Java图形-在Jbutton上绘制形状

Question

I am making a minimally small paint application for a class in Java. I need to make several buttons for the user to select different shapes, and on those buttons I am supposed to put an image of the shape they are using. For example, a button that lets a user draw a line should have have an image of a line on it. A button that draws a rectangle, a rectangle should be on it. I need to be able to do this from within the program without using an external image source.

Here is my current button code example.

lineB = new JButton();
lineB.setBounds(0, 25, 20, 20);
lineB.setBackground(Color.WHITE);
shapePanel.add(lineB);
lineB.addActionListener(this);

Answer 1

1. Create a BufferedImage of the desired size -- BufferedImage img = new BufferedImage(biWidth, biHeight, BufferedImage.TYPE_INT_ARGB);
2. Get its Graphics context by calling getGraphics() or createGraphics() (better because it gives you a Graphics2D object) on it.
3. I'd set the RenderingHints of this Graphics2D object to all for antialiasing using the setRenderingHints(...) method. This can smooth out jaggies.
4. Draw your shape with this object.
5. Dispose of the Graphics object.
6. Create an ImageIcon from the above Image using new ImageIcon(Image image) constructor.
7. Set your button's icon with the above icon using setIcon(...) .
8. Do not call setBounds(...) on the button or on anything.

---

eg,

import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import javax.swing.*;

@SuppressWarnings("serial")
public class ImageButton extends JPanel {
   private static final int IMG_WIDTH = 50;
   private static final Color SHAPE_COLOR = Color.RED;
   private static final int GAP = 4;
   private JButton circleButton = new JButton();
   private JButton squareButton = new JButton();

   public ImageButton() {
      BufferedImage circleImg = new BufferedImage(IMG_WIDTH, IMG_WIDTH, BufferedImage.TYPE_INT_ARGB);
      Graphics2D g2 = circleImg.createGraphics();
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setColor(SHAPE_COLOR);
      int x = GAP;
      int y = x;
      int width = IMG_WIDTH - 2 * x;
      int height = IMG_WIDTH - 2 * y;
      g2.fillOval(x, y, width, height);
      g2.dispose();
      circleButton.setIcon(new ImageIcon(circleImg));

      BufferedImage squareImg = new BufferedImage(IMG_WIDTH, IMG_WIDTH, BufferedImage.TYPE_INT_ARGB);
      g2 = squareImg.createGraphics();
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setColor(SHAPE_COLOR);
      g2.fillRect(x, y, width, height);
      g2.dispose();
      squareButton.setIcon(new ImageIcon(squareImg));

      add(circleButton);
      add(squareButton);
   }

   private static void createAndShowGui() {
      JFrame frame = new JFrame("ImageButton");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(new ImageButton());
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

Answer 2

One Easy way is to add an image to JButton and make it like an image button.

try {
 Image icon = ImageIO.read(getClass().getResource("icons/line.jpg"));
 lineButton.setIcon(new ImageIcon(icon));
} catch (IOException ex) {
}

edited :

since you are urged to create shapes in your code u can do the code below to create a image in memory draw on graphic of the image and then assign it to the button.

    final int BI_WIDTH = 50;
    final int BI_HEIGHT = 50;
    BufferedImage lineImage = new BufferedImage(BI_WIDTH, BI_HEIGHT,
            BufferedImage.TYPE_INT_RGB);
    lineImage.createGraphics().drawLine(2, 25, 48, 25);
    JButton lineButton = new JButton();
    lineButton.setIcon(new ImageIcon(lineImage));

graphic object has many different functions and you could draw whatever you like on it.