How to disable a RadioGroup until checkbox is checked

The real trick is to loop through all children view (in this case: CheckBox) and call it's setEnabled(boolean)

Something like this should do the trick:

//initialize the controls
final RadioGroup rg1 = (RadioGroup)findViewById(R.id.radioGroup1);
CheckBox ck1 = (CheckBox)findViewById(R.id.checkBox1);

//set setOnCheckedChangeListener()
ck1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

    @Override
    public void onCheckedChanged(CompoundButton checkBox, boolean checked) {
        //basically, since we will set enabled state to whatever state the checkbox is
        //therefore, we will only have to setEnabled(checked)
        for(int i = 0; i < rg1.getChildCount(); i++){
            ((RadioButton)rg1.getChildAt(i)).setEnabled(checked);
        }
    }
});

//set default to false
for(int i = 0; i < rg1.getChildCount(); i++){
    ((RadioButton)rg1.getChildAt(i)).setEnabled(false);
}

If you have just a few radio buttons, better way would be to setClickable(false) for all children

radiobutton1.setClickable(false);
radiobutton2.setClickable(false);
radiobutton3.setClickable(false);