This study evaluated the status of accessibility in mobile apps by investigating the graphical user interface (GUI) structures and conformance to accessibility guidelines of 479 Android apps in 23 business categories from Google Play. An automated tool, IBM Mobile Accessibility Checker (MAC), was used to identify the accessibility issues, which were categorized as a violation (V), potential violation (PV), or warning (W). The results showed 94.8%, 97.5%, and 66.4% of apps studied contained issues related to V, PV, or W, respectively. Five widget categories (TextView, ImageView, View, Button, and ImageButton) were used to create 92% of the total number of the GUI elements and caused 89%, 78%, and 86% of V, PV, and W, respectively. These accessibility issues were mainly caused by lack of element focus, missing element description, low text color contrast, lack of sufficient spacing between elements, and less than minimum sizes of text fonts and elements. Together, these accessibility issues accounted for 97.0%, 77.8%, and 94.5% of V, PV, and W, respectively.
This study proposed coverage measures to estimate the percentage of accessibility issues identified by an automated tool. The result showed that MAC, on average, identified about 67% of accessibility issues in mobile apps.
Two new accessibility conformance measures were proposed in this study: inaccessible element rate (IAER) and accessibility issue rate (AIR). IAER estimates the percentage of GUI elements that are inaccessible. AIR calculates the percentage of the actual number of accessibility issues relative to the maximum number of accessibility issues. Average IAER and AIR scores were 27.3%, 19.9%, 6.3% and 20.7%, 15.0%, 5.4% for V, PV, and W, respectively, for the studied apps. The IAER score showed approximately 30% of the GUI elements had accessibility issues, and the AIR score indicated that 15% of the accessibility issues remained and need to be fixed to make the apps accessible.