在为其创建标签时，Graphics类型变量绘制的线条会消失

时间：2018-04-05 21:13:22

标签： java swing graphics jframe label 

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

1 个答案:

答案 0 :(得分：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

enter image description here

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