Question

import java.awt.Color;
import java.awt.Graphics;
import javax.swing.*;

public class NewJFrame extends JFrame {
    private Graphics g1;
    private JLabel label = new JLabel();
    // holds information of all businesses
    private Object[][] busInfo = new Object[10][15];

    public NewJFrame() {
        initComponents();
        g1 = jPanel1.getGraphics();
    }

    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {
        jPanel1 = new javax.swing.JPanel();
        jButton1 = new javax.swing.JButton();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGap(0, 858, Short.MAX_VALUE));
        jPanel1Layout.setVerticalGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGap(0, 564, Short.MAX_VALUE));
        jButton1.setText("Click Me");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).addGroup(
                javax.swing.GroupLayout.Alignment.TRAILING,
                layout.createSequentialGroup().addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(jButton1).addGap(425, 425, 425))
                .addGroup(layout.createSequentialGroup().addGap(48, 48, 48)
                        .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE,
                                javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addContainerGap(61, Short.MAX_VALUE)));
        layout.setVerticalGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup().addGap(28, 28, 28)
                        .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE,
                                javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED).addComponent(jButton1)));
        pack();
    }// </editor-fold>

    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
        printBarChart(2, 1);
        System.out.println(getSize());
    }

    public static void main(String args[]) {
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
        }
        java.awt.EventQueue.invokeLater(() -> {
            new NewJFrame().setVisible(true);
        });
    }

    public void printBarChart(int bestBus, int worstBus) {
        busInfo[0][7] = 24325.08;
        busInfo[1][7] = 15394.59;
        busInfo[2][7] = 186719.84;
        int y = jPanel1.getSize().height;
        int x = jPanel1.getSize().width;
        double balance, maxScale = (double) busInfo[bestBus][7] + 650;
        int sameBusDistance, diffBusDistance = 0, scaleNum, maxPoint;
        for (int i = 0; i <= 2; ++i) {
            if (i == 0) {
                diffBusDistance = 0;
            } else {
                diffBusDistance += 65;
            }
            // color of best business
            if (i == bestBus) {
                g1.setColor(Color.YELLOW);
                // color of worst business
            } else if (i == worstBus) {
                g1.setColor(Color.RED);
                // color of other businesses (neither best nor worst)
            } else {
                g1.setColor(Color.BLACK);
            }
            balance = (double) busInfo[i][7];
            sameBusDistance = 25;
            scaleNum = y - 100;
            maxPoint = scaleNum - (scaleNum * (int) balance / (int) maxScale) + 50;
            g1.drawLine(125 + diffBusDistance, y - 50, 125 + diffBusDistance, maxPoint);
            g1.drawLine(125 + sameBusDistance + diffBusDistance, y - 50, 125 + sameBusDistance + diffBusDistance,
                    maxPoint);
            g1.drawLine(125 + sameBusDistance + diffBusDistance, maxPoint, 125 + diffBusDistance, maxPoint);
            jPanel1.add(label);
            jPanel1.setLayout(null);
            label.setSize(100, 50);
            label.setFont(label.getFont().deriveFont(8f));
            label.setLocation(125 + sameBusDistance + diffBusDistance - 30, maxPoint - 50);
            label.setText("" + busInfo[i][7]);
        }
    }

    // Variables declaration - do not modify
    private javax.swing.JButton jButton1;
    private javax.swing.JPanel jPanel1;
    // End of variables declaration

}

为图形类型变量绘制的线在为其制作标签时消失此代码位于企业数量的for循环中。我会附上问题的图片。第一个栏很好用：

然而，第二个栏从视图中删除第一个栏及其标签：

打印条形图的标签，导致其他酒吧及其标签消失

Answer 1

同样，我建议您不要使用组件上调用的getGraphics()。到目前为止，您应该最小化并恢复GUI，以便在最小化和恢复GUI时看到绘图不稳定。我建议您在JPanel的paintComponent中绘制。

但是有一个例外 - 如果你在BufferedImage中绘图，你可以使用从它获得的Graphics对象，然后在JLabel的ImageIcon中显示图像。例如，在下面的代码中，我创建了一个填充空图像的JLabel（给它大小）。然后我按下按钮按下一些条形图数据填充图像，将图像放入ImageIcon，然后通过调用setIcon(...)来设置带有该图标的JLabel：

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.image.BufferedImage;

import javax.swing.*;

@SuppressWarnings("serial")
public class DrawInImage extends JPanel {
    private static final int IMG_W = 900;
    private static final int IMG_H = 700;
    private static final int GAP = 20;
    private BufferedImage img = new BufferedImage(IMG_W, IMG_H, BufferedImage.TYPE_INT_ARGB);
    private Icon icon = new ImageIcon(img);
    private JLabel label = new JLabel(icon);
    private int[] data = { 4, 2, 9, 7, 3, 8, 2, 8 };

    public DrawInImage() {
        JPanel btnPanel = new JPanel();
        btnPanel.add(new JButton(new AbstractAction("Press Me") {

            @Override
            public void actionPerformed(ActionEvent arg0) {
                printBarChart();
            }
        }));
        setLayout(new BorderLayout());
        add(label);
        add(btnPanel, BorderLayout.PAGE_END);
    }

    private void printBarChart() {
        // create new image
        img = new BufferedImage(IMG_W, IMG_H, BufferedImage.TYPE_INT_ARGB);
        Graphics2D g2 = img.createGraphics(); // get image's graphics
        g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
        g2.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 18));

        // get sizes of drawing area
        int totalWidth = IMG_W - 2 * GAP;
        int totalHeight = IMG_H - 2 * GAP;
        // number of columns including gaps
        int columns = 2 * data.length + 1;

        // calc the max data + 1
        int maxData = 0;
        for (int i : data) {
            if (i > maxData) {
                maxData = i;
            }
        }
        maxData++; // + 1

        for (int i = 0; i < data.length; i++) {
            int x1 = GAP + ((2 * i + 1) * totalWidth) / columns;
            int x2 = GAP + ((2 * i + 2) * totalWidth) / columns;
            int y1 = GAP + (totalHeight * (maxData - data[i])) / maxData;
            int y2 = GAP + totalHeight;

            float hue = (float) i / (float) data.length;
            Color c = Color.getHSBColor(hue, 1f, 1f);
            g2.setColor(c);
            g2.fillRect(x1, y1, x2 - x1, y2 - y1);
            g2.setColor(Color.BLACK);
            String text = "Data " + (i + 1);
            int strX = x1;
            int strY = y1 - GAP / 2;
            g2.drawString(text, strX, strY);
        }

        g2.dispose(); // dispose of graphics objects *we* create
        icon = new ImageIcon(img); // create new icon
        label.setIcon(icon); // display in label
    }

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

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}

显示为

在为其创建标签时，Graphics类型变量绘制的线条会消失

1 个答案: