LifeCycles

MainActivity

package com.example.lifecycles;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.SystemClock;
import android.widget.Chronometer;

public class MainActivity extends AppCompatActivity {
    MyChronometer chronometer;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        chronometer=findViewById(R.id.TextView);
        getLifecycle().addObserver(chronometer);

    }
}

MyChronometer

package com.example.lifecycles;

import android.content.Context;
import android.os.SystemClock;
import android.util.AttributeSet;
import android.widget.Chronometer;

import androidx.lifecycle.Lifecycle;
import androidx.lifecycle.LifecycleObserver;
import androidx.lifecycle.OnLifecycleEvent;

public class MyChronometer extends Chronometer implements LifecycleObserver {
    private long elapseTime;
    public MyChronometer(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    private void pauseMeter(){
        elapseTime= SystemClock.elapsedRealtime()-getBase();
        stop();
    }
    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    private void resumeMeter(){
        setBase(SystemClock.elapsedRealtime()-elapseTime);
        start();
    }
}