Android连续点击两次返回键退出App

Android连续点击两次返回键退出App

   private long firstTime = 0;

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        long secondTime = System.currentTimeMillis();

        if (keyCode == KeyEvent.KEYCODE_BACK) {
            if (secondTime - firstTime < 2000) {
                System.exit(0);
            } else {
                Toast.makeText(getApplicationContext(), "再按一次返回键退出", Toast.LENGTH_SHORT).show();
                firstTime = System.currentTimeMillis();
            }

            return true;
        }

        return super.onKeyDown(keyCode, event);
    }