设置 Android RadioGroup 的选定索引

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.

This Worked For me, I created radio button dynamically by

  private void createRadioButton() {


RadioButton[] rb = new RadioButton[5];


RadioGroup.LayoutParams layoutParams = new RadioGroup.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT,
1.0f);


radioGroup.setOrientation(RadioGroup.HORIZONTAL);


for (int ID = 0; ID < 5; ID++) {
rb[ID] = new RadioButton(this);
rb[ID].setLayoutParams(layoutParams);
rb[ID].setText("Button_Text");
radioGroup.addView(rb[ID]); //the RadioButtons are added to the radioGroup instead of the layout
}
}

Now Check a button using,

int radio_button_Id = radioGroup.getChildAt(index).getId();


radioGroup.check( radio_button_Id );

Inside onBindViewHolder set the tag to Button Group

@Override
public void onBindViewHolder(final CustomViewHolder holder, final int position) {
...
holder.ButtonGroup.setTag(position);
}

and in the ViewHolder

ButtonGroup.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(RadioGroup radioGroup, int checkedId) {
...
int id = radioGroup.getCheckedRadioButtonId();


RadioButton radioButton = (RadioButton) radioGroup.findViewById(id);


int clickedPos = (Integer) radioGroup.getTag();


packageModelList.get(clickedPos).getPoll_quest()
}

Using Kotlin you can make it by

  (radio_group_id.getChildAt(index) as RadioButton).isChecked = true

or

radio_group_id.check(R.id.radio_button_id)