Multitasking on a mobile device is profoundly different from that of a desktop machine. Applications on desktop machines have deep system resources to draw from in terms of memory, processor speed, power, and even screen space. Most modern desktops can run multiple applications concurrently, allowing each application to operate efficiently and remain responsive to user interaction. The limited resources on a mobile device, however, require the system to closely monitor how applications are functioning, policing their use of system assets in a much stricter manner. Therefore, if an application is not at the foreground of the device, the system will place it in the background state. On iOS devices, this transition is called backgrounding, while on Android devices it is referred to as background processing. For the remainder of this discussion, we will use the terms backgrounded and backgrounding generically to describe the behavior on both platforms.

When an app is in the...