Adding an onclicklistener to listview (android)

listView.setOnItemClickListener(new OnItemClickListener() {

    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Object o = prestListView.getItemAtPosition(position);
        prestationEco str = (prestationEco)o; //As you are using Default String Adapter
        Toast.makeText(getBaseContext(),str.getTitle(),Toast.LENGTH_SHORT).show();
    }
});

If your Activity extends ListActivity, you can simply override the OnListItemClick() method like so:

/** {@inheritDoc} */
@Override  
protected void onListItemClick(ListView l, View v, int pos, long id) {  
    super.onListItemClick(l, v, pos, id);

    // TODO : Logic
}  

The prestListView.getItemAtPosition(position); returns the UI widget: Text, Icon, ...

Try this instead:

Object o = prestationAdapterEco.getItemAtPosition(position);

or

Object o = arg0.getItemAtPosition(position);

Get the object from the adapter. Not from the list-view.

2. Object o is a prestationEco object. Not a String.

list.setOnItemSelectedListener(new OnItemSelectedListener() {

        @Override
        public void onItemSelected(AdapterView<?> arg0, View arg1,
                int arg2, long arg3) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub

        }
    });