“What canvas size should my design be for Android / Material?”
ANSWER: It is hard with Android as there are 100s of different form factors of Android device screens. Here’s what I do…
If you can, it helps to use a dedicated UI design tool like Sketch App (Mac only). Here’s my method for Sketch or Photoshop:
1. Pick a typical “largish” screen. I currently use 360dp x 640dp (@1x or 100%) – which is 1080px x 1920px @ XXHDPI or @3x.
2. Place in guidelines, or draw a box, showing the dimensions for a typical smaller Android device, I use 320dp x 480dp – which is 960px x 1440px @ XXHDPI
3. Check the elements of your design regularly that they fits the minimum width and minimum height. Height is only really important if scrolling is not desired on smaller devices.
Should I work at the high or low density?
ANSWER: You need to be sure your artwork is scalable to the largest screen density – especially if you have bitmap graphics or photos in you design. Sketch requires you work @1x or 100% and leaves it up to you to make sure you source art at least x3 bigger. Photoshop offers no help, and I have previously worked at the with a canvas set to the @3x or 300% dimensions to be sure my artwork is high res enough.
XXHDPI or XXXHDPI?
ANSWER: Very few devices have screens that are actually set at XXXHDPI (@4x or 400%). Actually, as of this article, no devices are, only a few system icons – probably because no human eye could perceive the benefit. So I wouldn’t bother with XXXHDPI for you canvas, only for the icon output. If you want an XXXHDPI canvas, you can work out for yourself what the @4x canvas values would be.