CyclicAdapter.java

import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;

import java.util.ArrayList;
import java.util.Arrays;

public class CyclicPagesAdapter extends FragmentStatePagerAdapter {

	public CyclicPagesAdapter(FragmentManager fm) {
		super(fm);
	}

	@Override
	public Fragment getItem(int position) {
		return _fragments.get(position).createInstance();
	}

	@Override
	public int getCount() {
		return _fragments.size();
	}

	public interface FragmentCreator {
		Fragment createInstance();
	}

	public void clear() {
		_fragments.clear();
	}

	public void add(FragmentCreator fragmentCreator) {
		_fragments.add(fragmentCreator);
	}

	public void finishAdding() {
		if (_fragments.isEmpty()) {
			return;
		}

		ArrayList<FragmentCreator> arrayList = new ArrayList<>(Arrays.asList(new FragmentCreator[MAX_PAGES]));
		arrayList.addAll(MAX_PAGES / 2, _fragments);

		int mrPointer = _fragments.size() - 1;
		for (int i = MAX_PAGES / 2 - 1; i > -1; --i) {
			arrayList.set(i, _fragments.get(mrPointer));
			--mrPointer;
			if (mrPointer < 0) {
				mrPointer = _fragments.size() - 1;
			}
		}

		mrPointer = 0;
		for (int i = MAX_PAGES / 2 + _fragments.size(); i < arrayList.size(); ++i) {
			arrayList.set(i, _fragments.get(mrPointer));
			++mrPointer;
			if (mrPointer >= _fragments.size()) {
				mrPointer = 0;
			}
		}
		_fragmentsRaw = _fragments;
		_fragments = arrayList;
	}

	public int getStartIndex() {
		if (_fragments.isEmpty()) {
			return 0;
		}
		return MAX_PAGES / 2;
	}

	public int getRealPagesCount() {
		if (_fragmentsRaw == null) {
			return 0;
		}
		return _fragmentsRaw.size();
	}

	public int getRealPagePosition(int index) {
		if (_fragments.isEmpty() || _fragmentsRaw == null) {
			return 0;
		}
		final FragmentCreator fragmentCreator = _fragments.get(index);
		for (int i = 0; i < _fragmentsRaw.size(); ++i) {
			if (fragmentCreator == _fragmentsRaw.get(i)) {
				return i;
			}
		}
		//Fail...
		return 0;
	}

	private static final int MAX_PAGES = 500;
	public ArrayList<FragmentCreator> _fragments = new ArrayList<>();
	@Nullable
	public ArrayList<FragmentCreator> _fragmentsRaw;
}