radio group setOnCheckedChangeListener

RadioGroup yourRadioGroup = (RadioGroup) findViewById(R.id.radioGroup1);
        yourRadioGroup.setOnCheckedChangeListener(new OnCheckedChangeListener()
        {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId)
            {
                switch(checkedId)
                {
                case R.id.radio0:
                    // TODO Something
                    break;
                case R.id.radio1:
                    // TODO Something
                    break;
                case R.id.radio2:
                    // TODO Something
                    break;
                }
            }
        });

Or, if you prefer:

yourRadioGroupName.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener()
        {
            @Override
            public void onCheckedChanged(RadioGroup group, int checkedId)
            {
                int idRadioButtonChosen = yourRadioGroupName.getCheckedRadioButtonId();

                if(idRadioButtonChosen > 0){

                    radioButtonChosen = (RadioButton) findViewById(idRadioButtonChosen);
                    textViewOnclick.setText(radioButtonChosen.getText());

                }


            }
        });

 radioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener()
    {
        public void onCheckedChanged(RadioGroup group, int checkedId) {
            // checkedId is the RadioButton selected
            RadioButton rb=(RadioButton)findViewById(checkedId);
            Toast.makeText(getApplicationContext(), rb.getText(), Toast.LENGTH_SHORT).show();
        }
    });