java - 从 JTable 中删除对象时出现 ArrayOutOfBoundsException

Question

我是 Java 的新手。我现在才学半年。现在我正在为学校做一个项目，但我遇到了障碍:

我基本上正在制作一个程序来管理您自己的书籍。我有一个类“Books”，它保存书籍对象的数据。然后是“Library”类，它包含书籍的ArrayList。对于 TableModel，我使用扩展 AbstractTableModel 的类(“LibraryTableModel”)。然后我有一个 GUI 类来显示该表。

该表实际上可以工作，但有两个实例导致程序崩溃:

当我将一本书添加到空图书馆时，表格不会更新。但是，当我重新启动程序时，这本书被添加了(我将 Library 类保存为 .ser 文件)。

然后是我要询问的实例:我有一个按钮可以从表中删除书籍。按钮本身工作正常，但是当我删除一本书时，程序会抛出 ArrayOutOfBoundsException。当我重新创建表时，它会更新并且书籍会被删除。这里有什么问题，为什么程序崩溃而不是更新表？

TableModel 代码:

public class LibraryTableModel extends AbstractTableModel
{
private String[] columnNames = {"Titel", "Autor", "Status", "Genre", "Verlag", "Seitenzahl", "ISBN", "Sprache", "Bewertung"};
private Object[][] data = {};
ArrayList<Book> lib;

public LibraryTableModel(Library l)
{
    //This Method returns the ArrayList in the Library class
    lib = l.getList();

    int libSize = lib.size();
    data = new Object[bib.size()][];

    for (Book b : lib)
    {
        int index = bib.indexOf(b);
        //(...)
        //CODE HERE gets all the data that is supposed to be displayed 
        //from each book in the ArrayList      
        Object[] oA = {tit, aut, sta, gen, ver, sei, isb, spr, bew};

        data[index] = oA;
    }
}

public int getColumnCount()
{
    return columnNames.length;
}

public int getRowCount()
{
    return data.length;
}

public String getColumnName(int col) 
{
    return columnNames[col];
}

public Object getValueAt(int row, int col) 
{
    return data[row][col];
    //When I try to remove a Book, the ArrayOutOfBounds Exception comes from here
}

public Class getColumnClass(int c) 
{
    return getValueAt(0, c).getClass();
}

public void setValueAt(Object value, int row, int col) 
{
    data[row][col] = value;
    fireTableCellUpdated(row, col);
}

public void removeRow(int row)
{
    lib.remove(row);
    fireTableRowsDeleted(row, row);
}

GUI类中围绕表和表模型的代码:

public class GUI implements ActionListener
{
JTable table;
LibraryTableModel model;
TableRowSorter<BibliothekTableModel> sorter;
Library lib;
JMenuItem deleteBook;

(...) 库通过 .ser 文件加载

public void showTable() //This method is envoked in the GUI constructor through pressing a button
 {
    model = new LibraryTableModel(lib);
    table.setModel(model);

    deleteBook.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            int row = table.getSelectedRow();
            model.removeRow(row);

            //Code that saves the library at this point

            table.setModel(new LibraryTableModel(lib));
        }
    });

    popupMenu.add(deleteBook);
    table.setComponentPopupMenu(popupMenu);

    sorter = new TableRowSorter<BibliothekTableModel>(model);
    table.setRowSorter(sorter);
    JScrollPane scrollTable = new JScrollPane(table);

    //Next is code, that adds this ScrollPane to my Frame
 }

Answer 1

When I add a Book to an empty Library, the table doesn't update. However, the Book IS added when I start the program anew (I save the Library class as a .ser file).

没有提供任何信息来演示其工作原理...什么是 .ser 文件？

Then the instance which I am asking about: I have a button that removes Books from the table. the Button itself works fine, but when I remove a book, the program throws an ArrayOutOfBoundsException. When I create the table anew, it updates and the book is removed. What is the problem here, why does the program crash instead of update the table?

有两个问题...

首先，因为您在表上使用 RowSorter，所以 JTable#getSelectedRow 返回的可视行索引和模型中的物理行索引将不会被同样，您需要使用JTable#convertRowIndexToModel

int row = table.getSelectedRow();
row = table.convertRowIndexToModel(row);
model.removeRow(row);

//Code that saves the library at this point

其次，您将从 lib 中删除该书，但不更新内部缓存...

public void removeRow(int row)
{
    lib.remove(row);
    fireTableRowsDeleted(row, row);
}

模型未使用 lib 作为数据源，而是使用 data 数组，而您尚未更新该数组。

虽然您可以简单地重建 data 数组，但更好的解决方案是摆脱它并直接使用 lib，例如...

public class LibraryTableModel extends AbstractTableModel {

    private String[] columnNames = {"Titel", "Autor", "Status", "Genre", "Verlag", "Seitenzahl", "ISBN", "Sprache", "Bewertung"};
    private Object[][] data = {};

    private Library lib;

    public LibraryTableModel(Library l) {
        lib = l;
    }

    public int getColumnCount() {
        return columnNames.length;
    }

    public int getRowCount() {
        return lib.getList().size();
    }

    public String getColumnName(int col) {
        return columnNames[col];
    }

    public Object getValueAt(int row, int col) {
        Book book = lib.getList().get(row);
        Object value = null;
        switch (col) {
            case 0:
                value = ...;
                break;
            case 1:
                value = ...;
                break;
            case 2:
                value = ...;
                break;
            case 3:
                value = ...;
                break;
            case 4:
                value = ...;
                break;
            case 5:
                value = ...;
                break;
            case 6:
                value = ...;
                break;
            case 7:
                value = ...;
                break;
            case 8:
                value = ...;
                break;
        }
        return value;
//When I try to remove a Book, the ArrayOutOfBounds Exception comes from here
    }

    public Class getColumnClass(int c) {
        // Don't do this, know the actualy value and return it
        // Otherwise you could end up with a NullPointerException
        return getValueAt(0, c).getClass();
    }

    public void setValueAt(Object value, int row, int col) {
        // Use a simular technquie to getValueAt to extract the Book for the give
        // row and update the Book's attributes
        fireTableCellUpdated(row, col);
    }

    public void removeRow(int row) {
        lib.remove(row);
        fireTableRowsDeleted(row, row);
    }

}