Impacts on Apps

The system “steals” touch events from apps to handle these navigation gestures. If your app relies upon touch events near the edges, you may run into some problems. In particular, the user may get confused when trying to use your app, trying to apply your gestures and winding up with system responses. While simple taps will be passed through to your app from these system edge areas, anything else is indeterminate.

For example, suppose that you have a ViewPager that spans the width of the screen. Based on a subtle and invisible line of demarcation, the same gesture might either switch pages in your pager or invoke a “back” action (probably navigating out of this screen).

You may need to consider redesigning your UI to:

• Avoid expecting swipe gestures near screen edges, and
• Provide a visual distinction of where swipe gestures are valid, to help the user learn where to swipe to control your UI

Technically, there is a way that you can tell the system to ignore “back” gestures and pass those along to your app. However, from a practical standpoint, this has problems:

• The user may not know how to exit this screen and may get frustrated as a result
• This approach may not be honored by manufacturer-specific nav schemes

Avoiding the edges is a safer approach.

The OS informs your app about “window insets”, to indicate areas where the system will steal your touch events. This library helps you leverage that information to adjust your UI based upon the particular device’s window insets, based on device model and whether the user has enabled gesture-based nav or not.