在我的应用程序中，我使用了 ToastForms 类向用户显示弹出通知以获取实时警报。我一直在尝试从数据库中轮询警报并经常将它们呈现给用户的最佳方法。我查询数据库，找到所有新警报，然后每隔 10 秒左右将这些警报作为弹出窗口呈现给用户。我一直在尝试为此过程确定最佳方法/实践，因为我不想在不断轮询数据库时导致任何高 CPU 使用率或程序挂起。
在进行了一些试验后，我决定将我的想法转移到使用 System.Timers.Timer 并将我的代码放在 Get_Alerts 过程中：
Private Sub frmNewDashboard_Load(sender As Object, e As EventArgs) Handles MyBase.Load
...
tmr_GetAlerts = New System.Timers.Timer(10000)
AddHandler tmr_GetAlerts.Elapsed, AddressOf GetAlerts
tmr_GetAlerts.AutoReset = False
tmr_GetAlerts.Start()
...
End Sub
Private Sub GetAlerts(source As Object, e As ElapsedEventArgs)
...
'Query the database and populate a datatable
'Determine all alert types
'Handle Major Alerts, Minor Alerts, etc.
If (Current_User.EnableNotifications = True) And (Current_User.NP_AMajor = True) Then
If MajorCount > 1 Then
Dim slice As ToastForm
slice = New ToastForm((Current_User.Notify_Seconds * 1000), MajorCount & " New Major Alert(s) Detected")
slice.Height = 100
slice.Show()
End If
End If
...
'Same code repeats to handle Minor Alerts
End Sub
上面的代码过去可以在普通的 Forms.Timer 上正常工作，但是，自从将它移到 System.Timers.Timer 后，我发现 ToastForm 会弹出很好，但似乎挂起并且永远不会关闭：
它没有产生任何错误，所以我不确定故障在哪里。我假设这与在与我的计时器不同的线程上打开 ToastForm 有关，但我不确定。
任何帮助，将不胜感激。谢谢。
更新 下面是运行 Toastform 的代码。我从网上找到的一些代码中导入了这个类，所以它不是我的代码。我只是传递论点。在我介绍 System.Timers.Timer 之前，一切正常（并且正在关闭）。
Imports System.Runtime.InteropServices
Public Class ToastForm
Private _item As ListViewItem = Nothing
Private TooltipVisible As Boolean = False
Private SelectedCallQueue As String = Nothing
Private SelectedOverduePeriod As String
Private OnlineUserCount As Integer
#Region " Variables "
''' <summary>
''' The list of currently open ToastForms.
''' </summary>
Private Shared openForms As New List(Of ToastForm)
''' <summary>
''' Indicates whether the form can receive focus or not.
''' </summary>
Private allowFocus As Boolean = False
''' <summary>
''' The object that creates the sliding animation.
''' </summary>
Private animator As FormAnimator
''' <summary>
''' The handle of the window that currently has focus.
''' </summary>
Private currentForegroundWindow As IntPtr
#End Region 'Variables
#Region " APIs "
''' <summary>
''' Gets the handle of the window that currently has focus.
''' </summary>
''' <returns>
''' The handle of the window that currently has focus.
''' </returns>
<DllImport("user32")> _
Private Shared Function GetForegroundWindow() As IntPtr
End Function
''' <summary>
''' Activates the specified window.
''' </summary>
''' <param name="hWnd">
''' The handle of the window to be focused.
''' </param>
''' <returns>
''' True if the window was focused; False otherwise.
''' </returns>
<DllImport("user32")> _
Private Shared Function SetForegroundWindow(ByVal hWnd As IntPtr) As Boolean
End Function
#End Region 'APIs
#Region " Constructors "
''' <summary>
''' Creates a new ToastForm object that is displayed for the specified length of time.
''' </summary>
''' <param name="lifeTime">
''' The length of time, in milliseconds, that the form will be displayed.
''' </param>
Public Sub New(ByVal lifeTime As Integer, ByVal message As String)
' This call is required by the Windows Form Designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
'Set the time for which the form should be displayed and the message to display.
Me.lifeTimer.Interval = lifeTime
Me.messageLabel.BackColor = ColorTranslator.FromHtml(Current_User.NWC)
Me.messageLabel.Text = message
'Display the form by sliding up.
Me.animator = New FormAnimator(Me, _
FormAnimator.AnimationMethod.Slide, _
FormAnimator.AnimationDirection.Up, _
200)
End Sub
#End Region 'Constructors
#Region " Methods "
''' <summary>
''' Displays the form.
''' </summary>
''' <remarks>
''' Required to allow the form to determine the current foreground window before being displayed.
''' </remarks>
Public Shadows Sub Show()
Try
'Determine the current foreground window so it can be reactivated each time this form tries to get the focus.
Me.currentForegroundWindow = GetForegroundWindow()
'Display the form.
MyBase.Show()
'Play a notification sound
If Current_User.NotifySound = True Then NotificationSound.Play()
Catch ex As Exception
ErrorTrap(ex, "ToastForm: Show()")
End Try
End Sub
#End Region 'Methods
#Region " Event Handlers "
Private Sub ToastForm_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Try
'Display the form just above the system tray.
Me.Location = New Point(Screen.PrimaryScreen.WorkingArea.Width - Me.Width - 5, _
Screen.PrimaryScreen.WorkingArea.Height - Me.Height - 5)
'Move each open form upwards to make room for this one.
For Each openForm As ToastForm In ToastForm.openForms
openForm.Top -= Me.Height + 5
Next
'Add this form from the open form list.
ToastForm.openForms.Add(Me)
'Start counting down the form's liftime.
Me.lifeTimer.Start()
Catch ex As Exception
ErrorTrap(ex, "ToastForm: ToastForm_Load()")
End Try
End Sub
Private Sub ToastForm_Activated(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Activated
Try
'Prevent the form taking focus when it is initially shown.
If Not Me.allowFocus Then
'Activate the window that previously had the focus.
SetForegroundWindow(Me.currentForegroundWindow)
End If
Catch ex As Exception
ErrorTrap(ex, "ToastForm: ToastForm_Activated()")
End Try
End Sub
Private Sub ToastForm_Shown(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Shown
Try
'Once the animation has completed the form can receive focus.
Me.allowFocus = True
'Close the form by sliding down.
Me.animator.Direction = FormAnimator.AnimationDirection.Down
Catch ex As Exception
ErrorTrap(ex, "ToastForm: ToastForm_Shown()")
End Try
End Sub
Private Sub ToastForm_FormClosed(ByVal sender As Object, ByVal e As FormClosedEventArgs) Handles MyBase.FormClosed
Try
'Move down any open forms above this one.
For Each openForm As ToastForm In ToastForm.openForms
If openForm Is Me Then
'The remaining forms are below this one.
Exit For
End If
openForm.Top += Me.Height + 5
Next
'Remove this form from the open form list.
ToastForm.openForms.Remove(Me)
Catch ex As Exception
ErrorTrap(ex, "ToastForm: ToastForm_FormClosed()")
End Try
End Sub
Private Sub lifeTimer_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles lifeTimer.Tick
Try
'The form's lifetime has expired.
Me.Close()
Catch ex As Exception
ErrorTrap(ex, "ToastForm: lifeTimer_Tick()")
End Try
End Sub
#End Region 'Event Handlers
End Class