android编程接口的问题

疯狂android讲义中的一段代码，OnCheckedChangeListener 是一个接口吧，为什么类的定义中不需要实现这个接口呢，新手求教。OnCheckedChangeListener listener = new OnCheckedChangeListener(){...}这段语法怎么表达，是不死记硬背的，这段为什么不能直接换成 listener.setOnCheckedChangeListener(new OnCheckedChangeListener(){...})public class Test0811 extends Activity{ ToggleButton toggle; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); toggle = (ToggleButton)findViewById(R.id.toggleButton1); final LinearLayout ll = (LinearLayout)findViewById(R.id.ll); OnCheckedChangeListener listener = new OnCheckedChangeListener(){ public void onCheckedChanged(CompoundButton botton,boolean isChecked){ if(isChecked){ ll.setOrientation(1); } else{ ll.setOrientation(0); } } }; toggle.setOnCheckedChangeListener(listener); }}