Below Sample code shows you how to download images from a url with progress in the notification bar.

Notification Access Download

package com.coderzheaven.customnotificationdownloaddemo;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;

import android.app.NotificationManager;
import android.content.BroadcastReceiver;
import android.content.ContentResolver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.provider.Settings;
import android.support.v4.app.NotificationCompat;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;

public class MainActivity extends ActionBarActivity {

	NotificationCompat.Builder mBuilder;
	NotificationManager mNotifyManager;
	int id = 1;
	String urlsToDownload[] = { "http://www.devoxx.be/wp-content/uploads/2014/10/android.png", "http://www.devoxx.be/wp-content/uploads/2014/10/android.png",
			"http://www.devoxx.be/wp-content/uploads/2014/10/android.png", "http://www.devoxx.be/wp-content/uploads/2014/10/android.png",
			"http://www.devoxx.be/wp-content/uploads/2014/10/android.png" };
	int counter = 0;
	private NotificationReceiver nReceiver;
	ArrayList<AsyncTask<String, String, Void>> arr;

	class NotificationReceiver extends BroadcastReceiver {
		@Override
		public void onReceive(Context context, Intent intent) {
			String event = intent.getExtras().getString(NLService.NOT_EVENT_KEY);
			Log.i("NotificationReceiver", "NotificationReceiver onReceive : " + event);
			if (event.trim().contentEquals(NLService.NOT_REMOVED)) {
				killTasks();
			}
		}
	}

	private void killTasks() {
		if (null != arr & arr.size() > 0) {
			for (AsyncTask<String, String, Void> a : arr) {
				if (a != null) {
					Log.i("NotificationReceiver", "Killing download thread");
					a.cancel(true);
				}
			}
			mNotifyManager.cancelAll();
		}
	}

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

		mNotifyManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
		mBuilder = new NotificationCompat.Builder(this);
		mBuilder.setContentTitle("Downloading images...").setContentText("Download in progress").setSmallIcon(R.drawable.ic_launcher);
		// Start a lengthy operation in a background thread
		mBuilder.setProgress(0, 0, true);
		mNotifyManager.notify(id, mBuilder.build());
		mBuilder.setAutoCancel(true);

		arr = new ArrayList<AsyncTask<String, String, Void>>();
		int incr;
		for (incr = 0; incr < urlsToDownload.length; incr++) {
			ImageDownloader imageDownloader = new ImageDownloader();
			imageDownloader.execute(urlsToDownload[incr]);
			arr.add(imageDownloader);
		}

		ContentResolver contentResolver = getContentResolver();
		String enabledNotificationListeners = Settings.Secure.getString(contentResolver, "enabled_notification_listeners");
		String packageName = getPackageName();

		// check to see if the enabledNotificationListeners String contains our
		// package name
		if (enabledNotificationListeners == null || !enabledNotificationListeners.contains(packageName)) {
			// in this situation we know that the user has not granted the app
			// the Notification access permission
			// Check if notification is enabled for this application
			Log.i("ACC", "Dont Have Notification access");
			Intent intent = new Intent("android.settings.ACTION_NOTIFICATION_LISTENER_SETTINGS");
			startActivity(intent);
		} else {
			Log.i("ACC", "Have Notification access");
		}

		nReceiver = new NotificationReceiver();
		IntentFilter filter = new IntentFilter();
		filter.addAction(NLService.NOT_TAG);
		registerReceiver(nReceiver, filter);

	}

	@Override
	protected void onDestroy() {
		super.onDestroy();
		killTasks();
		unregisterReceiver(nReceiver);
	}

	private void downloadImagesToSdCard(String downloadUrl, String imageName) {
		FileOutputStream fos;
		InputStream inputStream = null;

		try {
			URL url = new URL(downloadUrl);
			/* making a directory in sdcard */
			String sdCard = Environment.getExternalStorageDirectory().toString();
			File myDir = new File(sdCard, "DemoDownload");

			/* if specified not exist create new */
			if (!myDir.exists()) {
				myDir.mkdir();
				Log.v("", "inside mkdir");
			}

			/* checks the file and if it already exist delete */
			String fname = imageName;
			File file = new File(myDir, fname);
			Log.d("file===========path", "" + file);
			if (file.exists())
				file.delete();

