  A common need for mobile application development by end-users or in computing
education is to transform a sketch of a user interface into wireframe code
using App Inventor, a popular block-based programming environment. As this task
is challenging and time-consuming, we present the Sketch2aia approach that
automates this process. Sketch2aia employs deep learning to detect the most
frequent user interface components and their position on a hand-drawn sketch
creating an intermediate representation of the user interface and then
automatically generates the App Inventor code of the wireframe. The approach
achieves an average user interface component classification accuracy of 87,72%
and results of a preliminary user evaluation indicate that it generates
wireframes that closely mirror the sketches in terms of visual similarity. The
approach has been implemented as a web tool and can be used to support the
end-user development of mobile applications effectively and efficiently as well
as the teaching of user interface design in K-12.
