您好我试着关注this tutorial
我按照所有步骤操作，当我尝试执行应用程序时，我收到以下错误：
03-14 17:24:19.618 3532-3532/ar.com.taxiexpress.taxiexpress E/dalvikvm: Could not find class 'ar.com.taxiexpress.taxiexpress.Mail', referenced from method ar.com.taxiexpress.taxiexpress.EnvioMail$SendMail.doInBackground
03-14 17:24:19.618 3532-3532/ar.com.taxiexpress.taxiexpress W/dalvikvm: VFY: unable to resolve new-instance 2544 (Lar/com/taxiexpress/taxiexpress/Mail;) in Lar/com/taxiexpress/taxiexpress/EnvioMail$SendMail;
03-14 17:24:19.618 3532-3532/ar.com.taxiexpress.taxiexpress D/dalvikvm: VFY: replacing opcode 0x22 at 0x0001
03-14 17:24:19.618 3532-3532/ar.com.taxiexpress.taxiexpress W/dalvikvm: Unable to resolve superclass of Lar/com/taxiexpress/taxiexpress/Mail; (9576)
03-14 17:24:19.618 3532-3532/ar.com.taxiexpress.taxiexpress W/dalvikvm: Link of class 'Lar/com/taxiexpress/taxiexpress/Mail;' failed
03-14 17:24:19.618 3532-3532/ar.com.taxiexpress.taxiexpress D/dalvikvm: DexOpt: unable to opt direct call 0x51e4 at 0x07 in Lar/com/taxiexpress/taxiexpress/EnvioMail$SendMail;.doInBackground
03-14 17:24:19.650 3532-3676/ar.com.taxiexpress.taxiexpress W/dalvikvm: threadid=17: thread exiting with uncaught exception (group=0xa4d31b20)
03-14 17:24:19.650 3532-3676/ar.com.taxiexpress.taxiexpress E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #3
Process: ar.com.taxiexpress.taxiexpress, PID: 3532
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:300)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:841)
Caused by: java.lang.NoClassDefFoundError: ar.com.taxiexpress.taxiexpress.Mail
at ar.com.taxiexpress.taxiexpress.EnvioMail$SendMail.doInBackground(EnvioMail.java:51)
at ar.com.taxiexpress.taxiexpress.EnvioMail$SendMail.doInBackground(EnvioMail.java:34)
at android.os.AsyncTask$2.call(AsyncTask.java:288)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:841)
03-14 17:24:19.678 3532-3532/ar.com.taxiexpress.taxiexpress W/EGL_genymotion: eglSurfaceAttrib not implemented
03-14 17:24:19.854 3532-3532/ar.com.taxiexpress.taxiexpress W/EGL_genymotion: eglSurfaceAttrib not implemented
03-14 17:24:20.382 3532-3546/ar.com.taxiexpress.taxiexpress I/GMPM: Tag Manager is not found and thus will not be used
03-14 17:27:01.184 3532-3538/ar.com.taxiexpress.taxiexpress D/dalvikvm: GC_FOR_ALLOC freed 305K, 3% free 16909K/17288K, paused 8ms, total 8ms
03-14 17:29:19.670 3532-3676/ar.com.taxiexpress.taxiexpress I/Process: Sending signal. PID: 3532 SIG: 9
有人可以告诉我应该检查什么来解决这个问题，提前谢谢。