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Event Tracking

Artifact ID

Gradle

dependencies {
    compile "org.jtrim2:jtrim-event-track:${jtrimVersion}"
}

Maven

<dependencies>
    <dependency>
        <groupId>org.jtrim2</groupId>
        <artifactId>jtrim-event-track</artifactId>
        <version>${jtrimVersion}</version>
        <scope>compile</scope>
    </dependency>
</dependencies>

Dependencies

  • "org.jtrim2:jtrim-executor"
    • "org.jtrim2:jtrim-concurrent"
      • "org.jtrim2:jtrim-collections"
        • "org.jtrim2:jtrim-utils"

Description

This module allows tracking what action caused what. The causes are tracked by an implementation of the EventTracker interface. The EventTracker interface allows creating listener managers and they can track event causes the following ways:

  • If a listener notified by a listener manager of the EventTracker causes an event to be fired for another listener manager also created by the same EventTracker. The second event notification is said to be caused by the first (calling) event notification.
  • An EventTracker allows wrapping executors (TaskExecutor). If an event listener submits a task to such an executor (possibly indirectly), the submitted task is treated as if it was called synchronously for event cause tracking purposes.

This event tracking mechanism was designed to detect circular event notifications. Circular event notifications naturally happen when two components are kept in sync with each other regardless which is changed by the user. For example: When showing an image (possibly zoomed), one might display a small overview of the whole image. This small overview can display which part of the image is shown and might also allow the user to select which part of the image is to be shown in the main window. Since the image overview and the main image display must be kept sync, each of them must update the other one when the image is panned. This module allows one generic solution to such a problem to prevent the recursion by avoiding recursive event notification.

Core interface

  • EventTracker: Allows tracking causes of events.

Core classes

  • LinkedEventTracker: A generic implementation of EventTracker.
  • LocalEventTracker: An implementation of EventTracker allowing to remove all registered listeners in a single method call.