import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalInput;
import com.pi4j.io.gpio.PinPullResistance;
import com.pi4j.io.gpio.RaspiPin;
import com.pi4j.io.gpio.event.GpioPinListener;
import com.pi4j.io.gpio.event.GpioPinDigitalStateChangeEvent;
import com.pi4j.io.gpio.event.GpioPinListenerDigital;

/**
 * This example code demonstrates how to setup a listener
 * for GPIO pin state changes on the Raspberry Pi.
 *
 * @author Robert Savage
 */
public class ListenGpioExample
{
    public static void main(String args[]) throws InterruptedException
    {
        System.out.println("<--Pi4J--> GPIO Listen Example ... started.");

        // create gpio controller
        GpioController gpio = GpioFactory.getInstance();

        // provision gpio pin #02 as an input pin with its internal pull down resistor enabled
        GpioPinDigitalInput myButton0 = gpio.provisionDigitalInputPin(RaspiPin.GPIO_16, "MyButton-0", PinPullResistance.PULL_UP);
        GpioPinDigitalInput myButton1 = gpio.provisionDigitalInputPin(RaspiPin.GPIO_00, "MyButton-1", PinPullResistance.PULL_UP);
        GpioPinDigitalInput myButton2 = gpio.provisionDigitalInputPin(RaspiPin.GPIO_01, "MyButton-2", PinPullResistance.PULL_UP);
        GpioPinDigitalInput myButton3 = gpio.provisionDigitalInputPin(RaspiPin.GPIO_02, "MyButton-3", PinPullResistance.PULL_UP);
        GpioPinDigitalInput myButton4 = gpio.provisionDigitalInputPin(RaspiPin.GPIO_03, "MyButton-4", PinPullResistance.PULL_UP);
        GpioPinDigitalInput myButton5 = gpio.provisionDigitalInputPin(RaspiPin.GPIO_04, "MyButton-5", PinPullResistance.PULL_UP);
        GpioPinDigitalInput myButton6 = gpio.provisionDigitalInputPin(RaspiPin.GPIO_05, "MyButton-6", PinPullResistance.PULL_UP);
        GpioPinDigitalInput myButton7 = gpio.provisionDigitalInputPin(RaspiPin.GPIO_06, "MyButton-7", PinPullResistance.PULL_UP);

        // create and register gpio pin listener
        myButton0.addListener(new GpioExampleListener());
        myButton1.addListener(new GpioExampleListener());
        myButton2.addListener(new GpioExampleListener());
        myButton3.addListener(new GpioExampleListener());
        myButton4.addListener(new GpioExampleListener());
        myButton5.addListener(new GpioExampleListener());
        myButton6.addListener(new GpioExampleListener());
        myButton7.addListener(new GpioExampleListener());

        System.out.println(" ... complete the GPIO #02 circuit and see the listener feedback here in the console.");

        // keep program running until user aborts (CTRL-C)
        for (;;)
        {
            Thread.sleep(500);
        }
    }
}

/**
 * This class implements the GPIO listener interface
 * with the callback method for event notifications
 * when GPIO pin states change.
 *
 * @see GpioPinListener
 * @author Robert Savage
 */
class GpioExampleListener implements GpioPinListenerDigital
{
    @Override
    public void handleGpioPinDigitalStateChangeEvent(GpioPinDigitalStateChangeEvent event)
    {
        // display pin state on console
        System.out.println(" --> GPIO PIN STATE CHANGE: " + event.getPin() + " = "
                + event.getState());
    }
}