Background not changing in Processing

Question

I am trying to do a very simple task where if a user clicks on the screen then background color should change 10 times randomly after every 200 ms.

Here is my code:

void setup()
{
 size(400,400);
}

void draw()
{

}

void mousePressed()
{
  for(int i = 0; i < 10; i++)
  {
      int startTime = millis();
      background(int(random(255)), int(random(255)), int(random(255)));
      while(millis() - startTime < 200){
      }
  }
}

However, the above code changes background color only once and not 10 times. I am not able to understand where I am going wrong.

Answer 1

Look at this article... http://wiki.processing.org/w/I_display_images_in_sequence_but_I_see_only_the_last_one._Why%3F The render in Processing is done only at the end of each draw cycle, so you only see the last color... I would try something like:

// to avoid starting at program's start...
boolean neverClicked = true;

// global
int startTime = 0;

// a counter
int times = 0;

void setup() {
  size(400, 400);
}

void draw() {

  // if clicked and passed half sec and 10 series not complete...
  if ( !neverClicked && millis() - startTime > 500 && times < 9) { 

    // change bg
    background(int(random(255)), int(random(255)), int(random(255)));

    // reset clock
    startTime = millis();

    // count how many times
    times++;
  }
}



void mousePressed() { 

  neverClicked = false;

  // reset timer and counter
  startTime = millis();
  times = 0;

  // do first change immediately
  background(int(random(255)), int(random(255)), int(random(255)));
}