Java：无法共享 BoxLayout 错误

Question

我正在尝试制作一个简单的计算器，以熟悉我刚刚在计算机科学课程入门中学到的GUI的创建。我在以我想要的方式排列 GUI 时遇到问题。我认为BoxLayout将是完美的，但是每当我尝试使用它时，我的程序都会崩溃并显示此错误日志：

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)

这是我的代码：

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);
}
}

当我将BoxLayout更改为FlowLayout时，该程序工作正常，但这不是我想要的程序布局类型。

Answer 1

尝试类似操作：

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

这样，您就可以确保将BoxLayout添加到要用作框架内容窗格的面板中。

另一种选择是将所有组件直接添加到"contentPane"面板，然后将此面板添加到框架中：

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