Android Question Auto Update app

hi what the best way to update app when it is opned?

for exemple i open my app and show checking the version
if version is > of my version go to my host and download and instal new version

if user dont instal cant enter on the app only the new version

have a simple way to make this or is harder to make?

i m image use http2 to see the version but to download and install *-*

later download finish start instal i think this is not simple


any sugestion?