The covid-19 app I made was so that progress of covid disease could monitored. The WHO and other credible sources had data and charts about its progress in each country and I fetched data from those sources into the app.
The app consisted of windows and each displayed a specific information. The user could switched between windows, just by selecting one of the buttons below the screen. Each window contained a webView that displayed data from some website. One for viewing data about covid from credible sources, another takes you to general news about covid around the world, another takes you to a help page where you can email me (the developer) if there is an improvement or bug I need to address.
My covid-19 app did not become a hit, because I noticed there were such other apps already on the app markets after I built mine. So it became a hobby product and I did not draw much attention to it.
How I built the covid-19 app
I designed the app first on paper, then transferred the design onto ANDROID STUDIO. I coded the app in JAVA 8, while the default JAVA version for the ANDROID STUDIO release at the time was still JAVA 7, but it supported JAVA 8 anyway. That was good news because the generics and JAVA NIO functionality was only supported in JAVA 8 upwards. XML and JSON were also used include the labels used in the app and to fetch some data from website with covid data.
