Hello! I'm a student, and I've a project about the interconnection of a mobile device and a Bluetooth module.
I use a Processing (2.0b7) to program an application on my mobile (LG L7 Optimus under android 4.0.3)
I must receive a signal from a bluetooth module (FB155BC) which emits in  continuous.
My device is paired (tested through applications such as Bluetooth SPP) and I see "0" or "1".
I found a library that perfectly answer my needs: Btserial ( https://github.com/arduino/BtSerial)
But when I compile my program, there is 1 luck on 20 that it work!
And when the program run I have a square but when I change the button status, the application doesn't react, filling the square doesn't change color  ...
Did I make a mistake? Please

My program:

import cc.arduino.btserial.*;

BtSerial bt;                                         // Create object from BtSerial class
String remoteAddress;                         // MAC address of the device to which the Android will connect
int val;                                                // Data received from the Bluetooth serial port

void setup() {
  size(displayWidth, displayHeight);
  rectMode(CENTER);
  bt = new BtSerial(this);                              //create the BtSerial object that will handle the connection
  remoteAddress = "00:19:01:21:66:F1";        //my bluetooth Mac Address
  bt.connect(remoteAddress);
}

void draw() { 
  background(255);            // Set background to white
  if (val == 0) {                   // If the serial value is 0,
  fill(0);                             // set fill to black
  } 
  else {                             // If the serial value is not 0,
    fill(204);                        // set fill to light gray
  }

  rect(width/2, height/2, width/3, width/3);            // draw a square in the center of the screen
}

void btSerialEvent(BtSerial bt) {
val = bt.read();                                                //update val whenever new data is received
}

void pause() {
  if (bt != null) {
    bt.disconnect();
  }
  println("Bluetooth disconnected");
}

void stop() {
  if (bt != null) {
    bt.disconnect();
  }
  println("Bluetooth disconnected");
}

void resume() {
  if (bt != null) {
    while (!bt.isConnected ()) {
      bt.connect(remoteAddress);
    }
    println("Bluetooth reconnected");
  }
}


My console view:

debug:
btserial 0.1.6 by Andreas Göransson & David Cuartielles & Tom Igoe http://www.arduino.cc
FATAL EXCEPTION: Animation Thread
java.lang.NullPointerException
    at cc.arduino.btserial.BtSerial.connect(Unknown Source)
    at processing.test.simplereadbtserial_processing_.SimpleReadbtserial_processing_.setup(SimpleReadbtserial_processing_.java:34)
    at processing.core.PApplet.handleDraw(Unknown Source)
    at processing.core.PGraphicsAndroid2D.requestDraw(Unknown Source)
    at processing.core.PApplet.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:856)
Bluetooth disconnected


And my Arduino program:

 #include <SoftwareSerial.h>
 
 SoftwareSerial bluetooth(8,9);         // Modem Bluetooth série connecté à la broche 8 TX et 9 RX
 int switchPin = 2;                          // Interrupteur connecté à la broche 2
 
 void setup()
 {
 pinMode(switchPin, INPUT);           // Mettre la broche 0 en entrée
 bluetooth.begin(9600);                   // commencer la conversion série à 9600 bps
 }
 
 void loop()
 {
  if (digitalRead(switchPin) == HIGH)     // Si l'interrupteur est à "1",
   { 
    bluetooth.write(byte(1));                   // Envoie d'un 1 à Processing
    Serial.write("1");
   }
   else                                                // Sinon                                            
      {                                
       bluetooth.write(byte(0));                // Envoie d'un 0 à Processing
       Serial.write("0");
      }
 delay(100);                                        // temporisation de 100 milliseconds
 }