Bonjour à tous;
Je suis débutant en JAVA ;
Mon probleme c'est que j'ai creer une interface simple avec un bouton et 2 zones de textes
le programme doit copier le texte dans le champ 1 vers le champ 2
et je tombe dans ce problème.
voila le code de la premiere classe

import java.awt.FlowLayout;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;


public class Fenetre extends JFrame{
	private JTextField txt1;
	private JTextField txt2;
public Fenetre() {
	super();
	Build();
	
}
	public void Build(){
		setTitle("Mon App");
		setSize(200,200);
		setLocationRelativeTo(null);
		setResizable(true);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //On dit à l'application de se fermer lors du clic sur la croix
		setContentPane(buildContentPane());
	}
	private JPanel buildContentPane(){
		JPanel panel = new JPanel();
		panel.setLayout(new FlowLayout());
		
	JButton bouton = new JButton(new CopierAction(this,"Copier"));
	panel.add(bouton);
	
	JTextField txt1 = new JTextField("aa");
	txt1.setColumns(10);
	panel.add(txt1);
	
	JTextField txt2 = new JTextField();
	txt2.setColumns(10);
	panel.add(txt2);
	
		return panel;
		
	}
	public String getTxt1(){
		return txt1.getText();
	}
	
	public void SetTxt2(JTextField txt){
		txt2.setText(txt.getText());
	}
	public static void main(String[] args) {
		Fenetre fenetre = new Fenetre();
		fenetre.setVisible(true);
		
	}

}

le code de deuxième classe

import java.awt.event.ActionEvent;

import javax.swing.AbstractAction;
import javax.swing.JTextField;


public class CopierAction extends AbstractAction {
private Fenetre fenetre;

public CopierAction (Fenetre fenetre,String txt){
	super(txt);
	this.fenetre=fenetre;
	
}

	
	public void actionPerformed(ActionEvent arg0) {
		
		
		
		String txt = fenetre.getTxt1();
			//javax.swing.JOptionPane.showMessageDialog(null,txt);
		
		fenetre.SetTxt2((JTextField) txt);
		
	}

}

et voici le message d'erreur:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Fenetre.getTxt1(Fenetre.java:44)
at CopierAction.actionPerformed(CopierAction.java:21)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

peut-etre devrais tu appeler la méthode buildContentPane() dans ta classe Fenetre