Ok never mind. After some research I found out that the android documentation for creating a search interface isn't complete: some things were left out like
1) No string should be hardcoded in the searchable conifguration
2) I should have this code in the <activity>
which does the search:
<meta-data
android:name="android.app.searchable"
android:resource="@xml/your search configuration file's name" />
3) I should also have this code in the <activity>
where I want the SearchView
to show up in the ActionBar
<meta-data
android:name="android.app.default_searchable"
android:value=".ActivityWhichCarriesOutTheSearch" />
For the sake of completion: Here is my manifest file which works:
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="false"
android:theme="@style/AppTheme">
<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:theme="@style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
<meta-data
android:name="android.app.default_searchable"
android:value=".SearchActivity" />
</activity>
<activity android:name=".SearchActivity"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.SEARCH" />
</intent-filter>
<meta-data android:name="android.app.searchable"
android:resource="@xml/searchable"/>
</activity>
</application>