Android CheckBox 选择事件

package com.demo;
import android.app.Activity;
import android.os.Bundle;
import android.widget.CheckBox;
import android.widget.CompoundButton;
public  class MainMenu extends Activity implements  CompoundButton.OnCheckedChangeListener{

     CheckBox cb; 
    @Override
    protected void onCreate(Bundle savedInstanceState) {        
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main); 
         
        cb=(CheckBox)findViewById(R.id.check); 
        cb.setOnCheckedChangeListener(this); 
    }


    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        if (isChecked) { 
            cb.setText("This checkbox is: checked"); 
          } 
          else { 
            cb.setText("This checkbox is: unchecked"); 
          } 
        
    }
    
  

}

<?xml version="1.0" encoding="utf-8"?>

<CheckBox xmlns:android="http://schemas.android.com/apk/res/android"
 android:id="@+id/check" 
 android:layout_width="wrap_content"  
 android:layout_height="wrap_content"  
 android:text="This checkbox is: unchecked" />