饼图未显示预期输出

Question

我正在尝试使我的饼图与模拟器运行期间更改的数据保持同步。

我的问题是饼图没有以正确的方式显示数据，我不知道问题出在哪里。

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

        int totalAmountOfCars = this.adhocCars + this.reservationCars + this.parkpassCars;
        float percentageAdHoc = totalAmountOfCars <= 0 || this.adhocCars <= 0 ? 0 : adhocCars/totalAmountOfCars * 100;
        float percentageParkPass = totalAmountOfCars <= 0 || this.parkpassCars <= 0 ? 0 :parkpassCars/totalAmountOfCars * 100;
        float percentageReservation = totalAmountOfCars <= 0 || this.reservationCars <= 0 ? 0 :reservationCars/totalAmountOfCars * 100;


        float adHocAngle = totalAmountOfCars <= 0 || this.adhocCars <= 0 ? 0 : 360/percentageAdHoc*100;
        float parkPassAngle = totalAmountOfCars <= 0 || this.parkpassCars <= 0 ? 0 : 360/percentageParkPass*100;
        float reservationAngle = totalAmountOfCars <= 0 || this.reservationCars <= 0 ? 0 : 360/percentageReservation*100;

        Dimension prefSize = this.getPreferredSize();
        g.setColor(Color.WHITE);
        g.fillRect(prefSize.width/2, prefSize.height/2, 200, 200);

在这里我计算弧的角度..

g.setColor(Color.RED);
g.fillArc(prefSize.width/2 + 10, prefSize.height/2 + 10, 180, 180, 0,(int)adHocAngle);
g.setColor(Color.BLUE);
g.fillArc(prefSize.width/2 + 10, prefSize.height/2 + 10, 180, 180, (int)adHocAngle, (int)adHocAngle+(int)parkPassAngle);
g.setColor(Color.ORANGE);
g.fillArc(prefSize.width/2 + 10, prefSize.height/2 + 10, 180, 180,(int)adHocAngle+(int)parkPassAngle, (int)reservationAngle);

这部分应该填充它，在某些情况下，整个字符都填充为橙色，而在其他情况下，它是 99% 的红色和一条蓝色的细线。例如，而不是 30%、40%、30%。

黄图：

红/蓝图：

Answer 1

也许您想首先确保您的百分比计算是正确的。

adhocCars/totalAmountOfCars * 100;

应该是

100/totalAmountOfCars * adhocCars;

Answer 2

您的问题可能是您如何调用Graphics#fillArc(...)。如果您查看Graphics API，尤其是这种方法，您会看到：

public abstract void fillArc(int x,  
                             int y,
                             int width,
                             int height,
                             int startAngle,
                             int arcAngle)

注意最后一个参数 arcAngle 的描述是：

arcAngle - 弧的角度范围，相对于起始角度。

您可能会调用该方法，就好像它表示圆弧的最终度数，但这不是应该调用它的方式。同样，它应该以度数表示弧的范围。

例如：

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.util.Random;
import javax.swing.*;

@SuppressWarnings("serial")
public class PieDemo extends JPanel {
    private static final int PREF_W = 600;
    private static final int PREF_H = PREF_W;
    private static final Color BG = Color.WHITE;
    private static final int GAP = 40;
    public static final int TIMER_DELAY = 400;
    private int redPercent = 0;
    private int bluePercent = 0;
    // green will be remainder

    public PieDemo() {
        setBackground(BG);
        add(new JButton(new StartDemoAction("Start", KeyEvent.VK_S)));
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        int redAngle = (redPercent * 360) / 100;
        int blueAngle = (bluePercent * 360) / 100;
        int greenAngle = 360 - redAngle - blueAngle;
        greenAngle = Math.max(greenAngle, 0);
        int startAngle = 0;
        startAngle = drawPie(g, Color.green, startAngle, greenAngle);
        startAngle = drawPie(g, Color.RED, startAngle, redAngle);
        startAngle = drawPie(g, Color.BLUE, startAngle, blueAngle);
    }

    private int drawPie(Graphics g, Color color, int startAngle, int arcAngle) {
        int x = GAP;
        int y = GAP;
        int w = getWidth() - 2 * GAP;
        int h = getHeight() - 2 * GAP;
        g.setColor(color);
        g.fillArc(x, y, w, h, startAngle, arcAngle);
        return startAngle + arcAngle;
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    private class StartDemoAction extends AbstractAction {
        private Timer timer = null;
        public StartDemoAction(String name, int mnemonic) {
            super(name);
            putValue(MNEMONIC_KEY, mnemonic);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            if (timer != null && timer.isRunning()) {
                return;
            }
            redPercent = 0;
            bluePercent = 0;
            repaint();
            timer = new Timer(TIMER_DELAY, new TimerListener());
            timer.start();
        }
    }

    private class TimerListener implements ActionListener {
        private static final int BOUND = 10;
        private Random random = new Random();

        @Override
        public void actionPerformed(ActionEvent e) {
            if (redPercent + bluePercent >= 100) {
                ((Timer) e.getSource()).stop();
            } else {
                redPercent += random.nextInt(BOUND);
                bluePercent += random.nextInt(BOUND / 2);

                if (redPercent + bluePercent > 100) {
                    bluePercent = 100 - redPercent;
                }
                repaint();
            }
        }
    }

    private static void createAndShowGui() {
        PieDemo mainPanel = new PieDemo();

        JFrame frame = new JFrame("PieDemo");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

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