Windows NT Systems Programming: Spring 2000
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Building a Dialog Box in Visual C++: A simple example
Description: Allow the user to type a title for the
main window. To better understand the issues behind building dialog box, build this
version by hand, avoiding the use of the resource editor and CDialog class. This is done
to better understand the issues that determine what goes on behind the scenes in MFC, etc.
Step by step to building
- Start visual c++
- File/New/(Projects)/Win32Application: we'll add MFC as needed by hand
- After the project is built, change the settings to include MFC. Select
"Project/Settings"
- In the "General" tab set "Microsoft Foundation Classes" to
"Use MFC in a shared DLL"
- Create a header file called main.h (File/New/c++ header) with the code.
// full source here
#define IDC_EDIT_TITLE 200
#define IDC_CHANGE 201
#define IDC_CLEAR 202
#define IDC_CANCEL 203
class CMsgFolderApp : public CWinApp
{
public: virtual BOOL InitInstance(); // everybody overrides this one
};
class CMainWindow : public CFrameWnd
{
public: CMainWindow(); ~CMainWindow();
protected:
// Handlers for MainFrame when not in dialog mode
afx_msg void OnLButtonDown(UINT, CPoint);
// Handlers for Dialog Controls
afx_msg void OnChange();
afx_msg void OnClear();
afx_msg void OnCancel();
DECLARE_MESSAGE_MAP() // set up message map handling
private:
// Define the controls for the dialog
// they won't be visible until you call "makeDialog"
CButton m_btnChange;
CButton m_btnClear;
CButton m_btnCancel;
CStatic m_labelEdit; // label for selection
CEdit m_editTitle;
// helper functions for managing the dialog controls
//***
// Pass size and pointer to parent window
// remember each control is a child window
void makeDialog(CRect rect, CWnd* parent);
void cleanUpDialog();
};
- Each Control in the Dialog is assigned a unique number - used both for identification
and for message IDs routed between control and main window
- MainWindow can be either in dialog mode or not, Left Mouse Button Down takes window into
dialog mode
- These are the message handlers for messages from the three buttons
- We define the dialog controls here - but they won't be visible until we create their
windows. (done in "makeDialog")
BEGIN_MESSAGE_MAP( CMainWindow, CWnd )
ON_COMMAND(IDC_CHANGE, OnChange)
ON_COMMAND(IDC_CLEAR, OnClear)
ON_COMMAND(IDC_CANCEL, OnCancel)
ON_WM_LBUTTONDOWN()
END_MESSAGE_MAP()
void CMainWindow::OnLButtonDown(UINT nFlags, CPoint point)
{
//MessageBox("need code to open here","open"); // used for skeleton
CRect rect;
GetClientRect(rect);
makeDialog(rect, this);
}
//*************** Handlers for Dialog Control Messages
//** comes here when user clicks "Change" button
// using a MessageBox ask user if really want change
// If yes, make change, clean up dialog
// If No, no change, clean up dialog
// If cancel, go back to dialog
void CMainWindow::OnChange()
{
CString title, message;
m_editTitle.GetWindowText(title);
message = "Ok to change title to: \n " + title + "?";
// use Message Box with Yes/No/Cancel buttons
int result = MessageBox(message,"Open",MB_YESNOCANCEL);
if(result == IDYES) {
SetWindowText(title);
cleanUpDialog();
}
else if(result == IDNO) {
MessageBox("Title Unchanged","no change"); // tell user no change
cleanUpDialog();
}
else if(result == IDCANCEL) { // do nothing
}
}
void CMainWindow::OnClear()
{
m_editTitle.SetWindowText("");
// the following line will also work
//SetDlgItemText(IDC_EDIT_TITLE,"");
}
void CMainWindow::OnCancel()
{
if(MessageBox("Are you sure you want to Cancel?", "Change Title Cancel",
MB_YESNO) == IDYES) {
cleanUpDialog();
}
}
//*******
// create windows for all controls to make them visible
void CMainWindow::makeDialog(CRect rect, CWnd* parent)
{
rect.right -= 100; // make room for buttons on right
rect.bottom -= 100; // make room for selection on bottom
m_labelEdit.Create("Type New Title:", WS_CHILD|WS_VISIBLE,
CRect(CPoint(0,rect.bottom),CSize(200,25)),
parent);
m_editTitle.Create(WS_CHILD|WS_VISIBLE|WS_BORDER,
CRect(CPoint(0,rect.bottom+50),CSize(rect.right-110,25)),
parent,IDC_EDIT_TITLE);
m_btnChange.Create("Change", WS_CHILD|WS_VISIBLE|WS_TABSTOP|BS_PUSHBUTTON,
CRect(CPoint(rect.right+5,0),CSize(75,30)),
parent,IDC_CHANGE);
m_btnClear.Create("Clear", WS_CHILD|WS_VISIBLE|WS_TABSTOP|BS_PUSHBUTTON,
CRect(CPoint(rect.right+5,40),CSize(75,30)),
parent,IDC_CLEAR);
m_btnCancel.Create("Cancel", WS_CHILD|WS_VISIBLE|WS_TABSTOP|BS_PUSHBUTTON,
CRect(CPoint(rect.right+5,80),CSize(75,30)),
parent,IDC_CANCEL);
}
void CMainWindow::cleanUpDialog()
{
m_editTitle.DestroyWindow();
m_labelEdit.DestroyWindow();
m_btnChange.DestroyWindow();
m_btnClear.DestroyWindow();
m_btnCancel.DestroyWindow();
}
- Symbolic constants used to identify messages sent from button controls (see below
for how buttons know which message ID to use)
- "MessageBox" conventient to use when developing a program to identify
when a skeleton function is entered.
- "makeDialog" turns on the dialog mode on the main window
- GetWindowText for a CEdit control returns the text the user typed in.
- Using "MessageBox" with Yes/No/Cancel buttons to confirm user's desires
- SetTitle - this changes the window title - all the rest is to support this function
call
- CleanUp - will remove dialog control windows from screen
- Clears any text in the edit window - shows two ways - one if you know the name of
the control object
- and one if you only have the ID assigned to this control (see makeDialog to see how
it is assigned)
- Have to figure out where to place all the controls regardless of size of window
- Here is where I associate ID with control. This ID is used both as a message ID to
send a message when the button is pushed as well as one way to access the control object
(see CEdit object above and the OnClear message handler)
Full source code here.
Copyright chris wild 1999/2000.
For problems or questions regarding this web contact [Dr.
Wild].
Last updated: January 25, 2000.