Copyright© Jeffrey Jongko, Ateneo de Manila University Custom ListAdapters

ListAdapter  Acts as the bridge between a ListView and the data that backs the list (the model)ListView  Interface found in android.widget package  Several subtypes are built-in to android

Custom ListAdapters  The true power of the ListView/ ListAdapter combination is the ability to define your own ListAdapter to best suit you application  ListAdapter is simply an interface that needs to be implemented

ListAdapter interface  ListAdapter contains several methods inside it that need to be implemented  Some methods: public int getCount() - returns the number of items public Object getItem(int arg0) – returns the object at a given position public long getItemId(int position) – return a unique ID for a given position

ListAdapter interface public View getView(int position, View convertView, ViewGroup parent) – returns a view object used to render the data  convertView represents an existing recyclable view that can be modified instead of creating a new view  All the basic ListAdapter methods are implemented in a class BaseAdapter  You will need to subtype this and implement the above methods

Application data  Many times application data comes in the form of lists of objects rather than lists of simple Strings  E.g. contacts are composed  Name  Phone Number   etc  This is the type of data that is best served by custom adapter classes since you will want to present all these somehow to the user

Creating your own Adapter  The most common customization to an adapter is the row’s layout  Given the many methods present in the ListAdapter interface, it is usually better to subclass BaseAdapter and fill the missing methods as stated earlier

getView() public View getView(int position, View convertView, ViewGroup parent) – returns a view object used to render the data  position – represents the position in your dataset  convertView - represents an existing recyclable view that can be modified instead of creating a new view  parent – represents the parent (usually the ListView object) that holds this view

Custom views  Views used for layout rows can be easily created using the Graphical Editor  Created the same way as with an Activity layout  These are the parsed using a LayoutInflater instance inside getView() and populated with the proper data

Example  NOTE: getLayoutInflater() is in the Activity class  i.e. you need access to the Activity to use it either as an inner class or pass the Activity to the Adapter public View getView(int position, View convertView, ViewGroup parent) { LayoutInflater inflater = getLayoutInflater(); View view = inflater.inflate(R.layout.row, null); // extract the views to be populated TextView name = (TextView) view.findViewById(R.id.name); TextView phone = (TextView) view.findViewById(R.id.phone); TextView = (TextView) view.findViewById(R.id. ); // extract the object that will fill these MyContact contact = internalList.get(position); name.setText(contact.getName()); phone.setText(contact.getPhone()); .setText(contact.get ()); // return the view return view; }

Output vs XML <LinearLayout xmlns:android=" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent">