Parse search a specific user - parse-platform

Question

I have found this code for searching for a specific user, using Parse. But when i run the code, it crashes.
What is wrong with the code???
The following is the link to the codes https://teamtreehouse.com/forum/tutorial-adding-search-to-ribbit-app
Here is the code
package com.twaa9l.isnap;
import java.util.List;
import android.app.AlertDialog;
import android.app.ListActivity;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.util.Log;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import com.parse.FindCallback;
import com.parse.ParseException;
import com.parse.ParseQuery;
import com.parse.ParseRelation;
import com.parse.ParseUser;
import com.parse.SaveCallback;
public class EditFriendsActivity extends ListActivity {
public static final String TAG = EditFriendsActivity.class.getSimpleName();
protected List<ParseUser> mUsers;
protected ParseRelation<ParseUser> mFriendsRelation;
protected ParseUser mCurrentUser;
protected EditText sUsername;
protected Button mSearchButton;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.activity_edit_friends);
// Show the Up button in the action bar.
setupActionBar();
getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
}
#Override
protected void onResume() {
super.onResume();
mCurrentUser = ParseUser.getCurrentUser();
mFriendsRelation = mCurrentUser.getRelation(ParseConstants.KEY_FRIENDS_RELATION);
sUsername = (EditText)findViewById(R.id.searchFriend);
mSearchButton = (Button)findViewById(R.id.searchButton);
///////////////////////////////////////////////////////////////////////////////////////////////////////////
//////////////The New Code for Search Users by Username///////////////////////////////////////////////////
/////////////////////////////////////////////////////////////////////////////////////////////////////////
mSearchButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//Get text from each field in register
String username = sUsername.getText().toString();
//String password = mPassword.getText().toString();
///Remove white spaces from any field
/// and make sure they are not empty
username = username.trim();
//password = password.trim();
//Check if fields not empty
if(username.isEmpty()){
AlertDialog.Builder builder = new AlertDialog.Builder(EditFriendsActivity.this);
builder.setMessage(R.string.login_error_message)
.setTitle(R.string.login_error_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
else{
//Login User
setProgressBarIndeterminateVisibility(true);
ParseQuery<ParseUser> query = ParseUser.getQuery();
query.whereEqualTo("username", username);
query.orderByAscending(ParseConstants.KEY_USERNAME);
query.setLimit(200);
query.findInBackground(new FindCallback<ParseUser>() {
#Override
public void done(List<ParseUser> users, ParseException e) {
setProgressBarIndeterminateVisibility(false);
if(e == null){
//Success we have Users to display
//Get users match us
mUsers = users;
//store users in array
String[] usernames = new String[mUsers.size()];
//Loop Users
int i = 0;
for(ParseUser user : mUsers){
usernames[i] = user.getUsername();
i++;
}
ArrayAdapter<String> adapter = new ArrayAdapter<String>(
EditFriendsActivity.this,
android.R.layout.simple_list_item_checked,
usernames
);
setListAdapter(adapter);
addFriendCheckmarks();
}
else{
//No Users to Display
Log.e(TAG, e.getMessage());
AlertDialog.Builder builder = new AlertDialog.Builder(EditFriendsActivity.this);
builder.setMessage(e.getMessage())
.setTitle(R.string.error_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
}
});
}
}
});
}
/**
* Set up the {#link android.app.ActionBar}.
*/
private void setupActionBar() {
getActionBar().setDisplayHomeAsUpEnabled(true);
}
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// This ID represents the Home or Up button. In the case of this
// activity, the Up button is shown. Use NavUtils to allow users
// to navigate up one level in the application structure. For
// more details, see the Navigation pattern on Android Design:
//
// http://developer.android.com/design/patterns/navigation.html#up-vs-back
//
NavUtils.navigateUpFromSameTask(this);
return true;
}
return super.onOptionsItemSelected(item);
}
#Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
if(getListView().isItemChecked(position)){
//Add Friends
mFriendsRelation.add(mUsers.get(position));
}
else{
//Remove Friend
mFriendsRelation.remove(mUsers.get(position));
}
mCurrentUser.saveInBackground(new SaveCallback() {
#Override
public void done(ParseException e) {
if(e != null){
Log.e(TAG, e.getMessage());
}
}
});
}
private void addFriendCheckmarks(){
mFriendsRelation.getQuery().findInBackground(new FindCallback<ParseUser>() {
#Override
public void done(List<ParseUser> friends, ParseException e) {
if(e == null){
//List Returned - look for a match
for(int i = 0; i < mUsers.size(); i++){
ParseUser user = mUsers.get(i);
for(ParseUser friend : friends){
if(friend.getObjectId().equals(user.getObjectId())){
//we have a match
getListView().setItemChecked(i, true);
}
}
}
}
else{
Log.e(TAG, e.getMessage());
}
}
});
}
}