Archive for the ‘code’ Category

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Using MQTT in Android mobile applications

Tuesday, February 1st, 2011

Overview

How to receive push notifications using MQTT in an Android mobile application

Background

I’ve written before about MQTT as a technology for doing push notifications to mobile. When I wrote that, I gave an example Android project. However, it was the first time I’d ever done Android development, and while it was an okay Java MQTT sample, it was a poor Android sample – I didn’t know anything about how Android works as a platform.

I’ve since written other Android MQTT apps, such as a hackday app for pushing updates from websites to your phone and learnt a lot about how to do it properly. Well… if not properly, at least a little better.

But Google is still directing people to my old, and probably unhelpful, sample. So it’s about time that I share something more useful.

I’ve put the full source for a sample implementation below. (Note that I’m using the Java J2EE client library from ibm.com). Hopefully the comments in it are clear enough, but here are a few of the key points.

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Posted in code | 68 Comments »

An API for twitter hashtags for TV programmes

Friday, December 31st, 2010

Overview
Hacking together an API that returns commonly-used hashtags for the programme you’re watching on the TV

Background
tweets on TVLast April, I wrote a quick-and-dirty Python script that displays tweets for a given hashtag on my TV screen so that I could follow the twitter backchannel about a programme that I watched.

Considering that it was a random idea that was hacked together in a few minutes, I’ve used it a lot since then: it’s made watching a bunch of programmes much more entertaining – Eurovision is probably the best example (the commentary on twitter is hysterical), but there are many others.

But I never made any changes to the script since I first wrote it. If I’m watching something on TV that I know has a hashtag, I ssh to my set-top box and run my hashtags script, giving it the hashtag to filter on in the command.

I was thinking – it’d be much better if it was all automatic. It’d be better if my set-top box automatically showed tweets with the hashtag for whatever programme I’m watching.

To do this, I needed some way of knowing what was the right hashtag for the programme currently on a given TV channel. I could’ve hacked this into my existing script, but I thought it might be a feature that people might find other uses for, so instead I’ve made a stand-alone thing, available as a web-service.

What it does
I’ve made a web feed that returns a blob of either JSON or XML. You can get either:

  • the commonly-used hashtag for the programme currently on a specified channel (e.g. “what is the hashtag for the programme that’s on BBC 1 now?”)
  • the next programme on TV that has a commonly-used hashtag (e.g. “what are the next five programmes on TV that have hashtags?”)

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Posted in code | 7 Comments »

Programmatically identifying DVDs by their barcodes from Android

Thursday, December 30th, 2010

Overview

A few Android code snipperts for how to identify a DVD by it’s barcode

Background

In November, I wrote a simple Android app that lets me add films to my LOVEFiLM list by taking a photo of a movie poster.

It also works by taking a photo of the front of a DVD case, as the DVD covers are essentially mini-posters. But a few people pointed out that using image recognition for the front of a DVD case is overkill, when DVD cases have a machine-readable barcode printed on them.

So I spent an evening adding the ability to scan barcodes to the app – and now you can add to your LOVEFiLM list either by photos of posters or barcodes.

I thought I’d quickly share how I did it, in case it’s useful to anyone else.

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Making YouTube (very slightly) more child-safe with a Firefox extension

Tuesday, November 16th, 2010

Kids stuff on YouTubeOur six year old daughter, Grace, has lost interest in kids TV recently – she’s discovered the joys of YouTube!

She can happily spend a half-hour sat in front of the TV on Firefox (our TV set-up is a Linux-based media centre, so it’s proper Firefox with a keyboard and mouse) clicking from video to video.

I’m fine with this. It’s good: she’s getting more familiar with how to use a web browser, getting used to starting the browser, typing “youtube” into the address bar, using the search box to search for what she wants, using the ‘Back’ button to go back to the search results if it’s not what she wanted, and so on. This is all good stuff, let alone the fact that there is a lot of content on YouTube that is actually ideal for kids.

