的Windows Phone 8滑盖绑定工作，只有在点击后 [英] Windows phone 8 slider binding works only after a click

问题描述

我写在Windows Phone 8，我创建了一个的MediaElement和寻求杆（滑块）的音频应用程序：

I am writing an audio app on Windows Phone 8. I've created a MediaElement and a seek-bar(slider):

<MediaElement x:Name="player" CurrentStateChanged="GetTrackDuration" />
<Slider x:Name="playerSeekBar" Value="{Binding ElementName=player, Path=Position, 
 Mode=TwoWay, Converter={StaticResource PositionConverter}}" SmallChange="1" LargeChange="1"/>

这是我的转换代码：

And this is my converter code:

public class PositionConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        double position = 0;
        TimeSpan timespan = TimeSpan.Parse(value.ToString());
        position = timespan.TotalSeconds;

        return position;
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
            return TimeSpan.FromSeconds((double)value);
    }
}

这里是CurrentStateChanged事件代码：

And here is the CurrentStateChanged event code:

private void GetTrackDuration(object sender, RoutedEventArgs e)
{
    var player = (MediaElement)sender;
    if (player.CurrentState == System.Windows.Media.MediaElementState.Playing)
        playerSeekBar.Maximum = player.NaturalDuration.TimeSpan.TotalSeconds;
}

这一切似乎工作确定，但是有一个问题与绑定滑块 - 它不更新，直到我点击某处里面的应用程序 - 我的意思是我可以点击不与滑块或媒体元素或一个空连接的按钮。我后，点击滑块正在更新，一切工作不错。当滑块不更新，甚至在开始 - 顺便说一句，音乐发挥正常。我试图寻找在互联网上，但我不知道要问什么，这就是为什么我要求你的帮助。如果有人只知道在那里我可以搜索解决方案，我将非常感激：！）

It all seems to work OK, however there is one problem with the binding to slider - it doesn't update until I click somewhere inside the app - I mean i may click on a button that isn't connected with slider or media element or on a empty space. After I click the slider is being updated and everything works nice. BTW, the music plays normally - even at the beginning when the slider is not being updated. I tried to look on the Internet, however I am not sure what to ask, that's why I am asking You for help. If someone just knows where I could search for the solution, I would be very grateful!:)

感谢您对提前帮助

推荐答案

它看起来像当滑块获得焦点的一个问题，我试图找到重定向对焦的解决方案，但到目前为止 - 我还没有找到它。相反，我有一个不同势提议，几句话对你的代码：

It looks like a problem when Slider gets Focus, I've tried to find a solution with redirecting Focus, but so far - I haven't found it. Instead I've a diffrent proposal and few remarks to your code:

1. 获取持续跟踪媒体时，打开是不是在PlayState变化

1. Get track duration when Media is Opened not when PlayState changes:

private void player_MediaOpened(object sender, RoutedEventArgs e)
{
    playerSeekBar.Maximum = (sender as MediaElement).NaturalDuration.TimeSpan.TotalSeconds;
}

您滑块可能会被MediaElement的立场的每一个小变化更新。我想是不是需要它 - 例如，它可以每秒进行更新。所以我的建议是 - 你的滑块绑定属性，并通知的PropertyChanged每一秒（使用 DispatcherTimer ）：

// In this case we need INotifyPropertyChanged - 
public partial class MainPage : PhoneApplicationPage, INotifyPropertyChanged
{

// implementing interface
public event PropertyChangedEventHandler PropertyChanged;
public void RaiseProperty(string property = null)
{
    if (this.PropertyChanged != null)
        this.PropertyChanged(this, new PropertyChangedEventArgs(property));
}

// Property for Binding
public double SlideValue
{
    get { return player.Position.TotalSeconds; }
    set { player.Position = TimeSpan.FromSeconds(value); }
}

DispatcherTimer timer = new DispatcherTimer(); // timer

// Get the duration when Media File is opened
private void player_MediaOpened(object sender, RoutedEventArgs e)
{
    playerSeekBar.Maximum = (sender as MediaElement).NaturalDuration.TimeSpan.TotalSeconds;
}

public MainPage()
{
    InitializeComponent();
    this.DataContext = this;  // Set the DataContext
    Play.Click += Play_Click;  // My play method
    timer.Interval = TimeSpan.FromSeconds(1);
    timer.Tick += (s, e) => { RaiseProperty("SlideValue"); };
}

private void Play_Click(object sender, RoutedEventArgs e)
{
    player.AutoPlay = true;
    player.Source = new Uri("music.mp3", UriKind.RelativeOrAbsolute);
    timer.Start();  // DON'T forget to start the timer.
}

在这种情况下，不再需要转换器，你的XAML代码可以是这样的：

In this case you no longer need Converters, and your XAML code can look like this:

<MediaElement x:Name="player" MediaOpened="player_MediaOpened"/>
<Slider x:Name="playerSeekBar" Value="{Binding SlideValue, Mode=TwoWay}" SmallChange="1" LargeChange="1"/>

以上代码可能仍然需要一些改进，但工作得很好。

Above code probably still needs some improvements, but works quite fine.

修改 - 方法，无需数据绑定和INotifyPropertyChanged的

EDIT - method without DataBinding and INotifyPropertyChanged

您也可以完成你的任务更简单的方法没有约束力，仅仅使用定时和 LostMouseCapture ：

You can also accomplish your task simpler way without Binding, just using Timer and LostMouseCapture:

public partial class MainPage : PhoneApplicationPage
{
    private double totalSeconds = 1;

    DispatcherTimer timer = new DispatcherTimer();

    private void player_MediaOpened(object sender, RoutedEventArgs e)
    {
        totalSeconds = (sender as MediaElement).NaturalDuration.TimeSpan.TotalSeconds;
    }

    public MainPage()
    {
        InitializeComponent();
        Play.Click += Play_Click;
        timer.Interval = TimeSpan.FromSeconds(1);
        timer.Tick += (s, e) => { playerSeekBar.Value += (double)(1 / totalSeconds); };
        playerSeekBar.LostMouseCapture += (s, e) =>
        { player.Position = TimeSpan.FromSeconds(playerSeekBar.Value * totalSeconds); };
    }

    private void Play_Click(object sender, RoutedEventArgs e)
    {
        player.AutoPlay = true;
        player.Source = new Uri("music.mp3", UriKind.RelativeOrAbsolute);
        timer.Start();  // DON'T forget to start the timer.
    }
}

在XAML：

<MediaElement x:Name="player" MediaOpened="player_MediaOpened"/>
<Slider x:Name="playerSeekBar" Value="0" SmallChange="0.01" Maximum="1.0"/>

希望这有助于。

Hope this helps.

这篇关于的Windows Phone 8滑盖绑定工作，只有在点击后的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！