MagstripeListener Class Reference

Description

Base class for receiving events related to the magstripe reader on a Grabba device.

At present, only one event is supported by this class:

• dataEvent - magnetic stripe was scanned with at least one track read successfully

Each event may invoke callbacks in two ways:

• Subclassing - the relevant event methods (e.g. dataEvent) are called directly
  • This approach is recommended wherever feasible, due to its simplicity
  • To use it, create an object of a suitable subclass, which overrides the desired event method(s)
• Delegation - event methods trigger method calls for a delegate object
  • This approach is only recommended when the callback handler must inherit from a different base class
  • To use it, create an object of this class, create an object of a class which implements MagstripeInterface, then call setDelegate() to provide the necessary linkage.

Note

Delegation will be disabled for an event if that event's method is subclassed, unless the subclass calls the superclass' equivalent method from within its override thereof.

By default, each listener object will receive event notifications from the driver for its entire lifetime; the enable() and disable() methods may be used if control is required over whether notifications are received.

The default behaviour for each event, if not overridden, on an enabled listener object is as follows:

• If setDelegate() has not been called, then take no action
• If the last call to setDelegate() accepted a null reference, then take no action
• If the last call to setDelegate() accepted a non-null object reference, then delegate to that object

Overrides need not call the superclass' equivalent method unless it is necessary to preserve the delegation (i.e. to support both subclassing and delegation from a single object).

Thread safety: This class is intended to be thread-safe; any classes deriving from it should ensure that the relevant methods are callable from any thread.

See also

MagstripeAPI for related API functions

Inheritance diagram for MagstripeListener:

Public Member Functions
	MagstripeListener ()
	Default constructor - builds a listener object then enables receipt of events from the driver.
	MagstripeListener (boolean startEnabled)
	Constructor - builds a listener object then optionally enables receipt of events from the driver. More...
void	dataEvent (@NonNull MagstripeData data)
	Callback which is invoked when one or more tracks are successfully read from a magstripe card. More...
final void	disable ()
	Disable receipt of events from the driver by this object. More...
final void	enable ()
	Enable receipt of events from the driver by this object. More...
final void	setDelegate (Delegate newDelegate)
	Set the delegate which will receive event callbacks if default listener behaviour is not overridden. More...

Constructor & Destructor Documentation

MagstripeListener()

MagstripeListener

(

boolean

startEnabled

)

Constructor - builds a listener object then optionally enables receipt of events from the driver.

Parameters

startEnabled

If set, the listener object is enabled immediately (equivalent of default constructor), otherwise it is disabled until the first call to enable()

Member Function Documentation

dataEvent()

void dataEvent

(

@NonNull MagstripeData

data

)

Callback which is invoked when one or more tracks are successfully read from a magstripe card.

This method will be triggered after a successful swipe of a magstripe card through the Grabba device's reading slot, providing the listener object is enabled.

Override this method to receive callbacks when the object is enabled (at construction or via enable()) and the event is triggered.

Note

Overrides of this method are required to be thread-safe; no guarantees are made about which thread(s) they will be called from.

Parameters

data	The data which was read from the magnetic stripe; see MagstripeData for details

Implements MagstripeInterface.

disable()

final void disable ( )

inherited

Disable receipt of events from the driver by this object.

This has no effect if the object was already disabled.

enable()

final void enable ( )

inherited

Enable receipt of events from the driver by this object.

This has no effect if the object was already enabled.

setDelegate()

final void setDelegate ( Delegate  newDelegate )

inherited

Set the delegate which will receive event callbacks if default listener behaviour is not overridden.

Delegation may alternatively be disabled by providing a null reference here.

Parameters

newDelegate

If null, disables delegation; if non-null, enables delegation and sets the delegate to the supplied object.