Question

I created a RadioGroup layout in XML. So I creating it dynamically:

RadioGroup segmentRadioGroup = new RadioGroup(parentActivity);
inflater.inflate(R.layout.segm_btn_stores, segmentRadioGroup);           
segmentRadioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(RadioGroup radioGroup, int i) {
            showMap();
        }
    });

Oh, it doesn’t work! showMap is not firing!

But… wait. What if we do it this way?

RadioGroup segmentRadioGroup = (RadioGroup) inflater.inflate(R.layout.segm_btn_stores, null);

It… works. Why? segmentRadioGroup is RadioGroup in both cases. And if I pass segmentRadioGroup created before instead of null it won’t work too.

Answer 1

RadioGroup segmentRadioGroup = new RadioGroup(parentActivity);

In the above line, you create an ’empty’ RadioGroup. Then…

inflater.inflate(R.layout.segm_btn_stores, segmentRadioGroup);

…in the above line, you inflate another RadioGroup from the layout file and it is then ‘added’ to the first RadioGroup. The logic here seems to be that as RadioGroup extends (and effectively IS) LinearLayout, it is legal for a RadioGroup to contain another RadioGroup.

segmentRadioGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() { ...});

Finally, on the line above, you set the listener on the outer / parent RadioGroup and not on the inner RadioGroup. As such, the onCheckedChanged(...) method is never called for the inner RadioGroup.

Well that’s the only logic I can come up with.

With your second approach…

RadioGroup segmentRadioGroup = (RadioGroup) inflater.inflate(R.layout.segm_btn_stores, null);

You are simply inflating one RadioGroup without an outer parent layout because you pass ‘null’ as the second parameter.