exercise21_6piechart.java

java程序设计导论（daniel liang著） 所有偶数课后习题答案

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

public class Exercise21_6PieChart extends JPanel implements ActionListener {
  BorderLayout borderLayout1 = new BorderLayout();
  private Exercise21_6ChartModel model;

  public Exercise21_6PieChart() {
    this.setLayout(borderLayout1);
  }

  Color[] colors = {Color.red, Color.yellow, Color.green, Color.blue,
    Color.cyan, Color.magenta, Color.orange, Color.pink, Color.darkGray};

  public void paintComponent(Graphics g) {
    super.paintComponent(g);

    if (model == null) return;

    int radius = (int)(Math.min(getWidth(), getHeight()) * 0.5 * 0.9);
    int x = getWidth() / 2 - radius;
    int y = getHeight()/2 - radius;

    String[] dataName = model.getDataName();
    double[] data = model.getData();

    double total = 0;
    for (int i = 0; i < data.length; i++)
      total += data[i];

    int angle1 = 0;
    int angle2 = 0;
    for (int i = 0; i < data.length; i++)
    {
      angle1 = angle1 + angle2;
      angle2 = (int)Math.ceil(360 * data[i] / total);
      g.setColor(colors[i % colors.length]);
      g.fillArc(x, y, 2 * radius, 2 * radius, angle1, angle2);
      g.setColor(Color.black);
      g.drawString(dataName[i],
        (int)(getWidth() / 2 + radius * Math.cos((angle1 + angle2 / 2) * 2 * Math.PI / 360)),
        (int)(getHeight() / 2 - radius * Math.sin((angle1+angle2 / 2) * 2 * Math.PI / 360)));
    }
  }

  public void setModel(Exercise21_6ChartModel newModel)
  {
    model = newModel;
    model.addActionListener(this);
  }

  public Exercise21_6ChartModel getModel()
  {
    return model;
  }

  public void actionPerformed(ActionEvent e)
  {
    repaint();
  }
}