wp8 异步调取数据怎么从委托中返回数据
wp8 异步调取数据怎么从委托中返回数据Imports System.ComponentModel
Imports System.Collections.ObjectModel
Imports System.IO
Public Class MainViewModel
Implements INotifyPropertyChanged
Dim uri As Uri
Public Sub New()
Me.Items = New ObservableCollection(Of ItemViewModel)()
AddHandler Play, AddressOf cl
End Sub
''' <summary>
''' ItemViewModel 对象的集合。
''' </summary>
Public Property Items() As ObservableCollection(Of ItemViewModel)
Private _sampleProperty As String = "Sample Runtime Property Value"
''' <summary>
''' 示例 ViewModel 属性；此属性在视图中用于使用绑定显示它的值
''' </summary>
''' <returns></returns>
Public Property SampleProperty() As String
Get
Return _sampleProperty
End Get
Set(ByVal value As String)
If Not value.Equals(_sampleProperty) Then
_sampleProperty = value
NotifyPropertyChanged("SampleProperty")
End If
End Set
End Property
''' <summary>
''' 返回本地化字符串的示例属性
''' </summary>
Public ReadOnly Property LocalizedSampleProperty() As String
Get
Return AppResources.SampleProperty
End Get
End Property
Public Property IsDataLoaded() As Boolean
''' <summary>
''' 创建一些 ItemViewModel 对象并将其添加到 Items 集合中。
''' </summary>
'''
Dim debug As System.Diagnostics.Debug
Dim resultString As String
Public Delegate Sub PlayHandler(ByVal e As String)
Public Event Play As PlayHandler
Private Sub request_Callback(asyncResult As IAsyncResult)
Try
Dim webRequest As HttpWebRequest = asyncResult.AsyncState
Dim webResponse As HttpWebResponse = webRequest.EndGetResponse(asyncResult)
Dim streamResult As Stream = webResponse.GetResponseStream()
Dim reader = New StreamReader(streamResult)
resultString = reader.ReadToEnd()
' If OnGetInfoCompleted(this, resultString) <> DBNull.Value Then
'fh1(resultString)
'RaiseEvent OnGetInfoCompleted(this, resultString)
' Me.Items.Add(New ItemViewModel() With {.LineOne = resultString, .LineTwo = "Maecenas praesent accumsan bibendum", .LineThree = "Facilisi faucibus habitant inceptos interdum lobortis nascetur pharetra placerat pulvinar sagittis senectus sociosqu"})
'End If
If resultString <> "" Then
RaiseEvent Play(resultString)
End If
Catch ex As WebException
MessageBox.Show(ex.Message, "提示", MessageBoxButton.OK)
End Try
End Sub
Public Sub fh(ByVal url As String)
Dim request As HttpWebRequest = HttpWebRequest.CreateHttp(url)
request.Method = "GET"
Dim resultString As String = String.Empty
request.BeginGetResponse(New AsyncCallback(AddressOf request_Callback), request)
End Sub
Public Sub cl(e As String)
'Me.Items.Add(New ItemViewModel() With {.LineOne = e, .LineTwo = e, .LineThree = e})
Diagnostics.Debug.WriteLine(e)
MessageBox.Show(e, "提示", MessageBoxButton.OK)
'Me.Items.Add(New ItemViewModel() With {.LineOne = e})
'Me.IsDataLoaded = True
End Sub
Public list As List(Of String)
Public Sub LoadData()
Dim uri As String = "http://www.baidu.com"
fh(uri)
End Sub
Public Event PropertyChanged As PropertyChangedEventHandler Implements INotifyPropertyChanged.PropertyChanged
Private Sub NotifyPropertyChanged(ByVal propertyName As String)
Dim handler As PropertyChangedEventHandler = PropertyChangedEvent
If Nothing IsNot handler Then
handler(Me, New PropertyChangedEventArgs(propertyName))
End If
End Sub
End Class
运行结果出现下面错误
请各位大神指教~ --------------------编程问答-------------------- 我看不懂VB的代码。。 --------------------编程问答-------------------- 题目和你给的图不对啊，另外你这不是WP8的代码吗。
wp8里面就没有同步的httpwebrequest
描述清楚啊楼主 --------------------编程问答--------------------
额，，参走眼了，，，
报错哪行放到begininvoke，跨线程访问的原因
补充：移动开发 , Windows Phone
