Callback asking you to start tracking the state of a printer. Tracking the state means that you should do a best effort to observe the state of this printer and notify the system if that state changes via calling PrinterDiscoverySession.addPrinters(java.util.List<android.print.PrinterInfo>).

Note: A printer can be initially added without its capabilities to avoid polling printers that the user will not select. However, after this method is called you are expected to update the printer including its capabilities. Otherwise, the printer will be ignored.

A scenario when you may be requested to track a printer's state is if the user selects that printer and the system has to present print options UI based on the printer's capabilities. In this case the user should be promptly informed if, for example, the printer becomes unavailable.

[Android Documentation]