Java: BoxLayout kann nicht geteilt werden Fehler

Question

Ich versuche, einen einfachen Rechner zu machen, um mich mit der Erstellung von GUIs vertraut zu machen, die ich gerade in meinem Intro zum Informatikunterricht gelernt habe. Ich habe ein Problem damit, die GUI so anzuordnen, wie ich es möchte. Ich dachte, dass BoxLayout wäre perfekt, aber wenn ich versuche, es zu benutzen, mein Programm stürzt mit diesem Fehlerprotokoll:

Exception in thread "AWT-EventQueue-0" java.awt.AWTError: BoxLayout can't be shared 
at javax.swing.BoxLayout.checkContainer(Unknown Source) 
at javax.swing.BoxLayout.invalidateLayout(Unknown Source) 
at javax.swing.BoxLayout.addLayoutComponent(Unknown Source) 
at java.awt.Container.addImpl(Unknown Source) 
at java.awt.Container.add(Unknown Source) 
at javax.swing.JFrame.addImpl(Unknown Source) 
at java.awt.Container.add(Unknown Source) 
at GUI.run(GUI.java:64) 
at java.awt.event.InvocationEvent.dispatch(Unknown Source) 
at java.awt.EventQueue.dispatchEventImpl(Unknown Source) 
at java.awt.EventQueue.access$500(Unknown Source) 
at java.awt.EventQueue$3.run(Unknown Source) 
at java.awt.EventQueue$3.run(Unknown Source) 
at java.security.AccessController.doPrivileged(Native Method) 
at java.security.ProtectionDomain$JavaSecurityAccessImpl.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) 

Hier ist mein Code:

import java.awt.FlowLayout; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.JLabel; 
import javax.swing.BoxLayout; 
import javax.swing.JButton; 

public class GUI implements Runnable{ 

@Override 
public void run() { 
    JFrame window = new JFrame("Calculator"); 
    window.setLayout(new BoxLayout(window, BoxLayout.Y_AXIS)); 

    JPanel display = new JPanel(); 
    JLabel label = new JLabel("display test"); 
    display.add(label); 

    JPanel row1 = new JPanel(); 
    JButton sevenButton = new JButton("7"); 
    JButton eightButton = new JButton("8"); 
    JButton nineButton = new JButton("9"); 
    JButton divideButton = new JButton("÷"); 

    JPanel row2 = new JPanel(); 
    JButton fourButton = new JButton("4"); 
    JButton fiveButton = new JButton("5"); 
    JButton sixButton = new JButton("6"); 
    JButton multiplyButton = new JButton("x"); 

    JPanel row3 = new JPanel(); 
    JButton oneButton = new JButton("1"); 
    JButton twoButton = new JButton("2"); 
    JButton threeButton = new JButton("3"); 
    JButton minusButton = new JButton("-"); 

    JPanel row4 = new JPanel(); 
    JButton periodButton = new JButton("."); 
    JButton zeroButton = new JButton("0"); 
    JButton enterButton = new JButton("="); 
    JButton addButton = new JButton("+"); 

    row1.add(sevenButton); 
    row1.add(eightButton); 
    row1.add(nineButton); 
    row1.add(divideButton); 

    row2.add(fourButton); 
    row2.add(fiveButton); 
    row2.add(sixButton); 
    row2.add(multiplyButton); 

    row3.add(oneButton); 
    row3.add(twoButton); 
    row3.add(threeButton); 
    row3.add(minusButton); 

    row4.add(periodButton); 
    row4.add(zeroButton); 
    row4.add(enterButton); 
    row4.add(addButton); 

    window.add(display); 
    window.add(row1); 
    window.add(row2); 
    window.add(row3); 
    window.add(row4); 

    window.pack(); 
    window.setVisible(true); 
    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
} 

} 

Das Programm funktioniert gut, wenn ich ändern das BoxLayout zu einem FlowLayout, aber das ist nicht die Art von Layout, die ich für mein Programm wünsche.

Answer 1

Versuchen Sie so etwas wie:

//window.setLayout(new BoxLayout(window, BoxLayout.Y_AXIS)); 
JPanel contentPane = new JPanel(); 
contentPane.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS)); 
window.setContentPane(contentPane); 

So können Sie sicher sind, dass die BoxLayout an der Platte hinzugefügt wird als Inhaltsfenster des Rahmens verwendet werden.

//window.setLayout(new BoxLayout(window, BoxLayout.Y_AXIS)); 
JPanel contentPane = new JPanel(); 
contentPane.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS)); 

... 

//window.add(display); 
//window.add(row1); 
//window.add(row2); 
//window.add(row3); 
//window.add(row4); 
contentPane.add(display); 
contentPane.add(row1); 
contentPane.add(row2); 
contentPane.add(row3); 
contentPane.add(row4); 
window.add(contentPane);