hid4java

To use hid4java in a Gradle project, ensure mavenCentral() is in your repositories and add the implementation dependency.

repositories {
    mavenCentral()
}

dependencies {
    implementation('org.hid4java:hid4java')
}

To build the project locally using Maven, clone the repository and run the mvn clean install command. The resulting JAR will be located in the target directory, and the install command will also place it in your local ~/.m2/repository for use in other local projects.

cd <workspace>
git clone https://github.com/gary-rowe/hid4java.git
cd hid4java

# Maven build
mvn clean install

If you need to use the latest development code (release candidates) from the Maven Central snapshot repository, you must add the Sonatype snapshot repository to your pom.xml.

  <!-- Enable Maven Central snapshots repository -->
<repositories>
  <repository>
    <id>oss.sonatype.org-snapshot</id>
    <url>https://oss.sonatype.org/content/repositories/snapshots</url>
    <releases>
      <enabled>false</enabled>
    </releases>
    <snapshots>
      <enabled>true</enabled>
    </snapshots>
  </repository>
</repositories>

To use hid4java in a Maven project, add the following dependency to your pom.xml. Note that the version in this example is 0.8.0; ensure you check for the latest stable version.

<dependencies>

  <!-- hid4java for cross-platform HID USB -->
  <dependency>
    <groupId>org.hid4java</groupId>
    <artifactId>hid4java</artifactId>
    <version>0.8.0</version>
  </dependency>

</dependencies>

The HidDeviceManager is the core component responsible for managing HID services. It provides access to the underlying JNA and hidapi library, handles device discovery, and manages device attachment/detachment events.

Key responsibilities include:

• Device Discovery: Scanning for connected HID devices.
• Event Handling: Detecting when devices are attached or detached (if configured).
• Lifecycle Management: Starting and stopping the device scanning daemon.
• Data Integration: Coordinating data read events and device write notifications.

Use start() to begin device discovery. If the scan interval in your HidServicesSpecification is greater than zero, start() will initiate a background daemon thread that periodically scans for changes.

Use stop() to shut down the scanning thread and close all currently attached HidDevice instances. This is typically called during application shutdown to ensure resources are released and the attached devices map is cleared.

// Assuming manager is already initialized
manager.start();

// ... perform operations ...

manager.stop();

The isScanning() method returns true if the background scanning thread is currently active and alive, and false otherwise.

if (manager.isScanning()) {
    // The background daemon is active
}

Call getAttachedHidDevices() to obtain a list of all currently connected HID devices. This method performs a fresh enumeration using the underlying hidapi library and wraps the results in HidDevice objects.

List<HidDevice> devices = manager.getAttachedHidDevices();
for (HidDevice device : devices) {
    System.out.println("Found device: " + device.getId());
}

The scan() method manually updates the internal list of attached devices. It compares the current state against the newly enumerated devices and fires HidServicesListener events (fireHidDeviceAttached or fireHidDeviceDetached) for any changes detected. This is useful if you need to force a refresh outside of the automated scanning interval.

manager.scan();