I'm a student javadevelopment in Brussels. The focus of the course lies on backend and webapp's, now we're currently covering spring(core, enterprise and mvc, we going to skip security and messaging).
I would like to be able to create graphic stand alone app's to, so I started a side project in swing, for a non-profit historical organisation I want to wright a app that connect's with a local database and let's them manage their members and the libary. Secondary there's going to be a webapp that lets de websitevisitors search the libary for availability and reserve the items.
I started with the adminapp (to manage members and the libary). It starts with a simple userloginform a textfield user, a other password and a loginbutton. On click it's stores the username and password and should open a other JPanel in the same frame, that's bassicly how the user is going to navigate through the app. When I click the loginbutton a new empty frame opens (what it shouldn't), when I maximize my new frame and minimalize it again, my old frame is showing what it's supposed to. I know the way I call my second Jpanel is not the most elegant way, but I had no pre knolledge of swing starting this, I just started experimenting and puzzled bits and piece together on the internet.
Anyway, this is the nullpointer exception I get:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at com.intellij.uiDesigner.core.GridLayoutManager.addLayoutComponent
(GridLayoutManager.java:134)
at java.awt.Container.addImpl(Container.java:1127)
at java.awt.Container.add(Container.java:417)
at be.kokw.views.MainApp$1.actionPerformed(MainApp.java:48)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed
(AbstractButton.java:2348)
at javax.swing.DefaultButtonModel.fireActionPerformed
(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased
(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6533)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6298)
at java.awt.Container.processEvent(Container.java:2236)
at java.awt.Component.dispatchEventImpl(Component.java:4889)
at java.awt.Container.dispatchEventImpl(Container.java:2294)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
at java.awt.Container.dispatchEventImpl(Container.java:2280)
at java.awt.Window.dispatchEventImpl(Window.java:2746)
at java.awt.Component.dispatchEvent(Component.java:4711)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl
.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.security.ProtectionDomain$JavaSecurityAccessImpl
.doIntersectionPrivilege(ProtectionDomain.java:90)
at java.awt.EventQueue$4.run(EventQueue.java:731)
at java.awt.EventQueue$4.run(EventQueue.java:729)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.
doIntersectionPrivilege(ProtectionDomain.java:80)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
at java.awt.EventDispatchThread.pumpOneEventForFilters
(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter
(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy
(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
My MainClass:
public class MainApp{
private JButton login;
private JPanel panel1;
private JLabel labelForUser;
private JTextField userField;
private JLabel labelForPassword;
private JTextField passwordField;
private String user;
private String password;
static JFrame frame = new JFrame("KokwApp");
public String getUser() {
return user;
}
public String getPassword() {
return password;
}
public MainApp() {
login.addActionListener(new ActionListener() {
/**
* Invoked when an action occurs.
*
* @param e
*/
@Override
public void actionPerformed(ActionEvent e) {
user = userField.getText();
password = passwordField.getText();
DbSelection db = new DbSelection();
frame.getContentPane().removeAll();
frame.getContentPane().add(db.getPanel1());
frame.repaint();
}
});
}
public static void main(String[] args) {
frame.setContentPane(new MainApp().panel1);
frame.pack();
frame.setVisible(true);
}
}
I asked my teacher today... His answer: I don't like to use swing. Read up on javafx... Lol
So any tips on what's wrong would be welcome. Just to be exact I use intelij. Finally, sorry for my crappy gramar, but as I said in the beginning, I'm Belgian
