WPF ListView 绑定 +错误

发布于 2024-11-03 02:12:14 字数 1200 浏览 0 评论 0原文

我收到异常“未将对象引用设置为对象的实例”。在“songs.DataContext =”行上。如果我添加歌曲= new ListView();在此之前，即使音频文件列表不是

XAML，我的列表视图也是空的：

<ListView  Height="Auto" HorizontalAlignment="Center" ItemsSource="{Binding}"
               VerticalAlignment="Center" Name="songList" Width="Auto" MinHeight="300" MinWidth="600">
        <ListView.View>
            <GridView>
                <GridViewColumn Width="Auto" Header="Title" DisplayMemberBinding="{Binding Path=Title}" />
                <GridViewColumn Width="Auto" Header="Artist" DisplayMemberBinding="{Binding Path=Artist}" />
                <GridViewColumn Width="Auto" Header="Album" />
                <GridViewColumn Width="Auto" Header="Length" />
            </GridView>
        </ListView.View>
    </ListView>

 public struct AudioFile
    {

        public String Artist;
        public String Title;
        public String Album;
        public String fileLocation;
        public String Length;
    }

//...
private List<AudioFile> songs = new List<AudioFile>();
//code that adds to array
songList.DataContext = songs;

原文

I am getting an exception "Object reference not set to an instance of an object." on the "songs.DataContext =" line. If I add songs = new ListView(); before it my listview is empty even though the list of audiofiles is not

XAML:

<ListView  Height="Auto" HorizontalAlignment="Center" ItemsSource="{Binding}"
               VerticalAlignment="Center" Name="songList" Width="Auto" MinHeight="300" MinWidth="600">
        <ListView.View>
            <GridView>
                <GridViewColumn Width="Auto" Header="Title" DisplayMemberBinding="{Binding Path=Title}" />
                <GridViewColumn Width="Auto" Header="Artist" DisplayMemberBinding="{Binding Path=Artist}" />
                <GridViewColumn Width="Auto" Header="Album" />
                <GridViewColumn Width="Auto" Header="Length" />
            </GridView>
        </ListView.View>
    </ListView>

 public struct AudioFile
    {

        public String Artist;
        public String Title;
        public String Album;
        public String fileLocation;
        public String Length;
    }

//...
private List<AudioFile> songs = new List<AudioFile>();
//code that adds to array
songList.DataContext = songs;

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月竹挽风 2024-11-10 02:12:14

我怀疑您的代码位于构造函数中，位于尚未创建songList 的位置。

//...
private List<AudioFile> songs = new List<AudioFile>();
//code that adds to array
songList.DataContext = songs;

尝试在 Loaded 事件中移动它。

I suspect your code to be in the constructor, in a place where songList is not yet created.

//...
private List<AudioFile> songs = new List<AudioFile>();
//code that adds to array
songList.DataContext = songs;

Try to move it in the Loaded event instead.

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微暖i 2024-11-10 02:12:14

您的歌曲 显然已经完成，但是songList 又如何呢？

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弥繁 2024-11-10 02:12:14

我认为您可能正在尝试在构造函数中设置 SongList.ItemsSource = list ，显然该对象尚未构建。

在您的 UI 类中，初始化的最佳位置仅在 Loaded 事件中或在 InitializeComponent 方法之后。

更好的方法是使用 MVVM。

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梦过后 2024-11-10 02:12:14

编写此代码

//...
private List<AudioFile> songs = new List<AudioFile>();
//code that adds to array
songList.DataContext = songs;

您是否在为视图调用 IniitializeComponent() 方法之前？您能否提供有关代码放置的更多见解，这将有助于更好地理解情况。

只是一个建议，但不相关。我会说使用类而不是结构对象，因为 WPF 数据绑定仅考虑属性，而不考虑字段。 当然，这不是错误的原因。

Are you writing this code -

//...
private List<AudioFile> songs = new List<AudioFile>();
//code that adds to array
songList.DataContext = songs;

before IniitializeComponent() method is called for a view?? Can you provide a bit more of insight regarding your code placement that will help in understanding the situation better.

And just a suggestion, not related though. I would say use class instead of structure objects because WPF data binding considers only properties, not fields. Definitely, this is not a cause of an error though.

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