"Multiple dex files" error with Eclipse + ADT

I haven't done much Android development in the last year but this week wanted to update my app a bit.  So I installed Eclipse Juno (4.2), grabbed the latest Android Developer Tools (r21), and the latest AWS SDK for Android (1.4.4) since my app persists data on AWS.

These are all pretty big jumps from what I used to have - Eclipse Indigo, probably a single digit ADT, and AWS SDK 0.2.X IIRC.  I've only been using my System76 laptop for grad school work of late, not "real" coding obviously.  Almost everything worked fine.  Thanks go out to these teams for honoring backward compatibility!  The one problem I had was "Unable to execute dex: Multiple dex files define X" (X being something in the AWS package).

So off to StackOverflow.  I tried all the suggestions:

• Open/close Eclipse a few times, doing project cleans
• Reinstalling ADT
• Deleting my /bin and /gen directories, then cleaning
• Made sure my build path was legit - several people traced it back to having /bin in the build path

The AWS JARs I imported were core, debug, and sdb (my app uses SimpleDB - don't ask).  Since my testing only consisted of moving the .apk to dropbox and making sure it worked on my Galaxy S3, I didn't need the debug JAR.  Once I removed it, everything worked okay.

Kinda perturbed this is still a problem - many SO posts and blogs I've seen are by people who appear to know what they're talking about so I don't think it's always a silly oversight by junior developers.  I'm thinking it's a dependency problem - maybe AWS SDK 1.4.4 wasn't developed with ADT r21?  If that was the case, Eclipse and SDK providers make it really hard to grab older versions like you would with a POM file.  If I needed to debug in this instance, I'd be in real trouble.

Thoughts about Google's Notepad Example 2

So I'm not going to rewrite the Example 2 app like I did for Example 1 but here are some thoughts after going through the exercise.

• Firing intents via startActivityForResult(): It's a little tedious packing items into the extra Bundle, especially if you have a lot of data but I'm sure it's much faster than hitting the database again.
• Local variables versus accessing the Dalvik VM: It's included as a note in the example text, but it bears repeating, especially for mobile developers: "Accessing a local variable is much more efficient than accessing a field in the Dalvik VM, so by doing this we make only one access to the field, and five accesses to the local variable, making the routine much more efficient."
• XML layouts are hard to debug: While the schema is pretty straightforward, it's not like there's a debugger for your XML files so any dumb mistake can make for very tedious troubleshooting.
• Once you get a Virtual Device going in Eclipse, don't turn it off!: Upon starting up Eclipse, the AVD fires up very quickly when executing a program. But if I shut it down, do some coding or whatnot, and try to run it again, it often sits on the "Waiting for HOME ('android.process.acore') to be launched..." step. Out of habit, I sometimes kill the AVD mistakenly.

Getting into SQLite

I grew bored drawing things on a Canvas so I moved on to the very helpful Notepad example. I like it because it's centered around the SQLite database package. Understand the importance of a good UI but the database interaction is much more my thing.

So I went through Exercise 1 then put it away and tried to code it myself. I'll spare the boring screenshots because my program doest exactly what Example 1 does - add dummy rows to a database and display them.

Couple things:

• Got some compile errors related to Cursor stuff (specifically setListAdapter) in my main class. I was extending Activity not ListActivity. Whoops - there is a difference.
• I like the idea of startManagingCursor and wonder why it's not default. Maybe only noobs like me use it but are people really managing their Cursor's lifecycles so thoroughly?
• When I tried to account for SQLExceptions, Eclipse never recognized its reference even though I imported android.database.SQLException. So I just removed it. I'll come back to that one. I'm sure I'm overlooking something obvious.
• Loving Eclipse's Ctrl-Shift-O shortcut to auto-import.
• Took me awhile to figure out the Context data type so I could access the SQLiteOpenHelper constructor. One difference between my code and Google's example was they kept the Context around as a private variable while I just discarded it. I wonder if keeping Contexts around is useful.

Oh, activities need to be defined within the application?

Continue to play around with the Android SDK. I'm working on a program that makes whatever kind of shape the user requests via a menu. Yes, very advanced which is why I named it Simple App. Anyway, the app was crashing when the shape was selected so I got some hands on experience with the Eclipse debugger.

I was getting ActivityNotFoundException and it was bombing on the startActivity() call. But how can that be? The class was properly included and I declared it in AndroidManifest.xml. Well, for some reason, I added this activity outside the application tag. Rookie mistake but it wasn't self evident in the debugger.

3 beginner lessons I’ve learned about Android development in Eclipse

My specs:

• OS: Ubuntu Maverick Meerkat 10.10 running in Desktop mode because Remix no worky for me.
• IDE: Eclipse Java EE IDE for Web Developers (Galileo)
• Hardware: Gateway LT31 Netbook w/ AMD Athlon 64
• JDK 1.6.0_22

1. If you’re using low resolution, keep in mind GNOME has a tendency to hide important things (like scrollbars) if it runs out of room. If you’re missing something obvious, increase your resolution. I ran into this when installing the Android plugin. Duh.
2. If Eclipse is throwing lots of timeout errors when you try to run something in the Android emulator, increase your timeout variable under Window -> Preferences -> Android -> DDMS -> ADB Connection Timeout. Mine’s at 50000 ms.
3. For some reason, I get a lot of “Error in an XML file” errors for no apparent reason. Here’s a good explanation. I found cleaning my project (Project -> Clean) seems to work. You have to be really careful about not keeping old XML files in your projects.