官方的一個簡單示例

// START SNIPPET: blink-gpio-snippet


/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Examples
 * FILENAME      :  BlinkGpioExample.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 - 2016 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
 * <http://www.gnu.org/licenses/lgpl-3.0.html>.
 * #L%
 */


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

/**
 * This example code demonstrates how to perform simple
 * blinking LED logic of a GPIO pin on the Raspberry Pi
 * using the Pi4J library.
 *
 * @author Robert Savage
 */
public class BlinkGpioExample {

    public static void main(String[] args) throws InterruptedException {

        System.out.println("<--Pi4J--> GPIO Blink Example ... started.");

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

        // provision gpio pin #01 & #03 as an output pins and blink
        final GpioPinDigitalOutput led1 = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_01);
        final GpioPinDigitalOutput led2 = gpio.provisionDigitalOutputPin(RaspiPin.GPIO_03);

        // provision gpio pin #02 as an input pin with its internal pull down resistor enabled
        final GpioPinDigitalInput myButton = gpio.provisionDigitalInputPin(RaspiPin.GPIO_02, PinPullResistance.PULL_DOWN);

        // create and register gpio pin listener
        myButton.addListener(new GpioPinListenerDigital() {
                @Override
                public void handleGpioPinDigitalStateChangeEvent(GpioPinDigitalStateChangeEvent event) {
                    // when button is pressed, speed up the blink rate on LED #2
                    if(event.getState().isHigh()){
                      led2.blink(200);
                    }
                    else{
                      led2.blink(1000);
                    }
                }
            });

        // continuously blink the led every 1/2 second for 15 seconds
        led1.blink(500, 15000);

        // continuously blink the led every 1 second
        led2.blink(1000);

        System.out.println(" ... the LED will continue blinking until the program is terminated.");
        System.out.println(" ... PRESS <CTRL-C> TO STOP THE PROGRAM.");

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

        // stop all GPIO activity/threads
        // (this method will forcefully shutdown all GPIO monitoring threads and scheduled tasks)
        // gpio.shutdown();   <--- implement this method call if you wish to terminate the Pi4J GPIO controller
    }
}

//END SNIPPET: blink-gpio-snippet

操作輸出

package com.xyes.pi4j.test;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;

import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalOutput;
import com.pi4j.io.gpio.RaspiPin;

public class EnvTest {
    public static void main(String[] args) {
        URL url = null;
        byte[] buffer = null;
        try {
            url = new URL("http://www.baidu.com");
            InputStream stream = url.openStream();
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            copy(stream, out);
            out.close();
            stream.close();
            buffer = out.toByteArray();
        } catch (Exception e1) {
            e1.printStackTrace();
        }
        final GpioController controller = GpioFactory.getInstance();
        final GpioPinDigitalOutput LED = controller.provisionDigitalOutputPin(RaspiPin.GPIO_15);
        for (byte b : buffer) {
            if (b > 100) {
                LED.high();
            } else {
                LED.low();
            }
            System.out.println("-->" + b);
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void copy(InputStream in, OutputStream out) throws IOException {
        byte[] buffer = new byte[1024];
        int len = 0;
        while ((len = in.read(buffer)) > 0) {
            out.write(buffer, 0, len);
        }
    }
}

操作輸入

import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalInput;
import com.pi4j.io.gpio.GpioPinDigitalOutput;
import com.pi4j.io.gpio.RaspiPin;
import com.pi4j.io.gpio.event.GpioPinListener;

public class ButtonTest implements GpioPinListener {
    private static final GpioController CONTROLLER = GpioFactory.getInstance();
    private static final GpioPinDigitalInput BUTTON = CONTROLLER.provisionDigitalInputPin(RaspiPin.GPIO_16);
    private static final GpioPinDigitalOutput LED = CONTROLLER.provisionDigitalOutputPin(RaspiPin.GPIO_15);

    public static void main(String[] args) {
        new ButtonTest().run();
    }

    public void run() {
        while (true) {
            if (BUTTON.isHigh()) {
                LED.high();
            } else {
                LED.low();
            }
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

監聽器方式讀取輸入

import java.util.Scanner;

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

public class GpioListener implements GpioPinListenerDigital {
    private static final GpioController CONTROLLER = GpioFactory.getInstance();
    private static final GpioPinDigitalInput BUTTON = CONTROLLER.provisionDigitalInputPin(RaspiPin.GPIO_16);
    private static final GpioPinDigitalOutput LED = CONTROLLER.provisionDigitalOutputPin(RaspiPin.GPIO_15);

    public static void main(String[] args) {
        new GpioListener().run();
    }

    public void run() {
        BUTTON.addListener(this);
        Scanner scanner = new Scanner(System.in);
        scanner.nextLine();
    }

    @Override
    public void handleGpioPinDigitalStateChangeEvent(GpioPinDigitalStateChangeEvent event) {
        boolean state = event.getState().isHigh();
        System.out.println("--->pin:" + event.getPin() + "|state:" + state);
        if (state) {
            LED.high();
        } else {
            LED.low();
        }
    }
}