How to show my toolTip in QTreeWidget?

[cspp]

where to user those code?
I just user like this:

QTreeWidgetItem* item = new QTreeWidgetItem();
//...
item->setToolTip(i,QString("My ToolTip Text"));

QTreeWidgetItem* item = new QTreeWidgetItem();
//...
item->setToolTip(i,QString("My ToolTip Text"));

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and my Qt version is Qt4.3.2