org.placelab.client.tracker
Class HamsterTracker

java.lang.Object
  org.placelab.client.tracker.Tracker
      org.placelab.client.tracker.HamsterTracker

All Implemented Interfaces:

EstimateListener, SpotterListener

public class HamsterTracker

extends Tracker

implements EstimateListener

A Tracker that wraps another Tracker and makes it behave like a Hamster in a ball. This makes it possible to reduce jitter in some Trackers. That is, the wrapped Tracker must produce Estimates whose positions lie outside the radius of a center circle in order to move the Estimate produced by the HamsterTracker. When such an Estimate is encountered, the HamsterTracker's Estimate is shifted by no more than 50% of the distance to the new Estimate's location.

Field Summary

double

RADIUS

Constructor Summary

HamsterTracker(Tracker insideTracker)

Method Summary

boolean	acceptableMeasurement(Measurement m) Returns true if the tracker can make use of this reading to meaningfully update the estimate.
void	estimateUpdated(Tracker t, Estimate e, Measurement m) Implement this method to respond to updates from the Tracker(s) you are registered with.
Estimate	getEstimate()
double	getRadius()
protected void	resetImpl() Subclasses should implement this to reset themselves to their initial state.
void	setRadius(double newRadius) Sets the radius for which Estimates produced by the wrapped Tracker must fall away from the previous center to be incorporated into this HamsterTracker's Estimate.
java.lang.String	toString()
void	updateEstimate(Measurement m) Called to give the tracker a new measurement.
protected void	updateEstimateImpl(Measurement m) Subclasses should implement this to do the actual work of updating their Estimate with the given Measurement.
void	updateWithoutMeasurement(long timeSinceMeasurementMillis) This method notifies a tracker that time has elapsed without a new mesurement.

Methods inherited from class org.placelab.client.tracker.Tracker

addEstimateListener, fireEstimateUpdate, getLastUpdatedTime, gotMeasurement, numberOfMeasurements, removeEstimateListener, reset, spotterExceptionThrown

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

RADIUS

public double RADIUS

Constructor Detail

HamsterTracker

public HamsterTracker(Tracker insideTracker)

Method Detail

getRadius

public double getRadius()

setRadius

public void setRadius(double newRadius)

Sets the radius for which Estimates produced by the wrapped Tracker must fall away from the previous center to be incorporated into this HamsterTracker's Estimate. Calling this method has the side effect of resetting the HamsterTracker, since the previous center will no longer be meaningful with a different radius.

updateEstimateImpl

protected void updateEstimateImpl(Measurement m)

Description copied from class: Tracker

Subclasses should implement this to do the actual work of updating their Estimate with the given Measurement.

Specified by:

updateEstimateImpl in class Tracker

Parameters:

m - use this to update your Estimate

updateEstimate

public void updateEstimate(Measurement m)

Description copied from class: Tracker

Called to give the tracker a new measurement.

Overrides:

updateEstimate in class Tracker

Parameters:

m - A measurement from a Spotter.

See Also:

Tracker.acceptableMeasurement(Measurement)

getEstimate

public Estimate getEstimate()

Specified by:

getEstimate in class Tracker

Returns:

The Tracker's latest Estimate

acceptableMeasurement

public boolean acceptableMeasurement(Measurement m)

Description copied from class: Tracker

Returns true if the tracker can make use of this reading to meaningfully update the estimate.

Specified by:

acceptableMeasurement in class Tracker

updateWithoutMeasurement

public void updateWithoutMeasurement(long timeSinceMeasurementMillis)

Description copied from class: Tracker

This method notifies a tracker that time has elapsed without a new mesurement. This gives the tracker a chance to update its estimate to account for predicted motion.

Specified by:

updateWithoutMeasurement in class Tracker

toString

public java.lang.String toString()

estimateUpdated

public void estimateUpdated(Tracker t,
                            Estimate e,
                            Measurement m)

Description copied from interface: EstimateListener

Implement this method to respond to updates from the Tracker(s) you are registered with.

Specified by:

estimateUpdated in interface EstimateListener

Parameters:

t - the Tracker producing the Estimate

e - the Estimate produced by the Tracker

m - the latest Measurement used by the Tracker to produce the Estimate

resetImpl

protected void resetImpl()

Description copied from class: Tracker

Subclasses should implement this to reset themselves to their initial state.

Specified by:

resetImpl in class Tracker