Java classes to create a common base adapter strategy that acts as base for common adapters and multiple view types adapters in an android app

BaseAllAdapters.java

public abstract class BaseAllAdapters<T> extends BaseAdapter {

    protected Context mContext;
    protected LongSparseArray<DelegateAdapter> mDelegateAdapterSparseArray;
    private int mViewLayoutId = 0;
    private List<ListItem<T>> mItems;

    /*Constructor if we dont use mutiple view types in the list*/
    public BaseAllAdapters(Context context, int viewLayoutId) {
        mContext = context;
        mViewLayoutId = viewLayoutId;
    }

    /*Constructor if we use the delegateAdapter to create multiple view types in the list*/
    public BaseAllAdapters(Context context, LongSparseArray<DelegateAdapter> delegateAdapterSparseArray) {
        mContext = context;
        Preconditions.checkNotNull(delegateAdapterSparseArray,"mDelegateAdapterSparseArray cannot be null");
        Preconditions.checkState(delegateAdapterSparseArray.size()!=0,"mDelegateAdapterSparseArray cannot be empty using a multiple view type adapter, If you dont want to specify muliple views, please use the \"BaseAllAdapters(Context context, int viewLayoutId)\" constructor.");
    }

    public void clear() {
        mItems.clear();
        notifyDataSetChanged();
    }

    public List<T> getItems() {
        List<T> listItems = new ArrayList<T>();
        for (ListItem<T> listItem : mItems) {
            listItems.add(listItem.getItem());
        }
        return listItems;
    }

    public void setItems(List<T> items) {
        List<ListItem<T>> listItems = Utils.createListItemList(items);
        if (!Objects.equal(items, mItems)) {
            mItems = listItems;
            notifyDataSetChanged();
        }
    }

    @Override
    public int getCount() {
        return mItems != null ? mItems.size() : 0;
    }

    @Override
    public ListItem<T> getItem(int position) {
        return mItems.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }
i
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ListItem<T> item = getItem(position);
        ViewHolder holder;
        if (convertView == null) {
            if (isMultipleViewAdapter()) {
                DelegateAdapter adapter = mDelegateAdapterSparseArray.get(getItemViewType(position));
                convertView = adapter.getView(mContext, position, convertView, parent, LayoutInflater.from(mContext), getItem(position));
            } else {
                convertView = LayoutInflater.from(mContext).inflate(mViewLayoutId, parent, false);
            }
            holder = getHolderInstance(convertView);
            if (holder == null) holder = new ViewHolder(convertView);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        bindView(position, convertView, item, holder);
        return convertView;
    }

    private boolean isMultipleViewAdapter() {
        return getViewTypeCount() > 1;
    }

    protected abstract void bindView(int position, View convertView, ListItem<T> item, ViewHolder parentHolder);

    protected abstract ViewHolder getHolderInstance(View view);

    public static class ViewHolder {
        public ViewHolder(View view) {
            ButterKnife.inject(this, view);
        }
    }
    
    public static <T> List<ListItem<T>> createListItemList(final List<T> items) {
        ArrayList<ListItem<T>> listItems = new ArrayList<ListItem<T>>(items.size());
        for (T item : items) {
            listItems.add(new ListItem<T>(item));
        }
        return listItems;
    }
}

BaseDelegateAdapter.java

public abstract class BaseDelegateAdapter<T> implements DelegateAdapter<T> {

    private final int mViewLayoutId;
    protected BaseDelegateAdapter(int viewLayoutId) {
        mViewLayoutId = viewLayoutId;
    }

    @Override
    public View getView(Context context, int position, View convertView, ViewGroup parent, LayoutInflater inflater, ListItem<T> item) {
        BaseAllAdapters.ViewHolder holder;
        if (convertView == null) {
            convertView = LayoutInflater.from(context).inflate(mViewLayoutId, parent, false);
            holder = getHolderInstance(convertView);
            if(holder== null) holder = new BaseAllAdapters.ViewHolder(convertView);
            convertView.setTag(holder);
        }else{
            holder = (BaseAllAdapters.ViewHolder) convertView.getTag();
        }

        bindView(position, convertView, item, holder);
        return convertView;
    }

    protected abstract void bindView(int position, View convertView, ListItem<T> item, BaseAllAdapters.ViewHolder parentHolder);

    protected abstract BaseAllAdapters.ViewHolder getHolderInstance(View convertView);
}

DelegateAdapter.java

public interface DelegateAdapter<T> {
    public View getView(Context context, int position, View convertView, ViewGroup parent, LayoutInflater inflater, ListItem<T> item);
}

ListItem.java

public class ListItem<T> {

    public static final int TYPE_ITEM = 0;
    public static final int TYPE_SECTION = 1;

    private final int type;
    private final T item;
    private final String sectionTitle;

    public ListItem(T item) {
        type = TYPE_ITEM;
        this.item = item;
        sectionTitle = null;
    }

    public ListItem(String sectionTitle) {
        type = TYPE_SECTION;
        item = null;
        this.sectionTitle = sectionTitle;
    }

    public int getType() {
        return type;
    }

    public T getItem() {
        return item;
    }

    public String getSectionTitle() {
        return sectionTitle;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        ListItem listItem = (ListItem) o;

        if (type != listItem.type) {
            return false;
        }
        if (item != null ? !item.equals(listItem.item) : listItem.item != null) {
            return false;
        }

        return true;
    }

    @Override
    public int hashCode() {
        int result = type;
        result = 31 * result + (item != null ? item.hashCode() : 0);
        return result;
    }
}