Java Android App Development Course, Job Scheduler

1. Introduction

In modern society, time management is a very important factor. Reflecting this need,
we will develop an app that allows users to manage their schedules and
conveniently schedule jobs using the Android platform.
This course focuses on creating Android apps using Java.

2. Job Scheduler App Overview

The job scheduler app provides users with the ability to add, modify, and delete schedules.
Users can easily receive notifications about schedule changes.
This course will be centered around implementing these basic features.

  • Key Features:
  • Add and delete schedules
  • Modify schedules
  • Notification feature
  • User Interface (UI) design

3. Setting Up the Development Environment

To develop Android apps, you need to set up a few tools and libraries.
Typically, Android Studio, JDK, and Gradle are required.
Below are the necessary tools.

  • Android Studio: Official IDE for Android development
  • Java Development Kit (JDK): Tools for compiling and running Java
  • Gradle: Dependency management and build tool

After installing Android Studio, create a new project.

4. Creating the Project and Basic Setup

Open Android Studio and create a new project.
Select ‘Empty Activity’ and enter the project name and package name.
Click ‘Finish’ to create the project.

5. UI Design

The user interface of the job scheduler needs to be designed.
Use XML to define the UI. Below is a simple layout example.


            <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:orientation="vertical">

                <TextView
                    android:id="@+id/titleTextView"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="Job Scheduler"
                    android:textSize="24sp"/>

                <EditText
                    android:id="@+id/jobEditText"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:hint="Please enter a schedule"/>

                <Button
                    android:id="@+id/addButton"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="Add"/>

                <ListView
                    android:id="@+id/jobListView"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"/>

            </LinearLayout>
        

6. Implementing Business Logic

Now that the UI is implemented, we need to implement the business logic.
We will write methods to handle user input and add and delete schedules.


            public class MainActivity extends AppCompatActivity {
                private EditText jobEditText;
                private Button addButton;
                private ListView jobListView;
                private ArrayAdapter<String> adapter;
                private ArrayList<String> jobList;

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

                    jobEditText = findViewById(R.id.jobEditText);
                    addButton = findViewById(R.id.addButton);
                    jobListView = findViewById(R.id.jobListView);
                    jobList = new ArrayList<>();

                    adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, jobList);
                    jobListView.setAdapter(adapter);

                    addButton.setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            String job = jobEditText.getText().toString();
                            if (!job.isEmpty()) {
                                jobList.add(job);
                                adapter.notifyDataSetChanged();
                                jobEditText.setText("");
                            }
                        }
                    });
                }
            }
        

7. Implementing Notification Feature

After adding the schedule, we will implement the notification feature.
We will use AlarmManager to send notifications. Here is an example of the notification feature implementation.


            private void setAlarm(long triggerAtMillis) {
                AlarmManager alarmManager = (AlarmManager) getSystemService(ALARM_SERVICE);
                Intent intent = new Intent(this, AlarmReceiver.class);
                PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, 0);
                alarmManager.setExact(AlarmManager.RTC_WAKEUP, triggerAtMillis, pendingIntent);
            }
        

8. Deployment and Testing of the App

Once the app’s functionality is complete, you need to test it on various devices and
prepare to distribute it on Google Play.
To deploy, you need to go through the app signing and build process.

9. Conclusion

Through this course, we learned how to develop an Android job scheduler app using Java.
I hope it helped enhance your understanding of Android app development as you added each feature.
By creating a real app, may you gain more experience and reference materials to further improve.

Java Android App Development Course, Types of Java Classes

In Android app development, Java is still one of the important languages. In this article, we will discuss the types of Java classes and how they are utilized in Android apps. Java is an object-oriented programming (OOP) language, and classes and objects are the basic concepts. A class is a blueprint for creating objects, and an object is an instance of a class.

1. Basic Concept of Java Class

A class in Java is a data structure that can contain variables and methods. The main components of a class are as follows:

  • Attribute: Represents the state of the class. Defined through variables.
  • Method: Defines the behavior that the class can perform.

