Archive for July, 2010

Android UI: Making an Analog Rotary Knob

Wednesday, July 28th, 2010

For some reason, I really enjoy recreating analog components on Android. Today I’d like to share my experience of re-creating a knob that looks like this:

As you can guess, this type of knob does not have min/max bounds and can be freely rotated as much as you want. This type of control is often used for browsing through a list of options that can be wrapped around. Also, an important property is that this knob does not rotate smoothly but switches from one nick to another. You can imagine that it also clicks when you rotate it – and our Android replica will also make that sound!

Here’s how the Android version looks:

I’ve included the source into this article. However, please be warned it is not completed and you will need to fix or finish few things before you can use this code in your own app.

And now, let’s get down to work!


Android Tricks: Multitouch AND 1.5 Support, Same App

Tuesday, July 20th, 2010

I don’t know about you but I have an emotional attachment to old platforms and APIs. They are often sweet and nice in their primordial simplicity, even with their well-understood limitations. Even when they become obsolete, we developers still remember and miss them.

In case of Android, version 1.5 / API level 3 is technically obsolete but is far from being extinct from the device market. In fact, as of the day I write this article, it is one of the most widely installed Android versions on the market. (And if you add the not-so-different 1.6, they take almost half of the market together.) While subsequent versions brought us a lot of goodies in various areas of the platform API, 80% or more of all functionality our apps need today is present in 1.5.

Sure, there are cases when your app just isn’t meant to run on 1.x. For example, its core functionality is based on the APIs that are absent from API level 3 (e.g. you’re making a live wallpaper), or when you don’t want to support old devices for performance reasons, or due to a marketing decision. However, in many cases what makes developers raise the minSdkVersion bar is the need to use some of the 1.6+ APIs, such as the new contact management facilities, signal strength detection or better animation support.

The good news I’m trying to bring in this article – to those who aren’t yet familiar with this trick – is that you can actually use the new API yet keep minSdkVersion at 3. This trick might not work in all cases, and might look like a hack, but it will work for many situations like this – and who knows, might allow your app to reach out to its grateful, ready-to-pay customers who still use 1.5.


Strictly For My Readers!

Monday, July 12th, 2010

Hey everyone!

I decided to write this post to say thanks to everyone who’s been reading my blog so far. I started MTR around a month ago, and it has been visited almost 10,000 times since then. What is very satisfying to me is that many people subscribe to MTR and watch for new articles. This means that you liked the content and found it at least somewhat useful. Thank you so much!

I am really motivated to continue writing articles for MTR. We will cover various stuff, such as loading OpenGL meshes from 3DS Max, porting native Unix libraries to Android, analyzing and modifying audio on the fly and so on and so on. Be sure to stay tuned.

Starting from this month, you can also find articles written by yours truly on WiseAndroid – along with lots of great articles written by other authors.

Right now, I would like to use the rest of this post to recommend to you some Android goodies that I learnt about from some of you guys – some of the readers of this blog who got in touch with me.


Android Beginners: NDK Setup Step by Step

Tuesday, July 6th, 2010

Most Android developers start their learning from pure Java, Android SDK based apps. While everyone is aware that there is the NDK (the Native Development Kit), they don’t face the need to use it. Since NDK is distributed separately from the SDK, including documentations and samples, you are not likely to get familiar with NDK before you actually try it as a solution to one of your development challenges.

Because of that, many people think of NDK as of “black magic” of Android development. Many developers who are not familiar with NDK think it is 1) complex to understand and use, and at the same time a lot of developers will think it is a sort of a 2) silver bullet that can solve any problem that can’t be solved with SDK.

Well, both opinions are rather wrong, as I hope to show further in this post. Although it does have a maintenance cost and does add technical complexity to your project, NDK is not difficult to install or use in your project. And, while there are cases where NDK will be really helpful for your app, NDK has a rather limited API that’s mostly focused on several performance-critical areas, such as:

  • OpenGL, including support for some newer versions that the (Java) SDK supports
  • Math (some, but not all, calculation-intensive algorithms might benefit from being done on the native layer)
  • 2D graphics – pixelbuffer support (only starting with 2.2)
  • libc – it’s there for compatibility and perhaps to allow you to port existing native code

In this tutorial we will take our basic Android development environment that we created in one of the previous articles and add NDK support to it. We will also create a basic skeleton project that uses NDK that you can use as the foundation for your NDK-powered apps.


Android Beatz: Making a Drum Machine App

Monday, July 5th, 2010

Hello again! I’m back from a wonderful vacation and ready to share some more experience of Android programming. Today I’m presenting a simple drum machine app that I made for fun. If you saw the video above, then you probably got the idea how a drum machine works. The design was inspired by one of the greatest drum machines ever – the AKAI MPC. You can have a look at how the original device looked like for example here. Our app is, of course, greatly simplified compared to AKAI MPC, but you can have some fun with it too.

Here’s a screenshot for a better idea of how the UI looks (clickable):

Some interesting features of this app:

  1. The UI is done using bitmaps and custom controls to imitate the original device
  2. The latency is low enough not to be annoying (at least on my Droid)
  3. You can press multiple buttons at once which is very good for long samples such as the bass drum
  4. The LCD screen control uses a 9-patch bitmap background, and switches between flashing, static and ticker text
  5. The LCD screen uses a custom TrueType font that is included within the app

Now let’s see how the most interesting features of this app were implemented (as usual, the source is available at the bottom of the article).