title: onbackpressed() method crash
body: <p>I am using authentication to enter into a page, after authenticated only the user enters into the page. i wrote a code for onbackpressed(), but it is not working. Here DatabaseDemo and Login are the two classes. when i press the back button the login class with username and password is displaying. </p>
  
  <pre><code>public class DatabaseDemo extends TabActivity {
      DatabaseHelper dbHelper;
      GridView grid;
      TextView txtTest;
      /** Called when the activity is first created. */
      @Override
      public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.main);
          SetupTabs();
      }
  
      @Override
      public boolean onCreateOptionsMenu(Menu menu)
      {
          menu.add(1, 1, 1, "Add Employee");
          return true;
      }
      public boolean onOptionsItemSelected(MenuItem item)
      {
          switch (item.getItemId())
          {
          //Add employee
          case 1:
              Intent addIntent=new Intent(this,AddEmployee.class);
              startActivity(addIntent);
              break;
          }
          super.onOptionsItemSelected(item);
          return false;
      }
      void SetupTabs()
      {
          TabHost host=getTabHost();
          TabHost.TabSpec spec=host.newTabSpec("tag1");
          Intent in1=new Intent(this, AddEmployee.class);
          spec.setIndicator("Add Employee");
          spec.setContent(in1);
  
          TabHost.TabSpec spec2=host.newTabSpec("tag2");
          Intent in2=new Intent(this, GridList.class);
  
          spec2.setIndicator("Employees");
          spec2.setContent(in2);
  
          host.addTab(spec);
          host.addTab(spec2);
      }
      @Override
      public void onBackPressed() 
      {
          Intent i = new Intent(DatabaseDemo.this, Login.class);
          startActivity(i);
      }
  }
  </code></pre>