圖像的 URL 始終返回 null
[英]URL to image always return null
問題描述
為什么文件名不指向圖片？ 我一開始嘗試使用斜線，但它仍然不起作用。 如果圖像在同一個文件夾中，那么 url 應該是什么樣子？ 我不知道為什么這不起作用。 Login_Form 和 download.png 文件都在同一個文件夾中。
package com.teamsea.langapp;
import javax.swing.*;
import java.awt.*;
import java.util.Objects;
import static com.sun.javafx.scene.control.skin.Utils.getResource;
public class Login_Form extends javax.swing.JFrame {
/**
* Creates new form Login_Form
*/
private void jTextField_Username_VarActionPerformed() { }
private void jTextField_Username_VarMouseClicked() { }
private void jPasswordField_Password_VarActionPerformed() { }
private void jButton_Login_VarKeyPressed() { }
public Login_Form() {
initComponents();
jButton_Login_Var.setBackground(Color.decode("#f8c200"));
jButton_Login_Var.setOpaque(true);
}
/**
* 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.
*/
private void jLabel6_VarMouseClicked() {
new Register_Form().setVisible(true);
Login_Form.this.setVisible(false);
}
private void jButton_Login_VarActionPerformed() {
String username_Var = jTextField_Username_Var.getText();
String password_Var = String.valueOf(jPasswordField_Password_Var.getPassword());
String sha256hex_Var = org.apache.commons.codec.digest.DigestUtils.sha256Hex(password_Var);
String registeredPassword_Var = UseTable.get("User", "username", username_Var, 4);
if(sha256hex_Var.equals(registeredPassword_Var)){
System.out.println("Login "+ UseTable.get("User", "username", username_Var, 1));
Application.sessionUser = Integer.parseInt(Objects.requireNonNull(UseTable.get("User", "username", username_Var, 1)));
new MainMenu().setVisible(true);
Login_Form.this.setVisible(false);
} else {
error_Label_Var.setText("Wrong credentials!");
}
}
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 | InstantiationException | IllegalAccessException |
UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Login_Form.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
/* Create and display the form */
java.awt.EventQueue.invokeLater(() -> new Login_Form().setVisible(true));
}
private javax.swing.JLabel error_Label_Var;
private javax.swing.JButton jButton_Login_Var;
private javax.swing.JPasswordField jPasswordField_Password_Var;
private javax.swing.JTextField jTextField_Username_Var;
private void initComponents() {
JPanel jPanel1_var = new JPanel();
JPanel jPanel2_Var = new JPanel();
JPanel jPanel3_var = new JPanel();
JLabel jLabel4_Var = new JLabel();
jTextField_Username_Var = new javax.swing.JTextField();
JLabel jLabel5_Var = new JLabel();
jButton_Login_Var = new javax.swing.JButton();
JLabel jLabel6_Var = new JLabel();
jPasswordField_Password_Var = new javax.swing.JPasswordField();
error_Label_Var = new javax.swing.JLabel();
JLabel jLabel3_Var = new JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setResizable(false);
setSize(new java.awt.Dimension(414, 896));
jPanel1_var.setBackground(new java.awt.Color(0, 0, 0));
jPanel2_Var.setBackground(new java.awt.Color(255, 255, 255));
jPanel3_var.setBackground(new java.awt.Color(51, 102, 255));
jPanel3_var.setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());
jLabel4_Var.setFont(new java.awt.Font("Tahoma", Font.PLAIN, 14)); // NOI18N
jLabel4_Var.setForeground(new java.awt.Color(255, 255, 0));
jLabel4_Var.setText("Password");
jPanel3_var.add(jLabel4_Var, new org.netbeans.lib.awtextra.AbsoluteConstraints(70, 140, -1, -1));
jTextField_Username_Var.setForeground(new java.awt.Color(255, 255, 0));
jTextField_Username_Var.setHorizontalAlignment(javax.swing.JTextField.CENTER);
jTextField_Username_Var.addMouseListener(new java.awt.event.MouseAdapter() {
public void mouseClicked(java.awt.event.MouseEvent evt) {
jTextField_Username_VarMouseClicked();
}
});
jTextField_Username_Var.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jTextField_Username_VarActionPerformed();
}
});
jPanel3_var.add(jTextField_Username_Var, new org.netbeans.lib.awtextra.AbsoluteConstraints(70, 60, 264, 49));
jLabel5_Var.setFont(new java.awt.Font("Tahoma", 0, 14)); // NOI18N
jLabel5_Var.setForeground(new java.awt.Color(255, 255, 0));
jLabel5_Var.setText("Username");
jPanel3_var.add(jLabel5_Var, new org.netbeans.lib.awtextra.AbsoluteConstraints(70, 40, -1, -1));
jButton_Login_Var.setFont(new java.awt.Font("Trebuchet MS", Font.BOLD, 18)); // NOI18N
jButton_Login_Var.setText("Login");
