小贝子编程

空指针异常- Netbeans gui项目



我一直得到这个错误:异常在线程"AWT-EventQueue-0" java.lang。NullPointerException，当我运行程序并单击我创建的任何jbutton时。我如何修复我的代码，使它将创建我的图像?

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
*/
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
/**
 *
 * @author Sara
 */
public class NewJFrame extends javax.swing.JFrame {
private static BufferedImage img;

/**
 * Creates new frame
 */
public NewJFrame() {
    initComponents();
}
/**
 * makes normal clothes
 */
public void normal(){
    try {
        img = ImageIO.read(new File("Nguyen_normal.png"));
    } catch (IOException e) {
    }
    jLabel2.setIcon(new ImageIcon(img));
}
/**
 * makes dress 1
 */
public void dress1() {
    try {
        img = ImageIO.read(new File("Nguyen_black_dress.png"));
    } catch (IOException e) {
    }
    jLabel2.setIcon(new ImageIcon(img));
}
/**
 * makes dress 2
 */
public void dress2() {
    try {
        img = ImageIO.read(new File("Nguyen_blue_dress.png"));
    } catch (IOException e) {
    }
        jLabel2.setIcon(new ImageIcon(img));
}
/**
 *makes dress 3
 */
public void dress3() {
    try {
        img = ImageIO.read(new File("Nguyen_cap_dress.png"));
    } catch (IOException e) {
    }
         jLabel2.setIcon(new ImageIcon(img));
}
/**
 * makes dress 4
 */
public void dress4() {
    try {
        img = ImageIO.read(new File("Nguyen_green_dress.png"));
    } catch (IOException e) {
    }
         jLabel2.setIcon(new ImageIcon(img));
}
/**
 * makes dress 5
 */
public void dress5() {
    try {
        img = ImageIO.read(new File("Nguyen_in_pink.png"));
    } catch (IOException e) {
    }
     jLabel2.setIcon(new ImageIcon(img));
}
/**
 * makes dress 6
 */
public void dress6() {
    try {
        img = ImageIO.read(new File("Nguyen_long_gown.png"));
    } catch (IOException e) {
    }
         jLabel2.setIcon(new ImageIcon(img));
}
/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {
    jPanel1 = new javax.swing.JPanel();
    jLabel1 = new javax.swing.JLabel();
    jLabel2 = new javax.swing.JLabel();
    jPanel2 = new javax.swing.JPanel();
    jButton2 = new javax.swing.JButton();
    jButton3 = new javax.swing.JButton();
    jButton4 = new javax.swing.JButton();
    jButton5 = new javax.swing.JButton();
    jButton6 = new javax.swing.JButton();
    jButton7 = new javax.swing.JButton();
    jButton1 = new javax.swing.JButton();
    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    jPanel1.setMaximumSize(new java.awt.Dimension(650, 400));
    jPanel1.setMinimumSize(new java.awt.Dimension(601, 349));
    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
    jPanel1.setLayout(jPanel1Layout);
    jPanel1Layout.setHorizontalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(jPanel1Layout.createSequentialGroup()
                    .addGap(668, 668, 668)
                    .addComponent(jLabel1))
                .addGroup(jPanel1Layout.createSequentialGroup()
                    .addGap(219, 219, 219)
                    .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 350, javax.swing.GroupLayout.PREFERRED_SIZE)))
            .addContainerGap(132, Short.MAX_VALUE))
    );
    jPanel1Layout.setVerticalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel1Layout.createSequentialGroup()
            .addGap(18, 18, 18)
            .addComponent(jLabel2, javax.swing.GroupLayout.DEFAULT_SIZE, 603, Short.MAX_VALUE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jLabel1))
    );
    jLabel2.getAccessibleContext().setAccessibleParent(jLabel1);
    jButton2.setText("Dress One");
    jButton2.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton2ActionPerformed(evt);
        }
    });
    jButton3.setText("Dress Two");
    jButton3.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton3ActionPerformed(evt);
        }
    });
    jButton4.setText("Dress Three");
    jButton4.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton4ActionPerformed(evt);
        }
    });
    jButton5.setText("Dress Four");
    jButton5.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton5ActionPerformed(evt);
        }
    });
    jButton6.setText("Dress Five");
    jButton6.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton6ActionPerformed(evt);
        }
    });
    jButton7.setText("Dress Six");
    jButton7.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton7ActionPerformed(evt);
        }
    });
    jButton1.setText("Start");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });
    javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
    jPanel2.setLayout(jPanel2Layout);
    jPanel2Layout.setHorizontalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel2Layout.createSequentialGroup()
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addComponent(jButton7, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(1398, 1398, 1398))
        .addGroup(jPanel2Layout.createSequentialGroup()
            .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(jPanel2Layout.createSequentialGroup()
                    .addContainerGap()
                    .addGroup(jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jButton2, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jButton3, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jButton4, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jButton5, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addComponent(jButton6, javax.swing.GroupLayout.PREFERRED_SIZE, 213, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addGroup(jPanel2Layout.createSequentialGroup()
                    .addGap(55, 55, 55)
                    .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 132, javax.swing.GroupLayout.PREFERRED_SIZE)))
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );
    jPanel2Layout.setVerticalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel2Layout.createSequentialGroup()
            .addGap(29, 29, 29)
            .addComponent(jButton2, javax.swing.GroupLayout.PREFERRED_SIZE, 66, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addComponent(jButton3, javax.swing.GroupLayout.PREFERRED_SIZE, 67, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addComponent(jButton4, javax.swing.GroupLayout.PREFERRED_SIZE, 62, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addComponent(jButton5, javax.swing.GroupLayout.PREFERRED_SIZE, 60, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(26, 26, 26)
            .addComponent(jButton6, javax.swing.GroupLayout.PREFERRED_SIZE, 62, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addComponent(jButton7, javax.swing.GroupLayout.PREFERRED_SIZE, 69, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(18, 18, 18)
            .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 43, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );
    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, 238, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addContainerGap())
    );
    pack();
}// </editor-fold>                        
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    dress1();
}                                        
private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    dress2();
}                                        
private void jButton6ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    dress5();
}                                        
private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    dress3();
}                                        
private void jButton5ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    dress4();
}                                        
private void jButton7ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    dress6();
}                                        
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    normal();
}                                        
/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    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 | InstantiationException | IllegalAccessException | javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(NewJFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>
    /* Create and display the form */
    java.awt.EventQueue.invokeLater(() -> {
        new NewJFrame().setVisible(true);
    });
}
// Variables declaration - do not modify                     
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JButton jButton3;
private javax.swing.JButton jButton4;
private javax.swing.JButton jButton5;
private javax.swing.JButton jButton6;
private javax.swing.JButton jButton7;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
// End of variables declaration                   
}

