java—侦听器中的变量不会更改

2j4z5cfb  于 2021-08-20  发布在  Java
关注(0)|答案(2)|浏览(565)

我正在尝试设计一个包含jdbc和swing的小java软件。我当前的问题是，我在一个按钮侦听器中更改了模型和表，但在另一个用于表的侦听器中，这两个变量仍然保持不变。模型和表都是静态的，可以从类中的任何位置访问。我查看了调试器，它显示变量在监听器外部发生了更改，但在监听器内部，变量仍然没有更改。为什么会发生这种情况？如何解决？
这个描述可能不够清楚，下面是一个更详细的问题产生过程：
表和模型存储在这里，它们是全局和静态的：

  1. public class MainView extends JFrame {
  3.     private static UserService userService = new UserService();
  4.     private static ItemService itemService = new ItemService();
  5.     private static JTable table;
  6.     private static JScrollPane tableScrollPane;
  7.     private static NewTableModel model = new NewTableModel(null);
  8.     private static JTextArea textArea = new JTextArea();
  9.     public MainView() {
  11.     }
  12.     public void addFrm() {
  13.       //here's where the main view window and listeners were put, this function will be called when the window needs to be displayed
  14.     }
  15. }

下面是一个表侦听器，它可以查找选定的行，并可以提取选定行的文本。每行对应一个类，该类存储一段文本。

  1. table.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
  2.     @Override
  3.     public void valueChanged(ListSelectionEvent e) {
  4.         if (!e.getValueIsAdjusting()) {
  5.             if ((table.getSelectedRow() > table.getRowCount()) || (table.getSelectedRow() < 0)) {
  6.                 textArea.setText("");
  7.             }//every time after the table changed, the model will be changed, sometimes the row that user selected before the table might become unavailable which could cause invalid index
  8.             else {
  9.                 textArea.setText(model.getNote(table.convertRowIndexToModel(table.getSelectedRow())));
  10.             }
  11.         }
  12.     }
  13. });

这是我前面提到的按钮侦听器，当单击此按钮时，将显示一个新窗口，用户可以在该新窗口中操作mysql数据库。这部分应该没有问题，因为数据可以正确写入mysql数据库。关闭此窗口后，窗口中会有一个窗口侦听器，它将调用 update() 新窗口关闭时的函数。

  1. jb1.addActionListener(new ActionListener() {//Add some items
  2.     @Override
  3.     public void actionPerformed(ActionEvent actionEvent) {
  4.         AddView addView = new AddView("adder");
  5.         addView.addFrm();//new Window was stored in the other class
  6.         addView.addWindowListener(new WindowAdapter() {
  7.             @Override
  8.             public void windowClosing(WindowEvent e) {
  9.                 update();
  10.                 super.windowClosing(e);
  11.             }
  12.         });
  13.     }
  14. });

这是我的建议 update() 功能：

  1. public static void update(){
  2.     String item = Objects.requireNonNull(comboBox.getSelectedItem()).toString();
  3.      //this is used to select different item from catagories
  4.     List<ItemInfo> list = itemService.getSelectedItem(item);
  5.      //this is used to get a item list from database
  6.     model.setItemInfo(list);//model has been override, it has a item list that stores list
  7.     model.fireTableDataChanged();
  8.     model.fireTableStructureChanged();
  9.     table.setModel(model);//give a new model to the table
  10.     table.validate();//update the table
  11.     table.updateUI();
  12.     tableScrollPane.validate();//table is put in a scrollpane, so update it as well
  13.     tableScrollPane.updateUI();
  14.     table.clearSelection();
  15. }

问题是，如果我从表中选择一行，然后单击按钮并打开一个新窗口来添加内容。在我关闭新窗口后，该内容被正确添加。模型也通过更新功能更新，但在我关闭新窗口后会出现异常。它显示indexoutofboundsexception。

  1. Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index 18 out of bounds for length 18
  2.     at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
  3.     at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
  4.     at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)
  5.     at java.base/java.util.Objects.checkIndex(Objects.java:372)
  6.     at java.base/java.util.ArrayList.get(ArrayList.java:458)
  7.     at com.Other.NewTableModel.getValueAt(NewTableModel.java:35)

但是，如果我只单击了按钮，但没有选择表中的任何行，程序将正常工作：新窗口关闭后，表也将刷新。
我检查了调试器，发现这是由于在我调用了 update() ，模型已在任何位置更新，侦听器中的零件除外。此侦听器中的模型保持不变，没有更改。这怎么会发生？只有一个模型是完全相同的变量，它是静态的和全局的。有人能帮我吗？
有些描述可能不清楚，因为我不会说英语，但如果你要求更多，我可以解释。
一些新增代码newtablemodel：

