Monday, November 25, 2019

The transformation of one of my 8-years-old kid-students

If properly trained, in an year time even a 7-years-old kid can transform himself vis-a-vis software knowledge. Have a look at the following videos.

- How to find the smallest number in an array - October 2018




-  Singleton Pattern - February 2019



- How to develop a Scramble - Unscramble app in Android - May 2019




-  App store - current

Google Play store profile of Ridit - an 8 years old boy...

Towards the end of 2018, this kid-student was practising some simple Java programs. After 4 months, he transformed himself and discussed about Singleton Design Pattern and after 7 months he started discussing about Android apps. And in October 2019, this kid has his own Google Play Portfolio ( the last link). i know its a long journey to become an ace developer, but proper training is very important for the Indian software engineers. I think people will agree with me about this point.

English is just a language - speaking English is not a skill...

English is just a language to communicate. This cannot be used as a substitute for skill. This video which explains Observer Design pattern in Bengali is dedicated to all those Bengali students who despite their Bengali medium schooling background have become bright engineers of India...


Engineering college study revisited - the simulation of PID Controller

Its really fascinating to revisit the stuffs that i studied so thoroughly during engineering. PID control is one such thing. Only difference is that, during my student life i did not know anything about software and now i know software pretty well... I have already spent approximately 15 days time in Robotics. Time to implement this kind of PID controller in the movement of a robot in ROS. Watch how the stability, robustness, time to reach the target, noise picking and all such things which are important in the control system are changing with the PID controller with varying values of Proportional gain (P), Integral Gain (I) and derivative gain (D).


Android Internals - UI Events...



i know the way we started learning computer science almost two decades ago is absolutely different from the way students learn computer science these days. people these days probably start programming keeping AI, Robotics and similar stuffs in mind. However, it is also the fact that the basics have remained the same. for example, the way event-handling works in different UI based OS is almost the same. I remember when i studied Windows/ Visual C++ in 90's, i was really awed (rather scared)  by the MFC's dreaded DECLARE_MESSAGE_MAP, BEGIN_MESSAGE_MAP and END_MESSAGE_MAP macros... That's why i have made this video to throw lights on the way UI event handling is done in Android... Here goes my investigation on the Android internals vis-a-vis an UI input event. i always wanted to get involved in my software job as an inquisitive engineer and not just as a programmer. Hence when Google made Android's frameork code open-source, it became a boon for me. It opened the door for doing in-depth investigation... Hope you like the video...

Tuesday, August 28, 2018

My first Flutter app - a keypad dialer


As flutter seems to be today's buzzword in the world of cross-platform mobile apps development, i myself tried it to get an idea and this is my first flutter app. The video of the app running on both iOS and Android emulator is shown here.


Here goes the main.dart file of this app. Hope it will help you as an example particularly for designing a simple layout in flutter.

main.dart

import 'package:flutter/material.dart';
import 'package:url_launcher/url_launcher.dart';

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or press Run > Flutter Hot Reload in IntelliJ). Notice that the
        // counter didn't reset back to zero; the application is not restarted.
        primarySwatch: Colors.blue,
      ),
      home: new MyHomePage(title: 'Keypad Dialer'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".

  final String title;

  @override
  _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  String phoneNumber = " ";
  TextEditingController _controller;

  @override
  void initState() {
    super.initState();
    _controller = new TextEditingController(text: '');
  }

  _launchURL(String url) async {
    if (await canLaunch(url)) {
      await launch(url);
    } else {
      throw 'Could not launch $url';
    }
  }

  void callPhone() {}

  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return new Scaffold(
        appBar: new AppBar(
          // Here we take the value from the MyHomePage object that was created by
          // the App.build method, and use it to set our appbar title.
          title: new Text("Keypad Dialer"),
        ),
        body: new Center(
          // Center is a layout widget. It takes a single child and positions it
          // in the middle of the parent.
          child: new Column(
            // Column is also layout widget. It takes a list of children and
            // arranges them vertically. By default, it sizes itself to fit its
            // children horizontally, and tries to be as tall as its parent.
            //
            // Invoke "debug paint" (press "p" in the console where you ran
            // "flutter run", or select "Toggle Debug Paint" from the Flutter tool
            // window in IntelliJ) to see the wireframe for each widget.
            //
            // Column has various properties to control how it sizes itself and
            // how it positions its children. Here we use mainAxisAlignment to
            // center the children vertically; the main axis here is the vertical
            // axis because Columns are vertical (the cross axis would be
            // horizontal).
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              new Container(
                  padding: const EdgeInsets.all(8.0),
                  child: new Column(children: [
                    new Container(
                      padding: const EdgeInsets.only(bottom: 100.0),
                      child: new TextField(
                        controller: _controller,
                      ),
                    ),
                    new Container(
                        padding: const EdgeInsets.all(8.0),
                        child: new Row(
                            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                            children: <Widget>[
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  _controller.text = _controller.text + "1";
                                  //appendToThePhoneNumber('1');
                                },
                                child: new Text("1"),
                              ),
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  //appendToThePhoneNumber('2');
                                  _controller.text = _controller.text + "2";
                                },
                                child: new Text("2"),
                              ),
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  //appendToThePhoneNumber('3');
                                  _controller.text = _controller.text + "3";
                                },
                                child: new Text("3"),
                              ),
                            ])),
                    new Container(
                        padding: const EdgeInsets.all(8.0),
                        child: new Row(
                            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                            children: <Widget>[
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  //appendToThePhoneNumber('4');
                                  _controller.text = _controller.text + "4";
                                },
                                child: new Text("4"),
                              ),
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  //appendToThePhoneNumber('5');
                                  _controller.text = _controller.text + "5";
                                },
                                child: new Text("5"),
                              ),
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  //appendToThePhoneNumber('6');
                                  _controller.text = _controller.text + "6";
                                },
                                child: new Text("6"),
                              ),
                            ])),
                    new Container(
                        padding: const EdgeInsets.all(8.0),
                        child: new Row(
                            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                            children: <Widget>[
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  //appendToThePhoneNumber('7');
                                  _controller.text = _controller.text + "7";
                                },
                                child: new Text("7"),
                              ),
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  //appendToThePhoneNumber('8');
                                  _controller.text = _controller.text + "8";
                                },
                                child: new Text("8"),
                              ),
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  //appendToThePhoneNumber('9');
                                  _controller.text = _controller.text + "9";
                                },
                                child: new Text("9"),
                              ),
                            ])),
                    new Container(
                        padding: const EdgeInsets.all(8.0),
                        child: new Row(
                            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                            children: <Widget>[
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  String number = _controller.text;
                                  _launchURL("tel://" + number);
                                },
                                child: new Text("Call"),
                              ),
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  //appendToThePhoneNumber('0');
                                  _controller.text = _controller.text + "0";
                                },
                                child: new Text("0"),
                              ),
                              new RaisedButton(
                                padding: const EdgeInsets.all(8.0),
                                textColor: Colors.white,
                                color: Colors.blue,
                                onPressed: () {
                                  int l = _controller.text.length;
                                  if (l != 0) {
                                    _controller.text =
                                        _controller.text.substring(0, l - 1);
                                  }
                                  //_controller.clear();
                                },
                                child: new Text("Clear"),
                              ),
                            ])),
                  ]))
            ],
          ),
        ));
  }
}

Thursday, June 7, 2018

Private Inheritance in C++

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