NoClassDefFoundError: com.easemob.chat.EMChat

01-03 21:39:11.725: E/AndroidRuntime(24625): FATAL EXCEPTION: main
01-03 21:39:11.725: E/AndroidRuntime(24625): java.lang.NoClassDefFoundError: com.easemob.chat.EMChat
01-03 21:39:11.725: E/AndroidRuntime(24625):  at com.example.im_test_one.UserApplication.onCreate(UserApplication.java:12)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:999)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4193)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at android.app.ActivityThread.access$1300(ActivityThread.java:138)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1267)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at android.os.Looper.loop(Looper.java:213)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at android.app.ActivityThread.main(ActivityThread.java:4787)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at java.lang.reflect.Method.invokeNative(Native Method)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at java.lang.reflect.Method.invoke(Method.java:511)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
01-03 21:39:11.725: E/AndroidRuntime(24625):  at dalvik.system.NativeStart.main(Native Method)