After creating a ViewPager (as I also described here ViewPager) we need to catch the changing of slides event.

To do this we have a listener OnPageChangeListener i.e, ViewPager.OnPageChangeListener that invokes whenever we chance the page or increment the page.

We simply use it through addOnPageChangeListener(OnPageChangeListener) this method.Below is the code

 mViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(int position) {
                if (position == 0) {
                   
                } else if (position == 1) {
                   
Toast.makeText(getActivity(),"Page : "+position,Toast.LENGTH_SHORT).show();

                } else if (position == 2) {
                 
Toast.makeText(getActivity(),"Page : "+position,Toast.LENGTH_SHORT).show();

                }
                else if (position == 3) {

                 Toast.makeText(getActivity(),"Page : "+position,Toast.LENGTH_SHORT).show();

                }   else if (position == 4) {

                    Toast.makeText(getActivity(),"Page : "+position,Toast.LENGTH_SHORT).show();
                }
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });

Hope it will help you.