jButton_Login_Var.setBorder(javax.swing.BorderFactory.createEmptyBorder(1, 1, 1, 1));
jButton_Login_Var.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton_Login_VarActionPerformed();
}
});
jButton_Login_Var.addKeyListener(new java.awt.event.KeyAdapter() {
public void keyPressed(java.awt.event.KeyEvent evt) {
jButton_Login_VarKeyPressed();
}
});
jPanel3_var.add(jButton_Login_Var, new org.netbeans.lib.awtextra.AbsoluteConstraints(130, 240, 151, 40));
jLabel6_Var.setForeground(new java.awt.Color(255, 255, 0));
jLabel6_Var.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
jLabel6_Var.setText("or click here to register..");
jLabel6_Var.addMouseListener(new java.awt.event.MouseAdapter() {
public void mouseClicked(java.awt.event.MouseEvent evt) {
jLabel6_VarMouseClicked();
}
});
jPanel3_var.add(jLabel6_Var, new org.netbeans.lib.awtextra.AbsoluteConstraints(30, 300, 360, -1));
jPasswordField_Password_Var.setForeground(new java.awt.Color(255, 255, 0));
jPasswordField_Password_Var.setHorizontalAlignment(javax.swing.JTextField.CENTER);
jPasswordField_Password_Var.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jPasswordField_Password_VarActionPerformed();
}
});
jPanel3_var.add(jPasswordField_Password_Var, new org.netbeans.lib.awtextra.AbsoluteConstraints(70, 160, 264, 49));
error_Label_Var.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
error_Label_Var.setMaximumSize(new java.awt.Dimension(0, 11));
error_Label_Var.setPreferredSize(new java.awt.Dimension(0, 11));
jPanel3_var.add(error_Label_Var, new org.netbeans.lib.awtextra.AbsoluteConstraints(0, 220, 394, -1));
jLabel3_Var.setBackground(new java.awt.Color(51, 153, 255));
jLabel3_Var.setFont(new java.awt.Font("Tw Cen MT", 1, 48)); // NOI18N
jLabel3_Var.setHorizontalAlignment(javax.swing.SwingConstants.CENTER);
jLabel3_Var.setIcon(new javax.swing.ImageIcon(getResource("/download.png"))); // NOI18N
jLabel3_Var.setText("LangApp");
javax.swing.GroupLayout jPanel2_VarLayout = new javax.swing.GroupLayout(jPanel2_Var);
jPanel2_Var.setLayout(jPanel2_VarLayout);
jPanel2_VarLayout.setHorizontalGroup(
jPanel2_VarLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel3_var, javax.swing.GroupLayout.DEFAULT_SIZE, 422, Short.MAX_VALUE)
.addComponent(jLabel3_Var, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
jPanel2_VarLayout.setVerticalGroup(
jPanel2_VarLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel2_VarLayout.createSequentialGroup()
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(jLabel3_Var, javax.swing.GroupLayout.PREFERRED_SIZE, 192, javax.swing.GroupLayout.PREFERRED_SIZE)
.addGap(48, 48, 48)
.addComponent(jPanel3_var, javax.swing.GroupLayout.PREFERRED_SIZE, 344, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap())
);
javax.swing.GroupLayout jPanel1_varLayout = new javax.swing.GroupLayout(jPanel1_var);
jPanel1_var.setLayout(jPanel1_varLayout);
jPanel1_varLayout.setHorizontalGroup(
jPanel1_varLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel2_Var, javax.swing.GroupLayout.Alignment.TRAILING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
jPanel1_varLayout.setVerticalGroup(
jPanel1_varLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1_varLayout.createSequentialGroup()
.addGap(0, 0, Short.MAX_VALUE)
.addComponent(jPanel2_Var, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1_var, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1_var, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
pack();
}
}
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "java.net.URL.toExternalForm()" because "location" is null
at java.desktop/javax.swing.ImageIcon.<init>(ImageIcon.java:232)
at com.teamsea.langapp.Login_Form.initComponents(Login_Form.java:129)
at com.teamsea.langapp.Login_Form.<init>(Login_Form.java:26)
at com.teamsea.langapp.Login_Form$7.run(Login_Form.java:242)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:773)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:720)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:714)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
Process finished with exit code 0
1 個解決方案
解決方案1
0 已采納 2022-07-06 18:16:33
您可以嘗試getClass().getResource("download.png")而不是完整路徑
這是因為您已經在 com.teamsea.langapp 的路徑中
url 圖像下載始終返回 null android
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