Android Volley Tutorial

Volley is an android library released by Google that can make your life easier when dealing with network operations. In this blog post I will mention the main features of the library and show a few example usages, in particular, how to make a request, how to download images, and how to use the cache.

Features of Volley library

a) Automatically schedules the network requests

b) Supports request prioritization. This means that you can load content depending of priorities, for example the main content could have a high priority, but the images a low priority.

c) Provides transparent disk and memory cache that allows for quick reloading of data. Transparent cache means that the caller doesn’t have to know about the existence of the cache. That is, the cache is implemented automatically. You do, however, have the possibility to disable the caching.

d) Provides a good API for canceling requests. You can cancel a single request, or cancel requests depending on some filters.

Besides the great features that Volley comes with, you don’t have to use it for everything. Volley is great for RPC-style network operations that populate UI, a typical example would be loading thumbnail images into a ListView, but not very good for streaming operations like downloading a video or mp3.

Getting started with Volley

1. Clone the Volley project:
git clone
2. Import the library into your project

The most frequent classes of Volley that you will work with are RequestQueue and Request, and ImageLoader when dealing with images loading.

RequestQueue is used for dispatching requests to the network. It is recommended to create it early and use it as a Singleton.
Request is the base class for creating network requests (GET, POST).
ImageLoader is a helper class that handles loading and caching images from remote URLs.

Step 1:

As recommended, lets create first a Singleton class that will return on demand an instance of RequestQueue and one of ImageLoader.

public class VolleySingleton {

    private static VolleySingleton instance;
    private RequestQueue requestQueue;
    private ImageLoader imageLoader;

    private VolleySingleton(Context context) {
        requestQueue = Volley.newRequestQueue(context);

        imageLoader = new ImageLoader(requestQueue, new ImageLoader.ImageCache() {
            private final LruCache<String, Bitmap> cache = new LruCache<String, Bitmap>(20);

            public Bitmap getBitmap(String url) {
                return cache.get(url);

            public void putBitmap(String url, Bitmap bitmap) {
                cache.put(url, bitmap);

    public static VolleySingleton getInstance(Context context) {
        if (instance == null) {
            instance = new VolleySingleton(context);
        return instance;

    public RequestQueue getRequestQueue() {
        return requestQueue;

    public ImageLoader getImageLoader() {
        return imageLoader;
Step 2: Add internet permission
<uses-permission android:name="android.permission.INTERNET" /> 
Step 3: Create an instance of RequestQueue
RequestQueue queue = VolleySingleton.getInstance(this).getRequestQueue();
Step 4: Create the request

Volley comes with a class called JsonRequest that you can use to make requests to a server that returns a json response.
However, in this example we will query an RSS feed which returns a response in XML format. Volley does not include a similar class for handling xml responses, like JsonRequest, but it has StringRequest class that can be used to retrieve the response body as a String.

There are two ways to construct a StringRequest:

StringRequest(int method, String url, Listener<String> listener,
            ErrorListener errorListener)


StringRequest(String url, Listener<String> listener, ErrorListener errorListener)

The second constructor does not take the request method as a parameter, when not specified, a GET request is created.

Listener is a callback interface for delivering the result, and
ErrorListener is a callback interface for delivering error responses.


String url = "";
StringRequest request = new StringRequest(url, new Listener<String>() {

            public void onResponse(String response) {
                // we got the response, now our job is to handle it 
        }, new ErrorListener() {

            public void onErrorResponse(VolleyError error) {
               //something happened, treat the error.
Step 6: Execute the request

And that is all! The execution of the request implies its addition to the RequestQueue.

Step 7: Loading thumbnail images

Loading images can be done easy if you replace the android’s ImageView with Volley’s NetworkImageView:

        android:src="@drawable/default_placeholder" />

then use setImageUrl() and you are done!

String url = "..."; // URL of the image
ImageView imageView = (ImageView)view.findViewById(;
ImageLoader imageLoader = VolleySingleton.getImageLoader(); 
imageView.setImageUrl(url, imageLoader); 

If, for some reason, you don’t want or can’t use NetworkImageView, then there’s an alternate method.
You can use the get() method of ImageLoader class which accepts the image url and an instance of ImageListener:

ImageLoader imageLoader = VolleySingleton.getImageLoader(); 
imageLoader.get(url, new ImageListener() {
            public void onErrorResponse(VolleyError error) {
                imageView.setImageResource(R.drawable.icon_error); // set an error image if the download fails
            public void onResponse(ImageContainer response, boolean arg1) {
                if (response.getBitmap() != null) {
Reading from cache

One of the Volley’s features is that it provides transparent disk and memory cache. The cache is implemented automatically for classes that extends Request, such as JsonRequest and StringRequest.

