Draw shapes example

With this tutorial we shall show you how to draw simple shapes in a Java Desktop Application. This is a very important step when designing your own graphics for your App.

Basically, all you have to do in order to draw shapes in a Java application is:

• Create a new Frame.
• Create a class that extends the Component class and override the paint method.
• Use Graphics2D.drawLine to draw a simple line.
• Use Graphics2D.drawOval to draw an oval shape in the screen.
• Use Graphics2D.drawRect to draw a rectangle on the screen.
• Use Graphics2D.drawArc to draw an arch.
• Create a new Polygon to add a polygon to your drawing, and use addPoint to add more points to the polygon.

Let’s see the code snippet that follows:

package com.javacodegeeks.snippets.desktop;

import java.awt.Component;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Polygon;

public class DrawShapesExample {

  public static void main(String[] args) {

// Create a frame

Frame frame = new Frame();

// Add a component with a custom paint method

frame.add(new CustomPaintComponent());

// Display the frame

int frameWidth = 300;

int frameHeight = 300;

frame.setSize(frameWidth, frameHeight);

frame.setVisible(true);

  }

 /**
  * To draw on the screen, it is first necessary to subclass a Component 
  * and override its paint() method. The paint() method is automatically called 
  * by the windowing system whenever component's area needs to be repainted.
  */
  static class CustomPaintComponent extends Component {

public void paint(Graphics g) {

  // Retrieve the graphics context; this object is used to paint shapes

  Graphics2D g2d = (Graphics2D)g;

  // Draw an oval that fills the window

  int x = 0;

  int y = 0;

  int w = getSize().width-1;

  int h = getSize().height-1;

  /**
    * The coordinate system of a graphics context is such that the origin is at the 
    * northwest corner and x-axis increases toward the right while the y-axis increases 
    * toward the bottom.
    */

  g2d.drawLine(x, y, w, h);

  // to draw a filled oval use : g2d.fillOval(x, y, w, h) instead

  g2d.drawOval(x, y, w, h);

  // to draw a filled rectangle use : g2d.fillRect(x, y, w, h) instead

  g2d.drawRect(x, y, w, h);

  // A start angle of 0 represents a 3 o'clock position, 90 represents a 12 o'clock position,

  // and -90 (or 270) represents a 6 o'clock position

  int startAngle = 45;

  int arcAngle = -60;

  // to draw a filled arc use : g2d.fillArc(x, y, w, h, startAngle, arcAngle) instead

  g2d.drawArc(x, y, w/2, h/2, startAngle, arcAngle);

  // to draw a filled round rectangle use : g2d.fillRoundRect(x, y, w, h, arcWidth, arcHeight) instead

  g2d.drawRoundRect(x, y, w, h, w/2, h/2);

  Polygon polygon = new Polygon();

  polygon.addPoint(w/4, h/2);

  polygon.addPoint(0, h/2);

  polygon.addPoint(w/4, 3*h/4);

  polygon.addPoint(w/2, 3*h/4);

  // Add more points...

  // to draw a filled round rectangle use : g2d.fillPolygon(polygon) instead

  g2d.drawPolygon(polygon);

}

  }

}

This was an example on how to draw shapes in a Java Desktop Application.