错误调用函数

问题描述

我有以下代码作为我的控件的一部分.SetReaderMode 函数创建结构并调用此处解释的函数，http://msdn.microsoft.com/en-us/library/bb775599(VS.85).aspx

I have the following code as part of my control. SetReaderMode function creates the structure and calls the function explained here, http://msdn.microsoft.com/en-us/library/bb775599(VS.85).aspx

当我运行此代码时，出现错误

When I run this code, i get the error

试图读取或写入受保护的内存.这通常表明其他内存已损坏.

我不确定可能是什么问题.我做错了什么?

I'm not sure what the issue may be. What am I doing wrong?

        <DllImport("Comctl32.dll", EntryPoint:="#383", _
         CallingConvention:=CallingConvention.StdCall)> _
    Private Shared Sub DoReaderMode(prmi As READERMODEINFO)

    End Sub

    <StructLayout(LayoutKind.Sequential)>
    Private Structure READERMODEINFO
        Dim cbSize As UInt32
        Dim hwnd As IntPtr
        Dim fFlags As UInt32
        Dim prc As IntPtr
        Dim pfnScroll As ReaderScrollCallbackDelegate
        Dim fFlags2 As TranslateDispatchCallbackDelegate
        Dim lParam As IntPtr
    End Structure

    Private Sub SetReaderMode()

        Dim Info As New READERMODEINFO
        Info.hwnd = Me.Handle
        Info.fFlags = 0
        Info.prc = IntPtr.Zero
        Info.pfnScroll = New ReaderScrollCallbackDelegate(AddressOf ReaderScrollCallback)
        Info.fFlags2 = New TranslateDispatchCallbackDelegate(AddressOf TranslateDispatchCallback)
        Info.lParam = IntPtr.Zero
        Info.cbSize = Marshal.SizeOf(Info)

        DoReaderMode(Info)

    End Sub


    Private Delegate Function ReaderScrollCallbackDelegate(ByVal prmi As READERMODEINFO, dx As Integer, dy As Integer) As Boolean
    Private Delegate Function TranslateDispatchCallbackDelegate(lpmsg As IntPtr) As Boolean

    <AllowReversePInvokeCalls()>
    Private Function TranslateDispatchCallback(lpmsg As IntPtr) As Boolean
        Return True
    End Function

    <AllowReversePInvokeCalls()>
    Private Function ReaderScrollCallback(ByVal prmi As READERMODEINFO, dx As Int32, dy As Int32) As Boolean
        Return True
    End Function

推荐答案

我已经想通了.在更仔细地查看文档后，我在 DoReaderMode 定义和 ReaderScrollCallback 定义中添加了一个 ByRef，因为参数被定义为指向结构的指针，而不仅仅是结构.我还添加了一些其他代码来在 ReaderModeInfo 结构中传递矩形.

I've figured it out. After reviewing the documentation more closely, I've added a ByRef to the DoReaderMode definition and to the ReaderScrollCallback definition, since the arguments where defined as pointers to structures, not just structures. I also added some other code to pass the rectangle in the ReaderModeInfo structure.

以下是工作代码.有趣的是，文档指出您单击以退出 ReaderMode，但是在测试时，您似乎必须按住按钮然后松开才能退出.

Below is the working code. Interestingly, the documentation states that you click to exit ReaderMode, however when testing it looks like you have to hold the button down and release to exit.

    <DllImport("Comctl32.dll", EntryPoint:="#383", _
         CallingConvention:=CallingConvention.StdCall)> _
    Private Shared Sub DoReaderMode(ByRef prmi As READERMODEINFO)

    End Sub

    <StructLayout(LayoutKind.Sequential)>
    Private Structure READERMODEINFO
        Dim cbSize As UInt32
        Dim hwnd As IntPtr
        Dim fFlags As UInt32
        Dim prc As IntPtr
        Dim pfnScroll As ReaderScrollCallbackDelegate
        Dim fFlags2 As TranslateDispatchCallbackDelegate
        Dim lParam As IntPtr
    End Structure


    Private Sub SetReaderMode()

        Dim SetReaderModeInfo As READERMODEINFO

        Dim rect As New Interop.RECT(Me.Width / 2 - 20, Me.Height / 2 - 20, Me.Width / 2 + 20, Me.Height / 2 + 20)

        Dim pnt As IntPtr = Marshal.AllocHGlobal(Marshal.SizeOf(rect))
        Marshal.StructureToPtr(rect, pnt, True)

        SetReaderModeInfo = New READERMODEINFO
        SetReaderModeInfo.hwnd = Me.Handle
        SetReaderModeInfo.fFlags = 1
        SetReaderModeInfo.prc = pnt
        SetReaderModeInfo.pfnScroll = New ReaderScrollCallbackDelegate(AddressOf ReaderScrollCallback)
        SetReaderModeInfo.fFlags2 = New TranslateDispatchCallbackDelegate(AddressOf TranslateDispatchCallback)
        SetReaderModeInfo.lParam = IntPtr.Zero
        SetReaderModeInfo.cbSize = Marshal.SizeOf(SetReaderModeInfo)

        DoReaderMode(SetReaderModeInfo)

        Marshal.FreeHGlobal(pnt)

    End Sub

    Private Delegate Function ReaderScrollCallbackDelegate(ByRef prmi As READERMODEINFO, dx As Integer, dy As Integer) As Boolean

    Private Delegate Function TranslateDispatchCallbackDelegate(ByRef lpmsg As Interop.MSG) As Boolean

    Private Function TranslateDispatchCallback(ByRef lpmsg As Interop.MSG) As Boolean
        Return False
    End Function

    Private Function ReaderScrollCallback(ByRef prmi As READERMODEINFO, dx As Int32, dy As Int32) As Boolean
        Return True
    End Function

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