How to write custom ExpandableListAdapter

Here’s an implementation I just whipped up. I have no idea if it works or not, but seems “smart” to me 🙂 By the way, how should one go about getting the combined child id or the combined group id, so I just kinda improvised there.

package example;

import java.util.ArrayList;
import java.util.List;
import java.util.Map.Entry;

import android.content.Context;
import android.database.DataSetObservable;
import android.database.DataSetObserver;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ExpandableListAdapter;

public abstract class AbstractExpandableListAdapter<A, B> implements ExpandableListAdapter {

    private final List<Entry<A, List<B>>> objects;

    private final DataSetObservable dataSetObservable = new DataSetObservable();

    private final Context context;

    private final Integer groupClosedView;

    private final Integer groupExpandedView;

    private final Integer childView;

    private final LayoutInflater inflater;

    public AbstractExpandableListAdapter(Context context, int groupClosedView, 
            int groupExpandedView, int childView, List<Entry<A, List<B>>> objects) {
        this.context = context;
        this.objects = objects;
        this.groupClosedView = new Integer(groupClosedView);
        this.groupExpandedView = new Integer(groupExpandedView);
        this.childView = new Integer(childView);

        this.inflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    public void add(Entry<A, List<B>> group) {
        this.getObjects().add(group);
        this.notifyDataSetChanged();
    }

    public void remove(A group) {
        for (Entry<A, List<B>> entry : this.getObjects()) {
            if (entry != null && entry.getKey().equals(group)) {
                this.getObjects().remove(group);
                this.notifyDataSetChanged();
                break;
            }
        }
    }

    public void remove(Entry<A, List<B>> entry) {
        remove(entry.getKey());
    }

    public void addChild(A group, B child) {
        for (Entry<A, List<B>> entry : this.getObjects()) {
            if (entry != null && entry.getKey().equals(group)) {
                if (entry.getValue() == null) 
                    entry.setValue(new ArrayList<B>());

                entry.getValue().add(child);
                this.notifyDataSetChanged();
                break;
            }
        }
    }

    public void removeChild(A group, B child) {
        for (Entry<A, List<B>> entry : this.getObjects()) {
            if (entry != null && entry.getKey().equals(group)) {
                if (entry.getValue() == null)
                    return;

                entry.getValue().remove(child);
                this.notifyDataSetChanged();
                break;
            }
        }
    }

    public void notifyDataSetChanged() {
        this.getDataSetObservable().notifyChanged();
    }

    public void notifyDataSetInvalidated() {
        this.getDataSetObservable().notifyInvalidated();
    }

    public void registerDataSetObserver(DataSetObserver observer) {
        this.getDataSetObservable().registerObserver(observer);
    }

    public void unregisterDataSetObserver(DataSetObserver observer) {
        this.getDataSetObservable().unregisterObserver(observer);
    }

    public int getGroupCount() {
        return getObjects().size();
    }

    public int getChildrenCount(int groupPosition) {
        return getObjects().get(groupPosition).getValue().size();
    }

    public Object getGroup(int groupPosition) {
        return getObjects().get(groupPosition).getKey();
    }

    public Object getChild(int groupPosition, int childPosition) {
        return getObjects().get(groupPosition).getValue().get(childPosition);
    }

    public long getGroupId(int groupPosition) {
        return ((Integer)groupPosition).longValue();
    }

    public long getChildId(int groupPosition, int childPosition) {
        return ((Integer)childPosition).longValue();
    }

    public boolean hasStableIds() {
        return true;
    }

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

        if (convertView != null && convertView.getId() != 
                (isExpanded ? getGroupExpandedView() : getGroupClosedView())) {
//          do nothing, we're good to go, nothing has changed.
        } else {
//          something has changed, update.
            convertView = inflater.inflate(isExpanded ? getGroupExpandedView() :
                    getGroupClosedView(), parent, false);
            convertView.setTag(getObjects().get(groupPosition));
        }

        return convertView;
    }

    public View getChildView(int groupPosition, int childPosition,
            boolean isLastChild, View convertView, ViewGroup parent) {

        if (convertView != null) {
//          do nothing 
        } else {
//          create
            convertView = inflater.inflate(getChildView(), parent, false);
            convertView.setTag(getObjects().get(groupPosition).getValue().get(childPosition));
        }

        return convertView;
    }

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

    public boolean areAllItemsEnabled() {
        return true;
    }

    public boolean isEmpty() {
        return getObjects().size() == 0;
    }

    public void onGroupExpanded(int groupPosition) {

    }

    public void onGroupCollapsed(int groupPosition) {

    }

    public long getCombinedChildId(long groupId, long childId) {
        return groupId * 10000L + childId;
    }

    public long getCombinedGroupId(long groupId) {
        return groupId * 10000L;
    }

    protected DataSetObservable getDataSetObservable() {
        return dataSetObservable;
    }

    protected List<Entry<A, List<B>>> getObjects() {
        return objects;
    }

    protected Context getContext() {
        return context;
    }

    protected Integer getGroupClosedView() {
        return groupClosedView;
    }

    protected Integer getGroupExpandedView() {
        return groupExpandedView;
    }

    protected Integer getChildView() {
        return childView;
    }
}

Any comments or criticisms are welcome.