try to display images from Pictures folder...

Hello hello ! A weird issue. I try to display images from picture folder of my android tablet..

I can display each name of file of the folder... But when I try to loadImage them, log tells me "Couldn't find the image ..."

It must be a simple stupid thing but I can't find it out... here's the code:

PImage img;
boolean FirstRun;
File images_dir=new File("/mnt/sdcard/Pictures/");
void setup()
{
  fullScreen();
  orientation(LANDSCAPE);
  FirstRun=true;
}

void draw()
{
  background(0, 0, 0);
  String [] images= images_dir.list();
  if (FirstRun) {
    for (String images_display : images)
    {
      println(images_display);
      img=loadImage(images_display);
      if (img!=null)   image(img, 0, 0);
      delay(5000);
    }
    FirstRun=false;
  }
}

thanks in advance for any help :-)