import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.image.MemoryImageSource;
import java.util.Random;
import javax.swing.JDialog;
import javax.swing.JPanel;
import javax.swing.Timer;

/**
* 黑客帝國—程式碼雨
* @author 52363
*
*/
@SuppressWarnings(“serial”)
public class Rain extends JDialog implements ActionListener {

private Random random = new Random();
private Dimension screenSize;
private JPanel graphicsPanel;
//行高,列寬
private final static int gap = 20;
//存放雨點頂部的位置資訊(marginTop)
private int[] posArr;
//行數
private int lines;
//列數
private int columns;

public Rain() {
    initComponents();
}

private void initComponents() {
    setLayout(new BorderLayout());
    graphicsPanel = new GraphicsPanel();
    add(graphicsPanel, BorderLayout.CENTER);
    //設定游標不可見
    Toolkit defaultToolkit = Toolkit.getDefaultToolkit();
    Image image = defaultToolkit.createImage(new MemoryImageSource(0, 0, null, 0, 0));
    Cursor invisibleCursor = defaultToolkit.createCustomCursor(image, new Point(0, 0), "cursor");
    setCursor(invisibleCursor);
    //ESC鍵退出
    KeyPressListener keyPressListener = new KeyPressListener();
    this.addKeyListener(keyPressListener);
    //this.setAlwaysOnTop(true);
    //去標題欄
    this.setUndecorated(true);
    //全屏
    this.getGraphicsConfiguration().getDevice().setFullScreenWindow(this);
    this.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);
    setVisible(true);

    screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    lines = screenSize.height / gap;
    columns = screenSize.width / gap;

    posArr = new int[columns + 1];
    random = new Random();
    for (int i = 0; i < posArr.length; i++) {
        posArr[i] = random.nextInt(lines);
    }

    //每秒10幀
    new Timer(100, this).start();
}

/**
 * @return 隨機字元
 */
private char getChr() {
    return (char) (random.nextInt(94) + 33);
}

@Override
public void actionPerformed(ActionEvent e) {
    graphicsPanel.repaint();
}

private class GraphicsPanel extends JPanel {
    @Override
    public void paint(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setFont(getFont().deriveFont(Font.BOLD));
        g2d.setColor(Color.BLACK);
        g2d.fillRect(0, 0, screenSize.width, screenSize.height);
        //當前列
        int currentColumn = 0;
        for (int x = 0; x < screenSize.width; x += gap) {
            int endPos = posArr[currentColumn];
            g2d.setColor(Color.CYAN);
            g2d.drawString(String.valueOf(getChr()), x, endPos * gap);
            int cg = 0;
            for (int j = endPos - 15; j < endPos; j++) {
                //顏色漸變
                cg += 20;
                if (cg > 255) {
                    cg = 255;
                }
                g2d.setColor(new Color(0, cg, 0));
                g2d.drawString(String.valueOf(getChr()), x, j * gap);
            }
            //每放完一幀，當前列上雨點的位置隨機下移1~5行
            posArr[currentColumn] += random.nextInt(5);
            //當雨點位置超過螢幕高度時，重新產生一個隨機位置
            if (posArr[currentColumn] * gap > getHeight()) {
                posArr[currentColumn] = random.nextInt(lines);
            }
            currentColumn++;
        }
    }
}

private class KeyPressListener extends KeyAdapter {
    @Override
    public void keyPressed(KeyEvent e) {
        if (e.getKeyCode() == KeyEvent.VK_ESCAPE) {
            System.exit(0);
        }
    }
}

public static void main(String[] args) {
    new Rain();
}
 

}