java.lang.Object | ||||
↳ | android.content.Context | |||
↳ | android.content.ContextWrapper | |||
↳ | android.app.Service | |||
↳ | android.printservice.PrintService |
This is the base class for implementing print services. A print service knows how to discover and interact one or more printers via one or more protocols.
A print service is responsible for discovering printers, adding discovered printers,
removing added printers, and updating added printers. When the system is interested
in printers managed by your service it will call onCreatePrinterDiscoverySession()
from which you must return a new PrinterDiscoverySession
instance. The returned session encapsulates the interaction
between the system and your service during printer discovery. For description of this
interaction refer to the documentation for PrinterDiscoverySession
.
For every printer discovery session all printers have to be added since system does not retain printers across sessions. Hence, each printer known to this print service should be added only once during a discovery session. Only an already added printer can be removed or updated. Removed printers can be added again.
When a new print job targeted to a printer managed by this print service is is queued,
i.e. ready for processing by the print service, you will receive a call to onPrintJobQueued(PrintJob)
. The print service may handle the print job immediately
or schedule that for an appropriate time in the future. The list of all active print
jobs for this service is obtained by calling getActivePrintJobs()
. Active
print jobs are ones that are queued or started.
A print service is responsible for setting a print job's state as appropriate
while processing it. Initially, a print job is queued, i.e. PrintJob.isQueued()
returns true, which means that the document to be printed is
spooled by the system and the print service can begin processing it. You can obtain
the printed document by calling PrintJob.getDocument()
whose data is accessed via PrintDocument.getData()
.
After the print service starts printing the data it should set the print job's
state to started by calling start()
after which
PrintJob.isStarted()
would return true. Upon successful
completion, the print job should be marked as completed by calling PrintJob.complete()
after which PrintJob.isCompleted()
would return true. In case of a failure, the print job should
be marked as failed by calling PrintJob.fail(
String)
after which PrintJob.isFailed()
would
return true.
If a print job is queued or started and the user requests to cancel it, the print
service will receive a call to onRequestCancelPrintJob(PrintJob)
which
requests from the service to do best effort in canceling the job. In case the job
is successfully canceled, its state has to be marked as cancelled by calling PrintJob.cancel()
after which PrintJob.isCacnelled()
would return true.
The lifecycle of a print service is managed exclusively by the system and follows
the established service lifecycle. Additionally, starting or stopping a print service
is triggered exclusively by an explicit user action through enabling or disabling it
in the device settings. After the system binds to a print service, it calls onConnected()
. This method can be overriden by clients to perform post binding setup.
Also after the system unbinds from a print service, it calls onDisconnected()
.
This method can be overriden by clients to perform post unbinding cleanup. Your should
not do any work after the system disconnected from your print service since the
service can be killed at any time to reclaim memory. The system will not disconnect
from a print service if there are active print jobs for the printers managed by it.
A print service is declared as any other service in an AndroidManifest.xml but it must
also specify that it handles the Intent
with action android.printservice.PrintService
. Failure to declare this intent
will cause the system to ignore the print service. Additionally, a print service must
request the android.permission.BIND_PRINT_SERVICE
permission to ensure that only the system can
bind to it. Failure to declare this intent will cause the system to ignore the print
service. Following is an example declaration:
<service android:name=".MyPrintService" android:permission="android.permission.BIND_PRINT_SERVICE"> <intent-filter> <action android:name="android.printservice.PrintService" /> </intent-filter> . . . </service>
A print service can be configured by specifying an optional settings activity which exposes service specific settings, an optional add printers activity which is used for manual addition of printers, vendor name ,etc. It is a responsibility of the system to launch the settings and add printers activities when appropriate.
A print service is configured by providing a meta-data
entry in the manifest when declaring the service. A service declaration with a meta-data
tag is presented below:
<service android:name=".MyPrintService" android:permission="android.permission.BIND_PRINT_SERVICE"> <intent-filter> <action android:name="android.printservice.PrintService" /> </intent-filter> <meta-data android:name="android.printservice" android:resource="@xml/printservice" /> </service>
For more details for how to configure your print service via the meta-data refer to
SERVICE_META_DATA
and <
.
print-service
>
Note: All callbacks in this class are executed on the main application thread. You should also invoke any method of this class on the main application thread.
