public class ForegroundService extends Service{
    //服务通信
    @Nullable
    @Override
    public IBinder onBind(Intent intent){
        //与Activity进行通信
        return null;
    }
    
    //服务创建时
    @Override
    public void onCreate(){
        super.onCreate();
        //服务创建时创建前台通知
        Notification notification = createForegroundNotification();
        //启动前台服务
        startForeground(1,notification);
		//有业务逻辑的代码可写在onCreate下
    }
    
    //服务销毁时
    @Override
    public void onDestroy(){
        //在服务被销毁时，关闭前台服务
        stopForeground(true);
        super.onDestroy();    
    }
    
    //创建前台通知，可写成方法体，也可单独写成一个类
    private Notification createForegroundNotification(){
        //前台通知的id名，任意
        String channelId = "ForegroundService";
        //前台通知的名称，任意
        String channelName = "Service";
        //发送通知的等级，此处为高，根据业务情况而定
        int importance = NotificationManager.IMPORTANCE_HIGH;
        //判断Android版本，不同的Android版本请求不一样，以下代码为官方写法
        if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.O){
            NotificationChannel channel = new NotificationChannel(channelId,channelName,importance);
            channel.setLightColor(Color.BLUE);
            channel.setLockscreenVisiability(Notification.VISIBILITY_PRIVATE);
            NotificationManager notificationManager = (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
            notificationManager.createNotificationChannel(channel);        
        }
        
        //点击通知时可进入的Activity
        Intent notificationIntent = new Intent(this,MainActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this,0,notificationIntent,0);
        
        //最终创建的通知，以下代码为官方写法
        //注释部分是可扩展的参数，根据自己的功能需求添加
        return new NotificationCompat.Builder(this,channelId)
        	 .setContentTitle("填写通知的标题")
          	 .setContentText("填写通知的内容")
            .setSmallIcon(Icon)//通知显示的图标
            .setContentIntent(pendingIntent)//点击通知进入Activity
            .setTicker("通知的提示语")
            .build();
            //.setOngoing(true)
            //.setPriority(NotificationCompat.PRIORITY_MAX)
            //.setCategory(Notification.CATEGORY_TRANSPORT)
            //.setLargeIcon(Icon)
            //.setWhen(System.currentTimeMillis())
    }
}

<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />

<application>
    ......
    <service
        android:name=".ForegroundService"
        android:enabled="true"
        android:foregroundServiceType="location" />
</application>

try{
    Intent intent = new Intent(this,ForegroundService.class);
    startForegroundService(intent);
}catch(Exception e){
    e.printStackTrace();
}