Java DrawingPanel MVC/OOP Guide

DrawingPanel in Java with MVC/OOP

• DrawingPanel is a class for creating graphics in Java, not part of the standard Java library. Download and use separately.
• This guide details using DrawingPanel in Java MVC/OOP programs.

Understanding DrawPanel

• DrawPanel is a subclass of javax.swing.JPanel.
• It handles window management and provides a Graphics object for drawing.

Creating a DrawingPanel

• Several constructors exist:
  • Default width/height.
  • Customizable width/height.
  • Loading an image from a file.
  • Loading an image from a filename.
• Modifications might be needed for Java 7 or lower, involving annotation changes (comment out or remove annotations).
  • Search the code for @FunctionalInterface.

Drawing on the Panel

• getGraphics() method retrieves Graphics2D object for drawing.
• Common methods:
  • drawLine(x1, y1, x2, y2): Draws a line.
  • drawRect(x, y, width, height): Draws a rectangle outline.
  • fillRect : Fills a rectangle.
  • drawOval / fillOval: Draws/fills an oval.
  • drawString(text, x, y): Draws text.
  • setColor(Color c): Sets drawing color.
  • drawRoundRect / fillRoundRect: Draws rounded corners.
  • setStroke: Sets line width.

Colors

• setColor() method sets drawing color.
• Predefined colors (e.g., Color.RED, Color.BLUE) or custom colors using Color(r, g, b).

Fonts

• setFont() method changes the font for text.
• Create Font objects with Font(name, style, size).

Advanced Features

• Event Listeners (e.g., addMouseListener) for user interaction.
• clear() method clears the drawing panel.
• Pixel information access (e.g., getPixel()).
• Image Loading using loadImage(File file) or loadImage(String filename).

Custom Drawing with paintComponent()

• Override paintComponent() in a subclass to create custom drawings.
• Call super.paintComponent() first.
• Cast Graphics to Graphics2D for advanced features.

Common Use Cases

• Simple Animations (using timers or loops).
• Interactive Games (responding to user input with mouse or keyboard).
• Data Visualization (charts, graphs, diagrams).

Drawing Techniques

• Shapes: Draw various shapes (rectangles, ovals, lines).
• Colors: Set drawing colors.
• Fonts: Change text fonts.

Connecting DrawPanel to the Main Frame

• Add DrawPanel to the JFrame's content pane using frame.add(panel).

Using DrawPanel with ArrayLists

• Store and manage graphical objects (e.g., Shape objects) in an ArrayList.
• Loop over to draw shapes.

Implementing DrawPanel with MVC

• Model: Holds data and business logic.
• View: Displays the data and handles user input.
• Controller: Intermediates model and view.
  • Example: Add a shape, the controller updates the model, view is repainted.

Implementing DrawPanel with OOP

• OOP principles used to create reusable drawing components.
• Create classes of graphical objects (e.g., Shape, Circle, Rectangle).
• Shape is an abstract base class.
• Inheritance - subclass to create specialized shapes.