Java 调用getPreferredSize（）的仅EDT代码中的BoxLayout异常
以下是：Java 调用getPreferredSize（）的仅EDT代码中的BoxLayout异常,java,swing,Java,Swing,以下是： public class TestCode { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { System.err.println("Showing popup"); // Create a popup menu
public class TestCode {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
System.err.println("Showing popup");
// Create a popup menu and fill it with some component
JPopupMenu basicPopupMenu = new JPopupMenu();
JTextArea textArea = new JTextArea();
textArea.setLineWrap(true);
basicPopupMenu.add(textArea);
// This is not necessary for the crash, just to verify the pref size is not null at this point
System.out.println("Popup pref size is : " + basicPopupMenu.getPreferredSize());
System.out.println("Text area pref size is : " + textArea.getPreferredSize());
basicPopupMenu.show(null, 0, 0);
// This is not necessary for the crash, just to verify the minimum size is not null at this point
System.out.println("Min size is : " + basicPopupMenu.getMinimumSize());
System.out.println("Text area min size is : " + textArea.getMinimumSize());
// If I uncomment the next line, then the crash does not occur
// textArea.getPreferredSize()
try {
basicPopupMenu.getPreferredSize();
}
catch (Exception e) {
System.err.println("getPreferredSize() exception!");
e.printStackTrace();
}
}
});
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("Test finished");
}
}
Showing popup
Popup pref size is : java.awt.Dimension[width=102,height=21]
Text area pref size is : java.awt.Dimension[width=100,height=16]
Min size is : java.awt.Dimension[width=102,height=21]
Text area min size is : java.awt.Dimension[width=100,height=16]
getPreferredSize() exception!
java.lang.NullPointerException
at javax.swing.BoxLayout.checkRequests(BoxLayout.java:466)
at javax.swing.BoxLayout.preferredLayoutSize(BoxLayout.java:281)
at javax.swing.plaf.basic.DefaultMenuLayout.preferredLayoutSize(DefaultMenuLayout.java:43)
at java.awt.Container.preferredSize(Container.java:1597)
at java.awt.Container.getPreferredSize(Container.java:1582)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1636)
at TestPopup$1.run(TestPopup.java:26)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:646)
at java.awt.EventQueue.access$000(EventQueue.java:84)
at java.awt.EventQueue$1.run(EventQueue.java:607)
at java.awt.EventQueue$1.run(EventQueue.java:605)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:87)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:616)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
Test finished
很难看出这在哪里误用了swing API，因为它应该完全在EDT中运行，并且首选大小应该在崩溃之前设置，事实上，在上面的堆栈中似乎没有一点最小/首选大小设置为null。这里是否可能调用了另一个线程，或者布局中缺少了什么？在我的Java环境中，唯一具有此跟踪的标记为fixed。这似乎是的一个功能，请参阅。它扩展了
BoxLayout容器BasicPopupMenuUIbasicPopupMenu.setLayout(new GridLayout());
这似乎是一个特征，可见。它扩展了
BoxLayout容器BasicPopupMenuUIbasicPopupMenu.setLayout(new GridLayout());
在BoxLayout源代码中，
checkRequests（）checkRequests（）.getPreferredSize（）.getPreferredSize（）