重构的步骤：
1. WxMyPainterMain.cpp中调用SetDirty(……)的地方，全部改为UpdateFileStatusUI()，包括我们在“Undo/Redo”响应函数中加上的那两行
这些位置分别在下面的函数中
//鼠标抬起函数
void wxMyPainterFrame::OnScrolledWindow1LeftUp(wxMouseEvent& event)
//置顶
void wxMyPainterFrame::OnMenuItemTopLevelSelected(wxCommandEvent& event)
//上浮
void wxMyPainterFrame::OnMenuItemFowardLevelSelected(wxCommandEvent& event)
//下降
void wxMyPainterFrame::OnMenuItemBackLevelSelected(wxCommandEvent& event)
//置底
void wxMyPainterFrame::OnMenuItemBottomLevelSelected(wxCommandEvent& event)
//删除
void wxMyPainterFrame::OnMenuItemDelItemSelected(wxCommandEvent& event)
//隐藏
void wxMyPainterFrame::OnMenuItemHideSelected(wxCommandEvent& event)
//Undo
void wxMyPainterFrame::OnMenuItemEditUndoSelected(wxCommandEvent& event)
//Redo
void wxMyPainterFrame::OnMenuItemEditRedoSelected(wxCommandEvent& event)
2. 原来需要判断“_is_dirty”的地方，都改成判断“_actionLink.IsDirty()”
3.完成修改之后，从类wxMyPainterFrame的定义及实现代码中，将_is_dirty和SetDirty()删除
运行效果：
