Adding Items to a Tree View Control

You can add items to a tree view control by sending the TVM_INSERTITEM message or by calling the associated TreeView_InsertItem macro. In MFC, use the InsertItem member function. For each item, you must fill out the TV_ITEM and TV_INSERTSTRUCT structures. When adding an item, you must specify the handle of the new item's parent item. If you specify NULL or TVI_ROOT instead of an item handle, the item is added as a root item.

The following example demonstrates how to add items to a tree view control. This sample handles the real estate listing you saw earlier, with three houses listed for each of three cities. A global structure keeps track of the handle to the parent item and its image.

typedef struct tagHOUSEINFO 

{

char szAddress [MAX_ADDRESS];

int iImage;

HTREEITEM hParent;

} HOUSEINFO;



BOOL AddTreeViewItems (HWND hwndTree)

{

static HTREEITEM hPrev;

char szText [MAX_LEN];

int index;



// First add the root item "Houses for Sale."

LoadString (hInst, IDS_FORSALE, szText, MAX_LEN);

hTRoot = AddOneItem ((HTREEITEM)NULL, szText,
(HTREEITEM)TVI_ROOT,

idxForSale, hwndTree);



// Now add the cities.

LoadString (hInst, IDS_REDMOND, szText, MAX_LEN);

hTRed = AddOneItem (hTRoot, szText, (HTREEITEM)TVI_FIRST,
idxRedmond, 

hwndTree);



LoadString (hInst, IDS_BELLEVUE, szText, MAX_LEN);

hTBel = AddOneItem (hTRoot, szText, hTRed, idxBellevue,
hwndTree);



LoadString (hInst, IDS_SEATTLE, szText, MAX_LEN);

hTSea = AddOneItem (hTRoot, szText, hTBel, idxSeattle, hwndTree);



// Fill out the structure for each house.

FillInStruct (hTRed, idxRedmond, 0, 3);

FillInStruct (hTBel, idxBellevue, 3, 6);

FillInStruct (hTSea, idxSeattle, 6, 9);



// Add the houses for each city.

hPrev = hTSea;

for (index = 0; index < NUM_HOUSES; index++)

{

hPrev = AddOneItem (rgHouseInfo[index].hParent, 

rgHouseInfo[index].szAddress,

hPrev,

rgHouseInfo[index].iImage,

hwndTree);

rgHouseInfo[index].hItem = hPrev;

}

return TRUE;

}



// This function saves the current image and the handle to the 

// parent of the tree view item.

VOID FillInStruct (HTREEITEM hParent, int iImage, int index, int
iMax)

{

for (; index < iMax; index++)

{

rgHouseInfo[index].iImage = iImage;

rgHouseInfo[index].hParent = hParent;

}

}



// This function fills out the TV_ITEM and TV_INSERTSTRUCT
structures 

// and adds the item to the tree view control.

HTREEITEM AddOneItem (HTREEITEM hParent, LPSTR szText,

HTREEITEM hInsAfter, int iImage, HWND hwndTree)

{

HTREEITEM hItem;

TV_ITEM tvI;

TV_INSERTSTRUCT tvIns;



// The pszText, iImage, and iSelectedImage members are filled
out.

tvI.mask = TVIF_TEXT | TVIF_IMAGE | TVIF_SELECTEDIMAGE |
TVIF_PARAM;

tvI.pszText = szText;

tvI.cchTextMax = lstrlen (szText);

tvI.iImage = iImage;

tvI.iSelectedImage = iImage;



tvIns.item = tvI;

tvIns.hInsertAfter = hInsAfter;

tvIns.hParent = hParent;



// Insert the item into the tree.

hItem = (HTREEITEM) SendMessage (hwndTree, TVM_INSERTITEM, 0, 

(LPARAM)(LPTV_INSERTSTRUCT)&tvIns);



return (hItem);

}

In MFCTREE, the MFC version of the TREEVIEW sample, the control is created in the view class. The preceding C code is nearly identical to the MFC code. You should note where I keep track of some of the data in MFCTREE, however. In the header file for the view class, MFCTRVW.H, the view class is defined. Within this class, I save the CTreeCtrl object, the image list, the indexes to the images associated with the tree view items, and information about the item being dragged.

class CMfctreeView : public CView

{

protected: // create from serialization only

CMfctreeView();

DECLARE_DYNCREATE(CMfctreeView);

CTreeCtrl m_TreeCtl; // tree view control

CImageList m_ImageList; // image list associated with tree

BOOL m_fDragging; // whether you are dragging an item

HTREEITEM m_hDragItem; // current item being dragged

int m_idxForSale; // index to For Sale icon

int m_idxRedmond; // index to Redmond icon

int m_idxBellevue; // index to Bellevue icon

int m_idxSeattle; // index to Seattle icon



// Attributes

public:

CMfctreeDoc *GetDocument ();



// Operations

public:

BOOL AddTreeViewItems ();

HTREEITEM AddOneItem (HTREEITEM, LPSTR, HTREEITEM, int);

VOID FillInStruct (HTREEITEM, int, int, int);

VOID BeginDrag (NM_TREEVIEW *);

VOID DropItem (HTREEITEM);



// Overrides

// ClassWizard generated virtual function overrides.

// {{AFX_VIRTUAL (CMfctreeView)

public:

virtual void OnDraw (CDC *pDC); // overridden to draw this

// view

protected:

virtual LRESULT WindowProc (UINT message, WPARAM wParam,

LPARAM lParam);

// }}AFX_VIRTUAL



// Implementation

public:

virtual ~CMfctreeView ();



protected:



// Generated message map functions

protected:

// {{AFX_MSG (CMfctreeView)

afx_msg int OnCreate (LPCREATESTRUCT lpCreateStruct);

afx_msg void OnSize (UINT nType, int cx, int cy);

afx_msg void OnDestroy ();

afx_msg void OnMouseMove (UINT nFlags, CPoint point);

afx_msg void OnLButtonUp (UINT nFlags, CPoint point);

// }}AFX_MSG

DECLARE_MESSAGE_MAP ()

};