I am creating an android app which also has an integrated XMPP chat feature using aSmack and ejabberd. I am using the user's application login and password to login to XMPP server. So how do I change a password using aSmack in case a user changes his application password
There is no way to do it unless you create a plugin for it.
The alternate is to delete the user and create him again.
one more alternate can be just married plugin https://www.igniterealtime.org/projects/openfire/plugins/justmarried/readme.html this plugin change the username. You can modify the plugin to change pssword. Note : just married plugin is also deleting the user and recreating it but restoring all the data