JTextArea in MigLayout引起NullPointerException
我不是一个专业的秋千布局经理，这种行为完全令我困惑。本质上，我不能在没有JTextArea或JTextPane的情况下向MigLayout添加NullPointerException。
我创建了一个扩展JPanel的类：
public ComponentPanel(TestComponent testComponent) {
setLayout(new MigLayout("", "[]", "[][][][][][]"));
JLabel lblNewLabel = new JLabel("New label");
add(lblNewLabel, "cell 0 0");
JButton button = new JButton("New button");
add(button, "cell 0 3");
JButton btnNewButton = new JButton("New button");
add(btnNewButton, "cell 0 5");
}这个很好用。但是，如果我尝试添加一个textArea，当我尝试构建时它会抛出一个异常：
public ComponentPanel(TestComponent testComponent) {
setLayout(new MigLayout("", "[grow]", "[][grow][][][][]"));
JLabel lblNewLabel = new JLabel("New label");
add(lblNewLabel, "cell 0 0");
JTextArea textArea = new JTextArea();
add(textArea, "cell 0 1,grow");
JButton button = new JButton("New button");
add(button, "cell 0 3");
JButton btnNewButton = new JButton("New button");
add(btnNewButton, "cell 0 5");
}我在eclipse中使用的是窗口设计器，所以我假设有什么东西在运行MigLayout构造函数？我在这个问题上已经花了一段时间了，我只知道添加textArea或textPanes会导致以下异常：
javax.swing.BoxLayout.preferredLayoutSize(Unknown源的
java.lang.NullPointerException (未知源)在java.awt.Container.preferredSize(未知源)在java.awt.Container.getPreferredSize(未知源)在javax.swing.JRootPane$RootLayout.preferredLayoutSize(Unknown源)在java.awt.Container.preferredSize(未知源)在java.awt.Container.getPreferredSize(未知源)在javax.swing.JComponent.getPreferredSize(Unknown(来源)在java.awt.BorderLayout.preferredLayoutSize(Unknown来源)在java.awt.Container.preferredSize(未知来源)在java.awt.Container.getPreferredSize(未知来源)在net.miginfocom.swing.MigLayout.layoutContainer(Unknown来源)在net.miginfocom.swing.MigLayout.preferredLayoutSize(Unknown来源)在java.awt.Container.preferredSize(未知来源)在java.awt.Container.getPreferredSize(未知源( javax.swing.JComponent.getPreferredSize(Unknown )在javax.swing.BoxLayout.checkRequests(未知源)在javax.swing.BoxLayout.layoutContainer(未知源)在java.awt.Container.layout(未知源)在java.awt.Container.doLayout(未知源)在java.awt.Container.validateTree(未知源)在java.awt.Container.validateTree(未知源)在java.awt.Container.validateTree(未知源)com.soartech.ssim.testbed.gui.TestbedApplication$1.run(TestbedApplication.java:25) at java.awt.event.InvocationEvent.dispatch(Unknown at java.awt.Container.validate(未知源) at java.awt.Window.show(未知源) at java.awt.Component.show(未知源)在java.awt.Component.setVisible(未知源)在java.awt.Window.setVisible(未知源)(未知源)在java.awt.EventQueue$1.运行(未知源)在java.awt.EventQueue$1.运行(未知源)在java.security.AccessController.doPrivileged(Native方法运行(未知源)在java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown来源)在java.awt.EventQueue.dispatchEvent(未知源)在java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown源)(在java.awt.EventDispatchThread.pumpEventsForFilter(Unknown源)在java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown源)在java.awt.EventDispatchThread.pumpEvents(Unknown源)在java.awt.EventDispatchThread.pumpEvents(Unknown源)在java.awt.EventDispatchThread.run(未知源)异常线程"AWT-EventQueue-0“java.lang.NullPointerException at javax.swing.SizeRequirements.calculateTiledPositions(Unknown Source)在javax.swing.BoxLayout.layoutContainer(未知源)在java.awt.Container.layout(未知源)在java.awt.Container.doLayout(未知源) at java.awt.Container.validateTree(未知源) at java.awt.Container.validateTree(未知源)在java.awt.Container.validate(未知源)在java.awt.Window.dispatchEventImpl(未知源)处(未知源)在java.awt.EventQueue$1.运行(未知源)在java.awt.EventQueue$1.运行(未知源)在java.security.AccessController.doPrivileged(Native方法运行(未知源)在java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown来源)在java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown源)在java.awt.EventQueue$2.运行(未知源)在java.security.AccessController.doPrivileged(Native方法)在java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown源)在java.awt.EventQueue.dispatchEvent(未知源在java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)在java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source(在java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)在java.awt.EventDispatchThread.pumpEvents(Unknown Source)java.awt.EventDispatchThread.pumpEvents(Unknown源) at java.awt.EventDispatchThread.run(未知源)
回答 2
Stack Overflow用户
发布于 2012-01-18 15:53:13
问题是，我需要让SwingUtilities为我创建面板，因为它们是以编程方式生成的。
Runnable doWorkRunnable = new Runnable() {
public void run() {
for(TestComponent c : Config.getComponents()){
frame.getContentPane().add(new ComponentPanel(c));
frame.getContentPane().add(Box.createRigidArea(new Dimension(5,0)));
}
}
};
SwingUtilities.invokeLater(doWorkRunnable);既然这已经到位了，我就可以在我的MigLayout中没有任何问题地包含文本区域。
Stack Overflow用户
发布于 2012-01-18 04:10:12
使用MigLayout 4.0，您的代码在我的计算机上运行良好。如果您修复了源附件，您可能会深入了解BoxLayout并更好地了解正在发生的事情。
在源代码中没有实际行号的情况下，我在BoxLayout.preferredLayoutSize()中看到的唯一可能抛出的东西是，如果您的UI正在设置返回空嵌入的Border。这似乎不太可能，但您可以尝试显式地在文本区域设置一个边框，就像一个实验一样。
https://stackoverflow.com/questions/8904716
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