ListView Header implementation

Question

I have an Adapter class that implements ListView with headers.

//Adapter Class
private class MyCustomAdapter extends BaseAdapter {

private static final int TYPE_ITEM = 0;
private static final int TYPE_SEPARATOR = 1;
private static final int TYPE_MAX_COUNT = TYPE_SEPARATOR + 1;
private static final int TYPE_GRAY_SEPARATOR = 2;
private TreeSet<Integer> mGraySeparatorsSet = new TreeSet<Integer>();

private ArrayList<ContentWrapper> mData = new ArrayList<ContentWrapper>();
private LayoutInflater mInflater;

private TreeSet<Integer> mSeparatorsSet = new TreeSet<Integer>();

public MyCustomAdapter(Context context)
{
    mInflater = LayoutInflater.from(context); 
}

public void addItem(ContentWrapper value) {
    mData.add(value);
    notifyDataSetChanged();
}

public void addSeparatorItem(ContentWrapper value) {
    mData.add(value);
    // save separator position
    mSeparatorsSet.add(mData.size() - 1);
    notifyDataSetChanged();
}


public ContentWrapper getItem(int position) {
    return mData.get(position);
}
@Override
public int getItemViewType(int position) {
    return mSeparatorsSet.contains(position) ? TYPE_SEPARATOR : TYPE_ITEM;
}

@Override
public int getViewTypeCount() {
    return TYPE_MAX_COUNT;
}

public int getCount() {
    return mData.size();
}

public long getItemId(int position) {
    Log.v("getItemId Position", ""+position);
    return position;

}

public View getView(final int position, View convertView, ViewGroup parent) {
    ViewHolder holder = null;
    int type = getItemViewType(position);
    if (convertView == null) {
        holder = new ViewHolder();
        switch (type) {
        case TYPE_ITEM:
            convertView = mInflater.inflate(R.layout.white, null);
            holder.textView = (TextView)convertView.findViewById(R.id.text);
            break;
        case TYPE_SEPARATOR:
            convertView = mInflater.inflate(R.layout.black, null);
            holder.textView = (TextView)convertView.findViewById(R.id.textSeparator);
            break;

        }
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder)convertView.getTag();
    } holder.textView.setText(mData.get(position).getItem());

    if (type == TYPE_ITEM) {
        holder.textView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                AlertDialog.Builder x = new AlertDialog.Builder(getActivity());
                       x.setIcon(R.drawable.ic_launcher)

                        .setTitle(mData.get(position).getItem())

                        .setMessage(mData.get(position).getItemDescription())

                        .setCancelable(true)
                        .setPositiveButton("OK",
                                new DialogInterface.OnClickListener() {
                                    @Override
                                    public void onClick(DialogInterface arg,
                                            int arg1) {
                                    }
                                });
                 AlertDialog a = x.create();
                 a.show();
             }
                return null;
                }


            });
    } else {
        holder.textView.setOnClickListener(null);
    }

return convertView;
}
}
public static class ViewHolder {
public TextView textView;
}

In this I truly understand the implementation of getView method (ViewHolder,convertView,etc).

The above code runs smoothy but I do not understand that why we are using the methods

• addItem
• addSeparatorItem
• getItemViewType
• getViewTypeCount
• getCount
• getItemId

Can Anyone explain me the scenario clearly !

Thanks in advance..

Answer 1

These all are the call back methods. You can have the clear definition of these methods in below mentioned link.

http://developer.android.com/reference/android/widget/BaseAdapter.html

Let me give you an example of getItem()

Whenever new listview row is created, adapte willl get item details from this call back method.

Similarly whenever list is created, getCount() is called.

Suppose you have 12 items in listview. But you pass 10 in getCount(). it will show only ten items in list view.