servicio de Android HttpURLConnection descargar datos de red

import android.app.Notification;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Intent;
import android.os.Bundle;
import android.os.Handler;
import android.os.IBinder;
import android.os.Message;
import android.widget.ImageView;
import android.widget.Toast;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class DownloadService extends Service {
    public static final String URL_PATH = "DownloadService_URL";
    private Notification.Builder notificationBuilder;
    private NotificationManager notificationManager;
    private ImageView imageView;
    private Handler handler = new Handler(){//消息队列，下载完成后发送消息通知下载完成
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if(msg.what ==1){
                stopSelf();
                Bundle bundle = msg.getData();
                byte[] data= bundle.getByteArray("data");
                Toast.makeText(getApplicationContext(), "下载完成" + data, Toast.LENGTH_LONG).show();
            }
        }
    };
    public DownloadService() {
    }
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        //定义一个通知显示下载进度。
        notificationManager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        notificationBuilder = new Notification.Builder(getApplicationContext());
        notificationBuilder.setSmallIcon(R.drawable.nav_task).setTicker("下载").setContentTitle("加载网络数据").setContentText("正在加载中…").setAutoCancel(true);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        final String PATH = intent.getStringExtra(URL_PATH);
        new Thread(new Runnable() {
            @Override
            public void run() {
                HttpURLConnection connection = null;
                ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();
                int len = 0;
                int len_data = 0;
                byte[] data = new byte[128];
                try {
                    URL url = new URL(PATH);
                    connection = (HttpURLConnection) url.openConnection();
                    connection.setRequestMethod("GET");//请求模式
                    connection.setConnectTimeout(8000);//连接等待时间
                    connection.setReadTimeout(8000);//读取等待时间
                    InputStream inputStream = connection.getInputStream();
                    int len_long = connection.getContentLength();
                    while ((len = inputStream.read(data)) != -1) {
                        arrayOutputStream.write(data, 0, data.length);
                        len_data += len;
                        int progress_value = (int) ((len_data / (float) len_long) * 100);// 进度条刻度计算
                        notificationBuilder.setProgress(100, progress_value, false);
                        notificationManager.notify(1000, notificationBuilder.build());
                    }
                    notificationBuilder.setContentText("下载完成!");
                    notificationManager.notify(1000, notificationBuilder.build());
                    Bundle bundle = new Bundle();
                    bundle.putByteArray("data",arrayOutputStream.toByteArray());

                    Message msg = new Message();//下载完成后将下载的数据通过Message发送到消息队列
                    msg.setData(bundle);
                    msg.what = 1;
                    handler.sendMessage(msg);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }).start();
        return START_REDELIVER_INTENT;
        //返回值代表了如果服务被系统杀死后启动的方式
        //START_REDELIVER_INTENT：系统在onStartCommand()返回后杀死了服务，则将重建服务并用上一个已送过的intent调用onStartCommand()。
    }


    @Override
    public void onDestroy() {
        super.onDestroy();
    }
}