Question

我的表单仅在我使用

时有效

Imports WindowsApplication1.FrameGrabber

但不是我用的时候

Imports FrameGrabber

我将在几个不同的项目中使用FrameGrabber，所以我真的更喜欢只说“Imports FrameGrabber”。

我的“FrameGrabber / CameraWindow”定义如下：

Imports System.Collections
Imports System.ComponentModel
Imports System.Drawing
Imports System.Data
Imports System.Windows.Forms
Imports System.Threading

Namespace FrameGrabber
    ''' <summary>
    ''' Summary description for CameraWindow.
    ''' </summary>
    Public Class CameraWindow
        Inherits System.Windows.Forms.Control
        Private m_camera As Camera = Nothing
        Private m_autosize As Boolean = False
        Private needSizeUpdate As Boolean = False
        Private firstFrame As Boolean = True

        ' AutoSize property
        <DefaultValue(False)> _
        Public Overrides Property AutoSize() As Boolean
            Get
                Return m_autosize
            End Get
            Set(value As Boolean)
                m_autosize = value
                UpdatePosition()
            End Set
        End Property

        ' Camera property
        <Browsable(False)> _
        Public Property Camera() As Camera
            Get
                Return m_camera
            End Get
            Set(value As Camera)
                ' lock
                Monitor.Enter(Me)

                ' detach event
                If m_camera IsNot Nothing Then
                    RemoveHandler m_camera.NewFrame, AddressOf Me.pCameraWindow_NewFrame
                End If

                m_camera = value
                needSizeUpdate = True
                firstFrame = True

                ' atach event
                If m_camera IsNot Nothing Then
                    AddHandler m_camera.NewFrame, AddressOf Me.pCameraWindow_NewFrame
                End If

                ' unlock
                Monitor.[Exit](Me)
            End Set
        End Property

        ' Constructor
        Public Sub New()
            InitializeComponent()

            SetStyle(ControlStyles.AllPaintingInWmPaint Or ControlStyles.DoubleBuffer Or ControlStyles.ResizeRedraw Or ControlStyles.UserPaint, True)
        End Sub

#Region "Windows Form Designer generated code"
        Private Sub InitializeComponent()
            Me.SuspendLayout()
            Me.ResumeLayout(False)

        End Sub
#End Region

        ' Paint control
        Protected Overrides Sub OnPaint(pe As PaintEventArgs)
            If (needSizeUpdate) OrElse (firstFrame) Then
                UpdatePosition()
                needSizeUpdate = False
            End If

            ' lock
            Monitor.Enter(Me)

            Dim g As Graphics = pe.Graphics
            Dim rc As Rectangle = Me.ClientRectangle

            If m_camera IsNot Nothing Then
                Try
                    m_camera.Lock()

                    ' draw frame
                    If m_camera.LastFrame IsNot Nothing Then
                        g.DrawImage(m_camera.LastFrame, rc.X + 1, rc.Y + 1, rc.Width - 2, rc.Height - 2)
                        firstFrame = False
                    Else
                        ' Create font and brush
                        Dim drawFont As New Font("Arial", 12)
                        Dim drawBrush As New SolidBrush(Color.White)

                        g.DrawString("Connecting ...", drawFont, drawBrush, New System.Drawing.PointF(5, 5))

                        drawBrush.Dispose()
                        drawFont.Dispose()
                    End If
                Catch generatedExceptionName As Exception
                Finally
                    m_camera.Unlock()
                End Try
            End If

            ' unlock
            Monitor.[Exit](Me)

            MyBase.OnPaint(pe)
        End Sub
        Public Function getImage() As Image

            If Not m_camera Is Nothing Then
                If Not m_camera.LastFrame Is Nothing Then
                    Return m_camera.LastFrame
                End If
            End If

            Return Nothing

        End Function
        ' Update position and size of the control
        Public Sub UpdatePosition()
            ' lock
            Monitor.Enter(Me)

            If (m_autosize) AndAlso (Me.Parent IsNot Nothing) Then
                Dim rc As Rectangle = Me.Parent.ClientRectangle
                Dim width As Integer = 320
                Dim height As Integer = 240

                If m_camera IsNot Nothing Then
                    m_camera.Lock()

                    ' get frame dimension
                    If m_camera.LastFrame IsNot Nothing Then
                        width = m_camera.LastFrame.Width
                        height = m_camera.LastFrame.Height
                    End If
                    m_camera.Unlock()
                End If

                '
                Me.SuspendLayout()
                Me.Location = New Point((rc.Width - width - 2) \ 2, (rc.Height - height - 2) \ 2)
                Me.Size = New Size(width + 2, height + 2)

                Me.ResumeLayout()
            End If
            ' unlock
            Monitor.[Exit](Me)
        End Sub

        ' On new frame ready
        Private Sub pCameraWindow_NewFrame(sender As Object, e As System.EventArgs)
            Invalidate()
        End Sub

    End Class
End Namespace

感谢您的帮助！

Answer 1

您需要更改项目的根名称空间或覆盖它。当您将类包装在Namespace块（例如Namespace FrameGrabber）中时，给定的命名空间相对于项目的根命名空间。换句话说，如果您的根命名空间是WindowsApplication1，那么当您说Namespace FrameGrabber时，所有包含的类型实际上都在WindowsApplication1.FrameGrabber命名空间中。

如果要覆盖一段代码的根名称空间，可以使用Global关键字，以便命名空间声明不是相对的，如下所示：

Namespace Global.FrameGrabber
    ' ...
End Namespace

在名称空间声明中使用Global关键字来覆盖根命名空间似乎是VB.NET的最新成员。据我所知，基于在the MSDN article中包含有关它的信息，Visual Studio 2012中添加了对该信息的支持。您还可以在this MSDN article中找到有关它的信息：

Global关键字也可以在Namespace语句中使用。这使您可以从项目的根命名空间中定义命名空间。有关详细信息，请参阅Visual Basic中命名空间中的“命名空间语句中的全局关键字”部分。

另一种选择是从项目属性中删除根命名空间，然后在项目中的每个代码文件上声明完整的命名空间。该设置可在项目设置设计器屏幕中找到：我的项目＆gt; 申请＆gt; 根名称空间。

或者提出一个更有利于VB.NET偏心的命名约定。例如，如果您为项目创建了公司名称的根命名空间，那么MyCompany.FrameGrabber肯定比WindowsApplication1.FrameGrabber更有意义。

VB.NET导入没有项目名称

1 个答案: