JFrame Basics - potatoscript/JavaSwing GitHub Wiki

🖥️ JFrame Basics in Java Swing 🎨

🎯 What is JFrame?

JFrame is the main window for Java Swing applications. It provides the basic framework for adding GUI components such as buttons, labels, text fields, and other elements.

✅ Key Features:

  • 🖼️ Window Creation: Main container where GUI components are added.
  • ❌ Close Operations: Handles application closing when the window is closed.
  • 🎨 Customizable Layouts: Supports layout managers to organize GUI components.
  • 🔥 Resizable & Draggable: Provides window resizing and dragging capabilities.

📚 Step 1: Creating a Basic JFrame

📝 Basic Syntax

import javax.swing.JFrame;

public class MyFrame {
    public static void main(String[] args) {
        // Create JFrame
        JFrame frame = new JFrame("My First JFrame");

        // Set frame size
        frame.setSize(400, 300);

        // Set default close operation
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        // Make the frame visible
        frame.setVisible(true);
    }
}

🎨 Explanation

✅ JFrame frame = new JFrame("My First JFrame");

  • Creates a new JFrame with the title "My First JFrame".

✅ frame.setSize(400, 300);

  • Sets the width to 400 pixels and height to 300 pixels.

✅ frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  • Closes the application when the window is closed.
  • Options available:
    • JFrame.EXIT_ON_CLOSE – Exit the application.
    • JFrame.HIDE_ON_CLOSE – Hide the window but keep the application running.
    • JFrame.DISPOSE_ON_CLOSE – Close the window but release only the resources of that frame.

✅ frame.setVisible(true);

  • Displays the window on the screen.

👩‍🎨 Output:

+------------------------+
|                        |
|  My First JFrame        |
|                        |
+------------------------+

🎨 Step 2: JFrame with Basic Components

📝 Adding JLabel to JFrame

import javax.swing.*;

public class MyFrame {
    public static void main(String[] args) {
        // Create JFrame
        JFrame frame = new JFrame("JFrame with Label");

        // Create JLabel
        JLabel label = new JLabel("🎉 Welcome to Swing!", SwingConstants.CENTER);

        // Add label to frame
        frame.add(label);

        // Set frame size and behavior
        frame.setSize(400, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

🎨 Explanation

✅ JLabel label = new JLabel("🎉 Welcome to Swing!", SwingConstants.CENTER);

  • Creates a label with the text "🎉 Welcome to Swing!" and centers it horizontally.

✅ frame.add(label);

  • Adds the label to the frame.

✅ frame.setSize(400, 200);

  • Sets the window size to 400x200 pixels.

👩‍🎨 Output:

+--------------------------------+
|                                |
|    🎉 Welcome to Swing!        |
|                                |
+--------------------------------+

🧩 Step 3: JFrame Properties and Methods

📝 Common JFrame Methods

Method Description Example Code
setSize(int width, int height) Sets the frame size in pixels. frame.setSize(500, 300);
setTitle(String title) Sets the title of the frame. frame.setTitle("My Frame");
setVisible(boolean b) Makes the frame visible or hidden. frame.setVisible(true);
setDefaultCloseOperation(int operation) Sets what happens when the window closes. frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setResizable(boolean b) Enables/disables frame resizing. frame.setResizable(false);
setLocation(int x, int y) Sets frame position on the screen. frame.setLocation(200, 100);
setLocationRelativeTo(null) Centers the frame on the screen. frame.setLocationRelativeTo(null);
pack() Automatically sizes the frame to fit components. frame.pack();
dispose() Closes the frame and releases resources. frame.dispose();

📦 Step 4: Adding More Swing Components

🔥 Example: Adding Multiple Components to JFrame

import javax.swing.*;

public class MyFrame {
    public static void main(String[] args) {
        // Create JFrame
        JFrame frame = new JFrame("Multiple Components Example");

        // Create JLabel
        JLabel label = new JLabel("Enter your name:");

        // Create JTextField
        JTextField textField = new JTextField(20);

        // Create JButton
        JButton button = new JButton("Submit");

        // Set layout
        frame.setLayout(new java.awt.FlowLayout());

        // Add components to frame
        frame.add(label);
        frame.add(textField);
        frame.add(button);

        // Set frame properties
        frame.setSize(300, 150);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

🎨 Explanation

✅ JLabel label = new JLabel("Enter your name:");

  • Displays the text "Enter your name:".

✅ JTextField textField = new JTextField(20);

  • Creates a text field with a width of 20 columns.

✅ JButton button = new JButton("Submit");

  • Creates a button with the text "Submit".

✅ frame.setLayout(new java.awt.FlowLayout());

  • Sets a simple layout that arranges components in a row.

✅ frame.add(label);

  • Adds components to the frame.

👩‍🎨 Output:

+--------------------------------+
| Enter your name:  ___________  |
|                                |
|         [Submit]               |
+--------------------------------+

🎮 Step 5: JFrame Layout Managers

🎛️ What is a Layout Manager?

A Layout Manager controls the arrangement and positioning of components within a JFrame.

Layout Manager Description Usage Example
FlowLayout Arranges components in a row. frame.setLayout(new FlowLayout());
BorderLayout Divides the frame into 5 regions. frame.setLayout(new BorderLayout());
GridLayout Arranges components in a grid. frame.setLayout(new GridLayout(2, 2));
BoxLayout Arranges components vertically/horizontally. frame.setLayout(new BoxLayout(frame.getContentPane(), BoxLayout.Y_AXIS));
GridBagLayout Advanced layout for complex GUIs. frame.setLayout(new GridBagLayout());

🎨 Example: Using BorderLayout

import javax.swing.*;
import java.awt.*;

public class BorderLayoutExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("BorderLayout Example");

        // Create buttons
        JButton button1 = new JButton("NORTH");
        JButton button2 = new JButton("SOUTH");
        JButton button3 = new JButton("EAST");
        JButton button4 = new JButton("WEST");
        JButton button5 = new JButton("CENTER");

        // Set BorderLayout
        frame.setLayout(new BorderLayout());

        // Add buttons to regions
        frame.add(button1, BorderLayout.NORTH);
        frame.add(button2, BorderLayout.SOUTH);
        frame.add(button3, BorderLayout.EAST);
        frame.add(button4, BorderLayout.WEST);
        frame.add(button5, BorderLayout.CENTER);

        // Set frame properties
        frame.setSize(400, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

🎨 Output:

+--------------------------+
|         NORTH             |
+------+------------+-------+
| WEST |   CENTER    | EAST  |
+------+------------+-------+
|         SOUTH             |
+--------------------------+

🚀 Step 6: Handling Window Events in JFrame

📝 Handling Window Close Events

import javax.swing.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class WindowEventExample {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Window Event Example");

        // Add Window Listener
        frame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.out.println("Window is closing!");
                System.exit(0);
            }
        });

        frame.setSize(400, 200);
        frame.setVisible(true);
    }
}

👩‍🎨 Explanation

  • addWindowListener(new WindowAdapter() { ... }) – Listens for window events.
  • windowClosing() – Called when the window is about to close.

🎁 Bonus: Center JFrame on Screen

To center a JFrame on the screen:

frame.setLocationRelativeTo(null);

✅ Add this line before frame.setVisible(true);.