There exist strict guidelines available 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 supplied in two distinct states: unselected and selected. It is recommended that tab icons are drawn as simple, flat shapes as opposed to graphics shown in 3D or isometric projection.
Android OS and Android apps are used on a wide range of hardware platforms using a wide range of hardware. In connection 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 shown on low, medium, and high density screens. Resolution-wise, the outer boundaries for the three resolutions are defined as 24×24, 32×32, and 48×48 pixels. Inner dimensions 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 display properly on a variety of devices 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, grayscale images. Just as tab icons, developers should not use 3D or isometric projections.
Pixel resolutions for menu icons are described in a slightly more complex way compared to tab icons. Instead of two resolutions defined for tab icons (inner shape and boundary box), the inner shape of menu icons can be smaller or bigger depending on whether they are square-shaped or not. If a menu icon is square-shaped, its dimensions should be smaller than for icons shaped otherwise. The reason for specifying two different size limits is to establish a consistent visual size across the two icon types.
The outer dimensions for low, medium, and high resolution icons are defined 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 boxes, while high-definition images should fit into 44×44 and 48×48 pixel boundaries respectively.
Instead of designing your own graphics conforming to these guidelines, Android developers have an option of getting ready-made images from professional designers. As an example, Android Tab Icons by Aha-Soft offer 112 unique tab graphics in selected and unselected states and all standard sizes. If an additional size is needed, developers can render images at any size by opening scalable vector sources. Android Tab Icons can be viewed and downloaded at www.aha-soft.com.