Here is a basic example of defining a Java class:

public class Dog {
    // Attributes
    String name;
    int age;

    // Constructor
    public Dog(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Method
    public void bark() {
        System.out.println(name + " is barking.");
    }
}

2. Types of Java Classes

In Java, various types of classes can be defined. The main types of classes are as follows:

2.1. Object Class

All classes in Java inherit from the Object class. Therefore, the Object class is the top-level parent class in Java. It contains basic methods that can be used in all classes (e.g., toString(), equals(), hashCode()).

2.2. User-defined Class

A user-defined class is a class defined by a developer to meet their needs. The Dog class mentioned above is an example.

2.3. Abstract Class

An abstract class is a class that contains one or more abstract methods. An abstract method is a method without an implementation, which must be implemented by the subclass that inherits from that class. An abstract class cannot be instantiated.

abstract class Animal {
    abstract void sound();

    void eat() {
        System.out.println("Animal is eating");
    }
}

class Cat extends Animal {
    void sound() {
        System.out.println("Meow");
    }
}

2.4. Interfaces

An interface contains only the definition of methods and requires classes that implement those methods. Interfaces provide multiple inheritance. That is, a class can implement multiple interfaces.

interface Flyable {
    void fly();
}

class Bird implements Flyable {
    public void fly() {
        System.out.println("The bird is flying.");
    }
}

2.5. Inner Class

An inner class is a class defined as a member of another class. An inner class has the ability to access members of the outer class.

class Outer {
    class Inner {
        void display() {
            System.out.println("This is an inner class.");
        }
    }
}

2.6. Static Class

A static class is a class defined as a static member of the outer class. Instances of the static class can be created without an instance of the outer class.

class Outer {
    static class StaticInner {
        void display() {
            System.out.println("This is a static inner class.");
        }
    }
}

3. Utilization of Classes in Android Apps

Classes are very important in Android app development. Classes are used to implement various UI elements and functionalities. For example, Activity and Fragment can be seen as classes that define the UI state, which are major components of Android.

3.1. Activity Class

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

The code above is an example of defining a basic Activity class. The onCreate() method is called when the Activity is created.

3.2. Fragment Class

public class SampleFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_sample, container, false);
    }
}

Fragment is a class that allows for the reuse of UI. The onCreateView() method creates the UI for the Fragment.

3.3. View Class

All UI components (buttons, text views, etc.) are implemented by inheriting the View class. Each UI element is based on this class and provides various attributes and methods.

public class CustomButton extends Button {
    public CustomButton(Context context) {
        super(context);
    }

    public void changeColor() {
        setBackgroundColor(Color.RED);
    }
}

4. Conclusion

By understanding the types of Java classes, one can effectively utilize the concepts of object-oriented programming in Android app development. Utilizing various classes and the concept of objects allows for writing more efficient and reusable code. Additionally, the types of Java classes can guide the structure of code in a better direction by leveraging OOP characteristics (inheritance, polymorphism, etc.).

In this article, we explored various classes in Java and how to utilize them in Android app development. If you understand and utilize Java’s class concepts well, it will greatly help in developing more effective Android apps.

Java Android App Development Course, Introduction to Java Language

In Android app development, Java is one of the most important programming languages. While Google has been developing the Android platform, Java has established itself as the core language. Understanding the advantages and basic concepts of Java can greatly assist in Android app development. This course will start with the fundamental concepts of the Java language and progressively explain the basics to advanced topics for Android app development.

1. What is Java?

Java is a general-purpose programming language that was developed by Sun Microsystems (now Oracle) in 1995. It is an object-oriented programming (OOP) language that makes the code more structured and reusable. Java has the following key features:

  • Platform Independence: Once written, the code can run on any platform through the JVM (Java Virtual Machine).
  • Object-Oriented: It allows for structured management of data and methods using classes and objects.
  • Robust Memory Management: Java efficiently performs memory management with automatic garbage collection.
  • Diverse Libraries: Java provides a wide range of standard libraries and APIs for developers to use conveniently.
  • Multithreading Support: It facilitates easy management of multiple threads, making concurrent programming easier.

2. Basic Syntax of Java

The syntax of Java is simple and intuitive. Let’s take a look at the basic syntax of Java through example code.

2.1 Hello World Example


public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

    

The above code shows the basic structure of Java. It defines a class, and the program starts through the main method. The System.out.println() method is responsible for printing messages to the console.

