Android SQLite - Correct Usage

I'm reading from an URL with format

name \n
bio \n
URL link to image \n
name \n
bio \n
...

MainActivity:

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    editText = (EditText) findViewById(R.id.URL_edit_text);
    editText.setText("http:...txt");
    db = new DatabaseHelper(this, null, null, 1);

}

public void To_URL(View view){
    Button button = (Button) findViewById(R.id.URL_Button);
    final String url = "http:....txt";

    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, DisplayActivity.class);
            intent.putExtra(url, "url_string");
            startActivity(intent);
        }
    });
}

DisplayActivity

public class DisplayActivity extends AppCompatActivity {
DatabaseHelper db;
String url;
String name, bio;
TextView name_text_view, bio_text_view;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.db_layout);
    name_text_view = (TextView) findViewById(R.id.name);
    bio_text_view = (TextView) findViewById(R.id.bio);

    url = getIntent().getStringExtra("url_string");
    try {
        InputStream source = new URL(url).openStream();
        Scanner scanner = new Scanner(source).useDelimiter("\\n");
        name = scanner.next();
        bio = scanner.next();
       // name = new Scanner(new URL(url).openStream(), "UTF-8").useDelimiter("\\n").next();
    } catch (IOException e) {
        e.printStackTrace();
    }
    db = new DatabaseHelper(this, null, null, 1);
    printDatabase();
}

public void searchButtonClick(View view) {
}

public void populateButtonClick(View view) {
    Person person = new Person(name, name);
            db.addPerson(person);

}
public void clearButtonClick(View view) {

}

public void printDatabase(){
    String dbStringName = db.dbToNameString();
    String dbStringBio = db.dbToBioString();
    name_text_view.setText(dbStringName);
    bio_text_view.setText(dbStringBio);
}
}

DatabaseHelper

public class DatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME="bio.db";
private static final int SCHEMA=1;
static final String COLUMN_NAME="name";
static final String COLUMN_BIOGRAPHY="bio";
static final String COLUMN_ID = "_id";
static final String TABLE_PERSONS="persons";
static final String PIC_URL="url";
String url_val;

public DatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
    super(context, DATABASE_NAME, null, SCHEMA);
}

public void parseURL(String url){
    url_val = url;
}

@Override
public void onCreate(SQLiteDatabase db) {
    String query = "CREATE TABLE " + TABLE_PERSONS + " (" + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
            COLUMN_NAME + " TEXT, " + COLUMN_BIOGRAPHY + " TEXT " + ");";

    db.execSQL(query);

    /*
    cv.put(TITLE, "Gravity, Death Star I");
    cv.put(VALUE, SensorManager.GRAVITY_DEATH_STAR_I);
    db.insert(TABLE, TITLE, cv);
    */
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_PERSONS);
    onCreate(db);
}

public void addPerson(Person person){
    ContentValues values = new ContentValues();
    values.put(COLUMN_NAME, person.get_name());
    values.put(COLUMN_BIOGRAPHY, person.get_biography());

    SQLiteDatabase db = getWritableDatabase();
    db.insert(TABLE_PERSONS, null, values);
    db.close();
}

public void deletePerson(String personName){
    SQLiteDatabase db= getWritableDatabase();
    db.execSQL("DELETE FROM " + TABLE_PERSONS + " WHERE " + COLUMN_BIOGRAPHY + "=\"" + personName + "\";");
}

//Print out database as String
public String dbToNameString(){
    String dbString = "";
    SQLiteDatabase db = getWritableDatabase();
    String query = "SELECT * FROM " + TABLE_PERSONS + " WHERE 1";

    Cursor c = db.rawQuery(query, null);
    c.moveToFirst();

    while(!c.isAfterLast()){
        if(c.getString(c.getColumnIndex("name"))!= null){
            dbString += c.getString(c.getColumnIndex("name"));
            dbString += "\n";
        }
    }
    c.close();
    db.close();
    return dbString;
}

//Print out database as String
public String dbToBioString(){
    String dbString = "";

    SQLiteDatabase db = getWritableDatabase();
    String query = "SELECT * FROM " + TABLE_PERSONS + " WHERE 1";

    Cursor c = db.rawQuery(query, null);
    c.moveToFirst();

    while(!c.isAfterLast()){
        if(c.getString(c.getColumnIndex("bio"))!= null){
            dbString += c.getString(c.getColumnIndex("bio"));
            dbString += "\n";
        }
    }
    c.close();
    db.close();
    return dbString;
}

}

Right now I'm getting this error message

 Attempt to invoke virtual method 'java.lang.String DatabaseHelper.dbToNameString()' on a null object reference

I don't know if I'm storing my name & bio in the SQLite correctly. How to properly auto-store name & bio fields into the SQLite database until the entirety of the URL is read?