Creating a User Interface

Abstract

Many MIDP applications are built to run on many different devices without modification. This is particularly difficult in the area of the user interface because devices have screens of all sizes, in grayscale and in color. Furthermore, devices vary widely in their input capabilities, from numeric keypads to alphabetic keyboards, soft keys, and even touch screens. The minimum screen size mandated by MIDP is 96×54 pixels, with at least one bit of color depth.¹ As for input, MIDP is fairly open ended: devices are expected to have some type of keyboard, or a touch screen, or possibly both.

Color depth is the number of bits that determine the color of a pixel on the screen. One bit allows for two colors (usually black and white). Four bits allows for 16 colors, which could be different levels of gray or a palette of other colors. In general, N bits allow 2 to the power of N colors or levels of gray.