2.2 Variables and Data Types

Java has primitive data types and reference data types. Primitive data types include int, float, double, char, boolean, etc., while reference data types represent complex data structures like classes and arrays.


public class VariableExample {
    public static void main(String[] args) {
        int age = 25;
        double height = 175.5;
        char initial = 'A';
        boolean isStudent = true;

        System.out.println("Age: " + age);
        System.out.println("Height: " + height);
        System.out.println("Initial: " + initial);
        System.out.println("Is a student: " + isStudent);
    }
}

    

2.3 Operators

Java provides various operators to process data.

  • Arithmetic Operators: +, -, *, /, %
  • Comparison Operators: ==, !=, >, <, >=, <=
  • Logical Operators: &&, ||, !

public class OperatorExample {
    public static void main(String[] args) {
        int a = 10;
        int b = 20;
        boolean result;

        result = (a < b) && (b > 15);
        System.out.println("Result: " + result);
    }
}

    

2.4 Control Statements

Control statements are used to control the flow of the program. Java includes conditional statements (if, switch) and loops (for, while, do-while).


public class ControlFlowExample {
    public static void main(String[] args) {
        int num = 5;

        if (num > 0) {
            System.out.println(num + " is a positive number.");
        } else {
            System.out.println(num + " is a negative number.");
        }

        for (int i = 1; i <= 5; i++) {
            System.out.println("Iteration: " + i);
        }
    }
}

    

3. Object-Oriented Programming (OOP)

Object-oriented programming is a paradigm that solves problems from the perspective of objects. Java supports the four main characteristics of OOP: encapsulation, inheritance, polymorphism, and abstraction.

3.1 Classes and Objects

A class is a blueprint that defines an object. An object is an instance created based on a class.


class Dog {
    String name;
    int age;

    void bark() {
        System.out.println(name + " barks.");
    }
}

public class Main {
    public static void main(String[] args) {
        Dog dog = new Dog();
        dog.name = "Bongchi";
        dog.age = 3;
        dog.bark();
    }
}

    

3.2 Inheritance

Inheritance is a feature that allows a child class to inherit properties and methods from an existing class (parent class).


class Animal {
    void eat() {
        System.out.println("Eating.");
    }
}

class Cat extends Animal {
    void meow() {
        System.out.println("Meow!");
    }
}

public class Main {
    public static void main(String[] args) {
        Cat cat = new Cat();
        cat.eat();
        cat.meow();
    }
}

    

3.3 Polymorphism

Polymorphism is the ability to use different implementations through the same interface.


class Bird {
    void fly() {
        System.out.println("The bird is flying.");
    }
}

class Ostrich extends Bird {
    void fly() {
        System.out.println("The ostrich cannot fly.");
    }
}

public class Main {
    public static void main(String[] args) {
        Bird myBird = new Ostrich();
        myBird.fly();
    }
}

    

3.4 Abstract Classes and Interfaces

An abstract class is an incomplete class, while an interface is a collection of methods that a class must implement.


abstract class Shape {
    abstract void draw();
}

class Circle extends Shape {
    void draw() {
        System.out.println("Drawing a circle");
    }
}

public class Main {
    public static void main(String[] args) {
        Shape shape = new Circle();
        shape.draw();
    }
}

    

4. Android App Development with Java

Now, let's explore how to develop Android apps using Java. We will install Android Studio and create a simple app.

4.1 Setting Up the Android Development Environment

To develop Android apps, you need to install Android Studio. After installing Android Studio, create a new project.

4.2 Creating a Simple "Hello World" App

First, after creating a new project in Android Studio, take a look at the provided "Hello World" app.


package com.example.helloworld;

import android.os.Bundle;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView textView = findViewById(R.id.text_view);
        textView.setText("Hello, Android!");
    }
}

    

The above code displays the text "Hello, Android!" in the main activity.

4.3 Setting Up Layouts

The UI of Android is primarily defined in XML. Below is an example of a basic layout file.




    


    

5. Conclusion

In this course, we covered various topics from the basic concepts of the Java language to object-oriented programming and Android app development. Java is a very important language for Android development, and a thorough understanding and practice are required. Continue studying and practicing for a deeper understanding of Java and Android. In the next course, we will cover various functionality implementations for Android apps.

