-I edited file includes/mambolanguage.class.php, add a function for convert charset of attribute of this class from utf-8 to "encoding" attribute in xml file.Therefore I check edit or install language in save() function,if $page_ is "addpage",it is install language. 
-I edited file administrator\components\com_languages\views\templates\langform.tpl.php, add 2 hidden fields for assigned "page_" to be "addpage" or "editpage" for each mission.