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PhoneGap 1.8 with Urban Airship

I've been doing some iOS coding using phonegap and JQuery Mobile. It's a great combination and means I can develop for iOS without having to touch ObjectiveC, a language frankly made of evil.

Wanting to be able to do push notifications, a quick google pointed me to this post on using urban airship. However, the articles incomplete, and it's for a very old version of phonegap. About 8 million googles, some pathetic attempts at attempting to understand objective C, and I got it all working together nicely. I thought I'd blog about the experience of how to get it up and running, so anyone else banging their head against a brick wall can save themselves 4 hours of pain.

1) Download SACordova

This is the basic template for push notifications and should be enough to get you going. It's fine if you're wanting to introduce push to an existing app, you'll still need the code from this app. The original code was by PhoneGap/Airship, and is in the link above. This was then adapted for 1.5 by HMKang . All I've done is update it for 1.8. All the instructions are still valid;

- Overwrite your AppDelegate.h and AppDelegate.m with the ones from the project

- Add PushNotification.m and PushNotification.h to you plugins folder

- In Cordova.plist, add pushnotification/PushNotification to the plugins list:

- Paste the index.html and PushNotification.js into your www folder. You can pick and choose which bits of index you need, but I recommend just using the whole thing to start (I burnt a fair amount of time trying to be clever. I really should stop doing that).

You should now be set up except for your keys.

Apple & Urban Airship

Truely it is not an understatement to say that apple don't make it easy. You need a push certificate to be able to do push notifications. You can follow most of the instructions on the original phonegap tutorial for this, but just wanted to put in some gotchas.

- Generate a new CSR!! If you've got previous apps, it's tempting to use that cert but you can't. You must generate a new one from your Keychain Access.

- When I first attempted to export to a p12 it wasn't available as an option. I exported as a PEM, but then airship complained the private key wasn't available. A Quick google indicates that the cert was somehow corrupted. Basically, just go back, revoke your cert and re-generate it. In your keychain, you should be able to see a key underneath it, like below:

The private key name should match whatever you put in your CSR request. You should now be able to generate your p12 file.

Over to the airship

Go, sign up etc. When creating a new app, put your p12 in and your password. All should be well in the world.

Now the important bit. Plonk your application Key and Secret at the top of AppDelegate.m (keep the URL the same)

Pulling it all together

One last thing! You need to add '*.urbanairship.com' to your externals hosts. Else it can't contact the server.

Run the app on a device (emulators don't work!), and hit the button. You should get a nice pop up asking for permission to do push notifications. If it doesn't work, check the logs in xcode. I hit:

didFailToRegisterForRemoteNotificationsWithError:Error Domain=NSCocoaErrorDomain Code=3000 "no valid 'aps-environment' entitlement string found for application"

This is another one you'll hit if you've done an app before. You need to ensure you have a provisioning profile set up for your new application. Head over to the apple dev site again, and create and download a new provisioning profile. Drag and drop it into xcode. Now run it. Victory! (I hope).

When creating this, I did not have victory. I've been bashing my head trying to fix it. I've done all the fixes, which basically mean deleting provisioning profiles, regenerating them etc.

To save yourself an hour, ENSURE YOUR PROVISIONING PROFILE matches your full app ID, e.g.

XXXXX.com.yourname.app.

I'd just done

XXXX.app.

IF you do this, regenerate your App, do all the cert stuff again, reupload to urban airship, and all will be well!

New project: lastband.in

As someone who's mildly addicted to music, I spend a lot of time trying to find new music. For me, that often involves looking through my last.fm recommended artists list and trying to find the artist on emusic.co.uk, a website I get a lot of my music from.

However, recently a lot of my recommendations have been either new bands, or not available on emusic. As a result I've been checking out bandcamp.com more and more; If you've not used it, it's basically what myspace should have been: Unobtrusive ads, no blogs, just music, and a great interface. In the modern culture of giving music away, a lot of bands have been putting their records up for free, or pay-what-you-want, so it's a great way to find music on the cheap if you're struggling to justify dropping £6 on an album.

