Android devices come in a great deal of different flavors when compared to iPhone devices. They can be slow, fast, crappy, great, low-res and ultra-hd. To best honor the device running your app, you should provide assets for various screen densities.
When you want your app to look great in various screen densities, the app’s image assets should be exported for the following densities:
These densities use a 2:3:4:6 scaling ratio, which means that
- 1 MDPI = 1 MDPI
- 1 HDPI = 1.5 MDPI
- 1 XHDPI = 2 MDPI
- 1 XXHDPI = 3 MDPI
For instance, the launcher icon is 48, 72, 96 or 144 pixels (mdpi, hdpi, xhdpi, and xxhdpi), depending on the screen density. This will then result in the points on the screen, which may be fewer than the amount of pixels, based on the screen density.
If you look at the Android Developer Iconography Page, it suggests that you should create your launcher icon in 864x864 pixels. This gives you an image that can be evenly divided to the various sizes.
This means that when you design artwork for your apps, you should either use vector based assets that can be exported in any resolution, or create original graphics to be 18 times larger than the MDPI pixel size (864/18 = 48). This gives you an image that can be evenly divided for all available screen densities.