Method of operating handheld electronic device and touch interface apparatus and storage medium using the same

A method of operating a handheld electronic device using a touch operating interface, the method suitable for using an operating interface displayed on a touch screen of the handheld electronic device to operate a function module of the handheld electronic device, comprising:

• activating the function module of the handheld electronic device and displaying a user interface of the function module on the touch screen, wherein the user interface has a first size;
• activating an operating function of the function module and displaying the operating interface on the touch screen;
• reducing the user interface of the function module and displaying the reduced user interface on an area of the touch screen excluding the operating interface, wherein the reduced user interface has a second size;
• and
• receiving a touch input comprising a slide operation on the operating interface and switching the operating interface to another operating interface with a same size as the operating interface and different key arrangement in response to receiving the touch input.