How to unbold the selected text in Edittext Android?

Button btnNormal = (Button) findViewById(R.id.btnNormal );
        btnNormal .setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
               Spannable str = etx.getText();
               StyleSpan[] ss = str.getSpans(selectionStart, selectionEnd, StyleSpan.class);

       for (int i = 0; i < ss.length; i++) {
           if (ss[i].getStyle() == android.graphics.Typeface.BOLD){
            str.removeSpan(ss[i]);          
           }
       }
    etx.setText(str);

    }
});