Since I started to develop my first android application (Nearby Photos) I found the Android environment missing a lot of high level features which help the developer to produce high quality app.
One of the problem is the generation of assets for the numerous resolutions (l, m, h, x, xx) which should be part of the official ide not a third party tools.
Luckily a third party tool exists: Android Asset Studio. This online tools for Android let you upload an icon and it generates all the version for your project, even adapting them for dark or light themes.
It can manage generic icons, notification icons, action bar icons and many other assets.
For every Android developer this is a must! Here a screenshot from Android Asset Studio.