Application crash without any error

Question

I have 2 classes phone and dialpad.java. In phone class i have 5 lines when u click on these lines the dialpad.java class will open.i want to run multiActivities in a single Tab like

i have home tab and in home tab the phone activity is show when i click on lines the dialpad activity show in home tab so i use ActivityGroup to do this.But the problem im facing is when the dial activity is open and i select an other tab the program is close without any showing logcat eror.

plz help me to solve this problem

public class Phone extends ActivityGroup 
    {
    public void ShowDialPad(int nFreeLineNo, String sPhoneNo) 
       {
           Intent intent = new Intent(Phone.this , DialPad.class);

        //   intent.addFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
           intent.putExtra("LineNo", nFreeLineNo);
           intent.putExtra("PhoneNo", sPhoneNo);

           contentView("Activity", intent);

        //   startActivity(intent);
       }
    public void contentView(String id, Intent newIntent) 
        {
            View obj_view = getLocalActivityManager().startActivity(id, newIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)).getDecorView();

            this.setContentView(obj_view);

        }
    }