Unity timer count down not working when app killed android - unity3d

Question

I'm new to unity and c#, I have a code to increase energy after 10m, I have used PlayerPrefs to do so it is working in unity but not working on mobile please help.
I'm unable to understand what exactly is causing problem in phone. Also the timer pauses when the app is not killed but just minimized on mobile. I want the timer countdown to keep going game minimized and also if killed.
using System;
using UnityEngine;
using UnityEngine.UI;
public class EnergyAdder : MonoBehaviour
{
// Start is called before the first frame update
public float waitTime = 600;
Timer timer;
public GameRoot gameRoot;
public int count;
DateTime currentDate;
DateTime oldDate;
void Start()
{
//timer = new Timer(waitTime);
float remainingTime = PlayerPrefs.GetFloat("TimeOnExit");
timer = new Timer(remainingTime);
if (PlayerPrefs.HasKey("sysString"))
{
currentDate = DateTime.Now;
long temp = Convert.ToInt64(PlayerPrefs.GetString("sysString"));
oldDate = DateTime.FromBinary(temp);
TimeSpan difference = currentDate.Subtract(oldDate);
count = (int)(difference.TotalSeconds / waitTime);
Debug.Log("time remaining " + count);
gameRoot.AddEnergy(count);
timer = new Timer(remainingTime - (float)difference.TotalSeconds);
//PlayerPrefs.DeleteKey("TimeOnExit");
//PlayerPrefs.DeleteKey("sysString");
}
}
// Update is called once per frame
void Update()
{
if (Gameroot.isFull)
{
GetComponent<Text>().text = "Full";
count = 0;
timer.refresh();
}
else
{
//Debug.Log("deltatime ************************"+ secondstime);
timer.countDown();
if (timer.isFinished())
{
timer = new Timer(waitTime);
timer.refresh();
gameRoot.AddEnergy(1);
}
UpdateClock();
}
}
void UpdateClock()
{
int seconds = ((int)timer.timeLeft) % 60;
int minutes = (int)(timer.timeLeft / 60);
GetComponent<Text>().text = minutes.ToString() + ":" + seconds.ToString("00");
}
void OnApplicationQuit()
{
PlayerPrefs.SetFloat("TimeOnExit", timer.timeLeft);
var today = DateTime.Now;
PlayerPrefs.SetString("sysString", today.ToBinary().ToString());
PlayerPrefs.Save();
}
}
Please help what is wrong in above code or what is missing.

Answer 1

From OnApplicationQuit
Note: iOS applications are usually suspended and do not quit. You should tick "Exit on Suspend" in Player settings for iOS builds to cause the game to quit and not suspend, otherwise you may not see this call. If "Exit on Suspend" is not ticked then you will see calls to OnApplicationPause instead.
I suspect it is just the same with modern Android where your app is also not really closed but hibernate.
So I think you could use OnApplicationPause and OnApplicationFocus
On Android, when the on-screen keyboard is enabled, it causes a OnApplicationFocus(false) event. Additionally, if you press "Home" at the moment the keyboard is enabled, the OnApplicationFocus() event is not called, but OnApplicationPause() is called instead.
and just do the same as you do in OnApplicationQuit also for OnApplicationPause(true) and OnApplicationFocus(false)
and do the same as you do in Start also in OnApplicationPause(false) and OnApplictionFocus(true) like
public class EnergyAdder : MonoBehaviour
{
public float waitTime = 600;
public GameRoot gameRoot;
public int count;
// already reference this in the Inspector
[SerializeField] private Text timerText;
private Timer timer;
private DateTime currentDate;
private DateTime oldDate;
private void Awake()
{
// store this reference ONCE
if(!timerText) timerText = GetComponent<Text>();
}
private void Start()
{
GetTime();
}
private void Update()
{
// Note: probably a typo? shouldn't it be "gameRoot" ?
if (Gameroot.isFull)
{
timerText.text = "Full";
count = 0;
timer.refresh();
}
else
{
//Debug.Log("deltatime ************************"+ secondstime);
timer.countDown();
if (timer.isFinished())
{
timer = new Timer(waitTime);
timer.refresh();
gameRoot.AddEnergy(1);
}
UpdateClock();
}
}
private void UpdateClock()
{
int seconds = ((int)timer.timeLeft) % 60;
int minutes = (int)(timer.timeLeft / 60);
timerText.text = $"{minutes}:{seconds:00}";
}
private void OnApplicationQuit()
{
StoreTime();
}
// pauseStatus is True if the application is paused, else False.
private void OnApplicationPause(bool pauseStatus)
{
if(pauseStatus)
{
StoreTime();
}
else
{
GetTime();
}
}
// hasFocus is True if the GameObjects have focus, else False.
private void OnApplicationFocus(bool hasFocus)
{
if(hasFocus)
{
GetTime();
}
else
{
StoreTime();
}
}
private void StoreTime()
{
PlayerPrefs.SetFloat("TimeOnExit", timer.timeLeft);
var today = DateTime.Now;
PlayerPrefs.SetString("sysString", today.ToBinary().ToString());
PlayerPrefs.Save();
}
private void GetTime()
{
// NOTE: You should consider to pass a default value like
//float remainingTime = PlayerPrefs.GetFloat("TimeOnExit", 15);
float remainingTime = PlayerPrefs.GetFloat("TimeOnExit");
timer = new Timer(remainingTime);
if (PlayerPrefs.HasKey("sysString"))
{
currentDate = DateTime.Now;
long temp = Convert.ToInt64(PlayerPrefs.GetString("sysString"));
oldDate = DateTime.FromBinary(temp);
TimeSpan difference = currentDate.Subtract(oldDate);
count = (int)(difference.TotalSeconds / waitTime);
Debug.Log("time remaining " + count);
gameRoot.AddEnergy(count);
timer = new Timer(remainingTime - (float)difference.TotalSeconds);
}
}
}
Note: Typed on smartphone so I can't test it but I hope it goes into the right direction