How can i access all marker on my GoogleMap-Object (android maps v2) and set them (in)visible?

How can i access all marker on my GoogleMap-Object (android maps v2) and
set them (in)visible?

i am currently trying to implement an ActionBar-Button that on usage sets
all my markers on my GoogleMap-object visible or invisible. My problem is
that i don't know how i can get a reference to all my markers once they
have been created and are shown on my map. Im looking for a solution where
i stash all my marker-objects into an array, that i can access in other
parts of my code aswell. is this approach reasonable?
here is what i am thinking of:
private Marker[] mMarkerArray = null;
for (int i = 0; i < MainActivity.customers.size(); i++) {
LatLng location = new LatLng(mData.lat, mData.lng);
Marker marker = mMap.addMarker(new MarkerOptions().position(location)
.title(mData.title)
.snippet(mData.snippet));
mMarkerArray.add(marker);
}
and set all my markers invisible on within another method:
for (int i = 0; i < MainActivity.customers.size(); i++) {
marker[i].setVisible(false);
}
it refuses to add the markers to a Marker[]-array. how can i achieve it?
mMarkerArray.add(marker) doesnt work