事件已触发，但文本未更改

Question

What im trying to do is to change Splash window label content. App code behind is as follows

public partial class App : Application
{
    private const int splashMinTime = 2000;

    protected override void OnStartup(StartupEventArgs e)
    {
        Splash splashScr = new Splash();
        splashScr.Show();

        splashScr.SplashInfo = "Ładowanie ....";

        Stopwatch splashTimer = new Stopwatch();
        splashTimer.Start();
        base.OnStartup(e);
        MainWindow main = new MainWindow();

        splashTimer.Stop();

        int splashRemainingTime = splashMinTime - (int)splashTimer.ElapsedMilliseconds;
        if (splashRemainingTime > 0)
            Thread.Sleep(splashRemainingTime);

        splashScr.Close();
    }
}

Splash

public partial class Splash : Window, INotifyPropertyChanged
{
    public string _SplashInfo;
    public event PropertyChangedEventHandler PropertyChanged;

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

    public string SplashInfo
    {
        get { return _SplashInfo; }
        set { _SplashInfo = value; OnPropertyChanged("SplashInfo"); }
    }

    private void OnPropertyChanged(string PropertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(PropertyName));
        }
    }
}

And my Splash.xaml

<Grid>
    <Image Source="Img\Splash.jpg" Stretch="None"/>
    <Label x:Name="lblSplashInfo" Content="{Binding SplashInfo}" HorizontalAlignment="Left" Margin="10,204,0,0" VerticalAlignment="Top" Width="220"/>
</Grid>

Splash PropertyChangedEventHandler is fired but i don't see the changes in the splash window label.

Answer 1

Maybe I'm missing something, but for me it looks like you need some code like the following in your startup:

SplashScr.PropertyChanged += new PropertyChangedEventHandler<PropertyChangedEventArgs> (this.yourLabelChangerFunction);

And some function that changes the label:

public void yourLabelChangerFunction (object sender, EventArgs e){...}

Also, you seem to be setting string _SplashInfo before the window has been created, so maybe that's another reason why the window label doesn't change.

Answer 2

I think the binding is working but the window is not updated because you do Thread.Sleep in the Thread of the Splash window. You have to do it in its own Thread.

Answer 3

It's a treading issue as Marcel_Bonzelet said. Try this and you will see:

        protected override void OnStartup(StartupEventArgs e)
        {
            MainWindow window = new MainWindow();
            window.Visibility = Visibility.Hidden;
            new Task(() =>
            {
                Splash splashScr = null;
                Dispatcher.Invoke(() =>
                {
                    splashScr = new MainWindow();
                    splashScr.Show();
                });
                Stopwatch splashTimer = new Stopwatch();
                splashTimer.Start();

                splashScr.SplashInfo = "Ładowanie ....";

                splashTimer.Stop();

                int splashRemainingTime = splashMinTime - (int)splashTimer.ElapsedMilliseconds;
                if (splashRemainingTime > 0)
                    Thread.Sleep(splashRemainingTime);

                Dispatcher.Invoke(() =>
                {
                    splashScr.Close();
                    window.Visibility = Visibility.Visible;
                });
            }).Start();

            base.OnStartup(e);
        }

Some explanation: the OnStartup method is called on the same thread where your label would be updated. So if you block this thread, and after that you immediately close the window, you won't be able to see the result of the binding.