title: launch an activity using intent and disable back button press from launching the previous activity
body: <p>In my application. I have a <code>login</code> screen. If the login is successful, a <code>tab activity</code> will launch, in that there are 4 tabs. When I press one of the buttons in the tab, a new activity will launch. there is an event in my <code>login</code> class that will get fired in some cases. I want to go back to the tab activity when the event get fired. I have written a code using Intent. That code is working fine. But after reaching the tab activity I don't want to go back to the activity when back button is pressed. I want to remove this. I want to show login when Back is  pressed. Is there any way to do this? This is the code I have used:</p>
  
  <pre><code>Intent tabi=new Intent(getApplicationContext(),Tab.class);
  startActivity(tabi);
  </code></pre>
  
  <p>The code <code>onkeydown</code> in tab activity is:</p>
  
  <pre><code>    @Override
  public boolean onKeyDown(int keyCode, KeyEvent event) {
      if (keyCode == KeyEvent.KEYCODE_BACK) {
  
  
          super.onKeyDown(keyCode, event);
          return true;
      }
      return false;
  }
  </code></pre>