Busco todos los días y no puedo encontrar la respuesta ...

Todo está listo, pero el mapa de Google aún no se puede mostrar en el fragmento con pestaña

Verifico que ya haya activado google map android v2 y tengo razón API_KEY

¡No tengo idea de que pasó!

MainActivity.java:

public class MainActivity extends FragmentActivity implements
        ActionBar.TabListener {

    SectionsPagerAdapter mSectionsPagerAdapter;

    ViewPager mViewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        String titles[] = { this.getString(R.string.title_around),
                this.getString(R.string.title_map),
                this.getString(R.string.title_favorite),
                this.getString(R.string.title_achievement), };

        final ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        mSectionsPagerAdapter = new SectionsPagerAdapter(
                getSupportFragmentManager());

        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);
        mViewPager
                .setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
                    @Override
                    public void onPageSelected(int position) {
                        actionBar.setSelectedNavigationItem(position);
                    }
                });

        for (int i = 0; i < titles.length; i++) {
            actionBar.addTab(actionBar.newTab().setText(titles[i])
                    .setTabListener(this));
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public void onTabSelected(Tab tab, FragmentTransaction fragmentTransaction) {
        mViewPager.setCurrentItem(tab.getPosition());
    }

    @Override
    public void onTabUnselected(ActionBar.Tab tab,
            FragmentTransaction fragmentTransaction) {
    }

    @Override
    public void onTabReselected(ActionBar.Tab tab,
            FragmentTransaction fragmentTransaction) {
    }

    public class SectionsPagerAdapter extends FragmentPagerAdapter {

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            // TODO 在這邊決定哪個位置要給什麼 View（Fragment）
            Fragment fragment = null;
            // TODO 建議先在之前就初始化好 4 個 Fragment
            switch (position) {
            case 0:
                fragment = new AroundFragment();
                break;
            case 1:
                fragment = new MapsFragment();
                break;
            case 2:
                fragment = new FavoriteFragment();
                break;
            case 3:
                fragment = new AchievementFragment();
                break;
            default:
                break;
            }

            return fragment;
        }

        @Override
        public int getCount() {
            return 4;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            // TODO 在這邊決定每一個 View 的 title
            switch (position) {
            case 0:
                return getString(R.string.title_around);
            case 1:
                return getString(R.string.title_map);
            case 2:
                return getString(R.string.title_favorite);
            case 3:
                return getString(R.string.title_achievement);
            }
            return null;
        }
    }

}

MapsFragment.java:

public class MapsFragment extends Fragment{
    static final LatLng NKUT = new LatLng(23.979548, 120.696745);
    private GoogleMap map;
    SupportMapFragment mMapFragment;
    public MapsFragment() {

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.map_fragment,container, false);

        map = ((SupportMapFragment)getFragmentManager().findFragmentById(R.id.map)).getMap();

         mMapFragment = SupportMapFragment.newInstance();
         FragmentTransaction fragmentTransaction =
                 getFragmentManager().beginTransaction();
         fragmentTransaction.add(R.id.map,mMapFragment);
         fragmentTransaction.commit();

        return rootView;

    }
}

Map_fragment.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=".MainActivity" >

    <fragment
        android:id="@+id/map"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        class="com.google.android.gms.maps.SupportMapFragment" />

</RelativeLayout> 

Manifest.xml:

<!-- Google Map -->
<permission
        android:name="com.jertt.yummymap.permission.MAPS_RECEIVE"
        android:protectionLevel="signature"/>
<uses-permission android:name="com.jertt.yummymap.permission.MAPS_RECEIVE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES"/>
<!-- The following two permissions are not required to use
     Google Maps Android API v2, but are recommended. -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

<!-- end -->
    <!-- Google Map API Key -->

    <meta-data
        android:name="com.google.android.maps.v2.API_KEY"
        android:value="key" />

    <!-- end -->

Solución:

¡¡¡Encontré la solución !!!

Si usa un almacén de claves privado para aplicar API_KEY. No puedes subir e instalar la aplicación con eclipse.

Necesitas cargar el archivo .apk en tu dispositivo por ti mismo e instalarlo.

Gracias Tarsem y srikanth gr ayuda !!