Google地图未显示在我的设备上

我正在尝试实现Google Maps Android API v2地图应用程序。我的代码正常运行，没有任何错误。

我已经完成了GPS上的所有更改。但是每次都可能出现相同的结果。这是我的MainActivity代码。

public class MainActivity extends Activity {

    // Google Map
    private GoogleMap googleMap;

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

        try {
            // Loading map
            initilizeMap();

            // Changing map type
            googleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);


            // Showing / hiding your current location
            googleMap.setMyLocationEnabled(true);

            // Enable / Disable zooming controls
            googleMap.getUiSettings().setZoomControlsEnabled(false);

            // Enable / Disable my location button
            googleMap.getUiSettings().setMyLocationButtonEnabled(true);

            // Enable / Disable Compass icon
            googleMap.getUiSettings().setCompassEnabled(true);

            // Enable / Disable Rotate gesture
            googleMap.getUiSettings().setRotateGesturesEnabled(true);

            // Enable / Disable zooming functionality
            googleMap.getUiSettings().setZoomGesturesEnabled(true);

            double latitude = 17.385044;
            double longitude = 78.486671;




            // lets place some 10 random markers
            for (int i = 0; i < 10; i++) {
                // random latitude and logitude
                double[] randomLocation = createRandLocation(latitude,
                        longitude);

                // Adding a marker
                MarkerOptions marker = new MarkerOptions().position(
                        new LatLng(randomLocation[0], randomLocation[1]))
                        .title("Hello Maps " + i);

                Log.e("Random", "> " + randomLocation[0] + ", "
                        + randomLocation[1]);

                // changing marker color
                if (i == 0)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_AZURE));
                if (i == 1)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_BLUE));
                if (i == 2)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_CYAN));
                if (i == 3)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_GREEN));
                if (i == 4)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));
                if (i == 5)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_ORANGE));
                if (i == 6)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_RED));
                if (i == 7)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_ROSE));
                if (i == 8)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_VIOLET));
                if (i == 9)
                    marker.icon(BitmapDescriptorFactory
                            .defaultMarker(BitmapDescriptorFactory.HUE_YELLOW));

                googleMap.addMarker(marker);

                // Move the camera to last position with a zoom level
                if (i == 9) {
                    CameraPosition cameraPosition = new CameraPosition.Builder()
                            .target(new LatLng(randomLocation[0],
                                    randomLocation[1])).zoom(15).build();

                    googleMap.animateCamera(CameraUpdateFactory
                            .newCameraPosition(cameraPosition));
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    @Override
    protected void onResume() {
        super.onResume();
        initilizeMap();
    }

    /**
     * function to load map If map is not created it will create it for you
     * */
    private void initilizeMap() {
        if (googleMap == null) {
            googleMap = ((MapFragment) getFragmentManager().findFragmentById(
                    R.id.map)).getMap();

            // check if map is created successfully or not
            if (googleMap == null) {
                Toast.makeText(getApplicationContext(),
                        "Sorry! unable to create maps", Toast.LENGTH_SHORT)
                        .show();
            }
        }
    }

    /*
     * creating random postion around a location for testing purpose only
     */
    private double[] createRandLocation(double latitude, double longitude) {

        return new double[] { latitude + ((Math.random() - 0.5) / 500),
                longitude + ((Math.random() - 0.5) / 500),
                150 + ((Math.random() - 0.5) * 10) };
    }
}

清单API密钥：

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

<meta-data
        android:name="com.google.android.gms.version"
        android:value="@integer/google_play_services_version" />

完整的Manifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="info.androidhive.googlemapsv2"
    android:versionCode="1"
    android:versionName="1.0" >

    <permission
        android:name="info.androidhive.googlemapsv2.permission.MAPS_RECEIVE"
        android:protectionLevel="signature" />

    <uses-permission android:name="info.androidhive.googlemapsv2.permission.MAPS_RECEIVE" />

    <uses-sdk
        android:minSdkVersion="12"
        android:targetSdkVersion="17" />

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <!-- Required to show current location -->
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <!-- Required OpenGL ES 2.0. for Maps V2 -->
    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true" />

    <!-- Requires OpenGL ES version 2 -->
    <uses-feature
        android:glEsVersion="0x00020000"
        android:required="true" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name="com.googlemap.MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppBaseTheme" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <!-- Goolge API Key -->
        <meta-data
            android:name="com.google.android.maps.v2.API_KEY"
            android:value="" />
        <meta-data
            android:name="com.google.android.gms.version"
            android:value="@integer/google_play_services_version" />
    </application>

</manifest>

请提出这可能是什么错误