Android : CustomList view and TreeObserver

I have two textviews in my listview. I am setting text into them from two String arrays i.e substring and substringtwo. Here I have use treeobserver to get the width of first textview in term of characters. I am displaying only single line in first textview and rest part of that string in second textview. I have successfully implemented the above functionality. But now I want a list,wherein each row consists of two rows. I have used custom adapter,but I am getting NULL POINTER EXCEPTION.Please help me how to and where to use TreeObserver in this context.

  **MainActivity.java**

   public class MainActivity extends Activity {


  ListView lsview;
  ListViewCustomAdapter adapter;
  static float width;
   private static String chat[]={
   "Hi, How are you. I am fine.. you tell long time no seee.... 
   blaa blaaaaaaaaaaaaaaa     bla lvl","hashasahahahahjsaasasaasjasaj"};
  private static String rem_chat[]={"as","asa"};
  TextView tx,t2;


  static String substring[],substringtwo[];




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

    setContentView(R.layout.activity_main); 


   // setContentView(R.layout.listitem_row);
    tx=(TextView) findViewById(R.id.firsttv);
     t2=(TextView) findViewById(R.id.sectv);


     tx.getViewTreeObserver().addOnGlobalLayoutListener(new OnGlobalLayoutListener() {

        @SuppressLint("NewApi") @Override
        public void onGlobalLayout() {
            // TODO Auto-generated method stub

            initalize();

            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
                tx.getViewTreeObserver().removeOnGlobalLayoutListener(this);
            } else {
                tx.getViewTreeObserver().removeGlobalOnLayoutListener(this);
            }


        }
    });

    lsview = (ListView) findViewById(R.id.listView3);
     adapter = new ListViewCustomAdapter(this,substring,substringtwo);
    lsview.setAdapter(adapter); 

       }



  public void initalize(){

      width=tx.getWidth();
      System.out.println("Initailse"+width);
      int totalCharstoFit;

      for(int i=0;i<chat.length;i++)
      {

     totalCharstoFit=tx.getPaint().breakText(chat[i],  0, chat[i].length(), 
             true, width, null);


      System.out.println(totalCharstoFit);

      try{ 
   substring[i]=chat[i].substring(0,totalCharstoFit);
      substringtwo[i]=chat[i].substring(substring[i].length(),chat[i].length());


         //tx.setText(substring);
    // t2.setText(substringtwo);
    // System.out.println(substring);


   /*   
   lsview = (ListView) findViewById(R.id.listView3);
   adapter = new ListViewCustomAdapter(this,substring,substringtwo);
  lsview.setAdapter(adapter); */
      }catch(Exception e){System.out.println(e);
      }
       }
      }


     }




  **ListViewCustomAdapter.java**


     public class ListViewCustomAdapter extends BaseAdapter
    {
    public String title[];
  public String description[];
  public Activity context;
  public LayoutInflater inflater;

  public ListViewCustomAdapter(Activity context,String[] title, String[] description){
    super();

    this.context = context;
    this.title = title;
    this.description = description;

     this.inflater =    (LayoutInflater)context.getSystemService
         (Context.LAYOUT_INFLATER_SERVICE)
   }

  @Override
   public int getCount() {
    // TODO Auto-generated method stub
    return title.length;
    }

    @Override
  public Object getItem(int position) {
    // TODO Auto-generated method stub
    return null;
  }

  @Override
    public long getItemId(int position) {
    // TODO Auto-generated method stub
    return 0;
 }

   public static class ViewHolder
    {

    TextView txtViewTitle;
    TextView txtViewDescription;
    }

   @Override
   public View getView(int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub

    ViewHolder holder;
    if(convertView==null)
    {
        holder = new ViewHolder();
        convertView = inflater.inflate(R.layout.listitem_row, null);


        holder.txtViewTitle = (TextView) convertView.findViewById(R.id.firsttv);
        holder.txtViewDescription = (TextView) convertView.findViewById(R.id.sectv);

        convertView.setTag(holder);
    }
    else
        holder=(ViewHolder)convertView.getTag();


    holder.txtViewTitle.setText(title[position]);
    holder.txtViewDescription.setText(description[position]);

    return convertView;
   }

   }




     **activity_main.xml**

       <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
       tools:context="${relativePackage}.${activityClass}" >

    <ListView
     android:layout_height="wrap_content"
      android:layout_width="match_parent"
      android:id="@+id/listView3"
      android:layout_alignParentLeft="true">
    </ListView>

  </RelativeLayout>


  **listitem_row.xml**

   <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   tools:context="${relativePackage}.${activityClass}" >

    <Button android:id="@+id/btn"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:text="Button"/>

    <TextView
     android:id="@+id/firsttv"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:text="@string/hello_world"
     android:layout_toRightOf="@+id/btn"
     android:layout_alignBottom="@+id/btn"
     android:maxLines="1"
      />

  <TextView
    android:id="@+id/sectv"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello_world"
    android:layout_below="@+id/btn"
    android:textColor="#FF00FF" />

   </RelativeLayout>