title: Conversion to Dalvik format failed with error 1 - Why?
body: <p>I only added to an existing fully working project, the file <code>com/android/vending/billing/IMarketBillingService.aidl</code></p>
  
  <p>(I didn't add anything else (from the market_billing sample) yet, since I am not even trying to use the service yet)</p>
  
  <p>It compiles and builds perfectly, but when I try to run it, I receive the following in the console:</p>
  
  <pre><code>java.lang.IllegalArgumentException: already added: Lcom/android/vending/billing/IMarketBillingService$Stub$Proxy;
  Dx  at com.android.dx.dex.file.ClassDefsSection.add(ClassDefsSection.java:123)
  Dx  at com.android.dx.dex.file.DexFile.add(DexFile.java:163)
  Dx  at com.android.dx.command.dexer.Main.processClass(Main.java:486)
  Dx  at com.android.dx.command.dexer.Main.processFileBytes(Main.java:455)
  Dx  at com.android.dx.command.dexer.Main.access$400(Main.java:67)
  Dx  at com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:394)
  Dx  at com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:245)
  Dx  at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:131)
  Dx  at com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:109)
  Dx  at com.android.dx.command.dexer.Main.processOne(Main.java:418)
  Dx  at com.android.dx.command.dexer.Main.processAllFiles(Main.java:329)
  Dx  at com.android.dx.command.dexer.Main.run(Main.java:206)
  Dx  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  Dx  at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  Dx  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  Dx  at java.lang.reflect.Method.invoke(Unknown Source)
  Dx  at com.android.ide.eclipse.adt.internal.build.DexWrapper.run(DexWrapper.java:179)
  Dx  at com.android.ide.eclipse.adt.internal.build.BuildHelper.executeDx(BuildHelper.java:745)
  Dx  at com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.build(PostCompilerBuilder.java:634)
  Dx  at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:629)
  Dx  at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
  Dx  at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:172)
  Dx  at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:282)
  Dx  at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:363)
  Dx  at org.eclipse.core.internal.resources.Project$1.run(Project.java:545)
  Dx  at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:1975)
  Dx  at org.eclipse.core.internal.resources.Project.internalBuild(Project.java:524)
  Dx  at org.eclipse.core.internal.resources.Project.build(Project.java:123)
  Dx  at com.android.ide.eclipse.adt.internal.project.ProjectHelper.doFullIncrementalDebugBuild(ProjectHelper.java:961)
  Dx  at com.android.ide.eclipse.adt.internal.launch.LaunchConfigDelegate.launch(LaunchConfigDelegate.java:146)
  Dx  at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:853)
  Dx  at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:702)
  Dx  at org.eclipse.debug.internal.ui.DebugUIPlugin.buildAndLaunch(DebugUIPlugin.java:924)
  Dx  at org.eclipse.debug.internal.ui.DebugUIPlugin$8.run(DebugUIPlugin.java:1128)
  Dx  at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)
  Dx 3 errors; aborting
  Conversion to Dalvik format failed with error 1
  </code></pre>
  
  <p>Any idea <em>why</em> this is happening?</p>
  
  <p>Note: This added <code>.aidl</code> file is <strong>not</strong> an external jar, so the answer <a href="https://stackoverflow.com/questions/2680827/conversion-to-dalvik-format-failed-with-error-1-on-external-jar">here</a> doesn't help in my case.</p>
  
  <p><strong>Update:</strong> I removed that suspicious <code>.aidl</code> file, clean the project, but the problem didn't go away. Weird.</p>
  
  <p><strong>Update:</strong> I knew it! I just tried running an existing project that used to run perfectly before I "upgraded" the SDK from 9 to 16 and I get the same error there as well. I knew I should have avoided that "upgrade". Now I have to waste time on troubleshooting a problem that shouldn't have been there until I upgrade according to plan, not when I am <a href="https://stackoverflow.com/questions/8696820/how-do-i-download-rev-9-third-party-add-ons">forced</a> to, without being able to do a planned &amp; controlled migration. App release delayed...</p>
  
  <p><strong>Update:</strong> There seems to be a connection to the <strong>buggy</strong> automatic conversion from <code>default.properties</code> to <code>project.properties</code> but despite me correcting all conversion errors manually, the problem still persists. I am now left with no development environment. This is ridiculous.</p>