Null Pointer

[JMacos]

Buongiorno,

Nel mio applet java, quando clicco sull'evento cerca mi da questo errore:

Exception occurred during event dispatching:
java.lang.NullPointerException: null pData
at sun.awt.windows.WComponentPeer._requestFocus(Nativ e Method)
at sun.awt.windows.WComponentPeer.requestFocus(Unknow n Source)
at java.awt.Component.requestFocusHelper(Unknown Source)
at java.awt.Component.requestFocusHelper(Unknown Source)
at java.awt.Component.requestFocus(Unknown Source)
at sun.plugin2.main.client.PluginMain$2.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.Dialog$1.run(Unknown Source)
at java.awt.Dialog$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Dialog.show(Unknown Source)
at java.awt.Component.show(Unknown Source)
at java.awt.Component.setVisible(Unknown Source)
at java.awt.Window.setVisible(Unknown Source)
at java.awt.Dialog.setVisible(Unknown Source)
at upload.Upload.actionPerformed(Upload.java:126)
at java.awt.Button.processActionEvent(Unknown Source)
at java.awt.Button.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)


nell'evento il codice è:

        if (e.getActionCommand().equals("Cerca")) {

           FileDialog fd = new FileDialog((Frame) null);
            fd.setVisible(true);

            if (fd.getFile() != null) {
                this.directory = fd.getDirectory();
                this.nomeFile = fd.getFile();
                this.pathFile.setText("FILE: " + this.directory + fileSeparator + this.nomeFile);

                uploadFile.setEnabled(true);
                cercaFile.setEnabled(true);
            }
        } 

l'errore viene dato in:
fd.setVisible(true);

[LeleFT]

Originariamente inviato da JMacos

           FileDialog fd = new FileDialog((Frame) null); 

Il parametro passato al costruttore di FileDialog non può essere null.
Semplicemente, crea un Frame (invisibile) e passagli quello.

FileDialog fd = new FileDialog( new Frame() );

Non l'ho provato ed è una vita che non uso AWT (ti consiglio, infatti, di passare a Swing, se non è un problema).


Ciao.

[andbin]

Originariamente inviato da JMacos
l'errore viene dato in:
fd.setVisible(true);

Come già detto da LeleFT, il problema è il null passato. A parte la soluzione di passare un Frame "fittizio", la tua interfaccia utente è sicuramente in un Frame o Dialog .... beh, passa questo!!

[LeleFT]

Originariamente inviato da andbin
A parte la soluzione di passare un Frame "fittizio", la tua interfaccia utente è sicuramente in un Frame o Dialog .... beh, passa questo!!

Siccome ho letto che parla di una Applet, credo si riferisca proprio ad una Applet per il browser... se non è così, la soluzione è ancora più banale.


Ciao.

[JMacos]

Si, però togliendo il null e mettendo:

        if (e.getActionCommand().equals("Cerca")) {

            FileDialog fd = new FileDialog( new Frame() );
            //FileDialog fd = new FileDialog((Frame) null);
            boolean a = true;
            fd.setVisible(a);

            if (fd.getFile() != null) {
                this.directory = fd.getDirectory();
                this.nomeFile = fd.getFile();
                this.pathFile.setText("FILE: " + this.directory + fileSeparator + this.nomeFile);

                uploadFile.setEnabled(true);
                cercaFile.setEnabled(true);
            }
        } 

continua sempre a darmi null pointer sempre in quella riga

Comunque si mi riferisco ad un applet per il browser ...

[LeleFT]

A me quel codice funziona che è una meraviglia. Sei sicuro di aver ricompilato e di utilizzare i nuovi file compilati e non quelli vecchi?


Ciao.

[andbin]

Non avevo letto "applet" nel primo post (sorry). Comunque per curiosità ho fatto una prova con una applet (non firmata) e FileDialog accetta anche un Frame null.

[JMacos]

Si si certo...il codice che uso quando clicco su cerca adesso è:

        if (e.getActionCommand().equals("Cerca")) {

            FileDialog fd = new FileDialog( new Frame() );
            fd.setVisible(true);

            if (fd.getFile() != null) {
                this.directory = fd.getDirectory();
                this.nomeFile = fd.getFile();
                this.pathFile.setText("FILE: " + this.directory + fileSeparator + this.nomeFile);

                uploadFile.setEnabled(true);
                cercaFile.setEnabled(true);
            }
        } 

e continua a darmi:

Exception occurred during event dispatching:
java.lang.NullPointerException: null pData
at sun.awt.windows.WComponentPeer._requestFocus(Nativ e Method)
at sun.awt.windows.WComponentPeer.requestFocus(Unknow n Source)
at java.awt.Component.requestFocusHelper(Unknown Source)
at java.awt.Component.requestFocusHelper(Unknown Source)
at java.awt.Component.requestFocus(Unknown Source)
at sun.plugin2.main.client.PluginMain$2.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.Dialog$1.run(Unknown Source)
at java.awt.Dialog$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Dialog.show(Unknown Source)
at java.awt.Component.show(Unknown Source)
at java.awt.Component.setVisible(Unknown Source)
at java.awt.Window.setVisible(Unknown Source)
at java.awt.Dialog.setVisible(Unknown Source)
at upload.Upload.actionPerformed(Upload.java:123)
at java.awt.Button.processActionEvent(Unknown Source)
at java.awt.Button.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Exception occurred during event dispatching:
java.lang.NullPointerException: null pData
at sun.awt.windows.WComponentPeer._requestFocus(Nativ e Method)
at sun.awt.windows.WComponentPeer.requestFocus(Unknow n Source)
at java.awt.Component.requestFocusHelper(Unknown Source)
at java.awt.Component.requestFocusHelper(Unknown Source)
at java.awt.Component.requestFocus(Unknown Source)
at sun.plugin2.main.client.PluginMain$2.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.Dialog$1.run(Unknown Source)
at java.awt.Dialog$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Dialog.show(Unknown Source)
at java.awt.Component.show(Unknown Source)
at java.awt.Component.setVisible(Unknown Source)
at java.awt.Window.setVisible(Unknown Source)
at java.awt.Dialog.setVisible(Unknown Source)
at upload.Upload.actionPerformed(Upload.java:123)
at java.awt.Button.processActionEvent(Unknown Source)
at java.awt.Button.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(U nknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

[JMacos]

Si, lo so che accettata anche null per questo l'avevo impostato così...però l'errore lo da nel setVisible, quindi c'è qualcosa che sfugge !!!

Allora lo script comunque funziona, però se hai attiva la console di java ti riporta questo errore, infatti sul mac non va proprio...

[LeleFT]

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class AppletCerca extends Applet implements ActionListener {
   private Button btn;

   public void init() {
      disponiComponenti();
   }

   private void disponiComponenti() {
      setLayout( null );
      btn = new Button("Cerca");
      btn.setBounds(10, 10, 100, 30);
      btn.addActionListener( this );
      add( btn );
   }

   public void actionPerformed(ActionEvent ae) {
      // Controllo inutile, ma tant'è.
      if ( ((Button) ae.getSource()).equals( btn ) ) {
         FileDialog fd = new FileDialog(new Frame());
         fd.setVisible( true );
         if (fd.getFile() != null) {
            // Tutto ok.
            // ...
         }
      }
   }
}

Nessun errore nella consolle.


Ciao.