android - Androidでタブアクティビティからフラグメントアクティビティを開始するには?

Question

ユーザーがアプリを開くと、タブビューが次のようになります

public class MainCategory extends TabActivity {
TabHost tabs;
static TabHost mTabHost;

ImageView ivSettings;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
     requestWindowFeature(Window.FEATURE_NO_TITLE);

    setContentView(R.layout.maincategory);

 mTabHost = getTabHost();


    mTabHost.addTab(mTabHost
            .newTabSpec("three")
            .setIndicator("one",
                    getResources().getDrawable(R.drawable.ic_launcher))
            .setContent(new Intent(this, SettingsActivity.class)));


    mTabHost.addTab(mTabHost
            .newTabSpec("three")
            .setIndicator("three",
                    getResources().getDrawable(R.drawable.ic_launcher))
            .setContent(new Intent(this, MainActivity.class)));

    mTabHost.setCurrentTab(0);}

ユーザーが 3 番目のタブ アイコンをクリックすると、フラグメント アクティビティが起動します

public class MainActivity extends FragmentActivity implements
    ActionBar.TabListener {

private ViewPager viewPager;
private TabsPagerAdapter mAdapter;
private ActionBar actionBar;
// Tab titles
private String[] tabs = { "Top Rated", "Games", "Movies" };

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

    // Initilization
    viewPager = (ViewPager) findViewById(R.id.pager);
    actionBar = getActionBar();
    mAdapter = new TabsPagerAdapter(getSupportFragmentManager());

    viewPager.setAdapter(mAdapter);
    actionBar.setHomeButtonEnabled(false);
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);        

    // Adding Tabs
    for (String tab_name : tabs) {
        actionBar.addTab(actionBar.newTab().setText(tab_name)
                .setTabListener(this));
    }

    /**
     * on swiping the viewpager make respective tab selected
     * */
    viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

        @Override
        public void onPageSelected(int position) {
            // on changing the page
            // make respected tab selected
            actionBar.setSelectedNavigationItem(position);
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {
        }

        @Override
        public void onPageScrollStateChanged(int arg0) {
        }
    });
}

@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
    // on tab selected
    // show respected fragment view
    viewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
}

しかし、それは私のアプリをクラッシュさせます.これは私のログの猫の出力です

10-28 06:17:33.036: E/AndroidRuntime(775): FATAL EXCEPTION: main
10-28 06:17:33.036: E/AndroidRuntime(775): java.lang.RuntimeException: Unable to start activity ComponentInfo{info.androidhive.tabsswipe/info.androidhive.tabsswipe.MainActivity}: java.lang.NullPointerException
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.app.ActivityThread.startActivityNow(ActivityThread.java:2054)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.app.LocalActivityManager.moveToState(LocalActivityManager.java:135)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.app.LocalActivityManager.startActivity(LocalActivityManager.java:347)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.widget.TabHost$IntentContentStrategy.getContentView(TabHost.java:749)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.widget.TabHost.setCurrentTab(TabHost.java:413)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.widget.TabHost$2.onTabSelectionChanged(TabHost.java:154)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.widget.TabWidget$TabClickListener.onClick(TabWidget.java:546)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.view.View.performClick(View.java:4240)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.view.View$PerformClick.run(View.java:17721)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.os.Handler.handleCallback(Handler.java:730)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.os.Handler.dispatchMessage(Handler.java:92)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.os.Looper.loop(Looper.java:137)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.app.ActivityThread.main(ActivityThread.java:5103)
10-28 06:17:33.036: E/AndroidRuntime(775):  at java.lang.reflect.Method.invokeNative(Native Method)
10-28 06:17:33.036: E/AndroidRuntime(775):  at java.lang.reflect.Method.invoke(Method.java:525)
10-28 06:17:33.036: E/AndroidRuntime(775):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-28 06:17:33.036: E/AndroidRuntime(775):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-28 06:17:33.036: E/AndroidRuntime(775):  at dalvik.system.NativeStart.main(Native Method)
10-28 06:17:33.036: E/AndroidRuntime(775): **Caused by: java.lang.NullPointerException
10-28 06:17:33.036: E/AndroidRuntime(775):  at info.androidhive.tabsswipe.MainActivity.onCreate(MainActivity.java:31)**
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.app.Activity.performCreate(Activity.java:5133)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
10-28 06:17:33.036: E/AndroidRuntime(775):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
10-28 06:17:33.036: E/AndroidRuntime(775):  ... 18 more

次の出力が必要です（タブアクティビティとアクションバーの両方を使用）