Android 连续点击返回键退出程序

//记录用户首次点击返回键的时间
private long firstTime = 0;

//连续点击两次退出程序
@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_UP) {
long secondTime = System.currentTimeMillis();
if (secondTime - firstTime > 2000) {
MyToast.showToast(ImportantOtherActivity.this,"再按一次退出程序").show();
firstTime = secondTime;
return true;
} else {
System.exit(0);
}
}
return super.onKeyUp(keyCode, event);
}

onKeyDown(int keyCode, KeyEvent event)