Inserting data in SQLite Database in Android

I am doing a project in Android and i have a problem about database. I created database in SQLite Browser and imported to my project in Android Studio. I can access database and select data from tables. But i can not insert data. I would be very happy if you help me. Thanks :)

Here's my code:

public boolean putInfo(String name, String surname, String username, String 
mail, String pass, String address, String phone_no, String status) {
        boolean res = true;
        if (open()) {
            List<User> users = getUsers();

            for (int n = 0; n < users.size(); n++) {
                String db_username = users.get(n).username;
                String db_mail = users.get(n).mail;

                if(db_username.equals(username) || db_mail.equals(mail)) {
                    res = false;
                }
            }

            if(res == true) {
                ContentValues cv = new ContentValues();
                cv.put("uname",name);
                cv.put("usurname",surname);
                cv.put("uusername",username);
                cv.put("upassword",pass);
                cv.put("umail",mail);
                cv.put("uaddress",address);
                cv.put("ustatus",status);
                cv.put("uphoneno",Integer.parseInt(phone_no));
                db.insert("User", null, cv);
            }
        }
        else {
            // error opening DB.
        }

        return res;
    }