com.pi4j.wiringpi.GpioInterrupt Maven / Gradle / Ivy
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package com.pi4j.wiringpi;
/*
* #%L
* **********************************************************************
* ORGANIZATION : Pi4J
* PROJECT : Pi4J :: Java Library (Core)
* FILENAME : GpioInterrupt.java
*
* This file is part of the Pi4J project. More information about
* this project can be found here: http://www.pi4j.com/
* **********************************************************************
* %%
* Copyright (C) 2012 - 2015 Pi4J
* %%
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Lesser Public License for more details.
*
* You should have received a copy of the GNU General Lesser Public
* License along with this program. If not, see
* .
* #L%
*/
import com.pi4j.util.NativeLibraryLoader;
import java.util.Vector;
/**
*
* This class provides static methods to configure the native Pi4J library to listen to GPIO
* interrupts and invoke callbacks into this class. Additionally, this class provides a listener
* registration allowing Java consumers to subscribe to GPIO pin state changes.
*
*
*
* Before using the Pi4J library, you need to ensure that the Java VM in configured with access to
* the following system libraries:
*
* - pi4j
* - wiringPi
*
* This library depends on the wiringPi native system library. (developed by
* Gordon Henderson @ http://wiringpi.com/)
*
*
*
* @see http://www.pi4j.com/
* @author Robert Savage (http://www.savagehomeautomation.com)
*/
public class GpioInterrupt {
private static Vector listeners = new Vector<>();
private Object lock;
// private constructor
private GpioInterrupt() {
// forbid object construction
}
static {
// Load the platform library
NativeLibraryLoader.load("libpi4j.so");
}
/**
*
* This method is used to instruct the native code to setup a monitoring thread to monitor
* interrupts that represent changes to the selected GPIO pin.
*
*
*
* The GPIO pin must first be exported before it can be monitored.
*
*
* @param pin GPIO pin number (not header pin number; not wiringPi pin number)
* @return A return value of a negative number represents an error. A return value of '0'
* represents success and that the GPIO pin is already being monitored. A return value
* of '1' represents success and that a new monitoring thread was created to handle the
* requested GPIO pin number.
*/
public static native int enablePinStateChangeCallback(int pin);
/**
*
* This method is used to instruct the native code to stop the monitoring thread monitoring
* interrupts on the selected GPIO pin.
*
*
* @param pin GPIO pin number (not header pin number; not wiringPi pin number)
* @return A return value of a negative number represents an error. A return value of '0'
* represents success and that no existing monitor was previously running. A return
* value of '1' represents success and that an existing monitoring thread was stopped
* for the requested GPIO pin number.
*/
public static native int disablePinStateChangeCallback(int pin);
/**
*
* This method is provided as the callback handler for the Pi4J native library to invoke when a
* GPIO interrupt is detected. This method should not be called from any Java consumers. (Thus
* is is marked as a private method.)
*
*
* @param pin GPIO pin number (not header pin number; not wiringPi pin number)
* @param state New GPIO pin state.
*/
@SuppressWarnings("unchecked")
private static void pinStateChangeCallback(int pin, boolean state) {
Vector listenersClone;
listenersClone = (Vector) listeners.clone();
for (int i = 0; i < listenersClone.size(); i++) {
GpioInterruptListener listener = listenersClone.elementAt(i);
if(listener != null) {
GpioInterruptEvent event = new GpioInterruptEvent(listener, pin, state);
listener.pinStateChange(event);
}
}
//System.out.println("GPIO PIN [" + pin + "] = " + state);
}
/**
*
* Java consumer code can all this method to register itself as a listener for pin state
* changes.
*
*
* @see com.pi4j.wiringpi.GpioInterruptListener
* @see com.pi4j.wiringpi.GpioInterruptEvent
*
* @param listener A class instance that implements the GpioInterruptListener interface.
*/
public static synchronized void addListener(GpioInterruptListener listener) {
if (!listeners.contains(listener)) {
listeners.addElement(listener);
}
}
/**
*
* Java consumer code can all this method to unregister itself as a listener for pin state
* changes.
*
*
* @see com.pi4j.wiringpi.GpioInterruptListener
* @see com.pi4j.wiringpi.GpioInterruptEvent
*
* @param listener A class instance that implements the GpioInterruptListener interface.
*/
public static synchronized void removeListener(GpioInterruptListener listener) {
if (listeners.contains(listener)) {
listeners.removeElement(listener);
}
}
/**
*
* Returns true if the listener is already registered for event callbacks.
*
*
* @see com.pi4j.wiringpi.GpioInterruptListener
* @see com.pi4j.wiringpi.GpioInterruptEvent
*
* @param listener A class instance that implements the GpioInterruptListener interface.
*/
public static synchronized boolean hasListener(GpioInterruptListener listener) {
return listeners.contains(listener);
}
}