Crash no OutputStream

package com.eu.app.link;

import android.widget.TextView;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;

public class HttpPost {

    public boolean doLogin(String login, String senha, TextView textview) throws MalformedURLException, IOException {

        //link de envio
        String link = "http://meuserver.com.br/blabla.php";
        URL url = new URL(link);

        //prepara dos dados para serem enviados
        String data = URLEncoder.encode("login", "UTF-8") + "=" + URLEncoder.encode(login, "UTF-8");
        data += "&" + URLEncoder.encode("senha", "UTF-8") + "=" + URLEncoder.encode(senha, "UTF-8");

        URLConnection connection = url.openConnection();
        connection.setDoOutput(true);

        OutputStream os = connection.getOutputStream();
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
        writer.write(data.toString());

        writer.close();
        os.close();

        BufferedReader in = new BufferedReader( new InputStreamReader(connection.getInputStream()));
        String decodedString;
        while ((decodedString = in.readLine()) != null) {

            textview.setText(decodedString);

        }in.close();

        return false;

    }

}

OutputStream os = connection.getOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
writer.write(data.toString());