How to set selected index of a RadioGroup in Android

activity_main.xml

 <RelativeLayout     xmlns:android="http://schemas.android.com/apk/res/android"     xmlns:tools="http://schemas.android.com/tools"     android:id="@+id/rl"     android:layout_width="match_parent"     android:layout_height="match_parent"     android:padding="10dp"     tools:context=".MainActivity"     android:background="#d2ffe2"     >     <TextView         android:id="@+id/tv"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="Which is your most favorite?"         />     <RadioGroup         android:id="@+id/rg"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:orientation="vertical"         android:layout_below="@id/tv"         android:padding="15dp"         >         <RadioButton             android:id="@+id/rb_coldfusion"             android:layout_width="match_parent"             android:layout_height="wrap_content"             android:text="ColdFusion"             android:paddingRight="15dp"             />         <RadioButton             android:id="@+id/rb_flex"             android:layout_width="match_parent"             android:layout_height="wrap_content"             android:text="Flex"             android:paddingRight="15dp"             />     </RadioGroup>     <Button         android:id="@+id/btn"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="Set Index 1 Radio Button Checked"         android:layout_below="@+id/rg"         /> </RelativeLayout> 

MainActivity.java

 package com.cfsuman.me.androidcodesnippets;  import android.os.Bundle; import android.app.Activity; import android.view.View; import android.widget.Button; import android.widget.RadioButton; import android.widget.RadioGroup;  public class MainActivity extends Activity {      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_main);          Button btn = (Button) findViewById(R.id.btn);         selesai RadioGroup rg = (RadioGroup) findViewById(R.id.rg);          btn.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 // Set the index 1 Radio Button checked from RadioGroup                 // This will checked second Radio Button                 // RadioGroup index started from 0 (zero)                 ((RadioButton)rg.getChildAt(1)).setChecked(true);             }         });    } } 

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