Apps List view isn't updating in a fragment

When the user clicks a button, the listview is supposed to add another value to the list and show it. When I press the button nothing happens.


MatchesList.java
[HIGH]

import java.util.ArrayList;

import com.actionbarsherlock.app.SherlockListActivity;

import android.app.ListActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ArrayAdapter;
import android.widget.Button;

public class MatchesList extends SherlockListActivity{
ArrayList<String> listItems = new ArrayList<String>();
ArrayAdapter<String> adapter;

int matchNum=0;
Button addM;

@Override
public void onCreate(Bundle icicle){
super.onCreate(icicle);
setContentView(R.layout.fragment_matches);
adapter= new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1,
listItems);

setListAdapter(adapter);
Log.v("blah", "blah adsjfkd ");
addM = (Button) findViewById(R.id.addMatchBtn);
addM.setOnClickListener(new OnClickListener(){
public void onClick(View v){
addMatch(v);
}
});


}

public void addMatch(View view){
matchNum += 1;
listItems.add("Match " + matchNum);
adapter.add("Match " + matchNum);
adapter.notifyDataSetChanged();
System.out.println(adapter);
Log.d(UI_MODE_SERVICE, adapter.toString());
Log.v("blah", "blah adsjfkd ");
}

}

[/HIGH]

MatchesFragment.java

[HIGH]

import com.actionbarsherlock.app.SherlockFragment;

import android.os.Bundle;
import android.util.Log;
import android.view.*;

public class MatchesFragment extends SherlockFragment{

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
Log.v("test", "test message");

return inflater.inflate(R.layout.fragment_matches, container, false);
}
}
[/HIGH]

fragment_matches.xml

HTML:

1.  
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
3.    xmlns:tools="http://schemas.android.com/tools"
4.    android:layout_width="match_parent"
5.    android:layout_height="match_parent"
6.    tools:context=".MatchesList" >
7.    
8.     <Button
9.        android:id="@+id/addMatchBtn"
10.        android:layout_width="50dp"
11.        android:layout_height="40dp"
12.        android:text="Add a Match"
13.      
14.    
15.    />
16.    
17.    
18.     <ListView
19.        android:id="@android:id/list"
20.        android:layout_width="match_parent"
21.        android:layout_height="fill_parent"></ListView>
22.    
23. </LinearLayout>
24.  

MainActivity.java

[HIGH]


import com.actionbarsherlock.app.ActionBar.Tab;
import com.actionbarsherlock.app.ActionBar.TabListener;
import com.actionbarsherlock.app.*;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuInflater;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentTransaction;
import android.util.Log;
import android.view.View;
import android.widget.Button;


public class MainActivity extends SherlockFragmentActivity{

ActionBar actionBar;
Tab tabData;
Tab tabComp;

Tab tabMatches;
Tab tabRed;
Tab tabBlue;


@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// setContentView(R.layout.activity_main);

actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

tabData = actionBar.newTab();
tabData.setText("Match Data");
tabData.setTabListener(new MyTabListener());
actionBar.addTab(tabData);

// tabRed.setTabListener(new TabListener<TabFragment>(this, "tab1", TabFragment.class));
tabComp = actionBar.newTab();
tabComp.setText("New Competition");
tabComp.setTabListener(new MyTabListener());
actionBar.addTab(tabComp);
// tabBlue.setTabListener(new TabListener<TabFragment>(this, tabBlue, TabFragment.class));

tabMatches = actionBar.newTab();
tabMatches.setText("Matches");
tabMatches.setTabListener(new MyTabListener());

tabRed = actionBar.newTab();
tabRed.setText("Red Side");
tabRed.setTabListener(new MyTabListener());

tabBlue = actionBar.newTab();
tabBlue.setText("Blue Side");
tabBlue.setTabListener(new MyTabListener());





}

@Override
public boolean onCreateOptionsMenu(Menu menu){
MenuInflater inflater = getSupportMenuInflater();
inflater.inflate(R.menu.activity_main, menu);
return true;
}



private class MyTabListener implements ActionBar.TabListener{
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft){
if(tab.equals(tabData))
{
ScoreRedActivity frag = new ScoreRedActivity();
ft.replace(android.R.id.content, frag);

}
else if(tab.equals(tabComp))//new competition
{
FragmentBlueScorer frag = new FragmentBlueScorer();
ft.replace(android.R.id.content, frag);

actionBar.removeTab(tabData);
actionBar.removeTab(tabComp);
actionBar.addTab(tabMatches);
actionBar.addTab(tabRed);
actionBar.addTab(tabBlue);

}
else if(tab.equals(tabMatches))
{
MatchesFragment frag = new MatchesFragment();
ft.replace(android.R.id.content, frag);
}
}

@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft){

}

@Override
public void onTabReselected(Tab tab, FragmentTransaction ft){
}

}





}
[/HIGH]