hello

I have a problem, I would like to stop the timer when I press a key.
I know I need to use the function "keyPressed" but I can't do it... Can you please help me?
Thanks!

1. //timer
   int l;
   
2. 
   
3. //time
   int seconde = 0;
   
4. 
   
5. //display score and attempts's number
   void score() {
     fill(255);
     //results display
     text(score, -0.25*width_size, 0.565*height_size);
     text(essais, 0.12*width_size, 0.565*height_size);
   }
   
   //controls if a fiduciary is on the right planet or not and flash in green or in red
   void flashing() {
     //-1 for the loop "for"
     int myObjSize=myObj.size();
     int planetsPropsSize=planetsProps.size();
     //time in milliseconds
     int timer = millis();
     int a=timer/1000;
     //time is seconds
     float k=timer/1000;
     //yellow rectangle to follow a fiducial
     fill(255, 255, 0, 100);
     //rect(objectPositionX, (objectPositionY-50), 80, 80);
     rect(objectPositionX-30, objectPositionY-30, 60, 60);
     //initializing score
     score=0;
   
     //for each PLANET
     for (int j = 0; j < planetsPropsSize; j++) {
   
       //table with planets properties
       tobj0 = (ArrayList)planetsProps.get(j);
       // An ArrayList doesn't know what it is storing so we have
       // to cast the object coming out
       //center of the planet X and Y
       Float planetX = (Float) tobj0.get(0);
       Float planetY =  (Float)tobj0.get(1);
       //width of the planet
       Float planetW=(Float)tobj0.get(2);
       //height of the planet
       Float planetH=(Float)tobj0.get(3);
       //status of the fiducial moving on the table
       String statusP = (String)tobj0.get(5);
       String statusNew = "none";
   
       //go through each object and check if there is any on the planet
       //for ( int i=0; i < myObjSize; i++) {
       for ( int i=0; i < myObj.size(); i++) { 
         //chosen object
   
         currentObjectOnTable = (TuioObject)myObj.get(i);                        
   
         //object's position
         objPosition = currentObjectOnTable.getPosition();  
         objectPositionX = ((objPosition.getX()+tx)*width_size*scaleFact)-330; // <==
         objectPositionY = ((objPosition.getY()+ty)*height_size*scaleFact)-300; // <==
   
   
         //check if the object is on the planet
         //if (sqrt(((objectPositionX+40)-planetX)*((objectPositionX+40)-planetX) + ((objectPositionY-40)-planetY)*((objectPositionY-40)-planetY)) <= planetW/2 ) { 
         if (sqrt(((objectPositionX)-planetX)*((objectPositionX)-planetX) + ((objectPositionY)-planetY)*((objectPositionY)-planetY)) <= planetW/2 ) {
           //don't fill the ellipse j
           noFill();
           //check fiducial's number and it's the good one       
           if (currentObjectOnTable.getSymbolID()==j) {
             statusNew = "correct";
             //modify the status to "correct"
             if (!statusP.equals("correct"))
             {
               tobj0.set(5, "correct");
               //println("planet " + j + " is " + (String)tobj0.get(5));
             }
             //increment score
             score+=1;
             //display a green circle
             stroke(174, 221, 60); //outine green
             ellipse(planetX, planetY, planetW, planetH);  
             break;
           }
           //check fiducial's number and it's not the good one
           else {
             statusNew = "false";
             //display a red circle
             stroke(254, 0, 0); //outine red
             ellipse(planetX, planetY, planetW, planetH);
             //changes the status of discovery of planet to "false"
             if (!statusP.equals("false"))
             {
               //println("last frame was " + statusP);
               essais+=1;
               tobj0.set(5, "false");
               //println("planet " + j + " is " + (String)tobj0.get(5));
               break;
             }
             break;
           }
         }
       } //endfor each object
   
       //check if no object was found on the planet
       if (statusNew.equals("none")) {
         tobj0.set(4, "0");
         tobj0.set(5, "none");
         //println("planet " + j + " is " + (String)tobj0.get(5));
       }
     } //endfor each planet
   
     //display score and attempts's number
     score();
   
     //time
     if (k>=0) {
       l=timer/1000;
       //text(l, 0.5*width_size, 0.565*height_size);
       text(l, 0.5*width_size, 0.565*height_size);
     }
   
   
     //sound when the time is finished
     if (timer/1000==60) {
       if (ping.isPlaying()==false) {
         ping.play();
       }
     }
   }