			/* Open a connection */
			URLConnection ucon = url.openConnection();

			HttpURLConnection httpConn = (HttpURLConnection) ucon;
			httpConn.setRequestMethod("GET");
			httpConn.connect();
			inputStream = httpConn.getInputStream();

			/*
			 * if (httpConn.getResponseCode() == HttpURLConnection.HTTP_OK) {
			 * inputStream = httpConn.getInputStream(); }
			 */

			fos = new FileOutputStream(file);
			// int totalSize = httpConn.getContentLength();
			// int downloadedSize = 0;
			byte[] buffer = new byte[1024];
			int bufferLength = 0;
			while ((bufferLength = inputStream.read(buffer)) > 0) {
				fos.write(buffer, 0, bufferLength);
				// downloadedSize += bufferLength;
				// Log.i("Progress:", "downloadedSize:" + downloadedSize +
				// "totalSize:" + totalSize);
			}
			inputStream.close();
			fos.close();
			Log.d("test", "Image Saved in sdcard..");
		} catch (IOException io) {
			inputStream = null;
			fos = null;
			io.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {

		}

	}

	private class ImageDownloader extends AsyncTask<String, String, Void> {

		@Override
		protected Void doInBackground(String... param) {
			downloadImagesToSdCard(param[0], "Image" + counter + ".png");
			return null;
		}

		protected void onProgressUpdate(String... values) {
		}

		@Override
		protected void onPreExecute() {
			Log.i("Async-Example", "onPreExecute Called");
		}

		@Override
		protected void onPostExecute(Void result) {
			Log.i("Async-Example", "onPostExecute Called");

			float len = urlsToDownload.length;
			// When the loop is finished, updates the notification
			if (counter >= len - 1) {
				mBuilder.setContentTitle("Done.");
				mBuilder.setContentText("Download complete")
				// Removes the progress bar
						.setProgress(0, 0, false);
				mNotifyManager.notify(id, mBuilder.build());
			} else {
				int per = (int) (((counter + 1) / len) * 100f);
				Log.i("Counter", "Counter : " + counter + ", per : " + per);
				mBuilder.setContentText("Downloaded (" + per + "/100");
				mBuilder.setProgress(100, per, false);
				// Displays the progress bar for the first time.
				mNotifyManager.notify(id, mBuilder.build());
			}
			counter++;

		}

	}
}

“NLService” Class is the actual Notification Listener class that can hear events in your notification.
But before everything you need to be sure that, you have enabled notification access for your app.

package com.coderzheaven.customnotificationdownloaddemo;

import android.annotation.SuppressLint;
import android.content.Intent;
import android.service.notification.NotificationListenerService;
import android.service.notification.StatusBarNotification;
import android.util.Log;

@SuppressLint("NewApi")
public class NLService extends NotificationListenerService {
	private String TAG = this.getClass().getSimpleName();
	public static final String NOT_TAG = "com.coderzheaven.NOTIFICATION_LISTENER";
	public static final String NOT_POSTED = "POSTED";
	public static final String NOT_REMOVED = "REMOVED";
	public static final String NOT_EVENT_KEY = "not_key";

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

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

	@Override
	public void onNotificationPosted(StatusBarNotification sbn) {
		Log.i(TAG, "**********  onNotificationPosted");
		Intent i = new Intent(NOT_TAG);
		i.putExtra(NOT_EVENT_KEY, NOT_POSTED);
		sendBroadcast(i);
	}

	@Override
	public void onNotificationRemoved(StatusBarNotification sbn) {
		Log.i(TAG, "********** onNOtificationRemoved");
		Intent i = new Intent(NOT_TAG);
		i.putExtra(NOT_EVENT_KEY, NOT_REMOVED);
		sendBroadcast(i);
	}

}

Make sure you add the “services” in the AndroidManifest file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.coderzheaven.customnotificationdownloaddemo"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="22" />

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service
            android:name="com.coderzheaven.customnotificationdownloaddemo.NLService"
            android:label="@string/app_name"
            android:permission="android.permission.BIND_NOTIFICATION_LISTENER_SERVICE" >
            <intent-filter>
                <action android:name="android.service.notification.NotificationListenerService" />
            </intent-filter>
        </service>
    </application>

</manifest>

You can download the complete source code from here..

 

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