But…

Well, she’s six. Not every video on YouTube is suitable for her. I’m not just talking about the stuff for over-18s. I don’t even want her to come across stuff with, for example, more swearing and violence – such as stuff that you might be happy to show a 12 year old.

The real solution to this is what we do now – she’s doing this in the sitting room on the TV, while we’re in the room watching stuff with her. I’m not saying I want to give her a laptop, send her up to her room, and say “here’s YouTube – off you go, have fun!”.

Even so, I wanted something to help out a little.

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Posted in code | 1 Comment »

You need to ask if you want an Android to vibrate

Saturday, November 13th, 2010

I posted a few days ago about a new little app I stuck in the Android Market. An error report appeared from the app in the Market last night that I thought was interesting.

The app does some stuff in the background then when it’s finished, it sticks a notification in the top status bar. In my code, I just use the default notification settings – LED flash, vibrate, etc. And on every Android I’ve tested it on, it’s been fine.

But for one user, it caused the app to crash:

Exception class java.lang.SecurityException

Source method Parcel.readException()

java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:200)
at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
at java.util.concurrent.FutureTask.run(FutureTask.java:137)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
at java.lang.Thread.run(Thread.java:1102)
Caused by: java.lang.SecurityException: Requires VIBRATE permission
at android.os.Parcel.readException(Parcel.java:1247)
at android.os.Parcel.readException(Parcel.java:1235)
at android.app.INotificationManager$Stub$Proxy.enqueueNotificationWithTag(INotificationManager.java:368)
at android.app.NotificationManager.notify(NotificationManager.java:110)
at android.app.NotificationManager.notify(NotificationManager.java:90)
at com.dalelane.lovefilm.data.ImageProcessService.publishUpdateNotification(ImageProcessService.java:281)
at com.dalelane.lovefilm.data.ImageProcessService.access$0(ImageProcessService.java:234)
at com.dalelane.lovefilm.data.ImageProcessService$ImageProcesser.doInBackground(ImageProcessService.java:215)
at com.dalelane.lovefilm.data.ImageProcessService$ImageProcesser.doInBackground(ImageProcessService.java:1)
at android.os.AsyncTask$2.call(AsyncTask.java:185)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
... 4 more

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GaianDB – my talk at bathcamp 2010

Saturday, October 30th, 2010

Here are the slides I used for a talk on Gaian DB – a dynamic, distributed, federated database technology that we produced at work and have made available through IBM alphaWorks.

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Adjusting mobile web font-sizes to fit screen resolutions

Monday, August 9th, 2010

This might be obvious to someone less ignorant in the mystic ways of CSS, but I thought it was worth sharing anyway. 🙂

I was struggling to work out a suitable font-size for a mobile web page. Whether I tried using size names like “x-large”, or values with em, pt, px or %, the same basic problem remained:

CSS - not working

Font-sizes were either too small on smartphones with high-resolution screens, or too large on other smartphones.

If I increased the font-size to look better on a high-res screen, it was too big for other phones. If I decreased the font-size for those other phones, it looked tiny on a high-res screen.

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Posted in code | 14 Comments »

Making the RTM cow more sympathetic

Tuesday, June 15th, 2010

I am a big fan of Remember The Milk (RTM), the online to-do list manager. It’s one of the few sites (like flickr) that I’m happy to pay for.

For some reason, the logo for RTM is a cow’s face. Which means that I get a cow staring at me when I’m deciding what I need to do next.

I had a random thought this evening – that the cow should really look more sympathetic when my task list is so full. Because he’s really quite heartless, even when I’m manically busy. 😉

And once I had the idea, I kinda had to give it a quick try. (And I wonder why I’m busy…)

So I’ve knocked up a quick Greasemonkey script – which should work with Firefox with the Greasemonkey add-on, or with Google Chrome.

rememberthemilkcow.user.js

(more…)

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Posted in code | 8 Comments »

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