A multimedia system may include a main control unit of a bicycle lock, a display unit, and a cloud server. The display unit may include a plurality of display screens. The main control unit may report an electric quantity of the shared bicycle to the cloud server when the bicycle lock is unlocked. The cloud server may send multimedia information to the main control unit when the shared bicycle is at a high level of electric quantity. The main control unit may refrain from turning on the display unit when the shared bicycle is at a low level of electric quantity. The multimedia system may turn on or off a display screen according to the electric quantity of the shared bicycle, and the display screen may display the multimedia information for advertising. The multimedia system may further include a navigation module to provide navigation for users and facilitate user travel.