Android 再按一次退出应用的代码，android代码, private

Android 再按一次退出应用的代码，android代码, private

    private long exitTime = 0;      @Override      public boolean onKeyDown(int keyCode, KeyEvent event) {          if (keyCode == KeyEvent.KEYCODE_BACK                  && event.getAction() == KeyEvent.ACTION_DOWN) {              if ((System.currentTimeMillis() - exitTime) > 2000) {                  Toast.makeText(getApplicationContext(), "再按一下退出应用",                          Toast.LENGTH_SHORT).show();                  exitTime = System.currentTimeMillis();              } else {                  finish();                  System.exit(0);              }              return true;          }          return super.onKeyDown(keyCode, event);      }