An electronic reading apparatus comprises an input unit receiving input operations, a detect unit detecting and capturing images reflected by the input unit and a processing unit configured to receive the images to generate interruption signals; determine whether the number of the interruption signals reaches a pre-determined value in a pre-determined time; calculate a movement direction and a distance of the object on the input unit if the number of the interruption signals reaches the pre-determined value in the pre-determined time; determine a cursor displacement on the display unit and display a movement track of the cursor on a display unit. An input method for previewing files is also provided.