Set selected index of an Android RadioGroup

If your radio group is defined in a layout xml file, each button can be assigned an id. Then you just check a button like this

radioGroup.check(R.id.myButtonId);

If you created your radio group programmatically (I'm not even sure how you do this...), you might want to consider creating a special layout xml file just for the radio group so that you can assign R.id.* ids to the buttons.

Please see the answer below if you are, in fact, looking to set the radio button group by index, see the answer below.

((RadioButton)radioGroup.getChildAt(index)).setChecked(true);

Question said "set selected INDEX", here's how to set it by index:

((RadioButton)radioGroup.getChildAt(index)).setChecked(true);

........

Additional info: It seems that Google wants you to use id instead of index, because using id is more bug proof. For example, if you have another UI element in your RadioGroup, or if another developer re-orders the RadioButtons, the indices might change and not be what you expected. But if you're the only developer, this is totally fine.

you can do findViewById from the radio group .

((RadioButton)my_radio_group.findViewById(R.id.radiobtn_veg)).setChecked(true);`

Siavash's answer is correct:

((RadioButton)radioGroup.getChildAt(index)).setChecked(true);

But be aware that a radioGroup can contain views other than radioButtons -- like this example that includes a faint line under each choice.

<RadioGroup
    android:id="@+id/radioKb"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" >

    <RadioButton
        android:id="@+id/kb1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:button="@null"
        android:drawableRight="@android:drawable/btn_radio"
        android:text="Onscreen - ABC" />

    <View
        android:layout_width="fill_parent"
        android:layout_height="1dp"
        android:background="#33000000" />

    <RadioButton
        android:id="@+id/kb2"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:button="@null"
        android:drawableRight="@android:drawable/btn_radio"
        android:text="Onscreen - Qwerty" />

    <View
        android:layout_width="fill_parent"
        android:layout_height="1dp"
        android:background="#33000000" />

    <RadioButton
        android:id="@+id/kb3"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:button="@null"
        android:drawableRight="@android:drawable/btn_radio"
        android:text="Standard softkey" />

    <View
        android:layout_width="fill_parent"
        android:layout_height="1dp"
        android:background="#33000000" />

    <RadioButton
        android:id="@+id/kb4"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:button="@null"
        android:drawableRight="@android:drawable/btn_radio"
        android:text="Physical keyboard" />

    <View
        android:layout_width="fill_parent"
        android:layout_height="1dp"
        android:background="#33000000" />

</RadioGroup>

In this case using an index of 1, for example, would generate an error. The item at index 1 is the first separator line -- not a radioButton. The radioButtons in this example are at indexes 0, 2, 4, 6.