Being a big geek, I started looking into the APIs, and discovered that both last.fm and bandcamp had APIs, and so put together lastband.in. The original intent was for it to look up your recommended artists from last.fm, however I had issues with the authentication API so decided to roll with just the open APIs, which I think actually works better as a way of discovering music, particularly as it doesn't mandate having a last.fm account.

It's been a fun crash course in javascript (who knew a language could be worse than flex/actionscript!), and although I had grand plans to add support from other APIs in I think it will remain as-is for now. The eMusic API I wanted to add has severe call throttling and whilst it's possible to work around, it won't provide a good user experience. I'd like to add the price per album too, but the bandcamp API is very immature currently. IF they expand it then perhaps I'll do some more work on it.

For now, it's getting a few hits per day, and I'm using it myself to great effect, so overall I'm happy with the outcome.

Spring Integration: Dropping Messages

Spring Integration is a great little framework for taking the sting out of working with JMS, particularly if you like programming in XML ala Spring. Whilst it does have a comprehensive guide, and forums, if you dare to spread out from the Path Of Happiness, then you can often get into trouble.

A prime example of this; In the system I'm working on, we have RPC implemented over the top of Spring Integration. A message comes in, we process it, and return it. Spring Integration kindly takes 95% of the workload from this. However, we were intermittently losing messages. using a jms:inbound-gateway, Calls would be processed off the queue, go through our code, and then be lost in a magical ether of nothingness. As can often be the case, google came up with no rescue.

The answer? reply-timout. This little attribute, is used to ensure the gateway doesn't get blocked by waiting for a null response in the case that null responses are allowed. From the docs:

If a component downstream returns 'null' and no reply-timeout has been configured, the Gateway method call will hang indefinitely unless: a) a reply-timeout has been configured or b) the requires-reply attribute has been set on the downstream component (e.g., service-activator) that might return 'null'. In this case, an Exception would be thrown and propagated to the Gateway.

However, it turns out it's actually defaulted to 1 second. This means if your processing isn't quick, then your message is going to disappear. This wouldn't be so much of an issue, but there is absolutely no logging whatsoever to indicate this. So, if you're missing messages, keep your eyes out for this one. Either set it high, or set it to 0 which will have infinite time out (but be careful if you're in a synchronous env, as you could get blocked via null responses. Check out 7.2.3 of the documentation )

Android: Am I connected to the internet?

Easy way to find out!

private boolean connectedToInternet() { ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); NetworkInfo activeNetworkInfo = cm.getActiveNetworkInfo(); return activeNetworkInfo != null && activeNetworkInfo.isConnectedOrConnecting(); }

#Android

Threading in Android

So, Threading; Fairly sensible you'll be wanting to do some of it in your app if you're doing anything vaguely complex. Turns out you definitely need to do it when doing complex stuff, so as not to hog the UI thread.

As someone who doesn't come from a swing background, this hadn't been as obvious as it probably is to some of you. Now, you're all capable of threading, however, it turns out you can't do that on android!

the Android UI toolkit is not thread-safe and must always be manipulated on the UI thread.

Fortunately Androids got your back with AsyncTask. You can read all about it in lovely googleydetail on this googlepage. However, there are so, so many gotchas it's like Noel's house party. And hence I thought I'd try and share some of them with you.

Never, ever call doInBackground() manually. A lot of the doc isn't clear about this (particularly if you're a skim-googler like me). Android calls it for you, in the background (hence the entire point of AsyncTask). Just call the execute() method.

If you're trying to do things UI related, such as kill dialogs, or start intents, you may find it doesn't function, or you get a runtime error, or you'll get strange things happening such as progress dialogs not spinning. You need to use the preExecute() and postExecute() for all these things: They're executed in the UI Thread!

You'll discover this quickly: You can't launch an AsyncTask from an AsyncTask. Chances are if you were trying to do this you'll be able to find an alternate way to do this, you just need to put a bit more thought into your design.

There's plenty of other ones, but unfortunately I keep forgetting to blog on the go. I'll update as I hit more myself!

#Android #Threading

Android Data Services

One of the most common things people need to do in Android is to call remote services. It's not a particularly difficult task, and one of the few things that actually has some documentation around it!

