Tracker

public class Tracker extends Object

A tracker is used to receive notifications for a detected item over time. Subclasses should override the relevant methods below to implement the logic associated with tracking an item in a particular way. Note that Tracker requires the Detector return stable IDs across frames for the same object. As a result, some Detectors (such as TextRecognizer) currently do not work well with Tracker, and developers may need to implement their own tracking mechanism.

Public Constructor Summary

Tracker()

Public Method Summary

void
onDone()
Called to indicate that the item associated with the ID previously reported via onNewItem(int, Object) has been assumed to be gone forever.
void
onMissing(Detections<T> detections)
Called if either the tracked item was not detected at all in a frame, or if the specific item identity associated with the tracker is not present in the current frame.
void
onNewItem(int id, T item)
This method is called to initially assert a new item when it is detected.
void
onUpdate(Detections<T> detections, T item)
As an item is detected over time, this method is called to give an update for the item in the context of the overall detection.

Inherited Method Summary

Public Constructors

public Tracker ()

Public Methods

public void onDone ()

Called to indicate that the item associated with the ID previously reported via onNewItem(int, Object) has been assumed to be gone forever.

public void onMissing (Detections<T> detections)

Called if either the tracked item was not detected at all in a frame, or if the specific item identity associated with the tracker is not present in the current frame. It's possible that the item may be missed for a few frames, and will reappear later, depending upon the detector settings. onUpdate(Detector.Detections, T) would then be called.

Parameters
detections full detection results for the frame and associated frame metadata

public void onNewItem (int id, T item)

This method is called to initially assert a new item when it is detected. The ID will remain constant for all calls to onUpdate(Detector.Detections, T) until onDone() is called.

onUpdate(Detector.Detections, T) is always called immediately following this method call, with the same item that was passed into this method.

Parameters
id ID representing the specific detected item
item detection information for the newly detected item

public void onUpdate (Detections<T> detections, T item)

As an item is detected over time, this method is called to give an update for the item in the context of the overall detection. Each item that is received has the same ID as the most recent call of onNewItem(int, Object). That is, it has been determined to be the same tracked item as was initially seen.

Parameters
detections full detection results and associated frame metadata
item detection information for the tracker's associated item