There are precise guidelines available in reference to Android icons. Different design guidelines are available for tab icons and menu icons.
Tab icons represent individual tabs in tabbed interface. Tab icons should be supplied in two distinct states: unselected and selected. It is recommended that tab icons are drawn as simple, flat shapes as opposed to graphics drawn in 3D or isometric projection.
Android OS and Android apps can run on a variety of hardware platforms using a wide range of hardware. In reference to icon graphics, those platforms can have different display sizes, screen resolutions, pixel dimensions and density. 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 displays. Pixel-wise, the outer boundaries for the three resolutions 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 including all three standard resolutions, designers can ensure that their apps will be shown properly on a wide range of platforms running the Android OS.
Menu icons are displayed in the “options” menu, and are displayed to the user when they press the Menu button. Similar to tab icons, menu icons should be flat, greyscale images. Just as tab icons, developers cannot use 3D or isometric projections.
Pixel resolutions for menu icons are defined in a slightly more complex way compared to tab icons. Instead of just two resolutions described for tab icons (inner shape and boundary box), the inner shape of menu icons can be smaller or larger depending on whether they are square-shaped or not. If a menu icon is square-shaped, its dimensions should be smaller than for icons with different shapes. The reason for specifying two different size limits is to establish a consistent visual weight across the two icon types.
The outer dimensions for low, medium, and high resolution 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 dots. Similarly, medium-definition 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 graphics conforming to these guidelines, Android developers have an option of ordering stock icons from professional designers. As an example, Android Tab Icons by Aha-Soft offer 112 unique tab icons in both states and all three standard resolutions. Should additional resolutions be required, developers can render icons at any resolution by accessing scalable vector sources. Android Tab Icons can be viewed and downloaded at www.aha-soft.com.