However, for those who don't want to look massively into this, I thought I'd provide my utility class. Should make things nice and easy to pull data in!

If you've any comments or suggestions let me know.

package com.samatkinson.android; import java.io.IOException; import java.io.InputStream; import java.net.MalformedURLException; import java.net.URL; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.FactoryConfigurationError; import javax.xml.parsers.ParserConfigurationException; import org.w3c.dom.Document; import org.xml.sax.SAXException; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import com.samatkinson.android.exception.AndroidRemoteCallException; public class RemoteServiceCall { public static Document getRemoteXml(String url) throws AndroidRemoteCallException { Document document = null; InputStream stream = getRemoteInput(url); try { document = DocumentBuilderFactory.newInstance() .newDocumentBuilder().parse(stream); } catch (SAXException e1) { throw new AndroidRemoteCallException("Error parsing result Data", e1); } catch (IOException e1) { throw new AndroidRemoteCallException( "Error connecting to remote service", e1); } catch (ParserConfigurationException e1) { throw new AndroidRemoteCallException("Parser Config", e1); } catch (FactoryConfigurationError e1) { throw new AndroidRemoteCallException("Error creating factory", e1.getException()); } return document; } public static Bitmap getRemoteBitmap(String url) throws AndroidRemoteCallException { InputStream is = getRemoteInput(url); return BitmapFactory.decodeStream(is); } private static InputStream getRemoteInput(String url) throws AndroidRemoteCallException { URL feedUrl = null; InputStream stream = null; try { feedUrl = new URL(url); stream = feedUrl.openConnection().getInputStream(); } catch (MalformedURLException e2) { throw new AndroidRemoteCallException("Value " + url + " is malformed URL", e2); } catch (IOException e1) { throw new AndroidRemoteCallException( "Error connecting to remote service", e1); } return stream; } }

The custom exception is nothing special, just a simple extension of Exception. You may want to implement better error handling, but you get the idea.

#Android #Samples

Stub XML Data in android

I'm currently working on a personal Android project. Like many, it relies on a web API, which returns data in an XML Format. Traditionally, to build a translator I take an example XML result as stub data, then create a translator for it. This allows quick easy testing without worrying about the web connection. (Preferably I'd TDD the translator, but stub data is always useful in development.

I'm also a huge fan of Dependency Injection. It reduces coupling, allows easy switching around of implementations (again, great for stubbing), and is just plain good. I've been using RoboGuice on my projects, an android specific variant on Google Guice, google's DI framework. It's very nice, and is great for those who don't like to program in XML (Hello Spring :) ).

However, I've been wracking my brains for days on getting XML injected. I've created a stub XML file under the res/xml folder where it should live, and then attempted to use DI as so:

@InjectResource(R.xml.myxml) public Object xml;

However, I was consistently hit with runtime exceptions: It can't inject a null value unless labelled with @nullable. So, why is it null?

So, having tested around the subject, and done almost everything I could think of, I have come this conclusion: XML is special in android; You can only access it using the special Resources.getXml(), which gives an XmlResourceParser. Now, from what I can tell via google, this is used almost exclusively used for file based XML: Not remote services. To make the stub data useful, it must be parsed in the same way as the remote service.

So, what is the solution? One of the most read articles on working with XML services in android is this one from IBM. It shows how to pull remote data as an InputStream, which in turn can be used to create an XML Document via a DocumentBuilder, leading nicely to this code:

InputStreamReader inputReader = null; InputStream openRawResource = resources.openRawResource(R.raw.myxml); inputReader = new InputStreamReader(openRawResource); Document document = null; try { document = DocumentBuilderFactory.newInstance().newDocumentBuilder().parse(openRawResource); } catch (SAXException e1) {

By placing the xml file in the raw folder, and treating it as a raw resource, we can access it using the openRawResources method. This allows you to treat xml as the same irrelevant of where it's from.

Apologies if any of my assertions about android are incorrect, please let me know if this it's a case. Just wanted to post this to hopefully save someone hours of going crazy!

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