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NullPointer O.o
Hallo Community
Ich bin gerade am verzweifeln
Ich versuche einen BufferedImage und eine Graphic an die 2. Klasse zu übergeben.
Dabei funktioniert es so: (Habe ein Teil unwichtiges weggeschnitten)
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Java source code
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BufferedImage image;
Graphics buffer;
public Main() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setLayout(new BorderLayout(0, 0));
setContentPane(contentPane);
image = new BufferedImage(this.getWidth(), this.getHeight(), BufferedImage.TYPE_INT_ARGB);
buffer = image.getGraphics();
}
public void paint(Graphics g)
{
Ball b = new Ball(image, buffer);
b.zeigeDich(40, 40, 20, Color.red, g);
}
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So funktioniert es nicht... Aber wieso? Möchte es gerne so machen, da die paint Methode in zusammenhang mit repaint(); eine Dauerschleife ist und ich nicht tausende Objekte von Ball erzeugen will.
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Java source code
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public Main() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setLayout(new BorderLayout(0, 0));
setContentPane(contentPane);
image = new BufferedImage(this.getWidth(), this.getHeight(), BufferedImage.TYPE_INT_ARGB);
buffer = image.getGraphics();
}
Ball b = new Ball(image, buffer);
public void paint(Graphics g)
{
b.zeigeDich(40, 40, 20, Color.red, g);
}
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Ball.class
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Java source code
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public class Ball {
BufferedImage image;
Graphics buffer;
public Ball(BufferedImage image, Graphics buffer) {
this.image = image;
this.buffer = buffer;
}
public int runde(double x){
return (int) Math.round(x);
}
public void zeigeDich(double x, double y, int radius, Color c, Graphics g){
buffer.setColor(c);
buffer.fillOval(runde(x), runde(y), radius*2,radius*2);
g.drawImage(image, 0, 0, null);
}
}
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Fehlermeldung
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Source code
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Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at main.Ball.zeigeDich(Ball.java:21)
at main.Main.paint(Main.java:56)
at javax.swing.RepaintManager$3.run(Unknown Source)
at javax.swing.RepaintManager$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.prePaintDirtyRegions(Unknown Source)
at javax.swing.RepaintManager.access$1100(Unknown Source)
at javax.swing.RepaintManager$ProcessingRunnable.run(Unknown Source)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$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)
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Was ist den Zeile 21 von Ball?
In der zeigeDich()-Methode?
Standard Standart eines Flamingos ist einbeinig.
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Java source code
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buffer.setColor(c);
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buffer bzw. image sind null bzw. werdem gar nicht richtig übergeben: Wenn ich es mit System.out.println() ausgebe kommt auch null. Deswegen kann es an der ball.class eig nicht liegen
Initialisier das Ball-Attribut b mal erst im Konstruktor und nicht außerhalb eines Methoden-Rumpfs.
Standard Standart eines Flamingos ist einbeinig.
@BtoBastian
Aber dann kann ich ja nicht auf b zugreifen, da es in einer anderen Methode ist
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Java source code
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public Main() {
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setBounds(100, 100, 450, 300);
contentPane = new JPanel();
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
contentPane.setLayout(new BorderLayout(0, 0));
setContentPane(contentPane);
image = new BufferedImage(this.getWidth(), this.getHeight(), BufferedImage.TYPE_INT_ARGB);
buffer = image.getGraphics();
Ball b = new Ball(image, buffer);
}
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Edit:// klappt jetzt
War nur zu doof
Muss b ja nur initialisieren und nicht erzeugen
Definieren kannst du es außerhalb, aber initialisieren nicht.
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Java source code
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Ball b;
public Main() {
// blabla
image = new // usw.
buffer = image.getGraphics();
b = new Ball(image, buffer);
}
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image und buffer unbedingt zuvor initialisieren!
Standard Standart eines Flamingos ist einbeinig.
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