Win32 - 将文本附加到编辑控件

Question

试图将文本附加到对话框内的编辑控件。我无法让 _tcscat_s 正确附加。它崩溃并说明缓冲区太小或以空字符结尾的字符串。

int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow )
{
    return DialogBox( hInstance, MAKEINTRESOURCE( IDD_MAIN ), NULL, DlgProc );
}

BOOL CALLBACK DlgProc( HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam ) 
{
    switch( Message )
    {
        case WM_INITDIALOG:
            OpenAndReadFile( hwnd );
            return TRUE;
        case WM_COMMAND:
            switch( LOWORD( wParam ) )
            {
                case IDSTART:
                    EndDialog( hwnd, IDSTART );
                    break;
                case IDQUIT:
                    EndDialog( hwnd, IDQUIT );
                    break;
            }
            break;
        case WM_CLOSE:
            EndDialog( hwnd, 0 );
            break;
        default:
            return FALSE;
    }
    return TRUE;
}

BOOL OpenAndReadFile( const HWND &hwnd ) 
{   
    // Open the file

    HANDLE hFile;
    hFile = CreateFile( TEXT( "sites.txt" ),    // file to open
                        GENERIC_READ,           // open for reading
                        FILE_SHARE_READ,        // share for reading
                        NULL,                   // default security
                        OPEN_EXISTING,          // existing file only
                        FILE_ATTRIBUTE_NORMAL,  // normal file
                        NULL );                 // no attr. template

    if ( hFile == INVALID_HANDLE_VALUE )
    {
        SetDlgItemText( hwnd, IDC_OUTPUT, TEXT( "Error: File could not be opened\r\n" ) );
        return FALSE;
    }
    else
        SetDlgItemText( hwnd, IDC_OUTPUT, TEXT( "sites.txt opened\r\n" ) );

    AppendText( hwnd, TEXT("TEXT") );

    // Read data from file

    const DWORD BUFFERSIZE = GetFileSize( hFile, NULL );
    char *ReadBuffer = new char [BUFFERSIZE]();
    DWORD dwBytesRead = 0;

    // read one character less than the buffer size to save room for the
    // terminate NULL character.
    //if ( FALSE == ReadFile( hFile, ReadBuffer, BUFFERSIZE - 1, &dwBytesRead, NULL ) )
    {

    }

    return TRUE;
}

void AppendText( const HWND &hwnd, TCHAR *newText )
{
    // get size to determine buffer size
    int outLength = GetWindowTextLength( GetDlgItem( hwnd, IDC_OUTPUT ) );

    // create buffer to hold current text in edit control
    TCHAR * buf = ( TCHAR * ) GlobalAlloc( GPTR, outLength + 1 );

    // get existing text from edit control and put into buffer
    GetDlgItemText( hwnd, IDC_OUTPUT, buf, outLength + 1 );

    // append the newText to the buffer
    _tcscat_s( buf, outLength + 1, newText );

    // Set the text in the dialog
    SetDlgItemText( hwnd, IDC_OUTPUT, buf );
}

Answer 1

GetWindowTextLength() 返回文本中TCHAR 元素的数量，但GlobalAlloc() 需要一个字节数。如果您正在为 Unicode 编译，TCHAR 是 2 个字节，而不是 1 个字节，但您没有考虑到这一点。您也没有分配足够大的缓冲区来容纳现有文本和要附加的新文本。您还泄漏了您分配的内存。

试试这个：

void AppendText( const HWND &hwnd, TCHAR *newText )
{
    // get edit control from dialog
    HWND hwndOutput = GetDlgItem( hwnd, IDC_OUTPUT );

    // get new length to determine buffer size
    int outLength = GetWindowTextLength( hwndOutput ) + lstrlen(newText) + 1;

    // create buffer to hold current and new text
    TCHAR * buf = ( TCHAR * ) GlobalAlloc( GPTR, outLength * sizeof(TCHAR) );
    if (!buf) return;

    // get existing text from edit control and put into buffer
    GetWindowText( hwndOutput, buf, outLength );

    // append the newText to the buffer
    _tcscat_s( buf, outLength, newText );

    // Set the text in the edit control
    SetWindowText( hwndOutput, buf );

    // free the buffer
    GlobalFree( buf );
}

或者：

#include <vector>

void AppendText( const HWND &hwnd, TCHAR *newText )
{
    // get edit control from dialog
    HWND hwndOutput = GetDlgItem( hwnd, IDC_OUTPUT );

    // get new length to determine buffer size
    int outLength = GetWindowTextLength( hwndOutput ) + lstrlen(newText) + 1;

    // create buffer to hold current and new text
    std::vector<TCHAR> buf( outLength );
    TCHAR *pbuf = &buf[0];

    // get existing text from edit control and put into buffer
    GetWindowText( hwndOutput, pbuf, outLength );

    // append the newText to the buffer
    _tcscat_s( pbuf, outLength, newText );

    // Set the text in the edit control
    SetWindowText( hwndOutput, pbuf );
}

话虽如此，将窗口的当前文本放入内存，附加到它，然后替换窗口的文本是一种将文本附加到编辑控件的非常低效的方法。请改用EM_REPLACESEL 消息：

void AppendText( const HWND &hwnd, TCHAR *newText )
{
    // get edit control from dialog
    HWND hwndOutput = GetDlgItem( hwnd, IDC_OUTPUT );

    // get the current selection
    DWORD StartPos, EndPos;
    SendMessage( hwndOutput, EM_GETSEL, reinterpret_cast<WPARAM>(&StartPos), reinterpret_cast<WPARAM>(&EndPos) );

    // move the caret to the end of the text
    int outLength = GetWindowTextLength( hwndOutput );
    SendMessage( hwndOutput, EM_SETSEL, outLength, outLength );

    // insert the text at the new caret position
    SendMessage( hwndOutput, EM_REPLACESEL, TRUE, reinterpret_cast<LPARAM>(newText) );

    // restore the previous selection
    SendMessage( hwndOutput, EM_SETSEL, StartPos, EndPos );
}

Answer 2

http://support.microsoft.com/kb/109550

是你的答案：

   string buffer = "append this!"
   HWND hEdit = GetDlgItem (hDlg, ID_EDIT);
   int index = GetWindowTextLength (hEdit);
   SetFocus (hEdit); // set focus
   SendMessageA(hEdit, EM_SETSEL, (WPARAM)index, (LPARAM)index); // set selection - end of text
   SendMessageA(hEdit, EM_REPLACESEL, 0, (LPARAM)buffer.c_str()); // append!