How to update android app automatically without Google Play or user interaction

Question

I'm developping an application that will run on a tablet device in a store (eg restaurant). The device does not have Google Play and is rooted. How do I install an update to my application automatically, with absolutelly NO user interaction?

To clarify, checking for a new version of APK hosted on my server and downloading it are not part of this question, only the "silent" update part is.

Answer 1

First of all, your device needs to be rooted. It seems this is already done for you. Now all you have to do is to make your application check if a new version of the APK is available. If so, launch a service in background to download the required APK and run this code to silently install it.

public static void InstallAPK(String filename){
    File file = new File(filename); 
    if(file.exists()){
        try {   
            String command;
            command = "adb install -r " + filename;
            Process proc = Runtime.getRuntime().exec(new String[] { "su", "-c", command });
            proc.waitFor();
        } catch (Exception e) {
        e.printStackTrace();
        }
     }
  }

You can basically modify the ABD command to perform whatever you want. Please note that a rooted device can be dangerous and cause security breach.