Android: How to keep count down timer running and display a message when time out , while I am in another activity?

Question

https://codinginflow.com/tutorials/android/countdowntimer/part-3-run-in-background

I am watching this tutorial, i want to change some things : I want to display a message "Time Out" after 6 seconds, by using CountDownTimer. It works when i am in TimerActivity, but when i go to another activity (such as WelcomeActivity), then the application do not display the message. How to achieve the message "Time Out" in the WelcomeActivity ?

TimerActivity

class TimerActivity : AppCompatActivity() {
    companion object {
        var START_TIME_IN_MILLIS : Long = 6000
    }
    private var mTextViewCountDown: TextView? = null
    private var mButtonStartPause: Button? = null
    private var mButtonReset: Button? = null
    private var mCountDownTimer: CountDownTimer? = null
    private var mTimerRunning: Boolean = false
    private var mTimeLeftInMillis : Long =0

private var mEndTime : Long = 0

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_timer)
    mTextViewCountDown = findViewById(R.id.text_view_countdown)
    mButtonStartPause = findViewById(R.id.button_start_pause)
    mButtonReset = findViewById(R.id.button_reset)
    btnWelcomeAct.setOnClickListener {
        val intent = Intent(this@TimerActivity, Welcome::class.java)
        startActivity(intent)

    }

    mButtonStartPause!!.setOnClickListener {
        if (mTimerRunning) {
            pauseTimer()
        } else {
            startTimer()
        }

    }

    mButtonReset!!.setOnClickListener {
        resetTimer()
    }
    updateCountDownText()
}

private fun startTimer() {
    mEndTime = System.currentTimeMillis() + mTimeLeftInMillis

    mCountDownTimer = object : CountDownTimer(mTimeLeftInMillis, 1000) {
        override fun onTick(millisUntilFinished: Long) {
            mTimeLeftInMillis = millisUntilFinished
            updateCountDownText()
        }

        override fun onFinish() {
            mTimerRunning = false
            updateButton()
            Toast.makeText(applicationContext,"Time out", Toast.LENGTH_SHORT).show()
        }
    }.start()
    mTimerRunning = true
    updateButton()
}


private fun pauseTimer() {
    mCountDownTimer!!.cancel()
    mTimerRunning = false
    updateButton()
}

private fun resetTimer() {
    mTimeLeftInMillis = START_TIME_IN_MILLIS
    updateCountDownText()
    updateButton()
}


private fun updateCountDownText() {
    val minutes = mTimeLeftInMillis / 1000 / 60
    val seconds = mTimeLeftInMillis / 1000 % 60
    val timeLeftFormatted = String.format(Locale.getDefault(), "%02d:%02d", minutes, seconds)
    mTextViewCountDown!!.text = (timeLeftFormatted)

}

private fun updateButton() {
    if (mTimerRunning) {
        mButtonReset!!.setVisibility(View.INVISIBLE)
        mButtonStartPause!!.setText("Pause")
    } else {
        mButtonStartPause!!.setText("Start")
        if (mTimeLeftInMillis < 1000) {
            mButtonStartPause!!.setVisibility(View.INVISIBLE)
        } else {
            mButtonStartPause!!.setVisibility(View.VISIBLE)
        }
        if (mTimeLeftInMillis < START_TIME_IN_MILLIS) {
            mButtonReset!!.setVisibility(View.VISIBLE)
        } else {
            mButtonReset!!.setVisibility(View.INVISIBLE)
        }
    }
}

override fun onStop() {
    super.onStop()
    val prefs = getSharedPreferences("prefs", Context.MODE_PRIVATE)
    val editor = prefs.edit()
    editor.putLong("millisLeft", mTimeLeftInMillis)
    editor.putBoolean("timerRunning", mTimerRunning)
    editor.putLong("endTime", mEndTime)
    editor.apply()
    if (mCountDownTimer != null) {
        mCountDownTimer!!.cancel()
    }
}

override fun onStart() {
    super.onStart()
    val prefs = getSharedPreferences("prefs", Context.MODE_PRIVATE)
    mTimeLeftInMillis = prefs.getLong("millisLeft", START_TIME_IN_MILLIS)
    mTimerRunning = prefs.getBoolean("timerRunning", false)
    updateCountDownText()
    updateButton()
    if (mTimerRunning) {
        mEndTime = prefs.getLong("endTime", 0)
        mTimeLeftInMillis = (mEndTime - System.currentTimeMillis())
        if (mTimeLeftInMillis < 0) {
            mTimeLeftInMillis = 0
            mTimerRunning = false
            updateCountDownText()
            updateButton()
        } else {
            startTimer()
        }
    }
}

override fun onBackPressed() {
    val intent = Intent(this@TimerActivity, Welcome::class.java)
    startActivity(intent)
}
}

Class WelcomeActivity

How to display the message "Time Out" in this activiy when CountDownTimer in TimerActivity finished?

class Welcome : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_welcome)
}

Answer 1

There are so many way to update UI after switching another activity. I'm sharing some of way which may help you in updating UI from another activity:

1) Event Bus

2) Broadcast receiver

3) In case you use MVVM architecture, then you can create custom viewModel which is alive with application alive.

Event Bus

you need to add EventBus dependency

1) compile 'de.greenrobot:eventbus:2.4.0'

2) create a pojo

public class DataSyncEvent {
    private final String syncStatusMessage;
    public DataSyncEvent(String syncStatusMessage) {
        this.syncStatusMessage = syncStatusMessage;
    }
    public String getSyncStatusMessage() {
        return syncStatusMessage;
    }
}

3) call from your countdowntimer

EventBus.getDefault().post(new DataSyncEvent("Sync SuccessFully”);

4) Subscribe in activity which you want to get update

@Subscribe
public void onEvent(DataSyncEvent syncStatusMessage)
{
    Toast.makeText(this, syncStatusMessage.getSyncStatusMessage(), Toast.LENGTH_SHORT).show();
}

Note: Don't forgot register and unregister

@Override
protected void onStart() {
    super.onStart();
    EventBus.getDefault().register(this);
}

@Override
protected void onDestroy() {
    super.onDestroy();
    EventBus.getDefault().unregister(this);
}

Broadcast receiver:

1) call from countdowntimer

MyReceiver receiver = new MyReceiver(new Handler()); // Create the receiver
registerReceiver(receiver, new IntentFilter("some.action")); // Register receiver

sendBroadcast(new Intent("some.action"));

2) In another activity:

public static class MyReceiver extends BroadcastReceiver {

        private final Handler handler; // Handler used to execute code on the UI thread

        public MyReceiver(Handler handler) {
            this.handler = handler;
        }

        @Override
        public void onReceive(final Context context, Intent intent) {
            // Post the UI updating code to our Handler
            handler.post(new Runnable() {
                @Override
                public void run() {
                    Toast.makeText(context, "Toast from broadcast receiver", Toast.LENGTH_SHORT).show();
                }
            });
        }
    }   

Thanks