android监听返回键
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
return true;
}
return super.onKeyDown(keyCode, event);
}
event.getRepeatCount() == 0重复次数：1次
原文：http://www.cnblogs.com/zhaoleigege/p/4872123.html