Question

我正在尝试使用TextBlock通过Bluetooth LE接收数据（OneWay模式），但是我无法使其工作。

我有一个主页，其中包含另一个辅助页面。此辅助页面的TextBlock用作Grid列内的目标：

<Grid x:Name="DataPanel" 
              RelativePanel.Below="ControlPanel"
              RelativePanel.AlignLeftWithPanel="True"
              RelativePanel.AlignRightWithPanel="True">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            <Rectangle x:Name="ax_down0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Fill="Transparent" Grid.Column="0" />
            <StackPanel Orientation="Vertical" Margin="10" Grid.Column="0" HorizontalAlignment="Center"
                        DataContext="">
                <TextBlock Text="Accelerometr X" TextAlignment="Center" FontWeight="Bold"/>
                <TextBlock Name="ADataX" Text="{x:Bind Path=SData.Acceleration_x, Mode=OneWay}" TextAlignment="Center"/>
            </StackPanel>
            <Rectangle x:Name="ax_up0" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Fill="Transparent" Grid.Column="0"/>
            .
            .
            .
</Grid>

用作源的类如下：

public class SensorData : INotifyPropertyChanged
{

    public event PropertyChangedEventHandler PropertyChanged = delegate { };

    private UInt16 acceleration_x;
    public UInt16 Acceleration_x
    {
        get
        {
            return acceleration_x;
        }
        set
        {
            acceleration_x = value;
            OnPropertyChanged("Acceleration_x");
        }
    }
    .
    .
    .

    public SensorData()
    {
        Acceleration_x = 0;
        Acceleration_y = 0;
        Acceleration_z = 0;
    }

    public void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        // Raise the PropertyChanged event, passing the name of the property whose value has changed.
        this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

接下来，在C＃文件中，对于次要页面，是注册处理程序，该处理程序从Bluetooth设备接收通知并将其存储到SData属性（Property Accel_x具有GattCharacteristic类型，并且在MainPage中定义，该实例的实例可以通过rootPage变量进行访问）

public sealed partial class Page2 : Page
{
    private MainPage rootPage;
    public SensorData SData { get; set; }

protected async override void OnNavigatedTo(NavigationEventArgs e)
{
     rootPage.Accel_x.ValueChanged += delegate (GattCharacteristic sender, GattValueChangedEventArgs args)
            {
                var reader = DataReader.FromBuffer(args.CharacteristicValue);
                SData.Acceleration_x = reader.ReadByte();
            };
}

即使SData中的数据已更改，UI也不会更新。有谁知道为什么吗？我已经花了很多时间试图解决它。

但是，当PointerPressed事件处理程序更新SData时，通过矩形元素触发它就可以正常工作。

 ax_up0.PointerPressed += new PointerEventHandler(delegate (object sender, PointerRoutedEventArgs e)
            {
                e.Handled = true;
                ax_down0.Fill = new SolidColorBrush(Windows.UI.Colors.DimGray);
                UInt16 i = SData.Acceleration_x;
                i++;
                SData.Acceleration_x = i;
            });

有什么主意为什么要由一个hadler进行更新，而另一个就不行？可以通过在与目标页面不同的页面中定义Accel_x来引起这种情况吗？

Answer 1

最后，我弄清楚了。将Dispatcher添加到ValueChanged处理程序后，它开始工作：

rootPage.Accel_x.ValueChanged += async delegate (GattCharacteristic sender, GattValueChangedEventArgs args)
            {
                await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () => {
                    var reader = DataReader.FromBuffer(args.CharacteristicValue);
                    SData.Acceleration_x = reader.ReadByte();
                });
            };

UWP数据绑定：事件处理程序中的属性更改不会更新UI

1 个答案: