旋转后恢复CountDownTimer对象

public class MainActivity extends AppCompatActivity {
    private static final String KEY_COUNTDOWN_TIME = "countdown_time";
    private CountDownTimer countDownTimer;
    private long countdownTime;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        if (savedInstanceState != null) {
            countdownTime = savedInstanceState.getLong(KEY_COUNTDOWN_TIME);
            // 使用之前保存的倒计时时间来重新创建CountDownTimer对象
            countDownTimer = new CountDownTimer(countdownTime, 1000) {
                @Override
                public void onTick(long millisUntilFinished) {
                    // 倒计时进行中
                }

                @Override
                public void onFinish() {
                    // 倒计时结束
                }
            }.start();
        } else {
            // 创建新的CountDownTimer对象
            countDownTimer = new CountDownTimer(60000, 1000) {
                @Override
                public void onTick(long millisUntilFinished) {
                    // 倒计时进行中
                }

                @Override
                public void onFinish() {
                    // 倒计时结束
                }
            }.start();
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        // 保存倒计时时间到Bundle对象
        outState.putLong(KEY_COUNTDOWN_TIME, countdownTime);
    }
}