a ClassNotFoundException error when trying to excute a Cordova push notification plugin

a ClassNotFoundException error when trying to excute a Cordova push
notification plugin

i get a ClassNotFoundException error when i was trying to execute this
example of a push notification plugin:
java.lang.RuntimeException: Unable to instantiate activity
ComponentInfo{com.cordova2.gcm/com.cordova2.gcm.MainActivity}:
java.lang.ClassNotFoundException: Didn't find class
"com.cordova2.gcm.MainActivity" on path: /data/app/com.cordova2.gcm-1.apk
this is my AndroidManifest.xml :
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.cordova2.gcm"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="15" />
<supports-screens
android:largeScreens="true"
android:normalScreens="true"
android:smallScreens="true"
android:resizeable="true"
android:anyDensity="true" />
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission
android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission
android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission
android:name="android.permission.ACCESS_LOCATION_EXTRA_COMMANDS" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.RECEIVE_SMS" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission
android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.WRITE_CONTACTS" />
<uses-permission
android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission
android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.BROADCAST_STICKY" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission
android:name="com.google.android.c2dm.permission.RECEIVE" />
<permission android:name="com.cordova2.gcm.permission.C2D_MESSAGE"
android:protectionLevel="signature" />
<uses-permission
android:name="com.cordova2.gcm.permission.C2D_MESSAGE" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.cordova2.gcm.MainActivity"
android:label="@string/title_activity_main"
android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale"
>
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<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" />
<action
android:name="com.google.android.c2dm.intent.REGISTRATION"
/>
<category android:name="com.cordova2.gcm" />
</intent-filter>
</receiver>
<service android:name=".GCMIntentService" />
</application>
</manifest>