Android : Unfortunately google maps has stopped

I would get google map on my emulator. I followed the instructions on When I run the application an error's message appears:Unfortunately DemoGoogleMapsV2 has stopped.

my androidmanifest.xml:

<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="17" />
<permission android:name="com.demogooglemapsv2.permission.MAPS_RECEIVE"
android:protectionLevel="signature"/>
<uses-permission android:name="com.demogooglemapsv2.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"/>
<!-- The following two permissions are not required to use
Google Maps Android API, but are recommended. -->
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

<uses-feature
android:glEsVersion="0x00020000"
android:required="true"/>

<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >

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

<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>

</manifest>

my activity_main.xml:

<android:id="@+id/map"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:name="com.google.android.gms.maps.MapFragment"/>

my MainActivity.java:

 package com.demogooglemapsv2;
import android.app.Activity;
import android.os.Bundle;

public class MainActivity extends Activity {

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