java - 在 switch 循环中获取选定的 AbstractListModel 的项目

Question

从如下创建的 AbstractListModel 检索数据时出现问题:

warmup1List.setModel(new javax.swing.AbstractListModel<String>() {
        String[] strings = { "sleepIn", "monkeyTrouble", "sumDouble", "diff21", "parrotTrouble", "makes10", "nearHundred", "posNeg", "notString", "missingChar", "frontBack", "front3", "backAround", "or35", "front22", "startHi", "icyHot", "in1020", "hasTeen", "loneTeen", "delDel", "mixStart", "startOz", "intMax", "close10", "in3050", "max1020", "stringE", "lastDigit", "endUp", "everyNth" };
        public int getSize() { return strings.length; }
        public String getElementAt(int i) { return strings[i]; }
    });

我想从这个列表中获取项目，使用这样的 switch 方法:

public CodingBatGUI() {
    initComponents();

    switch(warmup1List.getSelectedValue()) {
        case "sleepIn":
            descriptionTextArea.setText("This is a test.");
            break;
        case "monkeyTrouble":
            descriptionTextArea.setText("This is another test");
            break;
        default: 
            descriptionTextArea.setText("Nothing selected");    
    }

}

但是每当我尝试这样做时，就会出现此错误:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Paketti.CodingBatGUI.<init>(CodingBatGUI.java:20)
at Paketti.CodingBatGUI$6.run(CodingBatGUI.java:321)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
at java.awt.EventQueue.access$500(EventQueue.java:97)
at java.awt.EventQueue$3.run(EventQueue.java:709)
at java.awt.EventQueue$3.run(EventQueue.java:703)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:80)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

我还尝试使用 switch(warmup1List.getSelectedIndex()) 但它只会显示默认的“case”，然后我有 case 1: case 2: 等，但我希望它们作为字符串，因为项目是 AbstractListModel 中的字符串。

那么，我如何真正从 switch 循环内的列表中获取值？提前致谢!

编辑:问题是我在 CodingBatGUI 类中添加了代码。这是更新的脚本:

public void addActionListener(final ActionListener al) {

    warmup1List.addKeyListener(new KeyAdapter() {
        public void keyPressed(KeyEvent e) {
            if (e.getKeyCode() == KeyEvent.VK_ENTER) {
                switch(warmup1List.getSelectedValue()) {
                    case "sleepIn":
                        descriptionTextArea.setText("This is a test.");
                        break;
                    case "monkeyTrouble":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "sumDouble":
                        descriptionTextArea.setText("This is another test");
                        break;    
                    case "diff21":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "parrotTrouble":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "makes10":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "nearHundred":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "posNeg":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "notString":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "missingChar":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "frontBack":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "front3":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "icyHot":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "in1020":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "hasTeen":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "loneTeen":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "delDel":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "mixStart":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "startOz":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "intMax":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "close10":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "in3050":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "max1020":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "stringE":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "lastDigit":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "endUp":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "everyNth":
                        descriptionTextArea.setText("This is another test");
                        break;
                    default: 
                        descriptionTextArea.setText("Nothing selected");  
                        break;
                }
            }
        }
    });
}

但是，它仍然不会显示任何内容。

Answer 1

通过此脚本解决:

public CodingBatGUI() {
    initComponents();

    warmup1List.addKeyListener(new KeyAdapter() {
        public void keyPressed(KeyEvent e) {
            if (e.getKeyCode() == KeyEvent.VK_ENTER) {
                switch(warmup1List.getSelectedValue()) {
                    case "sleepIn":
                        descriptionTextArea.setText("This is a test.");
                        break;
                    case "monkeyTrouble":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "sumDouble":
                        descriptionTextArea.setText("This is another test");
                        break;    
                    case "diff21":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "parrotTrouble":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "makes10":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "nearHundred":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "posNeg":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "notString":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "missingChar":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "frontBack":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "front3":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "icyHot":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "in1020":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "hasTeen":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "loneTeen":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "delDel":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "mixStart":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "startOz":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "intMax":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "close10":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "in3050":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "max1020":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "stringE":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "lastDigit":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "endUp":
                        descriptionTextArea.setText("This is another test");
                        break;
                    case "everyNth":
                        descriptionTextArea.setText("This is another test");
                        break;
                    default: 
                        descriptionTextArea.setText("Nothing selected");  
                        break;
                }
            }
        }
    });