How to get the default selected Radio Button in RadioGroup in Android

In this android programming source code example, we are going to get the default selected Radio Button in RadioGroup in Android.

You can copy and adopt this source code example to your android project without reinventing the wheel.

Below is a step by step source code to get the default selected Radio Button in RadioGroup in Android.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margin="10dp"
    android:orientation="vertical"
    tools:context=".radiobutton.RadioButton13">

    <TextView
        android:id="@+id/textView25"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="RadioGroup Get Default Selected RadioButton inRadioGroup" />

    <RadioGroup
        android:id="@+id/radio"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:divider="?android:attr/dividerHorizontal"
        android:showDividers="middle">

        <RadioButton
            android:id="@+id/radioButton1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="RadioButton1" />

        <RadioButton
            android:id="@+id/radioButton2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="RadioButton2" />

        <RadioButton
            android:id="@+id/radioButton3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="RadioButton3" />


        <RadioButton
            android:id="@+id/radioButton4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="RadioButton4" />

    </RadioGroup>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/index"/>

</LinearLayout>

MainActivity.java

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;

public class RadioButton9 extends AppCompatActivity {
    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_radio_button9);

        TextView textView = findViewById(R.id.index);

        RadioGroup radioGroup = findViewById(R.id.radio);
        ((RadioButton)radioGroup.findViewById(R.id.radioButton1)).setChecked(true);

        int checkedRadio = radioGroup.getCheckedRadioButtonId();
        RadioButton checkedRadioButton = findViewById(checkedRadio);
        String checkedBox = checkedRadioButton.getText().toString();
        textView.setText(checkedBox);
    }
}

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