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    <p>I finally found a working solution:</p> <p>My TreeElement class looks like this:</p> <pre><code>public class TreeElement { private int id; private TreeElementType type; private String name; /** * List that holds a set of all the children tree elements. */ private List&lt;TreeElement&gt; children = new ArrayList&lt;TreeElement&gt;(); /** * List that holds a set of the courses associated to the TreeElement. * * @see Course */ private List&lt;Course&gt; courses = new ArrayList&lt;Course&gt;(); public TreeElement() { this.type = TreeElementType.NODE; this.children = new ArrayList&lt;TreeElement&gt;(); } public TreeElement(int id) { this(); this.id = id; } public TreeElement(int id, String name) { this( id ); this.name = name; } public TreeElement(int id, TreeElementType type, String name) { this( id, name ); this.type = type; } public int getId() { return id; } public void setId(int id) { this.id = id; } public TreeElementType getType() { return type; } public void setType(TreeElementType type) { this.type = type; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List&lt;TreeElement&gt; getChildren() { return children; } public void setChildren(List&lt;TreeElement&gt; children) { this.children = children; } public void addChild(TreeElement child) { this.children.add(child); } public void addChildren(List&lt;TreeElement&gt; children) { this.children.addAll(children); } public List&lt;Course&gt; getCourses() { return courses; } public void setCourses(List&lt;Course&gt; courses) { this.courses = courses; } public void addCourse(Course course) { this.courses.add(course); } public void addCourses(List&lt;Course&gt; courses) { this.courses.addAll(courses); } } </code></pre> <p>These TreeElements thus generate a hierarchical tree. Each TreeElement can additionally hold some courses I want to show in the tree.</p> <p>The fragment holding all the pager with the pages is this one:</p> <pre><code>public class BrowserSectionFragment extends Fragment { private BrowserFragmentPagerAdapter mAdapter; private ViewPager mPager; private List&lt;Fragment&gt; fragments = new Vector&lt;Fragment&gt;(); public BrowserSectionFragment() { } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View view = inflater.inflate(R.layout.fragment_browser, container, false); /* * Add the root TreeElement-fragment, holding the categories of lowest * level. */ fragments.add(new BrowserPageFragment(this,TreeContainer.getTreeElement(TreeContainer.ROOT_ID))); mAdapter = new BrowserFragmentPagerAdapter(this.getFragmentManager(), fragments); mPager = (ViewPager) view.findViewById(R.id.pager); mPager.setAdapter(mAdapter); mPager.setOnPageChangeListener(new OnPageChangeListener() { @Override public void onPageScrollStateChanged(int arg0) {} @Override public void onPageScrolled(int arg0, float arg1, int arg2) {} @Override public void onPageSelected(int arg0) { while (arg0 &lt; fragments.size()-1) { fragments.remove(fragments.size()-1); } /* * notify the adapter of the changes being made * causes the adapter to check all elements, if they are still in the * list of fragments */ mAdapter.notifyDataSetChanged(); } }); return view; } /** * Adds a new fragment to the fragment manager. The data is taken from * the children list of the TreeElement. * * @param clickedElement */ public void addFragmentFromElement(TreeElement clickedElement) { fragments.add(new BrowserPageFragment((this),clickedElement)); mPager.setCurrentItem(fragments.size()-1, true); } } </code></pre> <p>Now I need a PagerAdapter, in this case a FragmentStatePagerAdapter, to organize the Fragments:</p> <pre><code>public class BrowserFragmentPagerAdapter extends FragmentStatePagerAdapter { /** * List that holds all the fragments which are currently accessible * through the Pager. */ private List&lt;Fragment&gt; mFragments; /** * Constructor that initializes the list of fragments. * * @param fm FragmentsManager * @param fragments */ public BrowserFragmentPagerAdapter(FragmentManager fm, List&lt;Fragment&gt; fragments) { super(fm); mFragments = fragments; } @Override public Fragment getItem(int position) { return mFragments.get(position); } @Override public int getCount() { return mFragments.size(); } @Override public int getItemPosition(Object item) { /* * See if fragment is still in the list. * If yes, the position in the list is returned, if not, POSITION_NONE, * which causes the Pager to delete the related view. */ Fragment fragment = (Fragment) item; int position = mFragments.indexOf(fragment); if (position &gt;= 0) { return position; } else { return POSITION_NONE; } } } </code></pre> <p>Finally I implemented a PageFragment which is showing a ListView:</p> <pre><code>public class BrowserPageFragment extends ListFragment { public static final String ARG_ELEMENT_ID = "element_id"; TreeElement element; BrowserSectionFragment frag; Context context; public BrowserPageFragment() { super(); } public BrowserPageFragment( BrowserSectionFragment frag, TreeElement element ) { this(); this.frag = frag; this.element = element; } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) { /* Creating an array adapter to store the list of countries **/ BrowserListAdapter adapter = new BrowserListAdapter(inflater.getContext(),element); /* Setting the list adapter for the ListFragment */ setListAdapter(adapter); return super.onCreateView(inflater, container, savedInstanceState); } @Override public void onListItemClick(ListView l, View v, int position, long id) { Object clickedElement = l.getAdapter().getItem(position); if (clickedElement instanceof TreeElement) { frag.addFragmentFromElement((TreeElement) clickedElement); } else if (clickedElement instanceof Course) { /* * Start a new fragment which shows a detail view of the course. */ Course course = (Course) clickedElement; int courseId = course.getId(); CourseContainer.setCourse(courseId, course); Fragment fragment = new DetailsFragment(); Bundle args = new Bundle(); args.putInt( DetailsFragment.ARG_COURSE_NUMBER, courseId); fragment.setArguments(args); getActivity().getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment).commit(); } } } </code></pre> <p>To make it complete, my custom ListAdapter looks like this:</p> <pre><code>public class BrowserListAdapter extends BaseAdapter { private final LayoutInflater mInflater; TreeElement element; List&lt;Object&gt; elements = new ArrayList&lt;Object&gt;(); public BrowserListAdapter(Context context, TreeElement element) { mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); this.element = element; elements.addAll(element.getChildren()); elements.addAll(element.getCourses()); } @Override public int getCount() { return elements.size(); } @Override public Object getItem(int position) { return elements.get(position); } @Override public long getItemId(int position) { Object item = elements.get(position); if (item instanceof TreeElement) { return ((TreeElement) item).getId(); } else if (item instanceof Course) { return ((Course) item).getId(); } return -1; } @Override public View getView(int position, View convertView, ViewGroup parent) { View itemView = (View) mInflater.inflate(android.R.layout.simple_list_item_1, parent, false); bindView(itemView, position); return itemView; } private void bindView(View itemView, int position) { Object item = getItem(position); String text = null; if (item instanceof TreeElement) { text = ((TreeElement) item).getName(); } else if (item instanceof Course) { text = ((Course) item).getTitle(); } itemView.setId((int) getItemId(position)); TextView title = (TextView) itemView; title.setText(text); } } </code></pre> <p>Maybe this solution helps somebody. The only remaining problems here are:</p> <ul> <li>The constructor of BrowserPageFragment has a constructor with arguments, which is not nice.</li> <li>When changing the orientation the Pager jumps to the first page.</li> <li>The back-button does not go to the previous page.</li> </ul>
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