QCombBox currentIndexChange( int ); // 选中的下拉框改变时候触发
QLineEdit textEdited （）; // 编辑框的内容被修改的时候触发
// 整个treeView设置为不可编辑，即只读模式
m_treeView ->setEditTriggers ( QAbstractItemView :: NoEditTriggers) ;
// 当一个QTreeView对象的某个数据子项被点击，发送信号 QModelIndex 类型参数提供点击的 item 的位置
void QAbstractItemView :: clicked ( const QModelIndex & index) [singal]
This signal is emitted when a mouse buttton is clicked ,the item the mouse was clicked on is specified by index .the signal is only emited when the index is valid.
// 从model里面根据index获取item QAbstractItemModel :: itemFromIndex (QModelIndex);
// [委托] 从model里面根据index获取data， index->model ()->data ( index , Qt :: EditRole)
