android - アクティビティ ComponentInfo を開始できません (別のクラスを開いています)

Question

TabsMain クラスを開こうとしています。これが私のコードです。

public class MainActivity extends Activity implements OnClickListener {
Button btnDiseaseIdentification, btnNutrientDeficiency;
Button btnInstruction, btnDiseaseInfo;
int flag;
ImageView iv;
Uri targetURI;
final static int cameraData = 0;
final static int galleryData = 1;
Bitmap bmpGallery;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    initialize();
}

private void initialize() {
    // iv = (ImageView) findViewById(R.id.imageView1);
    //btnCam = (Button) findViewById(R.id.btnCamera);
    btnDiseaseIdentification = (Button) findViewById(R.id.btnDiseaseIdentification);
    btnDiseaseIdentification.setOnClickListener(this);
    btnNutrientDeficiency = (Button) findViewById(R.id.btnNutrientDeficiency);  
    btnNutrientDeficiency.setOnClickListener(this);
    btnDiseaseInfo = (Button) findViewById(R.id.btnDiseaseInfo);    
    btnDiseaseInfo.setOnClickListener(this);


}

@Override
public void onClick(View v) {
    if (v.getId() == R.id.btnDiseaseIdentification) {
        Intent i = new Intent(this, DisplayImage.class);
        startActivity(i);
    } else if (v.getId() == R.id.btnNutrientDeficiency) {       
        Intent i = new Intent(this, NutrientDeficiency.class);
        startActivity(i);
    } else if (v.getId() == R.id.btnDiseaseInfo){
        Intent i = new Intent("com.example.thesis.TABSMAIN");
        startActivity(i);
    }
}

これは私の TabsMain クラスです

public class TabsMain extends SherlockFragmentActivity {

private ViewPager mViewPager;
private TabsAdapter mTabsAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    mViewPager = new ViewPager(this);
    mViewPager.setId(R.id.pager);
    getSupportActionBar().setDisplayShowHomeEnabled(false);
    getSupportActionBar().setDisplayShowTitleEnabled(false);
    setContentView(mViewPager);

    final ActionBar bar = getSupportActionBar();
    bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    mTabsAdapter = new TabsAdapter(this, mViewPager);
    mTabsAdapter.addTab(bar.newTab().setText("RICE BLAST"), RiceBlast.class, null);

TabsMain.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context = ".TabsMain">

<android.support.v4.view.ViewPager
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/pager" />

マニフェスト

<application
    android:allowBackup="true"
    android:icon="@drawable/thesisicon"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.NoTitleBar.Fullscreen" >
    <activity
        android:name="com.example.thesis.MainActivity"
        android:configChanges="orientation|screenSize"
        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=".TabsMain"
        android:label="@string/title_activity_tabs_main" >
         <intent-filter>
            <action android:name="com.example.thesis.TABSMAIN" />

            <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>

    </activity>

Logcat エラー

09-08 10:03:54.702: E/AndroidRuntime(900): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.thesis/com.example.thesis.TabsMain}: java.lang.NullPointerException
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.os.Handler.dispatchMessage(Handler.java:99)
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.os.Looper.loop(Looper.java:137)
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.app.ActivityThread.main(ActivityThread.java:5041)
09-08 10:03:54.702: E/AndroidRuntime(900):  at java.lang.reflect.Method.invokeNative(Native Method)
09-08 10:03:54.702: E/AndroidRuntime(900):  at java.lang.reflect.Method.invoke(Method.java:511)
09-08 10:03:54.702: E/AndroidRuntime(900):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
09-08 10:03:54.702: E/AndroidRuntime(900):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
09-08 10:03:54.702: E/AndroidRuntime(900):  at dalvik.system.NativeStart.main(Native Method)
09-08 10:03:54.702: E/AndroidRuntime(900): Caused by: java.lang.NullPointerException
09-08 10:03:54.702: E/AndroidRuntime(900):  at com.example.thesis.TabsMain.onCreate(TabsMain.java:22)
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.app.Activity.performCreate(Activity.java:5104)
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
09-08 10:03:54.702: E/AndroidRuntime(900):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
09-08 10:03:54.702: E/AndroidRuntime(900):  ... 11 more