文件和NewJFrame类在同一个文件夹

这自动提示图像是通常所说的嵌入资源。记住，类存在于包中，而包可以存在于Jar文件中。这使得访问这些资源不同于访问文件系统上的资源…

不要使用ImageIO.read(new File("Nguyen_black_dress.png"));，而应该使用Class#getResource(...)，例如…

try {
    img = ImageIO.read(getClass().getResource("Nguyen_black_dress.png"));
} catch (IOException e) {
    e.printStackTrace();
}

每次想要显示图像时读取它们是低效的，您可能不会看到像这样简单的事情有太多问题，但是请相信我们，这不是一个好习惯。

考虑在类实例化时加载图像，并将它们存储在某种Map中，以便于检索，例如…

private Map<String, BufferedImage> mapImages;
//...
mapImages = new HashMap<>(25);
mapImages.put("normal", ImageIO.read(new File("Nguyen_normal.png")));

然后当您想要"正常"图像时，只需从Map中检索它…

BufferedImage normal = mapImages.get("normal");

相关内容

最新更新


热门标签：

javascript python java c# php android html jquery c++ css ios sql mysql arrays asp.net json python-3.x ruby-on-rails .net sql-server django objective-c excel regex ruby linux ajax iphone xml vba spring asp.net-mvc database wordpress string postgresql wpf windows xcode bash git oracle list vb.net multithreading eclipse algorithm macos powershell visual-studio image forms numpy scala function api selenium