我怎样才能让这个函数不生成“不在所有路径上返回值"?警告? [英] How can I make this function not generate a "doesn't return a value on all paths" warning?

问题描述

我意识到这是一个非常具体的问题，在此场景之外并没有太大帮助，尽管我确信它适用于具有相同问题的其他问题.我有一个函数可以递归搜索窗口(及其子窗口)以查找特定窗口，它完全按预期工作，但是它会导致函数不会在所有路径上返回值"警告.这是我整个程序中唯一的警告，虽然它可能很愚蠢，但我很想知道是否有办法阻止此错误发生，但仍然允许该函数正常工作.

I realize this is a very specific question, and not very helpful outside of this scenario, although I am sure it applies to other questions with the same problem. I have a function to recursively search through windows (and their child windows) to find specific ones, it works exactly as expected, however it causes "function doesn't return a value on all paths" warning. This is the only warning in my entire program, and although it might be silly, I'm interested in knowing if there is a way to stop this error from occurring, but still allowing the function to work properly.

    Public Function FindQWidgetWindows() As Integer
    Dim hWndStart As Integer = 0
    Dim WindowText As String = "*"
    Dim Classname As String = "QWidget"
    Dim hwnd As Integer
    Dim sWindowText As String
    Dim sClassname As String
    Dim r As Integer
    Static level As Integer

    If level = 0 Then
        If hWndStart = 0 Then hWndStart = GetDesktopWindow()
    End If

    level = level + 1

    hwnd = GetWindow(hWndStart, GW_CHILD)

    Do Until hwnd = 0
        Call FindQWidgetWindows()

        'Get the window text and class name'
        sWindowText = Space$(255)
        r = GetWindowText(hwnd, sWindowText, 255)
        sWindowText = Microsoft.VisualBasic.Left(sWindowText, r)
        sClassname = Space$(255)
        r = GetClassName(hwnd, sClassname, 255)
        sClassname = Microsoft.VisualBasic.Left(sClassname, r)

        If (sWindowText Like WindowText) And (sClassname Like Classname) Then
            Dim aRECT As RECT
            Dim hwndInt As Int32 = hwnd
            GetWindowRect(hwndInt, aRECT)
            FindQWidgetWindows = hwnd

            'uncommenting the next line causes the routine to'
            'only return the first matching window.'
            'Exit Do'

        End If

        hwnd = GetWindow(hwnd, GW_HWNDNEXT)

    Loop

    level = level - 1
End Function

推荐答案

您依赖于这样一个事实，即 VB 会自动用您的函数名称声明一个返回变量.此变量可用作函数中的任何其他变量.所以它也可以得到一个默认的初始化.

You rely on the fact, that VB automatically declares a return variable with the name of your function. This variable can be used as any other variable in your function. So it also can get a default initialization.

正如已经提到的，您只能在非常嵌套的 If 语句中分配一个值.您应该简单地在 Do 循环之前和之前用

As already mentioned, you only assign a value in a very nested If statement. You should simply initialize your variable outside and before of your Do-loop with something like

FindQWidgetWindows = Nothing

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