一般按键的监控：
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
//点击返回键
if(keyCode==KeyEvent.KEYCODE_BACK){
//声明弹出对象并初始化
AlertDialog.Builder builder=new AlertDialog.Builder(this);
builder.setTitle("提示：");
builder.setMessage("是否退出?");
//设置确定按钮
builder.setNegativeButton("确定", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
finish();
}
});
//设置取消按钮
builder.setPositiveButton("取消",null);
//显示弹窗
builder.show();
}
return super.onKeyDown(keyCode,event);
}

请问全面屏的返回监控怎么做呢？？？？函数是》？？？？？？？？？？？