屏蔽HOME键与屏蔽BACK键不同

    今天看到“Android事件处理”一节&＃xff0c;根据示例中重写onKeyDown()方法来拦截用户单击后退按钮事件&＃xff0c;我试着运用onKeyDown()方法屏蔽HOME键&＃xff0c;但发现以下代码并不能屏蔽HOME键&＃xff1a;

 &＃64;Override
 public boolean onKeyDown(int keyCode, KeyEvent event) {
  // TODO Auto-generated method stub
  if(keyCode&＃61;&＃61;KeyEvent.KEYCODE_HOME){
   return true;
  }
  return super.onKeyDown(keyCode, event);
 }

通过Search in internet&＃xff0c;我发现重写onAttachedToWindow()方法可以实现屏蔽HOME键&＃xff0c;具体代码如下&＃xff1a;

&＃64;Override
 public void onAttachedToWindow() {
  // TODO Auto-generated method stub
  this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);
  super.onAttachedToWindow();
 }

 &＃64;Override
 public boolean onKeyDown(int keyCode, KeyEvent event) {
  // TODO Auto-generated method stub
  if(keyCode&＃61;&＃61;KeyEvent.KEYCODE_HOME){
   return true;
  }
  return super.onKeyDown(keyCode, event);
 }

但onAttachedToWindow()方法有何功能&＃xff0c; this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);一句又是什么意思我不甚理解&＃xff0c;盼前辈帮忙解惑&＃xff01;