Operating in island mode when failure occurs in the active distribution network(ADN) is an effective measure to maintain an uninterrupted power supply to signifi- cant loads. A two-stage approach that integrates optimal island partition and power dispatch is proposed in this paper, considering photovoltaics (PVs), batteries (BEs) and electric vehicles (EVs) as the power sources. In the first stage, energy indices are defined to describe the energy demand and the maximum energy that these distributed energy resources (DERs) can provide, and islands are partitioned based on an energy constraint. Considering the variability the loads and PVs, the energy constraint is a necessary but not sufficient condition for island operation, so in the second stage, a power dispatch model is proposed as a test for the island partition result. Sequential power flow is also simulated to guarantee a feasible and optimized island status. The situations when the tests are not passed are analyzed and classified, and corresponding modifications for the first stage model are provided. Multiple levels of constraints based on the energy index are established for the island partition model. The proposed approach has been validated through simulation using a modified IEEE 69-bus system which is divided into three districts with different load variability characteristics.