java.lang.IllegalArgumentException: already added: Lorg/apache/poi/EncryptedDocumentException;

java.lang.IllegalArgumentException: already added: Lorg/apache/poi/EncryptedDocumentException;
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.dex.file.ClassDefsSection.add(ClassDefsSection.java:123)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.dex.file.DexFile.add(DexFile.java:143)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.command.dexer.Main.processClass(Main.java:372)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.command.dexer.Main.processFileBytes(Main.java:346)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.command.dexer.Main.access$400(Main.java:59)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:294)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:244)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:130)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:108)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.command.dexer.Main.processOne(Main.java:313)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.command.dexer.Main.processAllFiles(Main.java:233)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.dx.command.dexer.Main.run(Main.java:185)
[2011-05-25 11:38:23 - RollCallSystem] Dx at sun.reflect.GeneratedMethodAccessor13.invoke(Unknown Source)
[2011-05-25 11:38:23 - RollCallSystem] Dx at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
[2011-05-25 11:38:23 - RollCallSystem] Dx at java.lang.reflect.Method.invoke(Method.java:585)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.ide.eclipse.adt.internal.build.DexWrapper.run(DexWrapper.java:179)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.ide.eclipse.adt.internal.build.BuildHelper.executeDx(BuildHelper.java:585)
[2011-05-25 11:38:23 - RollCallSystem] Dx at com.android.ide.eclipse.adt.internal.build.builders.PostCompilerBuilder.build(PostCompilerBuilder.java:490)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:629)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:172)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:203)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:255)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:258)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:311)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:343)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:144)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:242)
[2011-05-25 11:38:23 - RollCallSystem] Dx at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)
[2011-05-25 11:38:23 - RollCallSystem] Dx 1 error; aborting
[2011-05-25 11:38:23 - RollCallSystem] Conversion to Dalvik format failed with error 1

原因：包引用問題

解決方案：不能直接把jar包放在android工程裡面，要通過外部包引用的方式匯入進來，就不會存在衝突了。