How can i achieve Bokeh effect with custom camera in android?

Question

I need to generate Bokeh effect with the android custom camera. I am using a dual-camera device. But unable to find any option to take the picture and do Image segmentation.

I had a look at some library also and found https://github.com/RedApparat/FaceDetector library. If I could focus an object and blur rest of background then also it will be working for me.

Is there any hint how device with dual lens works?