To read the cache:

Entry entry = queue.getCache().get(url);
     String data = new String(, "UTF-8");
     // process data

To turn off the cache:


to remove the cache for a specific request:


to clear all cache:


to invalidate the cache: this will allow to display the cached data until the response is received. When the response is received, it will automatically override the cached data.

queue.getCache().invalidate(url, true);

For more details about Volley you can watch the full video at:

Google Maps API V2 Android Tutorial

In this tutorial we will walk through the process of integrating Google Maps API V2 into an Android project.

(Source code available on GitHub)

Android Google Maps API V2

The necessary steps in order to integrate the Google Maps V2 are :

1. Install Google Play services

The version 2 of Google Maps now is part of the Google Play services SDK, that is why google-play-services lib should be installed first.

Start the Android SDK Manager and choose to install Google Play services from the Extras category:
android sdk manager

After the sdk manager completes the installation, go to <android_sdk_folder>/extras/google/google_play_services/libproject and copy the google-play-services_lib to the location where you maintain your Android projects.

Then import the library project into your workspace, and reference it in your Android project.

2. Get the Google Maps API Key

In order to use Google Maps API in your project you need a valid Google Maps API key. The key can be obtained via the Google APIs Console. You will have to provide the SHA-1 fingerprint and the package name of your application.

Please note that if you already hold a map key from the Google Maps Android V1, also known as MapView, you still will need get a new API key, as the old key won’t work with the V2 API.

2.1 Generate SHA-1 certificate fingerprint

To display the SHA-1 fingerprint, first you need to decide for what type of certificate do you need to generate the fingerprint: for the debug certificate, or for the release certificate.
In this example we well consider displaying the fingerprint for the debug certificate.

The file name of debug certificate is called debug.keystore, and it is located on C:\Users\your_user_name\.android\ on Windows, and on ~/.android/ on Linux.

If you are on a Linux, open the terminal and run the following command:
keytool -list -v -keystore ~/.android/debug.keystore -alias androiddebugkey -storepass android -keypass android

If you are on a Windows, open the command prompt and run this:
keytool -list -v -keystore "%USERPROFILE%\.android\debug.keystore" -alias androiddebugkey -storepass android -keypass android

Copy the SHA1 fingerprint and store it somewhere for later use.
android sha1 certificate fingerprint

(Note that if the command prompt complains that keytool is not a recognizable command, you can find it your java JDK/bin folder. cd there and run the command from that folder.)

2.2 Create an API Project

Navigate to Google APIs Console and create a new project, if you haven’t used Google APIs Console before. Then click on the Services link from the left menu:
google services

and from the presented list of of services toggle Google Maps Android API V2:
google maps android api v2

(Please make sure you namely select “Google Maps Android API V2”, not Google Maps API v2, nor Google Maps API v3)

2.3 Obtain an API Key

a) From the left menu click on API Access
b) Then click on Create New Android Key
c) In the resulting dialog, enter the SHA-1 fingerprint, followed by a semicolon, and then your application package name.
For example:

As a result the page displays a new section entitled Key for Android apps (with certificates), followed by your API key that looks something like this:

2.4 Add the API key to AndroidManifest file

Open the AndroidManifest file and add the following element as a child of application tag:


replacing the YOUR_API_KEY with your real API key.

3. Update the AndroidManifest file with other settings

In order to use Google Maps Android API we need to declare a few permissions and specify that the application requires OpenGL ES version 2:

<manifest xmlns:android=""
    //... >

        android:required="true" />

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
4. Display a MapFragment

Displaying the maps is as simple as declaring a fragment in the xml layout with the name
If you would like to make your application compatible with older devices, then you’ll have to use the Android Support Library and reference SupportMapFragment instead of MapFragment. The below example uses the Android Support Library.

The activity_main.xml layout:

<fragment xmlns:android=""
    android:name="" />

and the

public class MainActivity extends FragmentActivity {

	protected void onCreate(Bundle savedInstanceState) {

If everything was configured correctly, then when running this example you should see a map.

Full source code can be downloaded from GitHub:

Your Google Play Publisher Console has been terminated, because of Copyright infringement..

This morning I found an email in my inbox that looked like this:
fake email google console
The first impression was like “What?!”. It’s true that recently Google Play Developer Policies were modified, and I heard stories from developers who had their accounts terminated because of violations of content policy. So in the current context this email seemed like true.

However, after a closer examination I noticed a few suspect things.
1. Firstly, the email address was too suspicious to believe that it is from Google.
2. Secondly, the email was sent not only to me, but to a list of people.
3. All the links appearing in the email pointed to the same and one url.
4. And lastly, the real urls were masked behind URL Shortener, which again I found it suspicious.

