There exist strict guidelines published for designing standard-compliant Android icons. Different design guidelines are published for tab icons and menu icons.
Tab icons are drawn in individual tabs in tabbed UI. Tab icons must be provided in two different states: selected and unselected. It is recommended that tab icons are created as simple, flat shapes as opposed to images drawn in 3D or isometric projection.
Android OS and Android apps are used on a multitude of hardware platforms employing a wide range of hardware. In reference to icon images, those devices can have different screen sizes, screen resolutions, pixel density and dimensions. To accommodate the variety of displays, Android developers must supply all tab icons used in their apps in at least three resolutions to be displayed on low, medium, and high density screens. Pixel-wise, the outer boundaries for the three sizes are defined as 24×24, 32×32, and 48×48 pixels. The size of the shape itself should not exceed 22×22, 28×28, and 42×42 pixels respectively. By providing all three standard resolutions, developers can ensure that their apps will be shown properly on a wide range of devices running the Android OS.
Menu icons are displayed in the “options” menu, and are shown to the user when they press the Menu button. Similar to tab icons, menu icons should be flat, grayscale images. Like tab icons, developers should not use 3D or isometric projections.
Pixel sizes for menu icons are described in a slightly more complex way compared to tab icons. Instead of just two sizes described for tab graphics (inner shape and boundary box), the inner shape of menu icons can be smaller or bigger depending on their shape. If a menu icon is square-shaped, its resolution should be smaller than for icons shaped otherwise. The reason for specifying two different sizes is to establish a consistent visual weight across the two icon types.
The outer dimensions for ldpi, mdpi and hdpi icons are described as 36×36, 48×48, and 72×72 pixels respectively. Inner shapes for square, low-definition icons is 22×22 pixels, while non-square icons should fit into a boundary box sized 24×24 pixels. Similarly, mdpi icons should fit 30×30 and 32×32 pixel boundaries, while high-definition images should fit into 44×44 and 48×48 pixel rectangles respectively.
Instead of designing your own icons matching these guidelines, Android developers have an option of ordering stock graphics from professional designers. As an example, Android Tab Icons by Aha-Soft include 112 unique tab images in selected and unselected states and all three standard resolutions. Should additional resolutions be required, developers can produce images at any size by opening scalable vector sources. Android Tab Icons can be viewed and downloaded at www.aha-soft.com.