Constants | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
String | EXTRA_PRINTER_INFO |
If you declared an optional activity with advanced print options via the
advancedPrintOptionsActivity
attribute, this extra is used to pass in the currently selected printer's
PrinterInfo to your activity allowing you to inspect it.
|
|||||||||
String | EXTRA_PRINT_JOB_INFO |
If you declared an optional activity with advanced print options via the
advancedPrintOptionsActivity
attribute, this extra is used to pass in the currently constructed PrintJobInfo to your activity allowing you to modify it.
|
|||||||||
String | SERVICE_INTERFACE |
The Intent action that must be declared as handled by a service
in its manifest for the system to recognize it as a print service.
|
|||||||||
String | SERVICE_META_DATA |
Name under which a PrintService component publishes additional information
about itself.
|
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Inherited Constants | |||||||||||
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Public Methods | |||||||||||
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Generates a global printer id given the printer's locally unique one.
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Gets the active print jobs for the printers managed by this service.
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Return the communication channel to the service.
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Protected Methods | |||||||||||
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Set the base context for this ContextWrapper.
| |||||||||||
The system has connected to this service.
| |||||||||||
Callback asking you to create a new
PrinterDiscoverySession .
| |||||||||||
The system has disconnected from this service.
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Called when there is a queued print job for one of the printers
managed by this print service.
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Called when cancellation of a print job is requested.
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If you declared an optional activity with advanced print options via the
advancedPrintOptionsActivity
attribute, this extra is used to pass in the currently selected printer's
PrinterInfo
to your activity allowing you to inspect it.
If you declared an optional activity with advanced print options via the
advancedPrintOptionsActivity
attribute, this extra is used to pass in the currently constructed PrintJobInfo
to your activity allowing you to modify it. After you are
done, you must return the modified PrintJobInfo
via the same extra.
You cannot modify the passed in PrintJobInfo
directly, rather you
should build another one using the PrintJobInfo.Builder
class. You
can specify any standard properties and add advanced, printer specific,
ones via PrintJobInfo.Builder.putAdvancedOption(String, String)
and PrintJobInfo.Builder.putAdvancedOption(String, int)
. The advanced options
are not interpreted by the system, they will not be visible to applications,
and can only be accessed by your print service via PrintJob.getAdvancedStringOption(String)
and PrintJob.getAdvancedIntOption(String)
.
If the advanced print options activity offers changes to the standard print
options, you can get the current PrinterInfo
using the
EXTRA_PRINTER_INFO
extra which will allow you to present the user
with UI options supported by the current printer. For example, if the current
printer does not support a given media size, you should not offer it in the
advanced print options UI.
The Intent
action that must be declared as handled by a service
in its manifest for the system to recognize it as a print service.
Name under which a PrintService
component publishes additional information
about itself. This meta-data must reference a XML resource containing a
<
tag. This is
a sample XML file configuring a print service:
print-service
>
<print-service android:vendor="SomeVendor" android:settingsActivity="foo.bar.MySettingsActivity" andorid:addPrintersActivity="foo.bar.MyAddPrintersActivity." . . . />
For detailed configuration options that can be specified via the meta-data
refer to android.R.styleable.PrintService
.
If you declare a settings or add a printers activity, they have to be exported,
by setting the exported
activity attribute to true
. Also in case you want only the system to be able to start any of these
activities you can specify that they request the android.permission
.START_PRINT_SERVICE_CONFIG_ACTIVITY permission by setting the
permission
activity attribute.
Generates a global printer id given the printer's locally unique one.
localId | A locally unique id in the context of your print service. |
---|
Gets the active print jobs for the printers managed by this service. Active print jobs are ones that are not in a final state, i.e. whose state is queued or started.
Return the communication channel to the service. May return null if
clients can not bind to the service. The returned
IBinder
is usually for a complex interface
that has been described using
aidl.
Note that unlike other application components, calls on to the IBinder interface returned here may not happen on the main thread of the process. More information about the main thread can be found in Processes and Threads.
intent | The Intent that was used to bind to this service,
as given to Context.bindService . Note that any extras that were included with
the Intent at that point will not be seen here. |
---|
Set the base context for this ContextWrapper. All calls will then be delegated to the base context. Throws IllegalStateException if a base context has already been set.
base | The new base context for this wrapper. |
---|
Callback asking you to create a new PrinterDiscoverySession
.
The system has disconnected from this service.
Called when there is a queued print job for one of the printers managed by this print service.
printJob | The new queued print job. |
---|
Called when cancellation of a print job is requested. The service
should do best effort to fulfill the request. After the cancellation
is performed, the print job should be marked as cancelled state by
calling cancel()
.
printJob | The print job to cancel. |
---|