I add some geojson layers to the map control once a layer is loaded and the control can show all the layer names. But I notice that all the checkboxes are unchecked by default. So that once I click the control to uncollapse it, all the layers disappear. And I have to check them one by one to display them again. Any way to fix this?
Have you tried something like
Although you may want to add your layer as a geojson layer: http://leafletjs.com/reference.html#geojson