<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical" android:layout_width="fill_parent"
 android:layout_height="fill_parent">
 <TextView
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:text="당신의 혈액형이 무엇입니까?"/>
 
 <RadioGroup
     android:id="@+id/Group"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:orientation="horizontal">
 <kr.co.naver.Radio1
     android:id="@+id/radiobtn1"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="A형" />
 <kr.co.naver.Radio1
     android:id="@+id/radiobtn2"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="B형" />
 <kr.co.naver.Radio1
     android:id="@+id/radiobtn3"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="O형" />
 <kr.co.naver.Radio1
     android:id="@+id/radiobtn4"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="AB형" />
 </RadioGroup>
 
 <TextView
     android:id="@+id/answer"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:textSize="10sp"/>
</LinearLayout>

/////////////////////////////////////////////////////////////////////////////

package kr.co.naver;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.AttributeSet;

import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.RadioButton;

public class Widget3Activity extends Activity {
   
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
       
        Radio1 radioB1 = (Radio1)findViewById(R.id.radiobtn1);
        Radio1 radioB2 = (Radio1)findViewById(R.id.radiobtn2);
        Radio1 radioB3 = (Radio1)findViewById(R.id.radiobtn3);
        Radio1 radioB4 = (Radio1)findViewById(R.id.radiobtn4);
       
        TextView text = (TextView)findViewById(R.id.answer);
        text.setText(radioB1.Ans1);
        text.setText(radioB2.Ans2);
        text.setText(radioB3.Ans3);
        text.setText(radioB4.Ans4);
      
    }
}
class Radio1 extends RadioButton{
 String Ans1="";
 String Ans2="";
 String Ans3="";
 String Ans4="";
 
 

 public Radio1(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);

    RadioGroup group = (RadioGroup)findViewById(R.id.Group);
    group.setOnCheckedChangeListener(mRadioCheck);
   }
   public Radio1(Context context, AttributeSet attrs){
    super(context, attrs);

    RadioGroup group = (RadioGroup)findViewById(R.id.Group);
    group.setOnCheckedChangeListener(mRadioCheck); 
   }
   public Radio1(Context context){
     super(context);

     RadioGroup group = (RadioGroup)findViewById(R.id.Group);
     group.setOnCheckedChangeListener(mRadioCheck); 
   }

 
 
 RadioGroup.OnCheckedChangeListener mRadioCheck = new RadioGroup.OnCheckedChangeListener() {
  
  public void onCheckedChanged(RadioGroup group, int checkedId) {
   
   if(group.getId() == R.id.Group){
    switch (checkedId) {
    case R.id.radiobtn1:
     Ans1="ㅇ";
     break;
    case R.id.radiobtn2:
     Ans2="ㅇ";
     break;
    case R.id.radiobtn3:
     Ans3="ㅇ";
     break;
    case R.id.radiobtn4:
     Ans4="ㅇ";
     break;
    }
   }
   
  }
 }; 
}

이렇게 소스입니다.

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