WPF无法从变量更新文本框

Question

使用WPF和VB.net,我想用当前日期和时间更新文本块中的文本框.我使用计时器,它似乎正在触发,并将对象属性设置为"现在".我正在使用iNotifyPropertyChanged.

我得到的只是一个没有数据的空文本框.你能帮我吗？也许我的背景是关闭的？

XAML

<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
    <TextBlock DataContext="oTime"> 
        <TextBox x:Name="myTextBox" 
                 Width="200" Height="50" Foreground="Black" 
                 Text="{Binding Path=oTime.TimeUpdate}"></TextBox>
    </TextBlock>
</Grid>
</Window>

VB代码

Imports System.ComponentModel
Imports System.Windows.Threading

Class MainWindow
  Public oTime As TimeUpdate = New TimeUpdate
  Private dpTimer As DispatcherTimer

  Private Sub TextBlock_SourceUpdated(ByVal sender As System.Object, ByVal e As System.Windows.Data.DataTransferEventArgs)

  End Sub

  Private Sub MainWindow_Loaded(ByVal sender As Object, ByVal e As System.Windows.RoutedEventArgs) Handles Me.Loaded
      dpTimer = New DispatcherTimer
      dpTimer.Interval = TimeSpan.FromMilliseconds(1000)
      AddHandler dpTimer.Tick, AddressOf TickMe
      dpTimer.Start()
  End Sub

  Private Sub TickMe()
      oTime.TimeUpdate = Now.ToString
      Debug.Print(oTime.TimeUpdate)
  End Sub

End Class

Public Class TimeUpdate
Implements INotifyPropertyChanged

  Private sTime As String

  'Declare the Event
  Public Event PropertyChanged(ByVal sender As Object, ByVal e As System.ComponentModel.PropertyChangedEventArgs) Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged

  Public Property TimeUpdate() As String
      Get
          Return sTime

      End Get
      Set(ByVal value As String)
          sTime = value
          'Call onPropertyChanged whenever the property is updated
          OnPropertyChanged("TimeUpdate")
      End Set

  End Property

  Protected Sub OnPropertyChanged(ByVal name As String)
      RaiseEvent PropertyChanged(Me, New PropertyChangedEventArgs(name))
  End Sub

End Class

Answer 1

似乎很少有东西丢失.首先,未设置窗口的DataContext.你可以做构造函数:

Public Sub New()
    DataContext = oTime
End Sub

这允许您的视图查看TimeUpdate类的内容.

然后更改您的XAML(直接绑定到TimeUpdate属性):

<Grid> 
    <TextBox x:Name="myTextBox" 
             Width="200" Height="50" Foreground="Black" 
             Text="{Binding Path=TimeUpdate}"></TextBox>
</Grid>

更新: 替代方法是在Window标记中添加DataContext行.这样,您的MainWindow类对视图可见,您可以绑定到公共属性.

<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
Title="MainWindow" Height="350" Width="525">

现在创建一个公共属性来访问该对象:

Public Property OTime() As TimeUpdate
    Get
        Return oTime
    End Get
    Set
        oTime = value
    End Set
End Property

并将文本框绑定到它:

<Grid> 
    <TextBox x:Name="myTextBox" 
             Width="200" Height="50" Foreground="Black" 
             Text="{Binding Path=OTime.TimeUpdate}"></TextBox>
</Grid>