public class ActivityMain extends Activity {
 public static ActivityMain MainAct; //定义一个本类型的成员变量
 String GetStr(){
  return "shao jian";
 }
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main); 
  MainAct = this; //在这里将本实例赋值给静态成员变量
 }
...
}

public class ActivityNew extends Activity {
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  String title = bundle.getString("Title");
  title = MainActicivity.MainAct.GetStr(); //调用成员方法
  t.setText(title.trim());
  super.onCreate(savedInstanceState);
 }
}