A liquid cartridge includes a liquid chamber with a liquid outlet configured to supply the liquid from an interior of the chamber to an exterior of the chamber. An actuator is movable between a first position in which the liquid outlet is closed, and a second position in which the liquid outlet is open. A detector is positioned in the chamber, and is movable from a restricted position to a released position in response to movement of the actuator from the first to the second position. The detector is movable from the released position to the restricted position in response to movement of the actuator from the second to the first position.