Uncheck all RadioButton in a RadioButtonGroup

RadioGroup radioGroup = (RadioGroup)findViewById(R.id.radiogroup);
radioGroup.clearCheck();

use this

RadioButton spec1=findViewById(yourRadioGroup.getCheckedRadioButtonId());
        if (spec1.isChecked())
        {
            spec1.setChecked(false);
        }

use clearCheck() for clearing all checked radiobutton when acticity is started or resumed

 @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
 RadioGroup rg=(RadioGroup)findViewById(R.id.RG);
rg.clearCheck();
}
@Override
protected void onResume() {  
RadioGroup rg=(RadioGroup)findViewById(R.id.RG);
rg.clearCheck();  
super.onResume();  
    }