How can I find the data usage on a per-application basis on Android?

The following links should help you figure out how to programmatically determine the data usage per application.

• Create a network monitor using Android's TrafficStats class

• Android Traffic Statistics Inside

You will need to implement your code to use the TraficStats API and track the number of bytes sent/received per UID (application).

Use this method after create a new class PackageInformationTotal.

public void getPakagesInfoUsingHashMap() {
    final PackageManager pm = getPackageManager();
    // get a list of installed apps.
    List<ApplicationInfo> packages = pm.getInstalledApplications(0);

    // loop through the list of installed packages and see if the selected
    // app is in the list
    for (ApplicationInfo packageInfo : packages) {
        // get the UID for the selected app
        UID = packageInfo.uid;
        String package_name = packageInfo.packageName;
        ApplicationInfo app = null;
        try {
            app = pm.getApplicationInfo(package_name, 0);
        } catch (NameNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        String name = (String) pm.getApplicationLabel(app);
        Drawable icon = pm.getApplicationIcon(app);
        // internet usage for particular app(sent and received)
        double received = (double) TrafficStats.getUidRxBytes(UID)

                / (1024 * 1024);
        double send = (double) TrafficStats.getUidTxBytes(UID)
                / (1024 * 1024);
        double total = received + send;

        if(total>0)
        {
            PackageInformationTotal pi=new PackageInformationTotal();
            pi.name=name;
            pi.packageName=package_name;
            pi.icon=icon;               
            pi.totalMB=String.format( "%.2f", total )+" MB";
            pi.individual_mb=String.format( "%.2f", total );
            totalData+=Double.parseDouble(String.format( "%.2f", total ));
            dataHash.add(pi);
        Log.e(name,String.format( "%.2f", total )+" MB");
        }

    }
    Editor edit=shared.edit();
    edit.putString("Total",String.format( "%.2f", totalData));
    edit.commit();
}

After that you can track all process usages in MB.