Android class for GPIO control

GPIO.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/**
This class allows you to control GPIO pins form android, by abstracting the command line excecution into a java class.
IMPORTANT NOTE: Requires root to run, since it is required to write to GPIO ports in /sys/class/gpio/
*/
public class GPIO {

	static String TAG = GPIO.class.getSimpleName();

	public static String DIRECTION_IN = "in";
	public static String DIRECTION_OUT = "out";

	public static int VALUE_ON = 1;
	public static int VALUE_OFF = 0;

	private String port;
	private int pin;
	
	//Constructors
	public GPIO(int pin) {
		this.port = "gpio" + pin;
		this.pin = pin;
	}

	public GPIO(int pin, String direction) {
		this.port = "gpio" + pin;
		this.pin = pin;

		initPin(direction);
	}

	/// Export GPIO pin
	private boolean activatePin() {
		String command = String.format("echo %d > /sys/class/gpio/export", this.pin);
		try {
			Runtime.getRuntime().exec(new String[]{"su", "-c", command});
			return true;
		} catch (IOException e) {
			log.e(TAG, "Failed to export " + port, e);
			return false;
		}
	}

	/// Unexport GPIO pin
	public boolean deactivatePin() {
		String command = String.format("echo %d > /sys/class/gpio/unexport", this.pin);
		try {
			Runtime.getRuntime().exec(new String[]{"su", "-c", command});
			return true;
		} catch (IOException e) {
			log.e(TAG, "Failed to unexport " + port, e);
			return false;
		}
	}

	/// Initialise the GPIO pin 
	public int initPin(String direction) {
		int retour = 0;
		boolean ret = true;

		// see if gpio is already set
		retour = getValue();
		if (retour == -1) {
			// unexport the gpio
			ret = deactivatePin();
			if (!ret) {
				retour = -1;
			}

			//export the gpio
			ret = activatePin();
			if (!ret) {
				retour = -2;
			}
		}

		// check if gpio direction is defined
		String ret2 = getDirection();
		if (!ret2.contains(direction)) {
			// set the direction (in or out)
			ret = setDirection(direction);
			if (!ret) {
				retour = -3;
			}
		}

		return retour;
	}

	/// Get direction of GPIO
	public String getDirection() {
		String command = String.format("cat /sys/class/gpio/%s/direction", this.port);
		try {
			Process p = Runtime.getRuntime().exec(new String[]{"su", "-c", command});
			BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
			StringBuilder text = new StringBuilder();
			String line;
			while ((line = reader.readLine()) != null) {
				text.append(line);
				text.append("\n");
			}
			String retour = text.toString();
			return retour;
		} catch (IOException e) {
			log.e(TAG, "Failed to get direction of " + port, e);
			return "";
		}
	}

	/// Get state of GPIO for input and output and test if it is configurate
	public int getValue() {
		String command = String.format("cat /sys/class/gpio/%s/value", this.port);
		try {
			Process p = Runtime.getRuntime().exec(new String[]{"su", "-c", command});
			BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
			StringBuilder text = new StringBuilder();
			String line;
			while ((line = reader.readLine()) != null) {
				text.append(line);
				text.append("\n");
			}
			try {
				String retour = text.toString();
				if (retour.equals("")) {
					return -1;
				} else {
					return Integer.parseInt(retour.substring(0, 1));
				}
			} catch (NumberFormatException nfe) {
				return -1;
			}
		} catch (IOException e) {
			log.e(TAG, "Failed to get value of " + port, e);
			return -1;
		}
	}

	/// Set the value of the GPIO output
	public boolean setValue(int value) {
		String command = String.format("echo %d > /sys/class/gpio/%s/value", value, this.port);
		try {
			String[] test = new String[]{"su", "-c", command};
			Runtime.getRuntime().exec(test);
			return true;
		} catch (IOException e) {
			log.e(TAG, "Failed to set value of " + port, e);
			return false;
		}
	}

	/// Set the direction of the GPIO pin
	public boolean setDirection(String direction) {
		String command = String.format("echo %s > /sys/class/gpio/%s/direction", direction, this.port);
		try {
			Runtime.getRuntime().exec(new String[]{"su", "-c", command});
			return true;
		} catch (IOException e) {
			log.e(TAG, "Failed to set direction of " + port, e);
			return false;
		}
	}

}