In practice, the mobile sensor networks have two important tasks: firstly, sensors should be able to locate themselves close to where major events are happening so that event tracking becomes possible; secondly, the sensor networks should also maintain a good area coverage over the environment in order to detect new events. Because these two tasks are usually conflicting with each other, a coverage control policy should be able to balance the event and area coverage of the environment. However, most existing work is to achieve either optimal event coverage or optimal area coverage over the environment. In this thesis, a Voronoi-based coverage control with task assignment is introduced: each sensor is allowed to switch between event and area coverage depending on the intensity of events within its Voronoi cell, and both continuous-time and discrete-time control for sensor positions are discussed.