6. References

  • Java Programming Language: https://www.oracle.com/java/technologies/javase/javase-jdk8-downloads.html
  • Android Developer Site: https://developer.android.com/
  • Principles of Object-Oriented Programming: https://www.tutorialspoint.com/java/java_object_oriented.htm

Java Android App Development Course, Java, Classes and Constructors

Hello! In this tutorial, we will take an in-depth look at two key concepts in Android app development using the Java language: ‘Class’ and ‘Constructor’. Java is an object-oriented programming language, and classes and objects play a very important role in Java. This allows us to improve code reusability and maintainability.

1. What is a Class?

A class is the basic unit of object-oriented programming and serves as a blueprint for creating objects. A class defines an object by bundling data (attributes) and methods (functions) together. For example, let’s assume we create a class called ‘Car’. This class can include the car’s attributes (e.g., brand, color, model) and functionalities (e.g., acceleration, deceleration, parking).

1.1. Basic Structure of a Class

A class in Java has the following structure:

public class Car {
        // Attributes
        String brand;
        String color;
        int model;

        // Constructor
        public Car(String brand, String color, int model) {
            this.brand = brand;
            this.color = color;
            this.model = model;
        }

        // Method
        public void accelerate() {
            System.out.println("The car is accelerating.");
        }
    }

2. What is a Constructor?

A constructor is a special method that is called when an object is created. The main role of a constructor is to handle the initialization of the object. The constructor has the same name as the class and does not have a return type.

2.1. Types of Constructors

In Java, constructors are broadly classified into two types:

  • Default Constructor: A constructor with no arguments. It initializes the attributes of the class to their default values.
  • Parameterized Constructor: A constructor that takes parameters to initialize the attributes of the object.

2.2. Example of Constructors

Let’s look at examples of the default constructor and the parameterized constructor:

public class Car {
        String brand;
        String color;
        int model;

        // Default Constructor
        public Car() {
            this.brand = "Undefined";
            this.color = "Undefined";
            this.model = 0;
        }

        // Parameterized Constructor
        public Car(String brand, String color, int model) {
            this.brand = brand;
            this.color = color;
            this.model = model;
        }
    }

3. Developing an Android App Using Classes and Constructors

Now, let’s create a simple Android application based on the concepts of classes and constructors. This application will have the functionality to input and output car information.

3.1. Creating an Android Studio Project

Launch Android Studio and create a new project. Select ‘Empty Activity’ and name it ‘MainActivity’.

3.2. MainActivity.java Code Example

In the MainActivity.java file, add the following code to create an app that receives and outputs car information:

package com.example.carapp;

    import androidx.appcompat.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.TextView;

    public class MainActivity extends AppCompatActivity {

        private EditText inputBrand, inputColor, inputModel;
        private TextView outputText;
        private Button submitButton;

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

            inputBrand = findViewById(R.id.inputBrand);
            inputColor = findViewById(R.id.inputColor);
            inputModel = findViewById(R.id.inputModel);
            outputText = findViewById(R.id.outputText);
            submitButton = findViewById(R.id.submitButton);

            submitButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    String brand = inputBrand.getText().toString();
                    String color = inputColor.getText().toString();
                    int model = Integer.parseInt(inputModel.getText().toString());

                    Car car = new Car(brand, color, model);
                    outputText.setText("Car Information:\nBrand: " + car.brand + "\nColor: " + car.color + "\nModel: " + car.model);
                }
            });
        }
    }

3.3. Setting Up activity_main.xml Layout

Add the following UI elements to the activity_main.xml file:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:padding="16dp">

        <EditText
            android:id="@+id/inputBrand"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Enter Brand"/>

        <EditText
            android:id="@+id/inputColor"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Enter Color"/>

        <EditText
            android:id="@+id/inputModel"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Enter Model"/>

        <Button
            android:id="@+id/submitButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Submit"/>

        <TextView
            android:id="@+id/outputText"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:paddingTop="20dp"/>

    </LinearLayout>

4. Utilizing Classes and Constructors

Through the example above, we can understand how classes and parameterized constructors work. When the user inputs the car’s brand, color, and model, a new Car object is created, and that information is displayed in the text view. The advantage of object-oriented programming is that it allows for code reusability and efficient management of data and functionality through objects.

