1. A method for controlling an electronic device having a child mode and an adult mode, the method executable by at least one processor of the electronic device, the method comprising: capturing a touch image of a finger contacting with a touch screen when a touch operation is applied to unlock the touch screen; calculating an area value of the captured touch image; comparing the calculated area value of the captured touch image with one or more predefined values to determine a comparison result; determining a type of user according to the comparison result, wherein a first area value A, a second area value B, and a parameter C are predefined, wherein the value of the parameter C is between 0 and 1, and A*(1−C)>B*(1+C); when the calculated area value of the touch image is larger than A*(1−C) and smaller than A*(1+C), the user is determined to be an adult; when the calculated area value of the touch image is larger than B*(1−C) and smaller than B*(1+C), the user is determined to be a child; and controlling the electronic device to alternatively enter the adult mode or the child mode according to the type of the user.