如何处理nm_customdraw事件以检索列表项

Question

我正在研究Win32 / MFC项目。 我有一个自定义clistctrl控件，我必须不时添加一些字符串。 我绝对需要在动态添加到我的Clistctrl的项目上执行一些操作。

超基本上，我需要：

1. 检测添加单个元素;
2. 检索 _single项_（理想情况下，InsertIdem（）调用后不久）;
3. 存储在地图中的单个项目的值，我将用来执行其他操作。

   我想在覆盖该方法dighitem（）的情况下。但是ondraw事件似乎不可用于我的clistctrl。

   事件永远不会生成。

   重要提示：请注意，Mycustomclistctrl在 True ，但“ View “属性是 not 设置为报告。 所以，我决定处理nw_customdraw事件，编写我的customdraw处理程序，如这里和这里：

   在这里您可以查看另一个代码示例。 然后，我需要一种方法来从我的clistctrl中检索单个itemids。
   更确切地说，我需要一种方法来从NMHDR STRUCT 中获取单项ID。

   我该怎么办？ 我只能获得我添加的最后项目的ID。 我相信这是一个我无法找到的一个简单错误。

   下面的示例代码：

   包含Clist Ctrl的对话框：

   /* file MyDlg.cpp */
   
   #include "stdafx.h"
   #include "MyDlg.h"
   
   // MyDlg dialog
   
   IMPLEMENT_DYNAMIC(MyDlg, CDialog)
   
   MyDlg::MyDlg(CWnd* pParent)
       : CDialog(MyDlg::IDD, pParent)
   {
   }
   
   MyDlg::~MyDlg()
   {
   }
   
   void MyDlg::DoDataExchange(CDataExchange* pDX)
   {
       CDialog::DoDataExchange(pDX);
       DDX_Control(pDX, IDC_LIST1, listView); /* listView is a MyCustomCListCtrl object */
   }
   
   BEGIN_MESSAGE_MAP(MyDlg, CDialog)
       ON_BN_CLICKED(IDC_BUTTON1, &MyDlg::OnBnClickedButton1) 
   END_MESSAGE_MAP()
   
   BOOL MyDlg::OnInitDialog()
   {
       CDialog::OnInitDialog();
       return TRUE;
   }
   
   /* OnBnClickedButton1 handler add new strings to MyCustomCListCtrl object */
   
   void MyDlg::OnBnClickedButton1()
   {
       listView.InsertItem(0, "Hello,");
       listView.InsertItem(1, "World!");
   }
   

   .

   我的自定义clist ctrl源：

   /* file MyCustomCListCtrl.cpp */
   
   #include "stdafx.h"
   #include "MyCustomCListCtrl.h"
   
   MyCustomCListCtrl::MyCustomCListCtrl()
   {
   }
   
   MyCustomCListCtrl::~MyCustomCListCtrl()
   {
   }
   
   BEGIN_MESSAGE_MAP(MyCustomCListCtrl, CListCtrl)
       //{{AFX_MSG_MAP(MyCustomCListCtrl)
       //}}AFX_MSG_MAP
       // ON_WM_DRAWITEM()                             /* WM_DRAWITEM NON-AVAILABLE */
       ON_NOTIFY_REFLECT(NM_CUSTOMDRAW, OnCustomDraw)
   END_MESSAGE_MAP()
   
   // 'Owner Draw Fixed' property is already TRUE
   /*  void CTranslatedCListCtrl::DrawItem(LPDRAWITEMSTRUCT lpDrawItemStruct)
   {
       bool inside = true; /* Member function removed: I never enter here... */
   }  */
   
   void MyCustomCListCtrl::OnCustomDraw(NMHDR* pNMHDR, LRESULT* pResult)
   {
       /* Here, I must retrieve single strings added to my MyCustomCListCtrl object */
   
       LPNMLISTVIEW plvInfo = (LPNMLISTVIEW)pNMHDR;
       LVITEM lvItem;
   
       lvItem.iItem = plvInfo->iItem;          /* Here I always get _the same_ ID: ID of last element...*/
       lvItem.iSubItem = plvInfo->iSubItem;    // subItem not used, for now...
   
       int MyID = 0;
   
       this->GetItem(&lvItem); // There mai be something error here?
       MyID = lvItem.iItem;
   
       CString str = this->GetItemText(MyID, 0); /* ...due to previous error, here I will always get the last string I have added("World!") */
   
       // Immediately after obtaining ALL IDS, I can Do My Work
   
       *pResult = 0;
   }
   

   .

   任何帮助都得到了赞赏！

   p.s。 请不要给我提示：

   1. 将“自己的绘制修复”属性设置为true;
   2. 检查您已插入“on_wmdrawitem（）”
   3. 将clistctrl转换为报告;

      我已经尝试过一切......： - ） 感谢所有人！

      它

Answer 1

first of all... Thank you wasted your precious time with this stupid question. I never found anything about LVN_INSERT event. I write scientific software(most on Linux platform); I am not a long-time Win32 developer, so I don't know Win32 APIs in depth. I have modified source file of MyCustomCListCtrl class, as you have suggested. Code below seems to be the best( and faster )way to achieve what I want:

    /* file MyCustomCListCtrl.cpp */

    #include "stdafx.h"
    #include "MyCustomCListCtrl.h"

    MyCustomCListCtrl::MyCustomCListCtrl()
    {
    }

    MyCustomCListCtrl::~MyCustomCListCtrl()
    {
    }

    BEGIN_MESSAGE_MAP(MyCustomCListCtrl, CListCtrl)
        //{{AFX_MSG_MAP(MyCustomCListCtrl)
        //}}AFX_MSG_MAP
        ON_NOTIFY_REFLECT(LVN_INSERTITEM, OnLvnInsertItem)
    END_MESSAGE_MAP()

    ...

    afx_msg void CTranslatedListCtrl::OnLvnInsertItem(NMHDR* pNMHDR, LRESULT* pResult)
    {
        LPNMLISTVIEW plvInfo = (LPNMLISTVIEW)pNMHDR;
        CString str = this->GetItemText(plvInfo->iItem, 0);

        // Add Some Logic

        *pResult = 0;
    }

Can You confirm? From what I can see, it seems to work. :-) Thanks again!

IT

Answer 2

First, if you need to detect adding of single items, why don't you handle the LVN_INSERTITEM message? I mean, that's what that message is for. Handling NM_CUSTOMDRAW instead is the wrong way, since you won't necessarily get that notification if the control is hidden, your window minimized, ...

In your OnCustomDraw() you always get the same ID: that's because the list control always draws all visible items, so you get the ID of the first visible item. If you set a breakpoint there, then on the next run the control gets refreshed and the drawing starts again from the first visible item.

Note: since you're handling NM_CUSTOMDRAW, you won't get any notification of added items that are not inserted into the visible part of the control! So as I mentioned, you should handle LVN_INSERTITEM instead.