Don't you find you have written the same segment of code many times to parse a subtree because the action you wanted to launch on the items was different. In order to avoid such code, I've written
CTreeViewIterator class. This class contains a method called
ApplyFunction to launch a function on each item/node of a subtree.
The class I've written is dedicated to Explorer like applications (those with a
CTreeView class on the left side). In that section, we're going to see how to use
CTreeViewIterator in that general case. In the section Adaptation, we'll see how to modify it to use it in other cases.
When you generate your application using the wizard, Visual C++ doesn't give you the capability to choose the
CTreeView class implementation. Therefore, you have to have a
CLeftView in your application. In the LeftView.cpp file, add the following line in the
You're now able to use the
CTreeViewIterator class in that module.
You must define the function that will receive the item/node as parameter. This function will be external to your
CLeftView class even if defined in the same module. If you don't define it in this module, do not forget to create a definition to set it visible from this module. If for any reason, you do want to set it as a method of your
CLeftView class, please read the Adaptation section. The signature of this function is predefined. It must be like this:
int ExternalFunction ( CLeftView *tvTreeView,
HTREEITEM tiItem )
- This function must return an integer set to
1 if ok,
- The first parameter is to be a
CLeftView*. It will receive a handle on the
CLeftView to let you use.
- The second parameter is to be a
HTREEITEM. It will receive a handle on the currently parsed item/node.
For example, let's consider this function:
int ExternalDisplayItem (
HTREEITEM tiItem )
CTreeCtrl &tTree= tvTree->GetTreeCtrl ();
tvTree->sFullList += tTree.GetItemText(tiItem) + "\r\n";
return ( 1);
The goal here, is to store the subtree as a list in a
string. So, the only thing the external function has to do is getting the name and concatenating it to the full list. To do so, it will use an attribute created in the
CString). Since we got a handle on the
CLeftView as first parameter, there's no problem till the attribute is
public (if not, we should have used
public methods like
set). Using this method, you may update the tree item/node or the
CLeftView the way you want.
Now you have the function to apply to each item/node, you have to call it. To do so, you'll have to implement first the iterator and then, to call the
ApplyFunction method with the right parameters.
ApplyFunction's signature is:
int CTreeViewIterator::ApplyFunction (
FuncPtrView fptrFunction )
- This function returns an integer set to
1 if ok,
-1 if problem when parsing subtree,
0 if problem when calling the external function.
- The first parameter is a handle on the
CLeftView derived from
- The second parameter is a handle on the item/node to consider as the root when parsing the subtree.
fptrFunction is a function pointer to the external function you previously created.
Using our precedent external function, we got this code:
void CLeftView::OnSelchanged (
LRESULT *pResult )
NM_TREEVIEW *pNMTreeView = (NM_TREEVIEW *) pNMHDR;
CTreeCtrl &tTree = this->GetTreeCtrl ();
CTreeViewIterator *ptrTree = (CTreeViewIterator *) &tTree;
ptrTree->ApplyFunction (this, pNMTreeView->itemNew.hItem,
GetDocument()->UpdateAllViews ( this, 1L, (CObject *) &sFullList );
*pResult = 0;
OnSelChanged is launched when the user has selected a new item/node in the
treeview. Here, we have caught it to add our function call. As you can see, we first add the iterator implementation with:
CTreeViewIterator *ptrTree = (CTreeViewIterator *) tTree;
In fact, we may consider the iterator on the
CTreeCtrl as a shell with a special method. Therefore, within
ApplyFunction method, we will see the content of the
CTreeCtrl to parse.
We now have to get the parameters:
That way, we obtain the following call:
ptrTree->ApplyFunction (this, pNMTreeView->itemNew.hItem, &ExternalDisplayItem );
Since this event may be caught many times, we initialize the variable
sFullList before we parse the subtree.
ApplyFunction is finished, we update the other views with the generated
string using the method
Here we are, catching the
UpdateAllViews event isn't the subject here but you may have a look at the sample project to get an idea.
That section is to explain you how to upgrade the
CTreeViewIterator to adapt it to your own case. I wrote it as a FAQ. I'll update it with the cases you will propose. So, what's your problem?
CTreeView class is not named
Answer: Change the
CTreeView classname in:
- The function pointer's signature
Question: I want to set the called function a method of my class
Answer: You just have to change the function pointer's signature to add your class. For example, try this:
- Change the External function to a
public method called
- Change the signature to:
typedef int ( CLeftView::*FuncPtrView ) ( CLeftView * tTree, HTREEITEM tiItem );
- Change the call of
ApplyFunction method to:
ptrTree->ApplyFunction (this, pNMTreeView->itemNew.hItem, &CLeftView::DisplayItem );
ApplyFunction implementation, change the function call to:
( tvView->*fptrFunction ) ( tvView, tiCurrItem )
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After years passed in services companies, I now work for Euromaster, an international group dedicated to vehicules maintenance. I also develop for my own usage. I both use Java and C++ languages and now, I integrate XML documents and XSL syntax in my applications even if SQL Databases like Oracle remain my main data sources