  1. import com.Model.ItemInfo;
  2. import javax.swing.table.AbstractTableModel;
  3. import java.util.List;
  5. public class NewTableModel extends AbstractTableModel {
  7.     private List<ItemInfo> itemInfo;
  8.     private String[] column = new String[]{"Id","Name","Type","Number","Exp_Date","Adder","Exp.(day)","Added_Date"};
  10.     public NewTableModel(List<ItemInfo> itemInfo){
  11.         this.itemInfo = itemInfo;
  12.     }
  14.     public void setItemInfo(List<ItemInfo> itemInfo) {
  15.         this.itemInfo = itemInfo;
  16.     }
  18.     @Override
  19.     public int getRowCount() {
  20.         return itemInfo.size();
  21.     }
  23.     @Override
  24.     public int getColumnCount() {
  25.         return column.length;
  26.     }
  28.     @Override
  29.     public Object getValueAt(int r, int c) {
  30.         Object data = "";
  31.         switch (c){
  32.             case 0:
  33.                 data = itemInfo.get(r).getItem_id().toString();
  34.                 break;
  35.             case 1:
  36.                 data = itemInfo.get(r).getItem_name();
  37.                 break;
  38.             case 2:
  39.                 data = itemInfo.get(r).getItem_type();
  40.                 break;
  41.             case 3:
  42.                 data = itemInfo.get(r).getItem_number().toString();
  43.                 break;
  44.             case 4:
  45.                 if(itemInfo.get(r).getItem_date() == null){
  46.                     return "Not Available";
  47.                 }
  48.                 data = itemInfo.get(r).getItem_date().toString();
  49.                 break;
  50.             case 5:
  51.                 data = itemInfo.get(r).getItem_adder();
  52.                 break;
  53.             case 6:
  54.                 data = itemInfo.get(r).getItem_expDay();
  55.                 break;
  56.             case 7:
  57.                 data = itemInfo.get(r).getItem_add_date();
  58.         }
  59.         return data;
  61.     }
  63.     @Override
  64.     public String getColumnName(int column) {
  65.         return this.column[column];
  66.     }
  68.     @Override
  69.     public boolean isCellEditable(int rowIndex, int columnIndex) {
  70.         return false;
  71.     }
  73.     public String getNote(int row){
  74.         return itemInfo.get(row).getItem_notes();
  75.     }
  77.     public int getId(int row){
  78.         return itemInfo.get(row).getItem_id();
  79.     }
  80. }

这里有完整的斯塔克追踪：

  1. Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index 19 out of bounds for length 19
  2.     at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)
  3.     at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)
  4.     at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)
  5.     at java.base/java.util.Objects.checkIndex(Objects.java:372)
  6.     at java.base/java.util.ArrayList.get(ArrayList.java:458)
  7.     at com.Other.NewTableModel.getNote(NewTableModel.java:76)
  8.     at com.View.MainView$2.valueChanged(MainView.java:163)
  9.     at java.desktop/javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:219)
  10.     at java.desktop/javax.swing.DefaultListSelectionModel.fireValueChanged(DefaultListSelectionModel.java:186)
  11.     at java.desktop/javax.swing.DefaultListSelectionModel.setValueIsAdjusting(DefaultListSelectionModel.java:723)
  12.     at java.desktop/javax.swing.plaf.basic.BasicTableUI$Handler.setValueIsAdjusting(BasicTableUI.java:972)
  13.     at java.desktop/javax.swing.plaf.basic.BasicTableUI$Handler.mouseReleased(BasicTableUI.java:1185)
  14.     at java.desktop/java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:298)
  15.     at java.desktop/java.awt.Component.processMouseEvent(Component.java:6651)
  16.     at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
  17.     at java.desktop/java.awt.Component.processEvent(Component.java:6416)
  18.     at java.desktop/java.awt.Container.processEvent(Container.java:2263)
  19.     at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5026)
  20.     at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
  21.     at java.desktop/java.awt.Component.dispatchEvent(Component.java:4858)
  22.     at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918)
  23.     at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547)
  24.     at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488)
  25.     at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
  26.     at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2773)
  27.     at java.desktop/java.awt.Component.dispatchEvent(Component.java:4858)
  28.     at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:778)
  29.     at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:727)
  30.     at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
  31.     at java.base/java.security.AccessController.doPrivileged(Native Method)
  32.     at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
  33.     at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
  34.     at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:751)
  35.     at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:749)
  36.     at java.base/java.security.AccessController.doPrivileged(Native Method)
  37.     at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
  38.     at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:748)
  39.     at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)
  40.     at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
  41.     at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
  42.     at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
  43.     at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
  44.     at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)
JavajdbcswingListenerIndexOutOfBoundsException

2条答案

按热度按时间
gj3fmq9x

gj3fmq9x1#

从[full]堆栈跟踪，方法 valueChanged 是调用方法吗 getNote(int) 并传递参数的无效值(根据堆栈跟踪，传递的值为19，并且 itemInfo 是19岁）。
调用 getNote :

  1. textArea.setText(model.getNote(table.convertRowIndexToModel(table.getSelectedRow())));

你需要调试你的代码，看看有什么价值 table.getSelectedRow() 他回来了。然后你需要看看什么是价值 table.convertRowIndexToModel(table.getSelectedRow()) 他回来了。然后，您需要找出它返回无效值的原因。
如果您希望我帮助您调试代码，那么您需要发布一个最小的、可复制的示例。

赞(0）分享  回复(0）举报  2021-08-20
zte4gxcn

zte4gxcn2#

我刚刚解决了这个问题，我想这是由一些过时的库引起的，我更新了它们，但是bug还是消失了。谢谢你帮助我。

赞(0）分享  回复(0）举报  2021-08-20
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