Issue with Expanding Multi-Level ExpandableListView

Question

I have a multi level (3 levels, Root -> Parent -> Child) ExpandableListView containing children that are also ExpandableListViews. I\'m having no issue filling them up; howe

Answer 1

This is the best example I have found and used also: http://androidcodesnips.blogspot.in/2011/09/three-level-expandable-list.html

Its working, I have changed it as my need.

tags: 3 level expandablelistview, multi level listview

Answer 2

I ended up using a multi level ExpandableListView adapter from another post in stackoverflow. Unfortunately I just can't find the link anymore so I'll just post my code here.

Top Level of the ExpandableListView adapter.

RootAdapter.java:

public class RootAdapter extends BaseExpandableListAdapter {

    private Object root;

    private final LayoutInflater inflater;

    public class Entry {
        public final CustExpListview cls;
        public final SecondLevelAdapter sadpt;

        public Entry(CustExpListview cls, SecondLevelAdapter sadpt) {
            this.cls = cls;
            this.sadpt = sadpt;
        }
    }

    public Entry[] lsfirst;

    // you can change the constructor depending on which listeners you wan't to use.
    public RootAdapter(Context context, Object root, ExpandableListView.OnGroupClickListener grpLst,
        ExpandableListView.OnChildClickListener childLst, ExpandableListView.OnGroupExpandListener grpExpLst) {
        this.root = root;
        this.inflater = LayoutInflater.from(context);

        lsfirst = new Entry[root.children.size()];

        for (int i = 0; i < root.children.size(); i++) {
            final CustExpListview celv = new CustExpListview(context);
            SecondLevelAdapter adp = new SecondLevelAdapter(root.children.get(i));
            celv.setAdapter(adp);
            celv.setGroupIndicator(null);
            celv.setOnChildClickListener(childLst);
            celv.setOnGroupClickListener(grpLst);
            celv.setOnGroupExpandListener(grpExpLst);

            lsfirst[i] = new Entry(celv, adp);
        }

    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return childPosition;
    }

    @Override
    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }

    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild,
        View convertView, ViewGroup parent) {
        // second level list
        return lsfirst[groupPosition].cls;
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        return 1;
    }

    @Override
    public Object getGroup(int groupPosition) {
        return root.children.get(groupPosition);
    }

    @Override
    public int getGroupCount() {
        return root.children.size();
    }

    @Override
    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView,
        ViewGroup parent) {

        // first level

        View layout = convertView;
        GroupViewHolder holder;
        final Object item = (Object) getGroup(groupPosition);

        if (layout == null) {
            layout = inflater.inflate(R.layout.item_root, parent, false);
            holder = new GroupViewHolder();
            holder.title = (TextView) layout.findViewById(R.id.itemRootTitle);
            layout.setTag(holder);
        } else {
            holder = (GroupViewHolder) layout.getTag();
        }

        holder.title.setText(item.title.trim());

        return layout;
    }

    private static class GroupViewHolder {
        TextView title;
    }

    @Override
    public boolean hasStableIds() {
        return true;
    }

    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }
}

Custom ExpandableListView with the solution to items sometimes not being displayed. There is also a workaround to a known bug for IllegalArgumentException being called when destroying the view (by pressing the back button essentially).

CustExpListview.java:

public class CustExpListview extends ExpandableListView {

    public CustExpListview(Context context) {
        super(context);

    }

    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // the value (2000) should not be fixed and be calculated
        // as follows: cell_height x root_items_count x root_items_children_count
        heightMeasureSpec = MeasureSpec.makeMeasureSpec(2000, MeasureSpec.AT_MOST);
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    @Override
    protected void onDetachedFromWindow() {
        try {
            super.onDetachedFromWindow();
        } catch (IllegalArgumentException e) {
            // TODO: Workaround for http://code.google.com/p/android/issues/detail?id=22751
        }
    }
}

Finally, the code to the last level adapter.

public class SecondLevelAdapter extends BaseExpandableListAdapter {

    public Object child;

    public SecondLevelAdapter(Object child) {
        this.child = child;
    }

    @Override
    public Object getChild(int groupPosition, int childPosition) {
        return child.children.get(groupPosition).children.get(childPosition);
    }

