El gesto de deslizar inicia varias instancias de la misma actividad

I am trying to implement a tab based view wherein the user can switch between the tabs using swipe gesture. However, multiple instances of the same activity open on swipe. How can I prevent this? Thanks

public boolean onTouch(View v, MotionEvent event) {
    switch(event.getAction() & MotionEvent.ACTION_MASK){

    case MotionEvent.ACTION_DOWN:
        initialx=event.getX();
        initialy=event.getY();
        break;

    case MotionEvent.ACTION_UP:
        break;

    case MotionEvent.ACTION_MOVE:
        finalx=event.getX();
        finaly=event.getY();

        if (initialx>(finalx+150.0)){

            RadioGroup Options = (RadioGroup) findViewById(R.id.vOptions);
            int selectedId = Options.getCheckedRadioButtonId();
            final EditText QuestionNo = (EditText)findViewById(R.id.vnumberofquestions);
            final EditText Time = (EditText)findViewById(R.id.vtimeperquestion);

            if ((QuestionNo.getText().toString().equals(" ")) || (Time.getText().toString().equals("")) ||(selectedId==-1)) { 
                Intent intenta=new Intent(VerbalSelect.this, TabDisplay.class );
                intenta.putExtra("index", 0);
                startActivity(intenta);
            }
            else {   
                RadioButton selectedButton = (RadioButton) findViewById(selectedId);
                String testtype = (String) selectedButton.getText(); 
                int questionno = Integer.parseInt(QuestionNo.getText().toString());
                int timeperquestion = Integer.parseInt(Time.getText().toString());
                long timeroffset = questionno*timeperquestion;
                Intent intent=new Intent(VerbalSelect.this, Main.class);

                intent.putExtra("testtype", testtype);
                intent.putExtra("timeroffset",timeroffset);
                intent.putExtra("questionno","1");
                intent.putExtra("questionlimit", questionno);
                startActivity(intent);
            }
            break;
        }
    }
    return true;
}