[kyocera]

gracias por responder mekawendie si si tengo la activity añadida al AndroidManifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.sudoku"
android:versionCode="1"
android:versionName="1.0">


<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".Sudoku"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".About"
android:label="@string/about_text"
android:theme="@android:style/Theme.Dialog">
</activity>
</application>
</manifest>