How to do it...

We have only two changes to make, and both are in MainActivity.java:

1. Add the following onPause() method to save the data before the activity closes:

@Override
protected void onPause() {
    super.onPause();
    SharedPreferences settings = getPreferences(MODE_PRIVATE);
    SharedPreferences.Editor editor = settings.edit();
    editor.putInt(KEY_COUNTER, mCounter);
    editor.commit();
}

2. Then, add the following code at the end of onCreate() to restore the counter:

SharedPreferences settings = getPreferences(MODE_PRIVATE);
int defaultCounter = 0;
mCounter = settings.getInt(KEY_COUNTER, defaultCounter);
((TextView)findViewById(R.id.textViewCounter))
        .setText("Counter: " + Integer.toString(mCounter));

3. Run the program and try it out.