Question

我有一个手动创建列表的工作解决方案。但是因为我想从一个文件读取，因此我必须更改为异步，并且因为未来数据量将改变为ObservableCollection，XAML不再显示9行。

调试我看到 {x：Bind Accounts} 仍然包含9行和两个值。但未列出 AccountName 和 SumAccountName 数据。只有页眉和页脚。我现在花了几个小时来比较两种解决方案，但不知道为什么这个解决方案没有显示数据。

Overview.xaml：

x:Class="Finance_Manager.Overview"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Finance_Manager"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:data="using:Finance_Manager.Models"
mc:Ignorable="d">

<StackPanel>
        <Grid Margin="20,20,20,20" Background="{ThemeResource ApplicationPageBackgroundThemeBrush}" Loaded="Grid_Loaded">
        <ListView ItemsSource="{x:Bind Accounts}" IsItemClickEnabled="True" ItemClick="ListView_ItemClick">
            <ListView.ItemContainerStyle>
                <Style TargetType="ListViewItem">
                    <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
                </Style>
            </ListView.ItemContainerStyle>
            <ListView.Header>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="4*" />
                        <ColumnDefinition Width="1*" />
                    </Grid.ColumnDefinitions>
                    <TextBlock FontWeight="Bold" Text="Konto" />
                    <TextBlock Grid.Column="1" FontWeight="Bold" Text="Total" TextAlignment="Right"/>
                </Grid>
            </ListView.Header>
            <ListView.ItemTemplate>
                <DataTemplate x:DataType="data:Account">
                    <Grid>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="4*" />
                            <ColumnDefinition Width="1*" />
                        </Grid.ColumnDefinitions>
                        <TextBlock Text="{x:Bind AccountName}" />
                        <TextBlock Grid.Column="1" Text="{x:Bind SumAccountName}" TextAlignment="Right"/>
                    </Grid>
                </DataTemplate>
            </ListView.ItemTemplate>
            <ListView.Footer>
                <Grid>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="4*" />
                        <ColumnDefinition Width="1*" />
                    </Grid.ColumnDefinitions>
                    <TextBlock FontWeight="Bold" Text="Gesamtvermögen" />
                    <!-- <TextBlock Grid.Column="1" FontWeight="Bold" x:Name="SumTextBlock" TextAlignment="Right"/> -->
                    <TextBlock Grid.Column="1" FontWeight="Bold" Text="CHF 326'979.74" TextAlignment="Right"/>
                </Grid>
            </ListView.Footer>
        </ListView>
    </Grid>
    <Grid>
        <TextBlock Margin="20,80,0,0" x:Name="TextBlockClicked" TextWrapping="Wrap" VerticalAlignment="Bottom" />
    </Grid>
    </StackPanel>

Accounts.cs：

namespace Finance_Manager.Models
{
    public class Account
    {
        public string AccountName { get; set; }
        public double SumAccountName { get; set; }
    }

    public class AccountOverview
    {
        public static async Task<ObservableCollection<Account>> GetAccounts()
        {
            var accounts = new ObservableCollection<Account>();

            //
            // Load file
            var folder = ApplicationData.Current.LocalFolder;
            var GetOverviewFile = await folder.GetFileAsync("overview.json");
            string jsonString = await FileIO.ReadTextAsync(GetOverviewFile);
            //

            JsonArray root = JsonValue.Parse(jsonString).GetArray();
            for (uint i = 0; i < root.Count; i++)
            {
                string account1 = root.GetObjectAt(i).GetNamedString("account");
                double sumaccount1 = root.GetObjectAt(i).GetNamedNumber("sumaccount");
                accounts.Add(new Account { AccountName = account1, SumAccountName = sumaccount1 });
            };

            //accounts.Add(new Account { AccountName = "Bank1", SumAccountName = 100.00 });
            //accounts.Add(new Account { AccountName = "Bank2", SumAccountName = 100.00 });
            //accounts.Add(new Account { AccountName = "Bank3", SumAccountName = 100.00 });
            //accounts.Add(new Account { AccountName = "Bank4", SumAccountName = 100.00 });
            //accounts.Add(new Account { AccountName = "Bank5", SumAccountName = 100.00 });
            //accounts.Add(new Account { AccountName = "Bank6", SumAccountName = 100.00 });
            //accounts.Add(new Account { AccountName = "Bank7", SumAccountName = 100.00 });
            //accounts.Add(new Account { AccountName = "Bank8", SumAccountName = 100.00 });
            //accounts.Add(new Account { AccountName = "Bank9", SumAccountName = 100.00 });

            return accounts;
        }
    }
}

Overview.xaml.cs：

namespace Finance_Manager
{
    /// <summary>
    /// An empty page that can be used on its own or navigated to within a Frame.
    /// </summary>
    public sealed partial class Overview : Page
    {

        public ObservableCollection<Account> Accounts;

        public Overview()
        {
            this.InitializeComponent();
        }

        public async void Grid_Loaded(object sender, RoutedEventArgs e)
        {
            Accounts = await AccountOverview.GetAccounts();
        }
    }
}

Answer 1

首先，绑定仅适用于属性而非字段（您的ObservableCollection帐户只是字段）。

另一个问题可能是加载XAML时Accounts属性为null，因此您可能需要在Accounts = new ObservableCollection<Accounts>();之前添加this.InitializeComponents();，而不是返回来自AccountOverview.GetAccounts();方法的全新ObservableCollection实例，但只填充已存在的对象。

Answer 2

1）将您的Accounts字段更改为属性

2）如果您正在使用绑定，则应在每次更改INotifyPropertyChanged属性时实现Accounts并调用OnPropertyChanged（）。这将更新View。

3）默认x:Bind使用mode=OneTime，您应将其更改为Mode=OneWay。

如果您想要最快速，最简单的解决方案，请删除绑定，然后执行ListView.ItemSource = MyClass.GetAccounts()。它对MVVM模式不利，但我发现你正在使用代码。

Answer 3

我做了所有解释，但它仍然无法正常工作。

我将Name="AccountList"添加到Overview.xaml中的ListView。和AccountList.ItemSource = Accounts;到Overview.xaml.cs。现在它有效。

UWP＃没有显示ListView.ItemTemplate，因为我从List更改为ObservableCollection和async

3 个答案: