17. An electronic device for gesture-based key input, comprising: a camera; a display configured to display a virtual keyboard; and a controller configured to: control a display of the virtual keyboard according to a typing mode selected from among a single-hand typing mode and a double-hand typing mode, recognize a gesture for an input region on a 3-D space corresponding to the virtual keyboard by analyzing an image obtained through the camera, and obtain a key input based on the recognized gesture, wherein: the controller displays a first virtual keyboard when the single-hand typing mode is selected and displays a second virtual keyboard when the double-hand typing mode is selected, and the number of keys of the second virtual keyboard is larger than the number of keys of the first virtual keyboard, the first virtual keyboard comprises any one of a 3×3 keyboard and a 3×4 keyboard, and the second virtual keyboard comprises a QWERTY keyboard.
18. The electronic device of claim 17 , wherein the controller displays the virtual keyboard larger when the double-hand typing mode is selected than when the single-hand typing mode is selected.