java – Apply Expiration Date to an application (Trial version)

Question:

In some paid applications, it shows you a dialog so you can buy the full version of the app, and in others it is the 30-day trial.

How to apply an expiration date to an application on Android?

Answer:

Response inspired by SO , SO , mobile-trial

Ways that could be implemented, from simpler to skip to more complex.

  • First method save the installation date in the base de datos , fichero interno o externo de la app or use shared preferences . But it is very likely that the user will skip the test time restriction :, uninstall and reinstall the app , if an external location is used for the file, the user may not be aware of the residue.

  • Second method: use a fixed deadline date hard bomb-time that is to say that for all users this date expires. It is easy to get around that restriction, just change the system time to a date before the deadline , for the user it can be a bit cumbersome to do it often and decide to buy.

  • Third method of all the other is the safest (but not infallible) that if it requires more resources, internet connection, servidor web propio , is to create a remote unique identifier checker, you can get the device's getDeviceId and check the base remote data if it exists, get the install date, if it doesn't exist add a new entry getDeviceId : fecha agregación . If the device does not have internet, the user can be warned and the app terminated.

Code of each method

not checked if they work:

Example of the first method using SharedPreference

private final SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
private final long ONE_DAY = 24 * 60 * 60 * 1000;

@Override
protected void onCreate(Bundle state){
    SharedPreferences preferences = getPreferences(MODE_PRIVATE);
    String installDate = preferences.getString("InstallDate", null);
    if(installDate == null) {
        // First run, so save the current date
        SharedPreferences.Editor editor = preferences.edit();
        Date now = new Date();
        String dateString = formatter.format(now);
        editor.putString("InstallDate", dateString);
        // Commit the edits!
        editor.commit();
    }
    else {
        // This is not the 1st run, check install date
        Date before = (Date)formatter.parse(installDate);
        Date now = new Date();
        long diff = now.getTimeInMillis() - before.getTimeInMillis();
        long days = diff / ONE_DAY;
        if(days > 30) { // More than 30 days?
             // Expired !!!
        }
    }

    ...
}

Example of the second method using time-bomb

protected void onResume()
{   
    super.onResume();

    Calendar expirationDate = Calendar.getInstance();
    expirationDate.set(2016, 12, 31);  //expirara final de año
    Calendar t = Calendar.getInstance();  //obtener fecha actual
    if (t.compareTo(expirationDate) == 1)
       finish();
}

Example of the third method response from user @Martin_christmman implement https://github.com/mobile-trial

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