[英]Binding to property not working with DispatcherTimer
我有一些TextBlock绑定到具有DependencyProperty的属性。 当DispatcherTimer更改此属性时,TextBlock不会更新。 即使在调试中,我也可以看到该属性已更新,但TextBlock保持不变。
详细信息:我有一堂课:
public class myTimer
{
public System.DateTime Duration { get; set; }
public System.DateTime Elapsed { get; set; }
public System.TimeSpan Remaining {
get {
return Duration.Subtract(new DateTime(Duration.Year, Duration.Month, Duration.Day, Elapsed.Hour, Elapsed.Minute, Elapsed.Second));
}
}
}
我的xaml代码中包含myTimer
类型的DependencyProperty
public static DependencyProperty currentTimerProperty = DependencyProperty.Register("CurrentTimer", typeof(myTimer), typeof(Question));
public myTimer CurrentTimer
{
get { return (myTimer)GetValue(currentTimerProperty); }
set { SetValue(currentTimerProperty, value); }
}
并且我有三个TextBlock绑定到此属性:
<TextBlock Style="{StaticResource myTimer}">
<TextBlock.Text>
<MultiBinding StringFormat="{}{0:00}:{1:00;00}">
<Binding ElementName="Questionctl" Path="CurrentTimer.Remaining.Minutes"/>
<Binding ElementName="Questionctl" Path="CurrentTimer.Remaining.Seconds"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
<TextBlock Text="{Binding ElementName=Questionctl,Path=CurrentTimer.Duration,StringFormat=HH:mm:ss}"/>
<TextBlock Text="{Binding ElementName=Questionctl,Path=CurrentTimer.Elapsed,StringFormat=HH:mm:ss}"/>
计时器初始化如下:
dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);
dispatcherTimer.Interval = new TimeSpan( 0 , 0, 1);
dispatcherTimer.Start();
如此简单,每一秒钟,它将在属性Elapsed中增加1秒:
CurrentTimer.Elapsed = CurrentTimer.Elapsed.AddSeconds(1);
更新您的myTimer
的类定义以实现INotifyPropertyChanged
如下所示:
public class myTimer : INotifyPropertyChanged
{
private System.DateTime _duration;
public System.DateTime Duration
{
get
{
return _duration;
}
set
{
_duration = value;
RaisePropertyChanged("Duration");
RaisePropertyChanged("Remaining");
}
}
private DateTime _elapsed;
public DateTime Elapsed
{
get { return _elapsed; }
set
{
_elapsed = value;
RaisePropertyChanged("Elapsed");
RaisePropertyChanged("Remaining");
}
}
public System.TimeSpan Remaining
{
get
{
return Duration.Subtract(new DateTime(Duration.Year, Duration.Month, Duration.Day, Elapsed.Hour, Elapsed.Minute, Elapsed.Second));
}
}
public event PropertyChangedEventHandler PropertyChanged;
private void RaisePropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
如果那是您的实际问题而不是简化,那么您将遇到另一个问题。
仅当并且仅在调度计时器事件每隔一秒发生一次时,您的代码才起作用。 该api不能保证这一点。
如果改为在定时器触发时捕获系统时间,则即使事件触发之间的时间是零星的,它也会计算正确的时间。
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