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; however, I need to expand a specific item in the Parent level when I first display the Activity (onCreate).

I successfully expand the related Root item of the Parent but I can't seem to expand the Parent item. The given listeners are called and yet the result isn't reflected in my multi level list.

Activity in which I call the expansion:

public class Activity {
    private int groupToExpand = 4, childToExpand = 3;
    protected void onCreate(Bundle savedInstance) {
        final ExpandableListView elv = (ExpandableListView) findViewById(R.id.elv);
        if (arrayList!= null && !arrayList.isEmpty()) {
            elv.setAdapter(new RootAdapter(this, arrayList);
            // this selects the correct group, but doesn't expand the child.
            elv.setSelectedChild(groupToExpand, childToExpand, true); 
            elv.expandGroup(groupToExpand); // this works.
        }
    }
}

My Root adapter:

public class RootAdapter extends BaseExpandableListAdapter {

private List<Objects> arrayList;
private Context context;
private LayoutInflater inflater;

public RootAdapter(Context context, List<Objects> arrayList) {
    this.context = context;
    this.arrayList = arrayList;
    this.inflater = LayoutInflater.from(context);
}

@Override
public Object getChild(int groupPosition, int childPosition) {
    final Objects parent = (Objects) getGroup(groupPosition);
    return parent.arrayList.get(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) {
    final Objects o = (Objects) getChild(groupPosition, childPosition);

    CustomExpandableListView elv = (CustomExpandableListView) convertView;
    ChildViewHolder holder;

    if (elv == null) {
        holder = new ChildViewHolder();

        elv = new CustomExpandableListView(context);
        elv.setGroupIndicator(null);
        elv.setDivider(null);
        elv.setCacheColorHint(Color.parseColor("#00000000"));
        elv.setChildDivider(null);
        elv.setChildIndicator(null);
        elv.setScrollingCacheEnabled(false);
        elv.setAnimationCacheEnabled(false);

        holder.cListView = elv;
        elv.setTag(holder);
    } else {
        holder = (ChildViewHolder) elv.getTag();
    }

    final ParentAdapter adapter = new ParentAdapter(context, o);
    holder.cListView.setAdapter(adapter);

    return elv;
}

private static class ChildViewHolder {
    CustomExpandableListView cListView;
}

@Override
public int getChildrenCount(int groupPosition) {
    final Objects parent = (Objects) getGroup(groupPosition);
    return parent.arrayList.size();
}

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

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

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

@Override
public View getGroupView(int groupPosition, boolean isExpanded,
        View convertView, ViewGroup parent) {
    View layout = convertView;
    GroupViewHolder holder;
    final Objects o = (Objects) getGroup(groupPosition);

    if (layout == null) {
        layout = inflater.inflate(R.layout.item_to_inflate, parent, false);
        holder = new GroupViewHolder();

        holder.title = (TextView) layout.findViewById(R.id.title);
        holder.image = (ImageView) layout.findViewById(R.id.image);
        layout.setTag(holder);
    } else {
        holder = (GroupViewHolder) layout.getTag();
    }

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

    return layout;
}

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

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

private static class GroupViewHolder {
    TextView title;
    ImageView image;
}

public class CustomExpandableListView extends ExpandableListView {

    public CustomExpandableListView(Context context) {
        super(context);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        heightMeasureSpec = MeasureSpec.makeMeasureSpec(2000, MeasureSpec.AT_MOST);
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

}

}

Finally my ParentAdapter :

public class ParentAdapter extends BaseExpandableListAdapter {

private Objects child;
private LayoutInflater inflater;

public ParentAdapter(Context context, Objects child) {
    this.child = child;
    this.inflater = LayoutInflater.from(context);
}

@Override
public Object getChild(int groupPosition, int childPosition) {
    return child.arrayList.get(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) {
    View layout = convertView;
    final Objects o = (Objects) getChild(0, childPosition);

    ChildViewHolder holder;

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

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

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

    return layout;
}

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

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

@Override
public int getGroupCount() {
    return 1;
}

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

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

    if (layout == null) {
        layout = inflater.inflate(R.layout.item_to_inflate, parent, false);
        holder = new GroupViewHolder();

        holder.image = (ImageView) layout.findViewById(R.id.image);
        holder.title = (TextView) layout.findViewById(R.id.title);
        layout.setTag(holder);  
    } else {
        holder = (GroupViewHolder) layout.getTag();
    }
    holder.title.setText(o.title.trim());

    return layout;
}

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

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

private static class GroupViewHolder {
    TextView title;
    ImageView image;
}

private static class ChildViewHolder {
    TextView title;
}

}

I can't expand the child lists within the root ExpandableListView; do you know any correct way to expand the items at the Parent level?

I tried in getChildView of the RootAdapter :

if (groupToExpand == groupPosition && childToExpand == childPosition) {
    elv.expandGroup(childToExpand);
}

Then in the activity i changed:

if (arrayList!= null && !arrayList.isEmpty()) {
    RootAdapter adapter = new RootAdapter(this, arrayList);
    elv.setAdapter(adapter);
    // this selects the correct group, but doesn't expand the child.
    elv.setSelectedChild(groupToExpand, childToExpand, true); 
    elv.expandGroup(groupToExpand); // this works.

    adapter.groupToExpand = groupToExpand;
    adapter.childToExpand = childToExpand;
    adapter.notifyDataSetChanged();
}

This expands the Parent level item, BUT, it generates duplicate items of the Parent. How do I do this correctly? Is this the correct way but my adapter is broken, therefore generating duplicate items?

I just can't find what I'm missing here...

Answer 1

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>();
    }
}