///Assets/1.JPG"),name = "Chenstry",price = 30 });
foreach(var item in OldBooks)
{
Books.Remove(item);
}
}
}
public class Book
{
public Uri logo { get; set; }
public string name { get; set; }
public int price { get; set; }
}