nice one!

The error does not occur because of :

• //sdcard//box/box00006.png versus 
• /storage/emulated/0/box/box00006.png

It occurs because folderSelected runs in a parallel thread and draw() tries to display the image before it is loaded by the parallel thread (my theory)


Solution:
load image in draw() when String pathGlobal is set and check whether it is check in draw()

[edited] or let draw() wait until image is ok - see next post...

I run a windows system

1. //  https://forum.processing.org/topic/selection-getabolutepath-to-loadimage
2. import java.io.File;
3. //
4. String pathGlobal;
5. PImage image1;
6. //
7. // ---------------------------------------------------------------
8. //
9. void setup()
10. {
11.   // init
12.   size(800, 600);
13. } // func
14. //
15. //
16. void draw()
17. {
18.   background(255);
19.   if ((!(pathGlobal==null)) &&
20.     image1==null )
21.   {
22.     image1=loadImage(  pathGlobal   );
23.   }
24.   if (!(image1==null ))
25.   {
26.     image ( image1, 0, 0 );
27.   }
28.   else {
29.     fill(0);
30.     text ("Please click mouse to load image.", 30, 30);
31.   }
32. } // func
33. //
34. //-------------
35. void chooseFolder() {
36.   File folderToStartFrom = new File( "D://*.*" );
37.   selectInput("Select an image ", "folderSelected", folderToStartFrom );
38. }
39. //
40. void folderSelected(File selection) {
41.   // this runs in another thread parallel to the main thread
42.   if (selection == null) {
43.     println("Window was closed or the user hit cancel.");
44.   }
45.   else {
46.     println("User selected " + selection.getAbsolutePath());
47.     pathGlobal = selection.getAbsolutePath();
48.     println (pathGlobal);
49.   }
50. }
51. // =====================================================================
52. void mouseReleased() {
53.   chooseFolder();
54. }
55. // =====================================================================

or in short: :

1. //  https://forum.processing.org/topic/selection-getabolutepath-to-loadimage
2. import java.io.File;
3. //
4. PImage image1;
5. //
6. // ---------------------------------------------------------------
7. //
8. void setup()
9. {
10.   // init
11.   size(800, 600);
12. } // func
13. //
14. //
15. void draw()
16. {
17.   background(255);
18.   if (image1!=null) {
19.     image ( image1, 0, 0 );
20.   }
21.   fill(0);
22.   text ("Please click mouse to load image.", 30, height-30);
23. } // func
24. //
25. //-------------
26. //
27. void chooseFolder() {
28.   File folderToStartFrom = new File( "D://*.*" );
29.   selectInput("Select an image ", "folderSelected", folderToStartFrom );
30. }
31. //
32. void folderSelected(File selection) {
33.   // this runs in another thread parallel to the main thread
34.   if (selection == null) {
35.     println("Window was closed or the user hit cancel.");
36.   }
37.   else {
38.     println("User selected " + selection.getAbsolutePath());
39.     image1=loadImage(  selection.getAbsolutePath()   );
40.   }
41. }
42. // =====================================================================
43. void mouseReleased() {
44.   chooseFolder();
45. }
46. // =====================================================================