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How to Add Tree-View Items

  • Article

You add an item to a tree-view control by sending the TVM_INSERTITEM message to the control. The message includes the address of a TVINSERTSTRUCT structure, specifying the parent item, the item after which the new item is inserted, and a TVITEM structure that defines the attributes of the item. The attributes include the item's label, its selected and nonselected images, and a 32-bit application-defined value.

What you need to know

Technologies

Prerequisites

  • C/C++
  • Windows User Interface Programming

Instructions

Add Items to the Tree-View

The example in this section demonstrates how to create a table of contents based on document heading information that is provided in an application-defined array. Each array element consists of a heading string and an integer that indicates the heading level. The example supports three heading levels (1, 2, and 3).

The example includes two functions. The first function extracts each heading and accompanying heading level and then passes them to the second function.

The second function adds an item to a tree-view control. It uses the heading text as the item's label, and it uses the heading level to determine the parent item for the new item. A level one heading is added to the root of the tree-view control, a level two heading is added as a child item of the previous level one item, and so on. The function assigns an image to an item based on whether it has child items. If an item has child items, it gets an image that represents a closed folder. Otherwise, it gets an image that represents a document. An item uses the same image for both the selected and nonselected states.

// Adds items to a tree-view control. 
// Returns the handle to the newly added item. 
// hwndTV - handle to the tree-view control. 
// lpszItem - text of the item to add. 
// nLevel - level at which to add the item. 
//
// g_nClosed, and g_nDocument - global indexes of the images.

HTREEITEM AddItemToTree(HWND hwndTV, LPTSTR lpszItem, int nLevel)
{ 
    TVITEM tvi; 
    TVINSERTSTRUCT tvins; 
    static HTREEITEM hPrev = (HTREEITEM)TVI_FIRST; 
    static HTREEITEM hPrevRootItem = NULL; 
    static HTREEITEM hPrevLev2Item = NULL; 
    HTREEITEM hti; 

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

    // Set the text of the item. 
    tvi.pszText = lpszItem; 
    tvi.cchTextMax = sizeof(tvi.pszText)/sizeof(tvi.pszText[0]); 

    // Assume the item is not a parent item, so give it a 
    // document image. 
    tvi.iImage = g_nDocument; 
    tvi.iSelectedImage = g_nDocument; 

    // Save the heading level in the item's application-defined 
    // data area. 
    tvi.lParam = (LPARAM)nLevel; 
    tvins.item = tvi; 
    tvins.hInsertAfter = hPrev; 

    // Set the parent item based on the specified level. 
    if (nLevel == 1) 
        tvins.hParent = TVI_ROOT; 
    else if (nLevel == 2) 
        tvins.hParent = hPrevRootItem; 
    else 
        tvins.hParent = hPrevLev2Item; 

    // Add the item to the tree-view control. 
    hPrev = (HTREEITEM)SendMessage(hwndTV, TVM_INSERTITEM, 
        0, (LPARAM)(LPTVINSERTSTRUCT)&tvins); 

    if (hPrev == NULL)
        return NULL;

    // Save the handle to the item. 
    if (nLevel == 1) 
        hPrevRootItem = hPrev; 
    else if (nLevel == 2) 
        hPrevLev2Item = hPrev; 

    // The new item is a child item. Give the parent item a 
    // closed folder bitmap to indicate it now has child items. 
    if (nLevel > 1)
    { 
        hti = TreeView_GetParent(hwndTV, hPrev); 
        tvi.mask = TVIF_IMAGE | TVIF_SELECTEDIMAGE; 
        tvi.hItem = hti; 
        tvi.iImage = g_nClosed; 
        tvi.iSelectedImage = g_nClosed; 
        TreeView_SetItem(hwndTV, &tvi); 
    } 

    return hPrev; 
} 

// Extracts heading text and heading levels from a global 
// array and passes them to a function that adds them as
// parent and child items to a tree-view control. 
// Returns TRUE if successful, or FALSE otherwise. 
// hwndTV - handle to the tree-view control. 

BOOL InitTreeViewItems(HWND hwndTV)
{ 
    HTREEITEM hti;

    // g_rgDocHeadings is an application-defined global array of 
    // the following structures: 
    //     typedef struct 
    //       { 
    //         TCHAR tchHeading[MAX_HEADING_LEN]; 
    //         int tchLevel; 
    //     } Heading; 
    for (int i = 0; i < ARRAYSIZE(g_rgDocHeadings); i++) 
    { 
        // Add the item to the tree-view control. 
        hti = AddItemToTree(hwndTV, g_rgDocHeadings[i].tchHeading, 
            g_rgDocHeadings[i].tchLevel); 

        if (hti == NULL)
            return FALSE;
    } 
           
    return TRUE; 
}

Using Tree-View Controls

CustDTv sample illustrates custom draw in a Tree-View control