5. Conclusion

In this tutorial, we have taken an in-depth look at the concepts of classes and constructors in Java. Classes and constructors play a central role in object-oriented programming and are essential elements in Android app development. In future tutorials, we will cover a variety of features and examples, so please look forward to it. Happy Coding!

Java Android App Development Course, Java, Inheritance for Reusing Classes

Hello! In this course, we will take a detailed look at one of the important concepts in Android app development using Java: ‘Inheritance’. Inheritance is a core element of object-oriented programming, which greatly helps in increasing code reusability and expressing hierarchical relationships. This course will comprehensively cover the concept of inheritance, how to use it, and practical examples in Android.

1. What is Inheritance?

Inheritance means that one class inherits the properties and functionalities of another class in object-oriented programming. This allows us to reuse the code and functionality of existing classes when defining new classes, reducing code duplication and making maintenance easier.

2. Basic Structure of Inheritance

To inherit a class in Java, the ‘extends’ keyword is used. A child class (subclass) that inherits properties from the parent class (superclass) can have its own additional fields and methods. The basic structure of inheritance is as follows:

class ParentClass {
    // Fields and methods of the parent class
}

class ChildClass extends ParentClass {
    // Additional fields and methods of the child class
}

3. Advantages of Inheritance

  • Code Reusability: You can easily create new classes by reusing existing ones.
  • Ease of Maintenance: By placing common functionalities in the parent class and modifying them, you can change the behavior of child classes.
  • Readability: It improves the readability of the code by clearly expressing the relationships between classes.

4. Example of Inheritance

Now, we will demonstrate the structure of inheritance by creating a simple Android app. In this hypothetical app, we will create a basic ‘User’ class and subclasses ‘Admin’ and ‘RegularUser’ that inherit from it.

4.1 Creating the User Class

public class User {
    private String name;
    private String email;

    public User(String name, String email) {
        this.name = name;
        this.email = email;
    }

    public String getName() {
        return name;
    }

    public String getEmail() {
        return email;
    }

    public void displayInfo() {
        System.out.println("Name: " + name + ", Email: " + email);
    }
}

4.2 Creating the Admin Class

public class Admin extends User {
    private String department;

    public Admin(String name, String email, String department) {
        super(name, email); // Calling the parent class constructor
        this.department = department;
    }

    public String getDepartment() {
        return department;
    }

    @Override
    public void displayInfo() {
        super.displayInfo(); // Calling the parent's method
        System.out.println("Department: " + department);
    }
}

4.3 Creating the Regular User Class

public class RegularUser extends User {
    private String username;

    public RegularUser(String name, String email, String username) {
        super(name, email);
        this.username = username;
    }

    public String getUsername() {
        return username;
    }

    @Override
    public void displayInfo() {
        super.displayInfo();
        System.out.println("Username: " + username);
    }
}

5. Using Inheritance in Android Apps

Android applications often abstract common behaviors that occur among multiple classes. For example, if multiple activities need to perform common actions, you can create a base activity class and inherit from it.

5.1 Creating a Base Activity Class

public class BaseActivity extends AppCompatActivity {
    protected void setContentViewWithToolbar(int layoutId) {
        setContentView(layoutId);
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
    }
}

5.2 Creating a User Management Activity

public class UserManagementActivity extends BaseActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentViewWithToolbar(R.layout.activity_user_management);

        // Initialization related to user management
    }
}

5.3 Creating a Settings Activity

public class SettingsActivity extends BaseActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentViewWithToolbar(R.layout.activity_settings);

        // Initialization related to settings
    }
}

6. Inheritance and Polymorphism

Inheritance supports polymorphism. In Java, you can use a variable of the parent class type to reference an object of a child class. This allows you to use subclass objects as if they were superclass objects.

public void displayUserInfo(User user) {
    user.displayInfo(); // Example of polymorphism
}

7. Conclusion

Today, we learned about inheritance in Android app development using Java. I hope you understood how to enhance code reusability and enable structural design through inheritance. In software development, inheritance is a crucial aspect, and utilizing it effectively can lead to more efficient code writing. In the next session, we will cover abstract classes and interfaces. Thank you!

8. References