Xamarin.Android - Integrated environment for building not only native Android but iOS and Windows apps too.
Jasonette - Make an app by adding JSON to this app.
Qt Creator - Qt Creator is a cross-platform C++, JavaScript and QML integrated development environment. It is the fastest, easiest and most fun experience a C++ developer could wish for.
AppyBuilder - An App Inventor 2 spin-off. Formerly called AILiveComplete.
Rider - Rider is a cross-platform .NET IDE based on the IntelliJ platform and ReSharper.
AppMySite - An automated no-code app builder