While I am creating an Open File button using `selectInput()`. The problem is that the program keeps opening windows every time a user selects a file. How do I prevent this from happening?

```
void setup()
{
  size(500, 500);
  background(255);
}

void draw()
{
  noStroke();
  fill(255, 0, 0);
  rect(0, 0, 50, 20);

  if (mousePressed)
  {
    if (mouseX <= 50 && mouseY <= 20)
    {
      selectInput("Select a file to open:", "fileSelected");
    }
  }
}

void fileSelected(File selection)
{
  if (selection != null)
  {
    String absolutePath = selection.getAbsolutePath();
    String[] locations = split(absolutePath, "\\");
    String fileName = locations[locations.length - 1];

    //addFile(fileList);
    println(fileName);
  }
}

```