Need help white adding items

Can somebody say whats wrong whit my code. When I add item in to a list in application, It wont come there. And if I click somewhere else in android application couple of times, then show added "item" sometimes.

This is my code:

package com.example.proov;

import java.util.ArrayList;

import com.example.proov.R;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

public class proovin extends Activity {
private ListView LView;

ArrayList ar = new ArrayList();

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
LView = (ListView) findViewById(R.id.ListView01);
// Set option as Multiple Choice. So that user can able to select more the one option
LView.setAdapter(new ArrayAdapter(this,
android.R.layout.simple_list_item_multiple_choice, ar));
LView.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);

Button b = (Button) findViewById(R.id.add_item);
final EditText d = (EditText) findViewById(R.id.title);
b.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {
ar.add(d.getText().toString());

}
});
}
}