This shows how to let your app know that it had been sent to the background. The only thing it doesn't detect is if you turn of the screen and unlock directly to the app. It will detect if you unlock to another app. It can also handle rotation just fine.

BackgroundAwareness.java

public class App extends Application {

    // Bunches of application code
    
    public boolean isAppInForeground() {
        ActivityManager activityManager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
        List<RunningAppProcessInfo> appProcesses = activityManager.getRunningAppProcesses();
        if (appProcesses != null) {
            final String packageName = getPackageName();
            for (RunningAppProcessInfo appProcess : appProcesses) {
                if (appProcess.importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND 
                  && appProcess.processName.equals(packageName)) {
                    return true;
                }
            }
        }
        return false;
    }
}

ExampleActivity.java

public class BaseActivity extends Activity {
    private static final String TAG = BaseActivity.class.getSimpleName();
    
    private boolean appSwitchedToBackground;

    // Activity code
    
    @Override
    protected void onStart() {
        super.onStart();
        Log.d(TAG, "App was in background: " + Boolean.toString(appSwitchedToBackground));
        if (appSwitchedToBackground && UserAccount.isUserLoggedIn()) {
            UserAccount.fetchUserDetails(UserAccount.getLoggedInUserToken());
        }
    }

    @Override
    protected void onStop() {
        super.onStop();
        appSwitchedToBackground = !EbatesApp.getInstance().isAppInForeground();
    }
    
    // Activity code
}