Play store downloads/updates app in sequence because of the performance issues but still there are the cases when you need to download/upload things in parallel like AppStore or WhatsApp.
Easy-AndroidAppUpdater is an easy-to-use and fully customizable library to show update dialog to users. The update dialog can contain different app stores or direct download links.
Unsplash Photo Picker is a modular and customizable Android View that allows you to quickly search Unsplash.com for free high-quality photos with just a few lines of code.