IllegalStateException in a GroupLayout

Question

我的面板使用GroupLayout：

GroupLayout layout = new GroupLayout(this);
this.setLayout(layout);
layout.setHorizontalGroup(
    layout.createParallelGroup()
        .addComponent(title_panel)
        .addComponent(subtitle_panel)
    );
layout.setVerticalGroup(
    layout.createSequentialGroup()
        .addComponent(title_panel)
        .addComponent(subtitle_panel)
    );

即使我定义了水平组和垂直组，它仍然会给我一个

java.lang.IllegalStateException

但并非总是如此。有时它做到了，有时却没有。即使出现这种异常，我的GUI也能正常工作并显示我想要的内容。

我想我已经有了答案。当我第一次显示面板所在的框架时，我没有这个例外。但是，当我第二次显示它时，它给了我这个例外。这就像程序在框架的两次启动之间保留了我的groupLayout的一部分，或者类似的东西。

这很令人沮丧，即使它能工作，尽管有这个例外^^'我不喜欢我自己的代码攻击我！

以下是我得到的错误示例（derp是我项目的名称，Panel是从JPanel继承的类）：

Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: derp.Panel[,0,0,0x0,invalid,layout=java.awt.FlowLayout,alignmentX=0.0,alignmentY=0.0,border=,flags=9,maximumSize=,minimumSize=,preferredSize=] is not attached to a horizontal group
at javax.swing.GroupLayout.checkComponents(GroupLayout.java:1086)
at javax.swing.GroupLayout.prepare(GroupLayout.java:1040)
at javax.swing.GroupLayout.layoutContainer(GroupLayout.java:910)
at java.awt.Container.layout(Container.java:1503)
at java.awt.Container.doLayout(Container.java:1492)
at java.awt.Container.validateTree(Container.java:1688)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validateTree(Container.java:1697)
at java.awt.Container.validate(Container.java:1623)
at javax.swing.RepaintManager$2.run(RepaintManager.java:679)
at javax.swing.RepaintManager$2.run(RepaintManager.java:677)
at java.security.AccessController.doPrivileged(Native Method)
at     java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:676)
at javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1650)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:721)
at java.awt.EventQueue.access$200(EventQueue.java:100)
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:691)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
juin 27, 2013 4:39:35 PM io.socket.IOConnection transportMessage

Answer 1

我认为问题来自这两行代码，"this"指的是类的实例，GroupLayout的父级必须是Swing容器，例如

GroupLayout layout = new GroupLayout(this);
this.setLayout(layout);

试试这个

JComponent panel = ...;
GroupLayout layout = new GroupLayout(panel);
panel.setLayout(layout);