Drag and Swipe with RecyclerView

Here is good tutorial.

Drag and Swipe with RecyclerView

Working with images

If you're working with images (as background for example) you could face with big sizes of files.
Something like JPEG file 1280X1920px could take about 0.5 - 1.0M depending of content.
And it increases APK size!
Very nice solution I found is WebP.
You can download one of converters here: xnconvert

In my case I have following result: 789kb -> 96 kb (80% quality)

TODO: Implement Realm

realm.io

Market coverage by Android app with minSdkVersion

According google report July 6, 2017. we have following situation:

Version	Codename	API	Distribution	Coverage by app with minSdkVersion
2.3.3 - 2.3.7	Gingerbread	10	0.70%	100.00%
4.0.3 - 4.0.4	Ice Cream Sandwich	15	0.70%	99.30%
4.1.x	Jelly Bean	16	2.80%	98.60%
4.2.x		17	4.10%	95.80%
4.3		18	1.20%	91.70%
4.4	KitKat	19	17.10%	90.50%
5	Lollipop	21	7.80%	73.40%
5.1		22	22.30%	65.60%
6	Marshmallow	23	31.80%	43.30%
7	Nougat	24	10.60%	11.50%
7.1		25	0.90%	0.90%

So, if you're developing with minSdkVersion=21 you cover about 3/4 of market.

And if you're developing with minSdkVersion=19 you cover more than 9/10 of market. 

MBaaS

Some useful links (Russian)