INotifyPropertyChanged不工作

Question

我有一个简单的对象(在App.xaml.cs中全局初始化)：

public class now_playing : INotifyPropertyChanged
{
    // notify
    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged(string p)
    {
        Debug.WriteLine(p + ": notify propertychanged");
        PropertyChangedEventHandler handler = PropertyChanged;
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(p));
    }

    // artist
    public string artist
    {
        get
        {
            return _artist;
        }
        set
        {
            _artist = value;
            NotifyPropertyChanged("artist");
        }
    }
    private string _artist;

    // album
    public string album
    {
        get
        {
            return _album;
        }
        set
        {
            _album = value;
            NotifyPropertyChanged("album");
        }
    }
    private string _album;

    // track title
    public string tracktitle
    {
        get
        {
            return _tracktitle;
        }
        set
        {
            _tracktitle = value;
            NotifyPropertyChanged("tracktitle");
        }
    }
    private string _tracktitle;
}

每当我更改这些值时，该类都会通知(我看到了调试)。所以我猜问题出在我的XAML或后面的代码中。

页面代码：

public sealed partial class nowplaying : Page
{
    // artistdata
    public string artist { get { return App.nowplaying.artist; } }
    // albumdata
    public string album { get { return App.nowplaying.album; } }
    // trackdata
    public string tracktitle { get { return App.nowplaying.tracktitle; } }

    public nowplaying()
    {
        this.InitializeComponent();
        this.DataContext = this;
    }
}

XAML：

<Grid Margin="50">
    <TextBlock Text="{Binding tracktitle}" Foreground="White" FontSize="40"/>
    <TextBlock Foreground="#dcdcdc" FontSize="20" Margin="0,50,0,0">
        <Run Text="{Binding artist}"/>
        <Run Text=" - "/>
        <Run Text="{Binding album}"/>
    </TextBlock>
</Grid>

当我更改值时，为什么UI不更新？

堆栈跟踪：

Music.exe!Music.App.InitializeComponent.AnonymousMethod__6(object sender = {Music.App}, Windows.UI.Xaml.UnhandledExceptionEventArgs e = {Windows.UI.Xaml.UnhandledExceptionEventArgs}) Line 50  C#

Music.exe!play_music.MessageReceivedFromBackground(object sender = null, Windows.Media.Playback.MediaPlayerDataReceivedEventArgs e = {Windows.Media.Playback.MediaPlayerDataReceivedEventArgs}) Line 57 C#

更新:问题解决了！在调用propertychanged事件时，我必须使用调度程序：

CoreDispatcher dispatcher = CoreWindow.GetForCurrentThread().Dispatcher;
if (PropertyChanged != null)
{
    await dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
    {
        this.PropertyChanged(this, new PropertyChangedEventArgs(p));
    });
}

Answer 1

您可以在Page的属性中“松绑”更改通知，因为这些属性没有任何更改通知操作。

尝试直接使用now_playing：

public sealed partial class nowplaying : Page
{
    public now_playing NowPlaying { get { return App.nowplaying; } }

    public nowplaying()
    {
        this.InitializeComponent();
        this.DataContext = this;
    }
}

和

<Run Text="{Binding NowPlaying.artist}"/>

否则，您需要在nowplaying中实现INotifiyPropertyChanged，并从now_playing转发事件。

Answer 2

您实际上绑定到了实现INotifyPropertyChanged的nowplaying类的艺术家、专辑和曲目标题