    @Override
    public long getChildId(int groupPosition, int childPosition) {
        return childPosition;
    }

    // third level
    @Override
    public View getChildView(int groupPosition, int childPosition, boolean isLastChild,
            View convertView, ViewGroup parent) {
        View layout = convertView;
        final Object item = (Object) getChild(groupPosition, childPosition);

        ChildViewHolder holder;

        if (layout == null) {
            layout = inflater.inflate(R.layout.item_child, parent, false);

            holder = new ChildViewHolder();
            holder.title = (TextView) layout.findViewById(R.id.itemChildTitle);
            layout.setTag(holder);
        } else {
            holder = (ChildViewHolder) layout.getTag();
        }

        holder.title.setText(item.title.trim());

        return layout;
    }

    @Override
    public int getChildrenCount(int groupPosition) {
        return child.children.get(groupPosition).children.size();
    }

    @Override
    public Object getGroup(int groupPosition) {
        return child.children.get(groupPosition);
    }

    @Override
    public int getGroupCount() {
        return child.children.size();
    }

    @Override
    public long getGroupId(int groupPosition) {
        return groupPosition;
    }

    // Second level
    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView,
            ViewGroup parent) {
        View layout = convertView;
        ViewHolder holder;

        final Object item = (Object) getGroup(groupPosition);

        if (layout == null) {
            layout = inflater.inflate(R.layout.item_parent, parent, false);
            holder = new ViewHolder();
            holder.title = (TextView) layout.findViewById(R.id.itemParentTitle);
            layout.setTag(holder);
        } else {
            holder = (ViewHolder) layout.getTag();
        }

        holder.title.setText(item.title.trim());

        return layout;
    }

    @Override
    public void registerDataSetObserver(DataSetObserver observer) {
        super.registerDataSetObserver(observer);
    }

    @Override
    public void unregisterDataSetObserver(DataSetObserver observer) {
        Log.d("SecondLevelAdapter", "Unregistering observer");
        if (observer != null) {
            super.unregisterDataSetObserver(observer);
        }
    }

    @Override
    public boolean hasStableIds() {
        return true;
    }

    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition) {
        return true;
    }

    private static class ViewHolder {
        TextView title;
    }

    private static class ChildViewHolder {
        TextView title;
    }

}

I hope this helps!!!

Update

This is an example of how I call the above adapter.

MainActivity:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    final List<Object> objects = yourItems;
    if (!objects.isEmpty()) {
        final ExpandableListView elv = (ExpandableListView) findViewById(R.id.yourExpandableListView);
        /* Item click listeners below */

        // First level items in the ExpandableListView
        elv.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {
            @Override
            public boolean onGroupClick(ExpandableListView eListView, View view, int groupPosition,
                    long id) {
                // TODO: whatever you need
                return false /* or true depending on what you need */;
            }
        });

        // Second level items in the ExpandableListView
        ExpandableListView.OnGroupClickListener grpLst = new ExpandableListView.OnGroupClickListener() {
            @Override
            public boolean onGroupClick(ExpandableListView eListView, View view, int groupPosition,
                    long id) {
                // TODO: whatever you need
                return false /* or true depending on what you need */;
            }
        };

        // Third (and last) level items in the ExpandableListView
        ExpandableListView.OnChildClickListener childLst = new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView eListView, View view, int groupPosition,
                    int childPosition, long id) {
                // TODO: whatever you need
                return false /* or true depending on what you need */;
            }
        };

        ExpandableListView.OnGroupExpandListener grpExpLst = new ExpandableListView.OnGroupExpandListener() {
            @Override
            public void onGroupExpand(int groupPosition) {
                /* this one is not required of course, you can delete it from the RootAdapter Constructor
                 * it is just an example as to how to implement Listeners on the second level items */
            }
        };

        final RootAdapter adapter = new RootAdapter(this, objects, grpLst, childLst, grpExpLst);
        elv.setAdapter(adapter);
    }
}

This is how my class Object would look like.

Object.java:

public class Object {
    public String title; // use getters and setters instead
    public List<Object> children; // same as above

    public Object() {
        children = new ArrayList<Object>();
    }
}