Java android Dropbox SDK不工作，NoClassDefFoundError即将出现

我试过跑步

Dropbox SDK版本3.1.1，于2014年10月10日更新

放

armeabi，armeabi-v7a，mips，x86，dropbox-sync-sdk-android.jar

文件夹到LIBS文件夹

也做了

项目属性->JavaBuild路径->添加jar->dropbox-sync-sdk-android.jar

也做了

项目属性->Java构建路径->订单和导出->dropbox-sync-sdk-android.jar上的勾号

但是在运行时出错

10-17 17:08:20.112: E/AndroidRuntime(5199): FATAL EXCEPTION: main
10-17 17:08:20.112: E/AndroidRuntime(5199): Process: com.dropbox.sample.hellodropbox, PID: 5199
10-17 17:08:20.112: E/AndroidRuntime(5199): java.lang.NoClassDefFoundError: com.dropbox.sync.android.DbxAccountManager
10-17 17:08:20.112: E/AndroidRuntime(5199):     at com.dropbox.sample.hellodropbox.HelloDropboxActivity.onCreate(HelloDropboxActivity.java:44)
10-17 17:08:20.112: E/AndroidRuntime(5199):     at android.app.Activity.performCreate(Activity.java:5403)
10-17 17:08:20.112: E/AndroidRuntime(5199):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
10-17 17:08:20.112: E/AndroidRuntime(5199):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
10-17 17:08:20.112: E/AndroidRuntime(5199):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2396)
10-17 17:08:20.112: E/AndroidRuntime(5199):     at android.app.ActivityThread.access$800(ActivityThread.java:139)
10-17 17:08:20.112: E/AndroidRuntime(5199):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293)
10-17 17:08:20.112: E/AndroidRuntime(5199):     at android.os.Handler.dispatchMessage(Handler.java:102)
10-17 17:08:20.112: E/AndroidRuntime(5199):     at android.os.Looper.loop(Looper.java:149)

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从“dropbox android sync sdk”中添加完整的“Lib/”文件夹

在“dropbox android sync sdk”中没有“Lib/”文件夹添加完整的“libs/***”你有没有发现这一点？