My goal is create a client android app deal with Hyperledger composer locally.
I created a network on Hyperledger composer on one physical machine and create a card for an admin.
I have some questions to go on:
how can I connect an android app to a local hyperledger composer on my physical machine?
How can I add new participant in my network from android app?
What I mean by add participate is registration new user using registration form not user interface of rest server of network
how can I connect an android app to a local hyperledger composer on my physical machine?
This is easily doable once you have a REST API running. To have multi-user support, see, for example, the Using Google OAUTH2.0 with a REST server tutorial.
Once you have the REST API up and running, all you need to do is to implement the HTTP requests in your Android app and point them to the correct IP address or host name.
How can I add new participant in my network from android app?
Think of what you need to do to issue a new identity: you would normally go to Playground (using an admin card) to create a new participant and then you need to create a new identity and bind it to the participant. Finally, you would issue the business network card and download it or load it onto your local environment. All these steps can be achieved directly via REST API endpoints if the REST API has the privileges to do so. If you are using a multi-user REST API, then an ordinary user should not have these privileges. This means that you will need a separate REST API server with admin privileges to handle the user registration requests.
In any case, you would definitely need to implement your own API calls and user interface.