I need to resize several images inside ImageView to screen size. Currently I use scaleType="centerInside", it works good for bigger images to scale them down to screen size but doesn't expand small images.
All other suggested options crop or deform image. Is there any way to expand images (keeping ratio) via XML or do I have to do it manually in code?
You will be limited in how much you can do from the XML alone. The simplest way to expand a small drawable is to set android:layout_width and android:layout_height properties to what is desired (using density independent pixels dip). android:layout_width="320dip" will expand you to the full width of the screen (in portrait view).
If your images are photos or something with varying aspect ratios, then your only choice may be to inflate the view from code (after determining the correct size).