android RadioButton和CheckBox组件的使用方法

package com.example.control1;

import android.app.Activity;
import android.os.Bundle;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

    //定义各控件的变量
    private TextView who = null;
    private TextView how = null;
    private RadioGroup who_group = null;
    private RadioButton china = null;
    private RadioButton america = null;
    private RadioButton others = null;
    private CheckBox less = null;
    private CheckBox thirty = null;
    private CheckBox forty = null;
    private CheckBox fifty = null;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //获得对应的控件
        who = (TextView)findViewById(R.id.who);
        how = (TextView)findViewById(R.id.how);
        who_group = (RadioGroup)findViewById(R.id.who_group);
        china = (RadioButton)findViewById(R.id.china);
        america = (RadioButton)findViewById(R.id.america);
        others = (RadioButton)findViewById(R.id.others);
        less = (CheckBox)findViewById(R.id.less);
        thirty = (CheckBox)findViewById(R.id.thirty);
        forty = (CheckBox)findViewById(R.id.forty);
        fifty = (CheckBox)findViewById(R.id.fifty);

        //设置who_group的监听器，其实是一句代码，其参数是一个带有重构函数的对象
        who_group.setOnCheckedChangeListener(new RadioGroup.OnCheckedChangeListener() {

   public void onCheckedChanged(RadioGroup group, int checkedId) {
       // TODO Auto-generated method stub
       if(checkedId == china.getId()){
  Toast.makeText(MainActivity.this,"中国", Toast.LENGTH_SHORT).show();
       }
       else if(checkedId == america.getId()){
  Toast.makeText(MainActivity.this, "美国", Toast.LENGTH_SHORT).show();
       }
       else if(checkedId == others.getId()){
  Toast.makeText(MainActivity.this, "其它国家", Toast.LENGTH_SHORT).show();
       }
   }
        });

        //下面为4个checkbox多选按钮分别建立监听器
        less.setOnCheckedChangeListener(new OnCheckedChangeListener() {

   public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
       // TODO Auto-generated method stub
       if(isChecked)
       {
  Toast.makeText(MainActivity.this, "30个以下", Toast.LENGTH_SHORT).show();
       }
       else{
  Toast.makeText(MainActivity.this, "不是30个以下", Toast.LENGTH_SHORT).show();
       }
   }
        });

       
      //下面为4个checkbox多选按钮分别建立监听器
        thirty.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

   public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
       // TODO Auto-generated method stub
       if(isChecked)
       {
  Toast.makeText(MainActivity.this, "30~39", Toast.LENGTH_SHORT).show();
       }
       else{
  Toast.makeText(MainActivity.this, "不是30~39", Toast.LENGTH_SHORT).show();
       }
   }
        });

      //下面为4个checkbox多选按钮分别建立监听器
        forty.setOnCheckedChangeListener(new OnCheckedChangeListener() {

   public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
       // TODO Auto-generated method stub
       if(isChecked)
       {
  Toast.makeText(MainActivity.this, "40~49", Toast.LENGTH_SHORT).show();
       }
       else{
  Toast.makeText(MainActivity.this, "不是40~49", Toast.LENGTH_SHORT).show();
       }
   }
        });

      //下面为4个checkbox多选按钮分别建立监听器
        fifty.setOnCheckedChangeListener(new OnCheckedChangeListener() {

   public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
       // TODO Auto-generated method stub
       if(isChecked)
       {
  Toast.makeText(MainActivity.this, "50以上", Toast.LENGTH_SHORT).show();
       }
       else{
  Toast.makeText(MainActivity.this, "不是50以上", Toast.LENGTH_SHORT).show();
       }
   }
        });

   

    }
}

<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:orientation="vertical"
    >
    <TextView
        android:id="@+id/who"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/who"
/>
    <RadioGroup
        android:id="@+id/who_group"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:orientation="vertical"
      >
       <RadioButton
  android:id="@+id/china"
  android:layout_height="wrap_content"
  android:layout_width="wrap_content"
  android:text="@string/china"
  />
       <RadioButton
  android:id="@+id/america"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="@string/america"
  />
       <RadioButton
  android:id="@+id/others"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="@string/others"
  />
       </RadioGroup>
       <TextView
  android:id="@+id/how"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="@string/how"
  />
        <CheckBox
  android:id="@+id/less"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="@string/less"
  />
       <CheckBox
  android:id="@+id/thirty"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="@string/thirty"
  />
       <CheckBox
  android:id="@+id/forty"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="@string/forty"
  />
       <CheckBox
  android:id="@+id/fifty"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:text="@string/fifty"
  />

</LinearLayout>