Why can't redraw SecondApplet with processing?

Question

I am working with processing 3 and I am actually trying to work with 2 windows.

I would like redraw the second window but redraw do nothing (In final project data incoming from serial port will make the redraw). I don't know why.

Here is my code :

/*
*  17.09.16 : Logan Gallois
*  future imporvement :
*  Windows print graph of PWMs values from RGB LED
*  Add autoDetect position to move windows at the good location
*/

import processing.serial.*;
Serial myPort;
SecondApplet sa;

int[] numbers = new int[600];
boolean flag = false;
float var1;
float var2;
float var3;
float var4;

void setup() {
  size(1024, 576); //Affiche en plein écran
  surface.setResizable(false);
  noStroke();
  println(Serial.list()); /* Verifier dans la liste ou se trouve l'arduino */
  /* Puis changer en dessous la valeur en fonction */
  /* En general 0 pour windows et 1 pour un mac */
  String os=System.getProperty("os.name"); /* Detection automatique de l'OS */
  if(os != "Mac OS X") {
    if(Serial.list().length > 0) {
      myPort = new Serial(this, Serial.list()[0], 115200);
    }
  } else {
    if(Serial.list().length > 1) { /* Module BLE en position 0 */
      myPort = new Serial(this, Serial.list()[1], 115200);
    }
  }
  //Important : se câler sur la valeur en baud du prog Arduino
  myPort.bufferUntil('\n');
  String[] args = {"TwoFrameTest"};
  sa = new SecondApplet();
  PApplet.runSketch(args, sa);
  delay(100);
}

void draw() {
  if(!flag) {
    surface.setLocation(displayWidth/2-width/2-400,displayHeight/2-height/2);
    sa.frame.setTitle("Monitoring RGB Values");
    flag = true;
  }
  background(color(int(var1), int(var2), int(var3)));
  //sa.background(0, 255, 0);
    /*for(int i = 0 ;i<=width/10;i++){
     sa.stroke(200);
     sa.line((-frameCount%10)+i*10,0,(-frameCount%10)+i*10,height);

     sa.line(0,i*10,width,i*10);
    }

    sa.noFill();
    sa.stroke(0);
    sa.beginShape();
    for(int i = 0; i<numbers.length;i++){
      sa.vertex(i,350-numbers[i]);
    }
    sa.endShape();
    for(int i = 1; i<numbers.length;i++){
      numbers[i-1] = numbers[i];
    }
    numbers[numbers.length-1]=mouseY;*/
}

void mouseClicked() {
  print("clicked");
  sa.background(0, 0, 255);
  sa.fill(100);
  sa.redraw(); //This line do not redraw my 'sa' window
  background(0, 0, 255);
  redraw();
}

void serialEvent (Serial myPort) {

  String inString = myPort.readStringUntil('\n');
  //println(inString);
  if (inString != null) {

    inString = trim(inString); 
    int inputs[] = int(split(inString,',')); // on élude les virgules

    // on affecte nos 4 valeurs
    if(inputs.length == 4) {
     var1 = inputs[0];
     var2 = inputs[1];
     var3 = inputs[2];
     var4 = inputs[3];

    // On ré-échelonne la valeur analogique en valeur RGB
    var1 = map(var1, 0, 1023, 0, 255);
    var2 = map(var2, 0, 1023, 0, 255);
    var3 = map(var3, 0, 1023, 0, 255);
    var4 = map(var3, 0, 1023, 0, 255);
    print(int(var1));
    print(" ,");
    print(int(var2));
    print(" ,");
    print(int(var3));
    print(" ,");
    println(var4);
    }
  }
}

public class SecondApplet extends PApplet {

  public void settings() {
    size(600, 600);
    noLoop(); //I tried with and without that
  }
  public void draw() {

  }

  public void mouseClicked() {
    print("clicked2");
    background(0, 255, 0);
    redraw(); //This line works great
  }
}

Any Ideas ?

Answer 1

When posting, please try to narrow your problem down to an MCVE. That means taking out all the Serial stuff and just using basic mouse events.

Your second sketch's draw() function is empty. What do you expect calling redraw() to actually do?

Here's an example MCVE:

SecondApplet sa;

void setup() {
  size(500, 500); //Affiche en plein écran

  String[] args = {"TwoFrameTest"};
  sa = new SecondApplet();
  PApplet.runSketch(args, sa);
  delay(100);
}

void draw() {
  background(255, 0, 0);
}

void mouseClicked() {
  sa.redraw();
}

public class SecondApplet extends PApplet {

  public void settings() {
    size(100, 100);
    noLoop();
  }
  public void draw() {
    background(0);
    ellipse(random(width), random(height), 25, 25);
  }

  public void mouseClicked() {
    redraw();
  }
}

This MCVE works perfectly, and correctly triggers the second sketch's draw() function from both the first and second sketch windows.

I'd recommend working from this MCVE. If you still can't get it working, feel free to post a follow-up question, preferably without the serial stuff (which makes your sketch impossible to run since we don't have access to your hardware). Good luck.