How to do circular scrolling on ViewPager?

Question

I would like to set my ViewPager to do circular scrolling. I want the first page to be able to scroll to page 2 AND the last page. And I would like my last page to scroll to

Answer 1

This is my solution:

myViewPager.java

public class myViewPager extends PagerAdapter {

    public myViewPager (Context context) {
        this.context = context;
    }

    @Override
    public int getCount() {
        return rank.length+2;
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        // Declare Variables

        TextView textViewRank;



        //Log.i(TAG, "get position = "+position);

        inflater = (LayoutInflater) context
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View itemView = inflater.inflate(R.layout.viewpager_item, container,
            false);

        textViewRank= (TextView) itemView.findViewById(R.id.textView1);

        if (position == getCount() - 1) {
            textViewRank.setText(rank[0]);
        } else if (position == 0) {
            textViewRank.setText(rank[rank.length-1]);
        } else {
            textViewRank.setText(rank[position-1]);
        }


        ((ViewPager) container).addView(itemView);

        return itemView;
    }
    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView((View) object);
    }
}

viewpager_item.xml

MainActivity.java

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getName();
    public static String[] rank;
    myViewPager adapter;
    private ViewPager viewPager;
    private static int currentPage;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        rank = new String[] { "1", "2", "3", "4", "5", "6", "7", "8", "9", "10" };
        viewPager = (ViewPager) findViewById(R.id.view_pager);
        adapter = new myViewPager(this);

        viewPager.setAdapter(adapter);

        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageSelected(int position) {
                Log.i(TAG, "onPageSelected = "+position);
                currentPage = position;
            }
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
                // not needed
            }
            @Override
            public void onPageScrollStateChanged(int state) {
                if (state == ViewPager.SCROLL_STATE_IDLE) {
                    int pageCount = rank.length+2;

                    if (currentPage == pageCount-1){
                        viewPager.setCurrentItem(1,false);
                    } else if (currentPage == 0){
                        viewPager.setCurrentItem(pageCount-2,false);
                    }
                }
            }
        });
    }


}

activity_main.xml

Assumed that the array has 10 elements. Then "add" 2 dummy elements, but not really add. When "get_count" function is called, just return size=10+2 elements.

dummy e[0] e[1] e[2] e[3] e[4] e[5] e[6] e[7] e[8] e[9] dummy

In viewPager.addOnPageChangeListener:

when you slide to the last element, viewPager should set the first element as next.

if (currentPage == pageCount-1){
    viewPager.setCurrentItem(1,false);
}

when you slide to the first element, viewPager should set the last element as next.

else if (currentPage == 0){
    viewPager.setCurrentItem(pageCount-2,false);
}

In instantiateItem :

 if (position == getCount() - 1) {
    textViewRank.setText(rank[0]);
 } else if (position == 0) {
    textViewRank.setText(rank[rank.length-1]);    
 } else {
    textViewRank.setText(rank[position-1]);
 }