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| java.lang.Object | |
| ↳ | android.printservice.PrinterDiscoverySession |
This class encapsulates the interaction between a print service and the system during printer discovery. During printer discovery you are responsible for adding discovered printers, removing previously added printers that disappeared, and updating already added printers.
During the lifetime of this session you may be asked to start and stop
performing printer discovery multiple times. You will receive a call to onStartPrinterDiscovery(List) to start printer
discovery and a call to onStopPrinterDiscovery()
to stop printer discovery. When the system is no longer interested in printers
discovered by this session you will receive a call to onDestroy() at
which point the system will no longer call into the session and all the session
methods will do nothing.
Discovered printers are added by invoking addPrinters(List). Added printers that disappeared are
removed by invoking removePrinters(List). Added
printers whose properties or capabilities changed are updated through a call to
addPrinters(List). The printers added in this
session can be acquired via getPrinters() where the returned printers
will be an up-to-date snapshot of the printers that you reported during the
session. Printers are not persisted across sessions.
The system will make a call to onValidatePrinters(List) if you
need to update some printers. It is possible that you add a printer without
specifying its capabilities. This enables you to avoid querying all discovered
printers for their capabilities, rather querying the capabilities of a printer
only if necessary. For example, the system will request that you update a printer
if it gets selected by the user. When validating printers you do not need to
provide the printers' capabilities but may do so.
If the system is interested in being constantly updated for the state of a
printer you will receive a call to onStartPrinterStateTracking(PrinterId)
after which you will have to do a best effort to keep the system updated for
changes in the printer state and capabilities. You also must
update the printer capabilities if you did not provide them when adding it, or
the printer will be ignored. When the system is no longer interested in getting
updates for a printer you will receive a call to onStopPrinterStateTracking(PrinterId).
Note: All callbacks in this class are executed on the main application thread. You also have to invoke any method of this class on the main application thread.
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Constructor.
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Adds discovered printers.
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Gets the printers reported in this session.
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Gets the printers that should be tracked.
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Gets whether the session is destroyed.
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Gets whether printer discovery is started.
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Notifies you that the session is destroyed.
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Callback asking you to start printer discovery.
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Callback asking you to start tracking the state of a printer.
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Callback notifying you that you should stop printer discovery.
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Callback asking you to stop tracking the state of a printer.
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Callback asking you to validate that the given printers are valid, that
is they exist.
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Removes added printers.
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Inherited Methods | |||||||||||
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From class
java.lang.Object
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Adds discovered printers. Adding an already added printer updates it. Removed printers can be added again. You can call this method multiple times during the life of this session. Duplicates will be ignored.
Note: Calls to this method after the session is
destroyed, that is after the onDestroy() callback, will be ignored.
| printers | The printers to add. |
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Gets the printers reported in this session. For example, if you add two printers and remove one of them, the returned list will contain only the printer that was added but not removed.
Note: Calls to this method after the session is
destroyed, that is after the onDestroy() callback, will be ignored.
Gets the printers that should be tracked. These are printers that are
important to the user and for which you received a call to onStartPrinterStateTracking(PrinterId) asking you to observer their
state and reporting it to the system via addPrinters(List).
You will receive a call to onStopPrinterStateTracking(PrinterId)
if you should stop tracking a printer.
Note: Calls to this method after the session is
destroyed, that is after the onDestroy() callback, will be ignored.
Gets whether the session is destroyed.
Gets whether printer discovery is started.
Notifies you that the session is destroyed. After this callback is invoked
any calls to the methods of this class will be ignored, isDestroyed()
will return true and you will also no longer receive callbacks.
Callback asking you to start printer discovery. Discovered printers should be
added via calling addPrinters(List). Added printers that disappeared
should be removed via calling removePrinters(List). Added printers
whose properties or capabilities changed should be updated via calling addPrinters(List). You will receive a call to onStopPrinterDiscovery()
when you should stop printer discovery.
During the lifetime of this session all printers that are known to your print
service have to be added. The system does not retain any printers across sessions.
However, if you were asked to start and then stop performing printer discovery
in this session, then a subsequent discovering should not re-discover already
discovered printers. You can get the printers reported during this session by
calling getPrinters().
Note: You are also given a list of printers whose availability
has to be checked first. For example, these printers could be the user's favorite
ones, therefore they have to be verified first. You do not need
to provide the capabilities of the printers, rather verify whether they exist
similarly to onValidatePrinters(List).
| priorityList | The list of printers to validate first. Never null. |
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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
addPrinters(List).
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.
| printerId | The printer to start tracking. |
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Callback notifying you that you should stop printer discovery.
Callback asking you to stop tracking the state of a printer. The passed
in printer id is the one for which you received a call to onStartPrinterStateTracking(PrinterId).
| printerId | The printer to stop tracking. |
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Callback asking you to validate that the given printers are valid, that
is they exist. You are responsible for checking whether these printers
exist and for the ones that do exist notify the system via calling
addPrinters(List).
Note: You are not required to provide the printer capabilities when updating the printers that do exist.
| printerIds | The printers to validate. |
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Removes added printers. Removing an already removed or never added printer has no effect. Removed printers can be added again. You can call this method multiple times during the lifetime of this session.
Note: Calls to this method after the session is
destroyed, that is after the onDestroy() callback, will be ignored.
| printerIds | The ids of the removed printers. |
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