delphi - 使用对话框时无法使 DragAcceptFiles 工作

Question

我正在使用 Delphi 编写一个简单的应用程序，该应用程序需要接受拖放到其上的目录名称。虽然我使用的是 Delphi，但这个程序是直接的 Windows API(没有 VCL，没有面向对象的东西)，就像在纯 C 中一样。

我有一些代码已经可以使用普通窗口(由 CreateWindowEx 创建)运行。当我将该代码转换为使用对话框时，拖放功能损坏了，我无法弄清楚原因。

这是我工作正常的代码(部分):

function WndProc (Wnd : hWnd; Msg, wParam, lParam : DWORD) : DWORD; stdcall;  { main application/window handler function                                  }const  DROPPED_FILE_COUNT  = -1;var  FileCnt     : integer;                            { number of files dropped }  Filename    : packed array[0..MAX_PATH] of char;  { filename buffer         }  DropInfo    : HDROP absolute wParam;              { wParam points to Drop...}  I           : integer;                            { for loop                }begin  WndProc := 0;  { let the Windows default handler take care of everything                   }  case msg of    WM_CREATE:       begin         InitCommonControls;         if CreateWindowEx(WS_EX_CLIENTEDGE or WS_EX_RIGHTSCROLLBAR,                           'LISTBOX',                           nil,                           WS_CHILD        or WS_HSCROLL      or WS_VSCROLL or                           WS_CLIPSIBLINGS or WS_CLIPCHILDREN or                           WS_VISIBLE      or LBS_NOINTEGRALHEIGHT,                           0,                           0,                           0,                           0,                           Wnd,                           IDC_LISTBOX,                           hInstance,                           nil) = 0 then         begin           MessageBox(Wnd,                      'Couldn''t create the listbox', 'Main Window', MB_OK);           WndProc := -1;         end;         { let Windows know that we accept files being dragged over our client}         { area.                                                              }         DragAcceptFiles(Wnd, TRUE);         { tell the listbox to use a nice font                                }         SendMessage(GetDlgItem(Wnd, IDC_LISTBOX),                     WM_SETFONT, GetStockObject(DEFAULT_GUI_FONT), 0);         exit;       end; { WM_CREATE }    WM_DROPFILES:       begin         { one or more files have been dropped on us!                         }         FileCnt := DragQueryFile(DropInfo, DROPPED_FILE_COUNT, nil, 0);         for I := 0 to FileCnt - 1 do           begin             { get the dropped files names and add them to the listbox        }             DragQueryFile(DropInfo, I, Filename, sizeof(Filename));             ListBox_AddString(GetDlgItem(Wnd, IDC_LISTBOX), Filename);           end;         { tell Windows that we are done grabbing the dropped files           }         DragFinish(DropInfo);         exit;       end; { WM_DROPFILES }    ... followed by other stuff that has nothing to do with drag and drop ... 

我将其转换为:

procedure ExecWM_INITDIALOG(wnd : hWnd);begin  { ensure that the listbox isn't accepting dropped files }  DragAcceptFiles(GetDlgItem(Wnd, IDC_DIRECTORIES), FALSE);  { ensure the main dialog window accept dropped files }  DragAcceptFiles(Wnd, TRUE);  { load the current values in the registry                                   }  LoadRegistrySettings(RegistryKey, RegistrySettings, RegistrySettingsCount)end;procedure ExecWM_DROPFILES(Wnd : hWnd; wParam : word; lParam : longint);const  DROPPED_FILE_COUNT  = -1;var  FileCnt     : integer;                            { number of files dropped }  Filename    : packed array[0..MAX_PATH] of char;  { filename buffer         }  DropInfo    : HDROP absolute wParam;              { wParam points to Drop...}  I           : integer;                            { for loop                }begin  { one or more files have been dropped on us!                         }  { -->>> The problem seems to show up at this statement:              }  {        the DropInfo (wParam) has a value that seems too low ($20)  }  {        when using the code that works the value is much larger     }  FileCnt := DragQueryFile(DropInfo, DROPPED_FILE_COUNT, nil, 0);  for I := 0 to FileCnt - 1 do    begin      { get the dropped files names and add them to the listbox        }      DragQueryFile(DropInfo, I, Filename, sizeof(Filename));      ListBox_AddString(GetDlgItem(Wnd, IDC_DIRECTORIES), Filename);    end;  { tell Windows that we are done grabbing the dropped files           }  DragFinish(DropInfo);end;function BackupConfigProc(wnd      : hWnd;                          msg      : word;                          wParam   : word;                          lParam   : longint) : bool; stdcall;begin  BackupConfigProc := FALSE;            { default return value                }  case msg of    WM_COMMAND:    begin      ExecWM_COMMAND (wnd, wParam, lParam);      BackupConfigProc := TRUE;    end;    WM_DROPFILES:    begin      ExecWM_DROPFILES(Wnd, wParam, lParam);      //BackupConfigProc := TRUE;    { this was a shot in the dark }    end;    WM_INITDIALOG:       begin         ExecWM_INITDIALOG (wnd);         BackupConfigProc := TRUE;       end;    WM_CLOSE:       begin         EndDialog(wnd, 0);     { and return the default FALSE                }       end;  end;end;begin  DialogBox(hInstance, 'BackupConfigDlg', 0, @BackupConfigProc);end.

看起来对话框接收到的 DropInfo (wParam) 值无效(因为它的值比有效的非对话框代码接收到的值低得多)。

我将感谢所有能够阐明为什么 Dialog 版本不起作用以及需要采取哪些措施才能使其起作用的人。

谢谢，

约翰。

Answer 1

procedure ExecWM_DROPFILES(Wnd : hWnd; wParam : word; lParam : longint);

wParam 不应输入 word，而应输入 Windows.WPARAM，它实际上是一个 long int(在 Win32 上)。