Detecting keyboard, D-Pad, and Trackball events

The most common input device among all is the keyboard. This is true for Android too. An Android keyboard can be physical: in the device front face (like traditional Blackberries) or on a slide-out screen. However, a keyboard is more commonly virtual, that is, emulated on the screen at the cost of a large portion of space taken. In addition to the keyboard itself, every Android device must include a few physical or emulated buttons such as Menu, Home, and Tasks.

A much less common type of input device is the Directional-Pad. A D-Pad is a set of physical buttons to move up, down, left, or right and a specific action/confirmation button. Although they often disappear from recent phones and tablets, D-Pads remain one of the most convenient ways to move across text or UI widgets. D-Pads are often replaced by trackballs. Trackballs behave similarly to a mouse (the one with a ball inside) that would be upside down. Some trackballs are analogical,...