java - SwingX AutoCompleteDecorator JTextField 错误

Question

我正在测试 SwingX AutoCompleteDecorator，我使用的代码是这样的:

import javax.swing.text.JTextComponent;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.JPanel;
import javax.swing.JList;

import org.jdesktop.swingx.autocomplete.*;

public class Test extends JFrame
{
    public Test()
    {
        this.setTitle("Testing");
        JPanel pan = new JPanel();
        JTextComponent test = new JTextField();
        ((JTextField)test).setColumns(20);
        String[] data = {"one", "two", "three", "four"}; 
        JList dataList = new JList(data); 
        AutoCompleteDecorator.decorate(dataList, test);
        pan.add(test);
        this.setContentPane(pan);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
        this.setBounds(280,150,500,200);

    }
    public static void main(String[] args)
    {
        Test t = new Test();
    }
}     

我最终收到大量运行时错误消息，我真的不想发布有关线程“AWT-EventQueue-0”java.lang.NullPointerException 中的异常的堆栈跟踪:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at org.jdesktop.swingx.autocomplete.ListAdaptor.valueChanged(ListAdaptor.java:77)
    at javax.swing.JList.fireSelectionValueChanged(JList.java:1798)
    at javax.swing.JList$ListSelectionHandler.valueChanged(JList.java:1812)
    at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:184)
    at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:164)
    at javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:211)
    at javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:405)
    at javax.swing.DefaultListSelectionModel.changeSelection(DefaultListSelectionModel.java:415)
    at javax.swing.DefaultListSelectionModel.setSelectionInterval(DefaultListSelectionModel.java:459)
    at javax.swing.JList.setSelectedIndex(JList.java:2212)
    at javax.swing.JList.setSelectedValue(JList.java:2362)
    at org.jdesktop.swingx.autocomplete.ListAdaptor.setSelectedItem(ListAdaptor.java:99)
    at org.jdesktop.swingx.autocomplete.AutoCompleteDocument.setSelectedItem(AutoCompleteDocument.java:355)
    at org.jdesktop.swingx.autocomplete.AutoCompleteDocument.insertString(AutoCompleteDocument.java:303)
    at javax.swing.text.JTextComponent.replaceSelection(JTextComponent.java:1386)
    at javax.swing.text.DefaultEditorKit$DefaultKeyTypedAction.actionPerformed(DefaultEditorKit.java:884)
    at javax.swing.SwingUtilities.notifyAction(SwingUtilities.java:1664)
    at javax.swing.JComponent.processKeyBinding(JComponent.java:2879)
    at javax.swing.JComponent.processKeyBindings(JComponent.java:2926)
    at javax.swing.JComponent.processKeyEvent(JComponent.java:2842)
    at java.awt.Component.processEvent(Component.java:6282)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.KeyboardFocusManager.redispatchEvent(KeyboardFocusManager.java:1895)
    at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(DefaultKeyboardFocusManager.java:762)
    at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(DefaultKeyboardFocusManager.java:1027)
    at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(DefaultKeyboardFocusManager.java:899)
    at java.awt.DefaultKeyboardFocusManager.dispatchEvent(DefaultKeyboardFocusManager.java:727)
    at java.awt.Component.dispatchEventImpl(Component.java:4731)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:729)
    at java.awt.EventQueue.access$200(EventQueue.java:103)
    at java.awt.EventQueue$3.run(EventQueue.java:688)
    at java.awt.EventQueue$3.run(EventQueue.java:686)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:702)
    at java.awt.EventQueue$4.run(EventQueue.java:700)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:699)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

我错过了什么？

Answer 1

这是一个错误:罪魁祸首是使用双参数方法用 JList 的项目装饰 textComponent 时的空 ObjectToStringConverter:

public static void decorate(JList list, JTextComponent textComponent) {
    decorate(list, textComponent, null);
}

快速修复是使用三参数方法并传入默认转换器:

JTextComponent test = new JTextField(20);
String[] data = {"one", "two", "three", "four"}; 
JList dataList = new JList(data); 
AutoCompleteDecorator.decorate(dataList, test, ObjectToStringConverter.DEFAULT_IMPLEMENTATION);

归档Issue #1570 - 从修订版 #4305 开始修复

---

晨间沉思(可以安全地忽略 :-)

技术原因是不正确的构造函数链接:插入默认值应该由全能构造函数处理(或者它应该抛出 NPE)

public ListAdaptor(JList list, JTextComponent textComponent) {
    this(list, textComponent, ObjectToStringConverter.DEFAULT_IMPLEMENTATION);
}

public ListAdaptor(JList list, JTextComponent textComponent, ObjectToStringConverter stringConverter) {
    this.list = list;
    this.textComponent = textComponent;
    this.stringConverter = stringConverter;
    // when a new item is selected set and mark the text
    list.addListSelectionListener(this);
}

根本原因是转换器所有权的微妙转变:它通常的所有者是处理自动完成的自定义文档，该文档保护自己免受 null。对于 JList 变体，它的 ListAdaptor 不习惯这种负担......这种转变并不是不正确的(事实上，确切的方法)，只是引入了一个很容易被忽视的非常轻微的不一致。