Hallo, mit ActionListener bekomme ich hier eine Fehlermeldung:
Wenn ich die Methode actionPerformed(ActionEvent e) entferne, den Befehl
in den Konstruktor schreibe und den eventListener entferne, klappt's.
Woran könnte es liegen?
Fehlermeldung:
(46: System.out.println(tFeld.getText()); )
Java:
import java.awt.event.*;
import java.awt.*;
import javax.swing.*;
import java.util.*;
public class Test extends JFrame implements ActionListener
{
private JButton bStart;
private JTextField tFeld;
public Test()
{
//JFrame
JFrame JFrame = new JFrame();
JFrame.setSize(140,100);
//Panel
JPanel panel = new JPanel(null);
panel.setPreferredSize(new Dimension(140,100));
//Startknopf
bStart = new JButton("Start");
bStart.setBounds(20,60,100,30);
bStart.setVisible(true);
bStart.addActionListener(this);
//Textfeld
JTextField tFeld = new JTextField("2");
tFeld.setBounds(20,20,100,20);
tFeld.setVisible(true);
//Bedienelemente werden panel hinzugefügt
panel.add(bStart);
panel.add(tFeld);
//Panel
this.add(panel);
this.pack();
this.setVisible(true);
}
public void actionPerformed (ActionEvent e) {
//Ausgeben des Inhalts des Textfeldes (bei Drücken des JButtons bStart)
if (e.getSource() == this.bStart)
{
System.out.println(tFeld.getText());
}
}
}
Wenn ich die Methode actionPerformed(ActionEvent e) entferne, den Befehl
in den Konstruktor schreibe und den eventListener entferne, klappt's.
Woran könnte es liegen?
Fehlermeldung:
(46: System.out.println(tFeld.getText()); )
Code:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Test.actionPerformed(Test.java:46)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2346)
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:6525)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
at java.awt.Component.processEvent(Component.java:6290)
at java.awt.Container.processEvent(Container.java:2234)
at java.awt.Component.dispatchEventImpl(Component.java:4881)
at java.awt.Container.dispatchEventImpl(Container.java:2292)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4898)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4533)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4462)
at java.awt.Container.dispatchEventImpl(Container.java:2278)
at java.awt.Window.dispatchEventImpl(Window.java:2750)
at java.awt.Component.dispatchEvent(Component.java:4703)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:751)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:702)
at java.awt.EventQueue$3.run(EventQueue.java:696)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:724)
at java.awt.EventQueue$4.run(EventQueue.java:722)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:721)
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)