Maps not showing on App

I've been reading the tutorial of "Getting started" of Google Maps API Google Maps Android API v2 and my map doesn't show up...

I've created a class called "MapTest.java" and a xml called "map_test.xml"

The "MapTest.java"

public class MapsTest extends android.support.v4.app.Fragment {

    View rootView;

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

And the "map_test.xml"

<?xml version="1.0" encoding="utf-8"?>
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:name="com.google.android.gms.maps.MapFragment"/> //<--- An error appeared.

On my Android Manifest I've included all of the Uses-permisions, but I don't know what i'm doing wrong...

And by the way on my AndroidManifest I've included this :

 <meta-data
        android:name="com.google.android.maps.v2.API_KEY"
        android:value="AIzaSyC87hhgd6kKJZUMe5ZBC6ybeO2nQNX4KZc" />

Hope you can help me. Cheers.