关于在Dialog中添加ComboBox控件的问题

[BeginnerCpp]

使用VS2003中的VC+MFC,
在VC的资源编辑器中创建一个对话框,对话框中添加一个ComboBox控件,
然后选中ComboBox控件,鼠标右键,添加一个变量m_comboboxForSort,类型是CComboBox.

接着,在对话框中调用comboboxForSort,发现几乎是100%会运行时候系统提示错误,
比如下面的代码:
BOOL CDialogNew::OnInitDialog()
{
CItem* pitemold;
for( POSITION pos = m_pitemlisOld->GetHeadPosition(); pos != NULL; )
{
pitemold = m_pitemlisOld->GetNext(pos);
CString stroldsort = pitemold->GetPItemRootName();

//m_comboboxForSort.AddString(stroldsort.GetBuffer());
TRACE("In BOOL CDialogNew::OnInitDialog(), add %s\n", stroldsort );
}

return CDialog::OnInitDialog();
}

//m_comboboxForSort.AddString(stroldsort.GetBuffer());这句调用必须注释掉,
要不然就会运行时候出错,
不要怀疑其它部分代码,经过TRACE观察,是正常的.

[BeginnerCpp]

然后怀疑是m_comboboxForSort它没有被创建,
有了下面的代码:
BOOL CDialogNew::OnInitDialog()
{
CItem* pitemold;
for( POSITION pos = m_pitemlisOld->GetHeadPosition(); pos != NULL; )
{
pitemold = m_pitemlisOld->GetNext(pos);
CString stroldsort = pitemold->GetPItemRootName();

//m_comboboxForSort.AddString(stroldsort.GetBuffer());
TRACE("In BOOL CDialogNew::OnInitDialog(), add %s\n", stroldsort );
}

CComboBox* pcomboboxSort = (CComboBox*)this->GetDlgItem(IDC_DLGNEW_COMBO_SORT);
TRACE("In BOOL CDialogNew::OnInitDialog(), pcomboboxSort is : %i\n", (int)pcomboboxSort );
pcomboboxSort->InitStorage(256, 10);
pcomboboxSort->AddString("test");

return CDialog::OnInitDialog();
}

结果就不会运行时候出错,其中IDC_DLGNEW_COMBO_SORT就是对话框上面ComboBox的控件ID,
但是,在对话框上面,还是空空如己,没有任何内容,很奇怪?

[BeginnerCpp]

最后,
这样的代码产生了:

BOOL CDialogNew::OnInitDialog()
{
CItem* pitemold;
for( POSITION pos = m_pitemlisOld->GetHeadPosition(); pos != NULL; )
{
pitemold = m_pitemlisOld->GetNext(pos);
CString stroldsort = pitemold->GetPItemRootName();

//m_comboboxForSort.AddString(stroldsort.GetBuffer());
TRACE("In BOOL CDialogNew::OnInitDialog(), add %s\n", stroldsort );
}

CComboBox* pcomboboxSort = (CComboBox*)this->GetDlgItem(IDC_DLGNEW_COMBO_SORT);
TRACE("In BOOL CDialogNew::OnInitDialog(), pcomboboxSort is : %i\n", (int)pcomboboxSort );
TRACE("In BOOL CDialogNew::OnInitDialog(), m_comboboxForSort is : %i\n", (int)(m_comboboxForSort.GetSafeHwnd()) );
pcomboboxSort->InitStorage(256, 10);
pcomboboxSort->AddString("test");
//m_comboboxForSort.AddString("test1");

return CDialog::OnInitDialog();
}

程序在调试模式下,
输出窗口上有这样信息:
In BOOL CDialogNew::OnInitDialog(), pcomboboxSort is : 3645484
In BOOL CDialogNew::OnInitDialog(), m_comboboxForSort is : 0

很奇怪,
pcomboboxSort 和 m_comboboxForSort 对应同一个控件ID,
为什么他们的结果会这样呢?

