我有两个活动：mainactivity6（父级）和tool1mode1（子级）
从父活动：

if (tool == 1) {
            switch (mode) {
                case 1:
                    intentTool1mode1.putExtra("Type", typekey);
                    intentTool1mode1.putExtra("Key", Key);
                    intentTool1mode1.putExtra("Tool", "Tool 1");
                    intentTool1mode1.putExtra("Mode", "Home");
                    Toast.makeText(MainActivity6.this, "Type: " + typekey + "\n" + "Key: " + Key + "\n" + "Tool: " + "1" + "\n" + "Mode: " + "Home" + "\n", Toast.LENGTH_LONG).show();
                  if(key_60.isChecked())
                        {
                        String number = "480000";
                        long val = Long.parseLong(number);
                        intentTool1mode1.putExtra("Time",val);
                        startActivityForResult(intentTool1mode1, 1);
                        }
                        if(key_90.isChecked())
                        {
                        String number = "720000";
                        long val = Long.parseLong(number);
                        intentTool1mode1.putExtra("Time",val);
                        startActivityForResult(intentTool1mode1, 1);
                        }

                    break;

这是儿童活动的一部分：

private long START_TIME_IN_MILLIS;
    private long mTimeLeftInMillis = START_TIME_IN_MILLIS;
    private CountDownTimer mCountDownTimer;

      ...

        protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        Intent intent = getIntent();
        START_TIME_IN_MILLIS = intent.getLongExtra("Time", 0);

        newbtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startTimer();
            }
        });

下面的代码表示我用于启动和更新子活动中计数器的两个函数：

private void startTimer()
    {
        mCountDownTimer = new CountDownTimer(mTimeLeftInMillis, 1000) {
            @Override
            public void onTick(long millisUntilFinished) {
                mTimeLeftInMillis = millisUntilFinished;
                updateCountDownText();
                progress++;
                pb.setProgress((int)progress*100/(480000/1000));

            }

            @Override
            public void onFinish()
            {
                progress++;
                pb.setProgress(100);
                //Vibration
                if (Build.VERSION.SDK_INT >= 26)
                {
                    ((Vibrator) getSystemService(VIBRATOR_SERVICE)).vibrate(VibrationEffect.createOneShot(150, VibrationEffect.DEFAULT_AMPLITUDE));
                    Toast.makeText(com.example.ticwatch_1.tool1mode1.this,"Done",Toast.LENGTH_SHORT).show();
                }
                else
                {
                    ((Vibrator) getSystemService(VIBRATOR_SERVICE)).vibrate(VibrationEffect.createWaveform(new long[]{150}, new int[]{VibrationEffect.EFFECT_CLICK},-1));
                }
            }
        }.start();
    }

  private void updateCountDownText()
    {

        //time in minutes and seconds
        int minutes = (int)(mTimeLeftInMillis/1000)/60;
        int seconds = (int)(mTimeLeftInMillis/1000)%60;
        //formating the above to appear as String
        String timeLeftFormatted = String.format("%02d:%02d",minutes,seconds);
        timer.setText(timeLeftFormatted);
    }

我想要的是从父活动获取值，并用我获取的值更新start\u time\u的值（以毫秒为单位）。所以我想让计时器运行8分钟，我去拿48万。我得到的是计数器是0，当我启动它，因为它已经完成，没有从8分钟或任何其他值开始。我不知道该怎么办，我累坏了。