A method for operating an electronic device having a flexible display (160; 860; 950; 1041) which comprises a first area (611; 811; 1311, 1331; 1511; 1711; 1811) and a second area (612; 812; 1312, 1332; 1512; 1712; 1812) separated by a bending axis, the method comprising: displaying a first graphic user interface, GUI, for character input on the first area and the second area of the flexible display (160; 860; 950; 1041); detecting a change in an angle between the first area and the second area of the flexible display from a first value to a second value which is different from the first value, at a first position of the flexible display, such that the first area of the flexible display approaches the second area of the flexible display; selecting a second GUI for character input corresponding to the second value based on pre-stored association information between angles between the first and second areas and GUIs; displaying the second GUI on the second area of the flexible display in replacement of the first GUI; detecting a change in the angle between the first area and the second area of the flexible display from the second value to a third value which is different from the first and second values, at the first position of the flexible display, such that the first area of the flexible display approaches the second area of the flexible display; selecting a third GUI for character input corresponding to the third value based on the pre-stored association information, the third GUI having a smaller size than the second GUI; and displaying the third GUI on the second area of the flexible display in replacement of the second GUI, wherein the third GUI is adjacent to an edge of the second area opposite to the bending axis, wherein a distance between the third GUI and the bending axis is greater than a distance between the second GUI and the bending axis. displaying a first graphic user interface, GUI, for character input on the first area and the second area of the flexible display (160; 860; 950; 1041); detecting a change in an angle between the first area and the second area of the flexible display from a first value to a second value which is different from the first value, at a first position of the flexible display, such that the first area of the flexible display approaches the second area of the flexible display; selecting a second GUI for character input corresponding to the second value based on pre-stored association information between angles between the first and second areas and GUIs; displaying the second GUI on the second area of the flexible display in replacement of the first GUI; detecting a change in the angle between the first area and the second area of the flexible display from the second value to a third value which is different from the first and second values, at the first position of the flexible display, such that the first area of the flexible display approaches the second area of the flexible display; selecting a third GUI for character input corresponding to the third value based on the pre-stored association information, the third GUI having a smaller size than the second GUI; and displaying the third GUI on the second area of the flexible display in replacement of the second GUI, wherein the third GUI is adjacent to an edge of the second area opposite to the bending axis, wherein a distance between the third GUI and the bending axis is greater than a distance between the second GUI and the bending axis.