So I opened one of the links in the email in a private window, and the following page was displayed.
The google Sign in box, the text that appears in the page, and the color scheme, makes it appear as something known for an Android developer.
However if you take a closer look at the page url, you may notice that the page is not hosted on Google servers, but on some address, savegaselectricity(dot)com. Also, it has a parameter named “continue” with the real google play page as value. Probably after successfully logging, to redirect you to real Google Play Developer Console page, so you won’t see notice anything strange.

The technique used by the attacker in fact is not new, it is one variation of impersonation attacks, where an attacker impersonates a legitimate site, tricking the users to log in and stealing their passwords.

So, if you will receive such an email, delete it, your google play account most probably is ok. If however you already used the fake page to login, change your password immediately.

As a rule of thumb, always be skeptical.
Do not click on links, download files or open attachments in emails from unknown senders. If you get one of these emails and are worried that there may be a real problem with your account, open up a new browser window, go directly to your Developer Console site and sign in there.

Using Custom Fonts in Android

By default Android comes with three standard fonts: Droid Sans (default font), Droid Serif, and Droid Sans Mono. They all can be applied to any view that supports styling, such as TextView, Button, by specifying the “android:typeface” attribute in the XML declaration with any of these values: sans, serif, monospace.

   android:typeface="sans" />

   android:typeface="serif" />

   android:typeface="monospace" />

android standard fonts


Using custom fonts in Android is pretty straightforward. First find a free font and put it in the assets/fonts directory. (It’s not mandatory to have a /fonts directory, but if I have a lot of stuff in the /assets directory I organize them in separate directories). Then get a reference to your TextView and create a Typeface object specifying the font path. Lastly, apply the typeface to the TextView.

In this particular example I used the font: christmaseve.ttf

TextView textView = (TextView) findViewById(;
Typeface tf = Typeface.createFromAsset(getAssets(), "fonts/christmaseve.ttf");

android custom fonts


RuntimeException: Native typeface cannot be made

If you get this exception while trying to integrate the custom font into your application, make sure the path to the font file is correct, and the font name is spelled correctly. I noticed I was getting this exception when my font path was misspelled, for example writing “.tff” instead of “.ttf”, or forgetting to add the “fonts/” prefix to the path.

Custom font used in this example provided by:

Integrating Google Analytics SDK (V2) with Android

The Google Analytics SDK for Android makes it easy for developers to collect valuable statics about how the users are using their app.

Here are some features that Android Google Analytics SDK offers:

  • The number of active users that are using the application
  • Usage of specific features
  • The number and type of application crashes
  • From where in the world the application is used
  • And many other useful metrics.

Just to illustrate the integration process lets create a simple proof of concept application with 2 activities: MainActivity and AboutActivity, and 2 buttons: Rate and Share.

Our mission is to integrate Google Analytics SDK with the application, to:

  • track activity views, (MainActivity and About)
  • track events (how many times the buttons “Rate”, and “Share” are clicked)

android google analytics sdk

If you are searching for Google Analytics I’m assuming you are already pretty familiar with Android and could create the proof of concept application yourself, so I will skip this step and concentrate solely on integration.


1. Downloading the SDK

Go to downloads page and download Version 2.0. Extract the archive and add libGoogleAnalyticsV2.jar to your project’s /libs directory.

At the moment of writing this post, Google provides two versions: version 1.5.1 (legacy), and version 2.0 beta. Still if the Version 2 of SDK is beta, I highly suggest you choose this version, over the 1.5.1 (legacy).
The reason not to choose SDK 1.5.1 is that it uses a tracking model that is designed to track visitors to traditional websites and interaction with widgets in traditional web pages.

The new “App” profiles and reports will only accept data from version 2 or higher of the SDK.


2. Creating a Google Analytics account

Before starting to use the SDK you first must create an account at:

  1. Sign in to your account.
  2. Click Admin.
  3. Click Account list (just below the menu bar)
  4. Click +New Account
  5. When asked what you would like to track, select App app profile
  6. Enter all the necessary information and click Get Tracking ID.

Now that you have a Tracking ID, you can begin the integration with the application. The first step is to update the AndroidManifest file.


3. Updating AndroidManifest file.

Add folowing permissions to the AndroidManifest file:

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


4. Creating the analytics.xml file

In version 2 of Google Analytics SDK for Android, the tracking settings are managed from an xml resource file called: analytics.xml. You will need to create this file in res/values directory, and add your tracking ID as well as other settings here.

