android - Cast exception when adding RadioButtons to RadioGroup in Android

Question

I need to dynamically add RadioButtons to the app, and when I add either buttons or group to the layout it works perfectly. But when I try to add RadioButtons to RadioGroup app crashes with cast exception: android.widget.RadioButton cannot be cast to android.widget.LinearLayout

I've used this post for reference: Creating RadioButtons programmatically. It must be something really basic, but I've been playing with it for a while now, so a bit overwhelmed trying to solve it.

Here is my code:

protected void addRadioButtons(LinearLayout layout, String switchOptions){  
    String[] optionsArray = switchOptions.split(",");
    int numberOfOptions = optionsArray.length;
    RadioButton[] radioButton = new RadioButton[numberOfOptions];
    RadioGroup radioGroup = new RadioGroup(this);
    radioGroup.setOrientation(RadioGroup.HORIZONTAL);
    LayoutParams radioGroupParams = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
    radioGroup.setLayoutParams(radioGroupParams);
    //layout.addView(radioGroup);

    for (int i = 0; i<numberOfOptions;i++){
        radioButton[i] = new RadioButton(this);
        radioButton[i].setText(i + "");
        radioGroup.addView(radioButton[i]);
    }
    layout.addView(radioGroup);
   }