Events are generated on a BlackBerry® device in response to specific situations that occur on the device, including the following:

• User input, such as pressing a key, clicking the trackball or trackpad, or touching the screen
• System status, such as wireless coverage changes, low battery power, or backlight changes
• Messages from other applications on the device

BlackBerry device applications that you create are typically event-driven, meaning that they monitor the device for particular events and respond accordingly. For example, if your application includes a UI with fields that a BlackBerry device user can click, your application should respond with appropriate actions when the user clicks the fields, such as displaying a new screen.

• Using listeners
  
• Add a generic listener for a field
  
• Add a custom listener for a field