package com.example.lesson16_radio;
import android.app.Activity;
import android.os.Bundle;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.Toast;
public class MainActivity extends Activity {
 private RadioGroup group_temo;
 private RadioButton checkRadioButton;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  group_temo = (RadioGroup) findViewById(R.id.radioGroup1);
  // 改变默认选项
  group_temo.check(R.id.radio1);
  // 获取默认被被选中值
  checkRadioButton = (RadioButton) group_temo.findViewById(group_temo
    .getCheckedRadioButtonId());
  Toast.makeText(this, "默认的选项的值是:" + checkRadioButton.getText(),
    Toast.LENGTH_LONG).show();
  // 注册事件
  group_temo
    .setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {
     @Override
     public void onCheckedChanged(RadioGroup group, int checkedId) {
      // 点击事件获取的选择对象
      checkRadioButton = (RadioButton) group_temo
        .findViewById(checkedId);
      Toast.makeText(getApplicationContext(),
        "获取的ID是" + checkRadioButton.getText(),
        Toast.LENGTH_LONG).show();
     }
    });
 }
}

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
 android:paddingLeft="@dimen/activity_horizontal_margin"
 android:paddingRight="@dimen/activity_horizontal_margin"
 android:paddingTop="@dimen/activity_vertical_margin"
 tools:context=".MainActivity" >
 <RadioGroup
  android:id="@+id/radioGroup1"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:layout_alignParentLeft="true"
  android:layout_alignParentRight="true"
  android:layout_alignParentTop="true" >
  <RadioButton
   android:id="@+id/radio0"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:checked="true"
   android:text="@string/text_java" />
  <RadioButton
   android:id="@+id/radio1"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="@string/text_net" />
  <RadioButton
   android:id="@+id/radio2"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="@string/text_php" />
 </RadioGroup>
</RelativeLayout>