Android Started Service Example

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:padding="10dp"
        android:layout_margin="10dp"
        android:textSize="25dp" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="START SERVICE"
        android:layout_margin="10dp"
        android:id="@+id/button1"/>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="STOP SERVICE"
        android:layout_margin="10dp"
        android:id="@+id/button2"/>

</LinearLayout>

package com.example.dialog;

import android.app.Service;
import android.content.Intent;
import android.os.IBinder;

import androidx.annotation.Nullable;

import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class MyService extends Service {

    ScheduledExecutorService myschedule_executor;

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        myschedule_executor = Executors.newScheduledThreadPool(1);
        myschedule_executor.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                MainActivity.textView.setText("Current Time: " + new Date());
            }
        }, 1, 1, TimeUnit.SECONDS);

        return super.onStartCommand(intent, flags, startId);
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        myschedule_executor.shutdown();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.dialog">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.Dialog">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service android:name=".MyService"/>
    </application>

</manifest>

package com.example.dialog;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

    static TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = findViewById(R.id.textView1);
        Button button1 = findViewById(R.id.button1);
        Button button2 = findViewById(R.id.button2);

        textView.setText("Current Time: " + new Date());

        Intent intent = new Intent(MainActivity.this, MyService.class);
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startService(intent);
            }
        });

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                stopService(intent);
            }
        });

    }

}