Xamarin。与数据触发器绑定的表单-值未更新

<Label Text="{Binding CurrentTime, StringFormat='{0:D3} seconds'}" />

这行得通,我得到一个字符串,比如 053 seconds .我想显示文本 Not playing

<Label Text="{Binding CurrentTime, StringFormat='{0:D3} seconds'}">
    <Label.Triggers>
        <DataTrigger TargetType="Label" Binding="{Binding IsPlaying}" Value="False">
            <Setter Property="Text" Value="Not playing" />
        </DataTrigger>
    </Label.Triggers>
</Label>

这将正确显示 000 seconds 永远出了什么问题?

编辑

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MyNamespace.VideoPage"
             x:Name="ThePage"
             BindingContext="{x:Reference Name=ThePage}">
    <StackLayout>
        <Label VerticalOptions="Center" Text="{Binding CurrentTime, StringFormat='{0:D3} seconds'}" HorizontalOptions="StartAndExpand">
            <Label.Triggers>
                <DataTrigger TargetType="Label" Binding="{Binding IsPlaying}" Value="False">
                    <Setter Property="Text" Value="Not playing" />
                </DataTrigger>
            </Label.Triggers>
        </Label>
        <!-- More stuff -->
    </StackLayout>
</ContentPage>

后面的代码如下所示:

public partial class VideoPage : ContentPage
{
    private int currentTime;

    public int CurrentTime
    {
        get { return currentTime; }
        set
        {
            currentTime = value;
            OnPropertyChanged();
        }
    }

    private bool isPlaying;

    public bool IsPlaying
    {
        get { return isPlaying; }
        set
        {
            isPlaying = value;
            OnPropertyChanged();
        }
    }

    ...
}

编辑2

<ContentPage.Resources>
    <ResourceDictionary>
        <Style TargetType="Label" x:Key="PlayingStyle">
            <Setter Property="Text" Value="Not playing" />
            <Style.Triggers>
                <DataTrigger TargetType="Label" Binding="{Binding IsPlaying}" Value="True">
                    <Setter Property="Text" Value="{Binding CurrentTime, StringFormat='{0:D3} seconds'}" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </ResourceDictionary>
</ContentPage.Resources>
...
<Label Style="{StaticResource PlayingStyle}" />