<?xml version="1.0" encoding="utf-8"?>

   <!-- Replace placeholder ID with your tracking ID -->
   <string name="ga_trackingId">UA-00000000-0</string>

   <!-- Enable Activity tracking -->
   <bool name="ga_autoActivityTracking">true</bool>

   <!-- Enable debug -->
   <bool name="ga_debug">true</bool>

   <!-- The screen names that will appear in your reporting -->
   <string name="com.testgoogleanalytics.MainActivity">MainActivity</string>
   <string name="com.testgoogleanalytics.About">About</string>

   The inverval of time after all the collected data
   should be sent to the server, in seconds.
   <integer name="ga_dispatchPeriod">30</integer>



5. Tracking activities.

To track activities add the tracking methods to the onStart() and onStop()  of each of your activities.

// Example of tracking MainActivity
public class MainActivity extends Activity {
   public void onCreate(Bundle savedInstanceState) {

   protected void onStart() {
      EasyTracker.getInstance().activityStart(this); // Add this method

   protected void onStop() {
      EasyTracker.getInstance().activityStop(this); // Add this method

One thing to note here is that EasyTraker requires a context before you can use it. If you attempt to call any of its methods but did not pass first a context, you may end up with an IllegalStateException.

In the above example, in  the onStart()  and onStop() methods the context is passed as an argument to activityStart() and activityStop(), but  if you need to make EasyTracker calls in other classes or methods, you’ll need to call EasyTracker’s setContext(Context context) method first:

Context context= this;  // Get current context.
EasyTracker.getInstance().setContext(context);  // Set context
// EasyTracker is now ready for use.


6. Tracking events

Tracking events is just as easy as tracking activities, you just need a Tracker object and call the trackEvent(String category, String action, String label, int value) method.

public class MainActivity extends Activity {

   private Tracker tracker;

   public void onCreate(Bundle savedInstanceState) {

      // Set context
      // Instantiate the Tracker
      tracker = EasyTracker.getTracker();

      // Add tracking functionality to "Rate" button
      Button rate = (Button) findViewById(;
      rate.setOnClickListener(new OnClickListener() {
         public void onClick(View arg0) {
            // The rest of your code
            tracker.trackEvent("Buttons Category", "Rate", "", 0L);

      // Add tracking functionality to "Share" button....

In this particular example I don’t need a label nor a value, that is why I set for the last 2 parameters of trackEvent() method, an empty string a 0 (zero), but depending of your needs you may populate them with some data.


7. Debugging

Debugging helps you deal with troubleshooting, and make you sure that the data actually is sent to the server. To set the Google Analytics in debug mode, add the following setting in the analytics.xml

<bool name="ga_debug">true</bool>

Once your are in debug mode, you can watch the log information in LogCat:


Waiting for the big moment!

If everything is configured correctly, the reports should appear on live. Usually it takes about 24 hours to see the data in your account.

android actions google analytics



What happens if my application is used when no network is available?

Just in case you asked this yourself…, all the events are persisted in a local storage, and they will be sent the next time your app is running and dispatch is called.


Last but not least

One important thing not to be forgotten: you must indicate to your users, either in the application itself or in your terms of service, that you reserve the right to anonymously track and report a user’s activity inside of your app.

Android Google Analytics SDK offers more than tracking activities and events, see: to get the most out of it.

Please visit the Android Tutorials page for more tutorials.

Android Asset Studio – The easiest way to create icons for your android apps!

Android asset studio

Android Asset Studio is an online utility that lets you generate all kind of icons you may need for your android applications, starting with launcher icons, action bar and tab icons, notification icons, and menu icons. It even includes a simple 9-patch generator allowing you to create 9-patch images.

One of the trickier parts when creating the icons is that you should create them for all kinds of resolutions: ldpi, mdpi, hdpi, and xhdpi. With Android Asset Studio this is as simple as uploading an image. The tool generates automatically for you all the versions of the icon under all resolutions, and make them available as a downloadable zip archive.

The icons may be generated from an image uploaded, or from a clipart library, or from text. It’s a very convenient tool and I highly recommend using it if you want to have professional, good looking icons on all resolutions.

Android – [APP] Amazing Drunk Detection Scanner

Ready to go to party? Then don’t forget to put Amazing Drunk Detection Scanner in your pocket!

Drunk Detection Scanner is a simple application that helps you make fun with your friends. Make fun of your best friends by scanning their eye, and determine how drunk are they!

Here is how the prank works:
1. Just in the middle of the party open the Drunk Detection Scanner and say something like “Alright gentlemen, time to do some analysis!”
2. Invite one of your friends and tell him that this app will reveal how drunk he is.
3. Aim the camera close to your friend’s eye
4. Focus
5. Press “Start Scanning”
6. Wait till the result is calculated
7. Have fun!

Amazing Drunk Detection Scanner is a simple application designed for entertainment purposes only. It does not encourage the consumption of alcohol, and it does not take any legal responsibility.

android drunk detection scanner