Eclipse Android: class not found

I am using Google App Engine to create the following tutorial on creating Android Applications: https://cloud.google.com/developers/articles/how-to-build-mobile-app-with-app-engine-backend-tutorial

I use eclipse in Windows 7. I went to the part of running the application to display the newly uploaded information in "places. CSV". The problem is that I received the following error:

03-15 17:00:31.137: E/AndroidRuntime(1151): FATAL EXCEPTION: main
03-15 17:00:31.137: E/AndroidRuntime(1151): Process: com.apps.mobileassistant, PID: 1151
03-15 17:00:31.137: E/AndroidRuntime(1151): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.apps.mobileassistant/com.apps.mobileassistant.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "com.apps.mobileassistant.MainActivity" on path: DexPathList[[zip file "/data/app/com.apps.mobileassistant-2.apk"],nativeLibraryDirectories=[/data/app-lib/com.apps.mobileassistant-2, /system/lib]]
03-15 17:00:31.137: E/AndroidRuntime(1151):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2102)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at android.app.ActivityThread.access$700(ActivityThread.java:135)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at android.os.Handler.dispatchMessage(Handler.java:102)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at android.os.Looper.loop(Looper.java:137)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at android.app.ActivityThread.main(ActivityThread.java:4998)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at java.lang.reflect.Method.invokeNative(Native Method)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at java.lang.reflect.Method.invoke(Method.java:515)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at dalvik.system.NativeStart.main(Native Method)
03-15 17:00:31.137: E/AndroidRuntime(1151): Caused by: java.lang.ClassNotFoundException: Didn't find class "com.apps.mobileassistant.MainActivity" on path: DexPathList[[zip file "/data/app/com.apps.mobileassistant-2.apk"],nativeLibraryDirectories=[/data/app-lib/com.apps.mobileassistant-2, /system/lib]]
03-15 17:00:31.137: E/AndroidRuntime(1151):     at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at java.lang.ClassLoader.loadClass(ClassLoader.java:497)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at java.lang.ClassLoader.loadClass(ClassLoader.java:457)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
03-15 17:00:31.137: E/AndroidRuntime(1151):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2093)

MobileAssistant App Manifest.xml

<?xml version="1.0" encoding="utf-8" standalone="no"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="com.apps.mobileassistant">

    <uses-sdk android:minSdkVersion="10" android:targetSdkVersion="19"/>

    <uses-permission android:name="android.permission.INTERNET"/>
   <permission android:name="com.apps.mobileassistant.permission.C2D_MESSAGE" android:protectionLevel="signature"/>

   <uses-permission android:name="com.apps.mobileassistant.permission.C2D_MESSAGE"/>
   <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE"/>
   <uses-permission android:name="android.permission.WAKE_LOCK"/>
   <uses-permission android:name="android.permission.GET_ACCOUNTS"/>
   <uses-permission android:name="android.permission.USE_CREDENTIALS"/>
   <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme">
        <activity android:label="@string/app_name" android:name="com.apps.mobileassistant.MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>

                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        <service android:name=".GCMIntentService"/>
        <receiver android:name="com.google.android.gcm.GCMBroadcastReceiver" android:permission="com.google.android.c2dm.permission.SEND">
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.RECEIVE"/>
                <category android:name="com.apps.mobileassistant"/>
            </intent-filter>
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.REGISTRATION"/>
                <category android:name="com.apps.mobileassistant"/>
            </intent-filter>
        </receiver>

        <activity android:launchMode="singleTop" android:name=".RegisterActivity"/>
</application>

</manifest>

In addition, when in debugging mode, I get "source not found" error in thread [< 1 >]

Can someone help me with this?

resolvent:

As your current error message tells you:

ComponentInfo{com.apps.mobileassistant/com.apps.mobileassistant.MainActivity}:
java.lang.ClassNotFoundException: 
Didn't find class "com.apps.mobileassistant.MainActivity" 
on path: DexPathList[[zip file "/data/app/com.apps.mobileassistant-2.apk"],
nativeLibraryDirectories=[/data/app-lib/com.apps.mobileassistant-2

You either made some mistakes in setting up the project and required libraries, or you just missed some classes, or you didn't notify the corresponding classes in the code through import and class name