title: How to call a method in another activity
body: <p>I have a question about communication between activities on implementation program of Android.</p>
  
  <p>Here is two activity classes.</p>
  
  <pre><code>public class HelloAndroidActivity extends TabActivity{
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.main);
  
          Resources res = getResources();
          TabHost tabHost = getTabHost();
          TabHost.TabSpec spec;
          Intent intent;
  
          intent = new Intent().setClass(this, Tab1Activity.class);
          spec = tabHost.newTabSpec("Tab1").setIndicator(
            "Tab1", res.getDrawable(R.drawable.ic_tab_icon))
            .setContent(intent);
          tabHost.addTab(spec);
      }
  }
  </code></pre>
  
  <p>_</p>
  
  <pre><code>public class Tab1Activity extends ListActivity {
      private ArrayList&lt;String&gt; list = null;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);  
  
          list = new ArrayList&lt;String&gt;();
          setListAdapter(new ArrayAdapter&lt;String&gt;(this,  
                  android.R.layout.simple_list_item_1, list)); 
  
          addColumn("one");
          addColumn("two");
          addColumn("three");
      }
  
      public void addColumn(String s){
          list.add(new String(s));
      }
  }
  </code></pre>
  
  <p>HelloAndroidActivity is main activity.
  Tab1Activity is sub activity and display listview.
  HelloAndroidActivity include Tab1Activity view.</p>
  
  <p>What I want to do is calling addColumn method from HelloAndroidActivity,
  because HelloAndroidActivity is added to new function like TwitterUserStreamAdapter.
  If the android receive messages from internet,
  application send message to Tab1Activity.</p>
  
  <p>However, I don't know how to implement communication between activities.</p>