Android Facedetector not working after switching activities

Question

I am working on an app that, on one activity takes pictures and on the next activity, uses the Facedetector api to find all the faces. I used this tutorial to make the face detection. The face detection works perfectly as expected when I first open it on my phone, but when I use the back button to return to the previous activity then go to the face detect activity again, it doesn't work. No faces are found the second time even when using the exact same pictures.

Answer 1

I found out that the problem was because I was using the get method of the faces SparceArray instead of the valueAt method. I switched it and now everything works perfectly.