At some point during the development you may see the following (or similar) exception:

trouble writing output: Too many field references: 68805; max is 65536.
You may try using --multi-dex option.
References by package:
     3 android
     2 android.accounts
    31 android.app
...

or

Conversion to Dalvik format failed:
Unable to execute dex: method ID not in [0, 0xffff]: 65536

This means that you’ve hit the 65k method limit which is imposed by DEX format. It usually happens after you add a few big (or many small) dependencies to your project. In order to make your project build again perform these steps:

• In project.clj add the following lines to :android map:

  :multi-dex true
  :multi-dex-proguard-conf-path "build/proguard-multi-dex.cfg"
      

• The file build/proguard-multi-dex.cfg should already be in your project folder if you created the project recently. Otherwise you can copy it from here.
• Remove “incremental” from :dex-opts option in :android map. Multidexing and incremental dexing are unfortunately incompatible.
• Make sure that you use the latest Neko version, and your application class is set to neko.App in AndroidManifest.template.xml.

  After you do these steps and rebuild your project, lein-droid will package classes into several DEX files. Multidexing build is somewhat slower but it is the only option to overcome the 65k limit.

  More about multidexing.