<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="horizontal" >
  <RadioGroup
    android:id="@+id/radioGroup1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal" >
    <RadioButton
      android:id="@+id/radio0"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:checked="true"
      android:text="男" />
    <RadioButton
      android:id="@+id/radio1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="女" />
  </RadioGroup>
</LinearLayout>

package com.example.hello;
import android.support.v7.app.ActionBarActivity;
import android.widget.RadioGroup;
import android.widget.Toast;
import android.widget.RadioGroup.OnCheckedChangeListener;
import android.os.Bundle;
public class MainActivity extends ActionBarActivity implements OnCheckedChangeListener{
  private RadioGroup rg;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    rg = (RadioGroup) findViewById(R.id.radioGroup1);
    rg.setOnCheckedChangeListener(this);
  }
  @Override
  public void onCheckedChanged(RadioGroup group, int checkedId) {
    switch(checkedId){
      case R.id.radio0:
        Toast.makeText(MainActivity.this, "男", 1).show();
        break;
      case R.id.radio1:
        Toast.makeText(MainActivity.this, "女", 1).show();
        break;
    }
  }
}