What is the usage of graphics in Java?

1 year ago
Olivia Parker
2 minutes

In Java, Graphics is an abstract class used for drawing graphics. It contains a set of methods for drawing geometric shapes, images, and text on a graphic device. The Graphics class is a part of the Java AWT (Abstract Window Toolkit) package, used for creating graphical user interface (GUI) applications.

Some common methods in the Graphics class include:

  1. Draw a straight line from point (x1, y1) to point (x2, y2).
  2. Draw a rectangle at the starting point (x, y) with the specified width and height.
  3. Create an oval shape starting at the point (x, y), with a width of width and a height of height.
  4. Draw a string at the starting point (x, y).
  5. Draw an image at the starting point of (x, y) using the drawImage method.

To draw using the Graphics class, it is usually necessary to override the paint(Graphics g) method in a custom component that inherits from the Component class. In this method, specific drawing operations can be implemented by calling methods of the Graphics object.

For example, here is a simple example of drawing shapes using Graphics.

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

public class MyCanvas extends JPanel {
  public void paint(Graphics g) {
    super.paint(g);
    g.drawLine(50, 50, 200, 200);
    g.drawRect(100, 100, 150, 100);
    g.drawOval(250, 250, 100, 100);
    g.drawString("Hello, World!", 300, 100);
    
    // 绘制一个图片
    Image image = new ImageIcon("image.jpg").getImage();
    g.drawImage(image, 400, 200, this);
  }
  
  public static void main(String[] args) {
    JFrame frame = new JFrame("My Canvas");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(500, 500);
    frame.add(new MyCanvas());
    frame.setVisible(true);
  }
}

The code above creates a custom JPanel component and overrides the paint method to draw shapes within it. It then creates a JFrame window and adds the custom component to it. Running the program will result in a window displaying a line, a rectangle, an ellipse, a string, and an image.

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