How to get session user id from webview

Question

Am trying get user session userid from android webview, but using the below code my app will forcefully stop working, without any error while building the apk. Please i am still trying to complete my first webview app am still very new in android

public String getCookie(String siteName,String CookieName){
    String CookieValue = null;

    CookieManager cookieManager = CookieManager.getInstance();
    String cookies = cookieManager.getCookie(siteName);
    String[] temp=cookies.split(";");
    for (String ar1 : temp ){
        if(ar1.contains(CookieName)){
            String[] temp1=ar1.split("=");
            CookieValue = temp1[1];
            break;
        }
    }
    return CookieValue;
}

Reference to above code https://stackoverflow.com/a/20241926/8778864

public void onPageFinished(WebView view, String url) {
  String cookies = CookieManager.getInstance().getCookie(url);
 showAlert(FoodShopMainActivity.this, "Cookies", "cookies string:" + cookies);
}

The above code will output PHPSESSID=g675654hghghf7ghgyty, but what is only the session userID.

public void onPageFinished(WebView view, String url) {
 /*String userCookie = getCookie("http://www.example.com","online_users");
  showAlert(FoodShopMainActivity.this, "Cookies", "cookies string:" + userCookie);*/
}

The above code will show app has stopped working once lunched