请看:
http://community.csdn.net/Expert/topic/3765/3765153.xml?temp=.288006
其实是同一个问题,
谁能给出思路来,
2个帖子的分一起散给他.

[BeginnerCpp]

上面的代码有点小小的问题,
更新的代码如下:

BOOL CDialogNew::OnInitDialog()
{
CItem* pitemold;
for( POSITION pos = m_pitemlisOld->GetHeadPosition(); pos != NULL; )
{
pitemold = m_pitemlisOld->GetNext(pos);
CString stroldsort = pitemold->GetPItemRootName();

//m_comboboxForSort.AddString(stroldsort.GetBuffer());
TRACE("In BOOL CDialogNew::OnInitDialog(), add %s\n", stroldsort );
}

CComboBox* pcomboboxSort = (CComboBox*)this->GetDlgItem(IDC_DLGNEW_COMBO_SORT);
TRACE("In BOOL CDialogNew::OnInitDialog(), pcomboboxSort is : %i\n", (int)pcomboboxSort );
TRACE("In BOOL CDialogNew::OnInitDialog(), pcomboboxSort'Hwnd is : %i\n", (int)pcomboboxSort->GetSafeHwnd() );
TRACE("In BOOL CDialogNew::OnInitDialog(), m_comboboxForSort is : %i\n", (int)(m_comboboxForSort.GetSafeHwnd()) );
pcomboboxSort->InitStorage(256, 10);
pcomboboxSort->AddString("test");
//m_comboboxForSort.AddString("test1");

return CDialog::OnInitDialog();
}

程序的输出信息是:
In BOOL CDialogNew::OnInitDialog(), pcomboboxSort is : 3645484
In BOOL CDialogNew::OnInitDialog(), pcomboboxSort'Hwnd is : 658288
In BOOL CDialogNew::OnInitDialog(), m_comboboxForSort is : 0

呵呵,
头大啊,SOS SOS

[王晓华-吹泡泡的小猫]

添加一行ReleaseBuffer，GetBuffer后一定要ReleaseBuffer

CString stroldsort = pitemold->GetPItemRootName();
m_comboboxForSort.AddString（stroldsort.GetBuffer());
stroldsort.ReleaseBuffer();

[快乐鹦鹉]

m_comboboxForSort.AddString(stroldsort.GetBuffer());
为什么要这样呢？
m_comboboxForSort.AddString(stroldsort);不就可以了么

[hongtog]

应该不是控件的问题..
检查一下Combox属性..
Owner Draw: NO.

[快乐鹦鹉]

你的错误很简单，因为你将return CDialog::OnInitDialog()写在了最后。应该如下：
BOOL CDialogNew::OnInitDialog()
{
CDialog::OnInitDialog();//基类调用放在第一句！这样才能正确创建各个控件！
CItem* pitemold;
for( POSITION pos = m_pitemlisOld->GetHeadPosition(); pos != NULL; )
{
pitemold = m_pitemlisOld->GetNext(pos);
CString stroldsort = pitemold->GetPItemRootName();

//m_comboboxForSort.AddString(stroldsort.GetBuffer());
TRACE("In BOOL CDialogNew::OnInitDialog(), add %s\n", stroldsort );
}

return TRUE;
}
必须首先调用基类的初始化，然后才能正确使用对话框中的各个控件！

[zhanghk]

up happyparrot(快乐鹦鹉)

[koko1998]

楼上正解

也可以写成
m_comboboxForSort.AddString(stroldsort.GetBuffer(0));

[legendhui]

up

[chuanke]

说完了

[chuanke]

m_comboboxForSort.AddString(stroldsort.GetBuffer(0));

[chuanke]

汉！怎么已经来过了呢？汉.....

[BeginnerCpp]

http://community.csdn.net/Expert/topic/3765/3765153.xml?temp=.8064234
谢谢上面的回复,又学到一些东西了.
结贴,散分

[sumjohn]

挂个号
呵呵