Extensible

The UI controls mentioned above were useful as a solid base that I could easily customize. All I was missing was a date and time picker in the style of Google Material. I programmed that within a few hours, and it is now available to the general public via the GitHub repository. I also found buttons, but not floating action buttons (FABs), which modern apps that use a Google Material style would need. Listing 1 shows the code to make a FAB from a button. Calling a FAB in the main program is then quite simple. Listing 2 shows you how.

Navigation, Data, and Structure

The major navigation elements are all used in the conference app. The Drawer navigation control with the hamburger menu (Figure 2) allows access to all areas of the program. A navigation bar at the bottom helps a user reach the main targets quickly.

Figure 2: The Drawer control at top left allows access to all areas of the program.

The conference schedule uses the SwipeView and TabBar elements, which users can use to switch between the days of the conference using swipe gestures or tabs. The StackView element lets users climb up through the different levels and view contextual details (Figure 3) relating to, for example, sessions, details, speakers, talks, and venues.

Figure 3: The contextual details can be designed as Pages with a StackView.

Developers can easily combine all these navigation elements; thus, even very complex apps are no problem for Qt. Because components and loaders dynamically generate the controls and pages, memory usage remains manageable, and the app remains fast as a whole.

The application pushes data into the filesystem in the usual way in the form of JSON files or stores them permanently in a SQLite database. Listing 3 contains the code for saving a list as a JSON array, and Figure 4 shows a typical application structure.

Figure 4: The complete app structure with Qt 5.7.

Conclusion

Following the release of version 5.7 and thanks to Qt Quick Controls 2, Qt is now an excellent choice for developing visually appealing, high-performance mobile apps. The advantage is that you need only one codebase for all platforms.

It can be somewhat difficult to find the appropriate pages in the documentation, because Qt is not just available for mobile devices, but also for desktop and embedded devices. The blog [7] gives developers a little assistance in this matter.

Qt is open source, but also available with a commercial license. Independent developers and start-ups need a license, which you can secure from $79 (EUR72) per month, because, unfortunately, the LGPL is not suitable for apps in Apple's App Store. If you have any questions about the licenses, your best bet is to watch the video [8] that discusses the legal situation in more detail.