Here is a more complete example of an XML filter (the example above by itself will not work since it just shows a snippet and is missing the <FindBugsFilter>
begin and end tags):
<FindBugsFilter>
<Match>
<Class name="com.mycompany.foo" />
<Method name="bar" />
<Bug pattern="NP_BOOLEAN_RETURN_NULL" />
</Match>
</FindBugsFilter>
If you are using the Android Studio FindBugs plugin, browse to your XML filter file using File->Other Settings->Default Settings->Other Settings->FindBugs-IDEA->Filter->Exclude filter files->Add.