当点击通知时，转到Mainactivity并恢复任务(Countdown timer应继续) Android Studio

// 创建通知
NotificationCompat.Builder builder = new NotificationCompat.Builder(this)
        .setSmallIcon(R.drawable.notification_icon)
        .setContentTitle("任务通知")
        .setContentText("点击通知返回任务")
        .setAutoCancel(true);

// 设置通知的点击行为
Intent intent = new Intent(this, MainActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_SINGLE_TOP);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
builder.setContentIntent(pendingIntent);

// 发送通知
NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify(0, builder.build());

// 在MainActivity中处理通知点击事件
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // 检查是否是从通知启动的
    Intent intent = getIntent();
    if (intent != null && (intent.getFlags() & Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY) == 0) {
        // 获取之前保存的任务状态
        SharedPreferences sharedPreferences = getSharedPreferences("TaskState", Context.MODE_PRIVATE);
        long remainingTime = sharedPreferences.getLong("RemainingTime", 0);

        // 根据任务状态进行处理，如恢复倒计时
        if (remainingTime > 0) {
            // 创建倒计时
            CountdownTimer countdownTimer = new CountdownTimer(remainingTime, 1000) {
                @Override
                public void onTick(long millisUntilFinished) {
                    // 更新倒计时显示
                }

                @Override
                public void onFinish() {
                    // 倒计时结束处理
                }
            };

            // 启动倒计时
            countdownTimer.start();
        }
    }
}

// 在MainActivity中保存任务状态
@Override
protected void onPause() {
    super.onPause();

    // 保存任务状态
    SharedPreferences sharedPreferences = getSharedPreferences("TaskState", Context.MODE_PRIVATE);
    SharedPreferences.Editor editor = sharedPreferences.edit();
    editor.putLong("RemainingTime", countdownTimer.getRemainingTime());
    editor.apply();
}