listview open alert dialog depending on choice android

Im desperately trying to get my listView to open an alert dialog or a normal dialog that is filled with information. I cant seem to get it to work. I want it to display different information aswell depending on which item on the list is clicked

public class learn_tab1 extends ListActivity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setListAdapter(new ArrayAdapter<String>(this, R.layout.list_item,
            BASICLIST));

    ListView lv = getListView();
    lv.setTextFilterEnabled(true);

    lv.setOnItemClickListener(new OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View view,
                int position, long id) {
                    AlertDialog dialog = new AlertDialog.Builder(this).create();

    dialog.setCancelable(false);
    dialog.setTitle("Instructions");
    dialog.setIcon(R.drawable.bone_icon);
    dialog.setMessage("test");
    开发者_开发百科dialog.setButton(DialogInterface.BUTTON_POSITIVE, "Done", new DialogInterface.OnClickListener() {


        @Override
        public void onClick(DialogInterface dialog, int which) {
            // TODO Auto-generated method stub
            finish();
        }
    });
    dialog.show();
            }
        }
    });
}

Try new AlertDialog.Builder(learn_tab1.this).create(); instead of new AlertDialog.Builder(this).create().

I'm wondering how it ever get complied....

EDIT

public void onItemClick(AdapterView<?> parent, View view, int position, long id) {   
    String item = (String)parent.getItemAtPosition(position);

    // ...
    dialog.setMessage(item);

    // ...
}