Question

我正在从我的程序打开的记事本中读取文本。这是我的代码

const int WM_GETTEXT = 0x000D;
const int WM_GETTEXTLENGTH = 0x000E;

[DllImport("User32.dll", EntryPoint = "SendMessage")]
extern static int SendMessageGetTextLength(IntPtr hWnd, int msg, IntPtr wParam,     IntPtr lParam);
[DllImport("User32.dll", EntryPoint = "SendMessage", CharSet = CharSet.Auto)]
extern static IntPtr SendMessageGetText(IntPtr hWnd, int msg, IntPtr wParam, [Out] StringBuilder lParam);

[DllImport("user32.dll", EntryPoint = "FindWindowEx")]
public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

public static string GetText(IntPtr hwnd)
{
    if (hwnd == IntPtr.Zero)
        throw new ArgumentNullException("hwnd");
    IntPtr handler = FindWindowEx(hwnd, new IntPtr(0), "Edit", null);
    int length = SendMessageGetTextLength(handler, WM_GETTEXTLENGTH, IntPtr.Zero, IntPtr.Zero);
    if (length > 0 && length < int.MaxValue)
    {
        length++;
        StringBuilder sb = new StringBuilder(length);

        SendMessageGetText(handler, WM_GETTEXT, (IntPtr)sb.Length, sb);
        return sb.ToString();
    }
    return String.Empty;
}

它正在获取文本，但采用特殊编码。例如，如果输入的文本是“hello”，则会得到“兴梀㇨ȿڳㇺ”。这个文本的编码是什么，所以我可以将其解码为ASCII？

Answer 1

您的问题实际上是您在sb.Length消息中传递了WM_GETTEXT，而实际上您应该通过sb.Capacity甚至只是length。

我会这样做：

if (length > 0 && length < int.MaxValue)
{
    StringBuilder sb = new StringBuilder(length+1);
    SendMessageGetText(handler, WM_GETTEXT, (IntPtr)length+1, sb);
    return sb.ToString();
}

我还要指出，WM_GETTEXT不会向length < int.MaxValue返回超过64k个字符，这不是您所需要的。

当然，从长远来看，最好始终使用Unicode，以便您可以支持国际文本。

我个人总是选择使用Unicode API并使用以下p / invoke声明：

[DllImport("User32.dll", EntryPoint = "SendMessage", 
    CharSet = CharSet.Unicode, SetLastError = true)]
extern static int SendMessageGetTextLength(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam);
[DllImport("User32.dll", EntryPoint = "SendMessage",
    CharSet = CharSet.Unicode, SetLastError = true)]
extern static IntPtr SendMessageGetText(IntPtr hWnd, int msg, IntPtr wParam, StringBuilder lParam);
[DllImport("user32.dll", EntryPoint = "FindWindowEx",
    CharSet = CharSet.Unicode, SetLastError = true)]
public static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

Answer 2

由于您使用托管代码编写，因此您也可以使用托管代码自动化界面，它可以为您完成所有互操作。为什么重新发明轮子？

using System.Windows.Automation;
public static string GetText(IntPtr hwnd)
{
  IntPtr hwndEdit = FindWindowEx(hwnd, IntPtr.Zero, "Edit", null);
  return (string)AutomationElement.FromHandle(hwndEdit).
     GetCurrentPropertyValue(AutomationElement.NameProperty);
}

您甚至可以让自动化为您执行FindWindowEx：

public static string GetText(IntPtr hwnd)
{
  var editElement = AutomationElement.FromHandle(hwnd).
                    FindFirst(TreeScope.Subtree,
                              new PropertyCondition(
                                     AutomationElement.ClassNameProperty, "Edit"));
  return (string)editElement.GetCurrentPropertyValue(AutomationElement.NameProperty);
}

记事本字符解码

2 个答案: