Question

大家！

在我的应用程序中，我需要创建一个被动的JTable。通过被动，我的意思是行的选择不是由JTable直接完成的，而是由另一个组件请求的。因此，当用户转到新行时，表不会立即做出反应，但首先要求数据集根据所需的新行更新其内部状态，然后数据集回调表以进行实际选择。所以我只是在表中选择新行之前尝试执行一个动作。

我为你创建了一个小原型，让我知道自己想要什么。在原型下面，你会发现我的问题。

import java.awt.BorderLayout;
import java.awt.Dimension;

import javax.swing.DefaultListSelectionModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.ListSelectionModel;
import javax.swing.SwingUtilities;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import javax.swing.table.AbstractTableModel;

public class SSCCE extends JPanel
{
    public SSCCE()
    {
        setLayout(new BorderLayout());

        final JLabel selectedRow = new JLabel();

        final Table table = new Table();
        table.getSelectionModel().addListSelectionListener(
            new ListSelectionListener()
            {
                @Override
                public void valueChanged(ListSelectionEvent e)
                {
                    if (!e.getValueIsAdjusting())
                    {
                        selectedRow.setText(
                            "Selected row: " + table.getSelectedRow());
                    }
                }
            }
        );

        new DataSet(table);

        add(new JScrollPane(table), BorderLayout.CENTER);
        add(selectedRow, BorderLayout.PAGE_END);
    }

    private static void createAndShowGUI()
    {
        JFrame frame = new JFrame("Table Test");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(new SSCCE());
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args)
    {
        SwingUtilities.invokeLater(
            new Runnable()
            {
                @Override
                public void run()
                {
                    createAndShowGUI();
                }
            }
        );
    }
}

class DataSet
{
    private final Table _table;
    private int _currentIndex;

    DataSet(Table table)
    {
        _table = table;
        _table.setDataSet(this);
    }

    int getCurrentIndex()
    {
        return _currentIndex;
    }

    void moveTo(int index) throws MovementException
    {
        if (index < 0 || index > 4)
        {
            throw new IndexOutOfBoundsException();
        }
        // Let's suppose there was a problem moving to the 2nd index. Maybe
        // the data set was in edit mode and couldn't persist the changes
        // because of a validation error.
        if (index == 2)
        {
            throw new MovementException();
        }
        _currentIndex = index;
        // Notifies the table that the data was moved so that the table can
        // update its selection model based on the current index of the
        // data set.
        _table.dataMoved();
    }
}

class MovementException extends RuntimeException
{
}

class Table extends JTable
{
    private DataSet _dataSet;
    // When true signals that the data was moved in the data set, so selection
    // is allowed.
    private boolean _dataMoved;
    // Previous selected column.
    private int _oldSelectedColumn;

    Table()
    {
        super(new Model());

        setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        setCellSelectionEnabled(true);
        getTableHeader().setReorderingAllowed(false);
        setPreferredScrollableViewportSize(new Dimension(500, 170));

        getColumnModel().setSelectionModel(new ColumnSelectionModel());
    }

    void setDataSet(DataSet dataSet)
    {
        _dataSet = dataSet;
    }

    // Called by DataSet#moveTo.
    void dataMoved()
    {
        _dataMoved = true;
        try
        {
            int rowIndex = _dataSet.getCurrentIndex();
            // Select the new row.
            setRowSelectionInterval(rowIndex, rowIndex);
        }
        finally
        {
            _dataMoved = false;
        }
    }

    @Override
    protected ListSelectionModel createDefaultSelectionModel()
    {
        return new RowSelectionModel();
    }

    private class ColumnSelectionModel extends DefaultListSelectionModel
    {
        @Override
        public void setSelectionInterval(int index0, int index1)
        {
            // Save the old selected column to be restored in
            // RowSelectionModel#setSelectionInterval in case of an error.
            _oldSelectedColumn = getSelectedColumn();
            super.setSelectionInterval(index0, index1);
        }
    }

    private class RowSelectionModel extends DefaultListSelectionModel
    {
        @Override
        public void setSelectionInterval(int index0, int index1)
        {
            if (_dataMoved || index1 == _dataSet.getCurrentIndex())
            {
                super.setSelectionInterval(index0, index1);
            }
            else
            {
                try
                {
                    _dataSet.moveTo(index1);
                }
                catch (MovementException ex)
                {
                    // There was a problem in the data set. Restore the old
                    // selected column.
                    setColumnSelectionInterval(
                    _oldSelectedColumn, _oldSelectedColumn);
                    throw ex;
                }
            }
        }
    }

    private static class Model extends AbstractTableModel
    {
        private String[] columnNames =
            {"First Name", "Last Name", "Sport", "# of Years", "Vegetarian"};
        private Object[][] data = {
            {"Kathy", "Smith", "Snowboarding", 5, false},
            {"John", "Doe", "Rowing", 3, true},
            {"Sue", "Black", "Knitting", 2, false},
            {"Jane", "White", "Speed reading", 20, true},
            {"Joe", "Brown", "Pool", 10, false}
        };

        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];
        }

        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);
        }
    }
}

你觉得这个设计有什么缺陷吗？
我是否需要覆盖 ColumnSelectionModel 和 RowSelectionModel 类中的更多方法来强制合同，或只是 setSelectionInterval 方法？到目前为止，我还没有发现这方面的任何缺陷。
拥有 ColumnSelectionModel 类让我感到很恼火。它的目的只是在选择新列之前捕获旧的选定列，以便在出现问题时可以在 RowSelectionModel＃setSelectionInterval 中恢复它。我只能使用 RowSelectionModel 类来完成它。还有另一种方式吗？

还有另一种方法不使用选择模型。你可以这样做：

在表构造函数中注释行getColumnModel().setSelectionModel(new ColumnSelectionModel());。

注释方法 Table＃createDefaultSelectionModel 方法。

替换 Table＃dataMoved 方法：

void dataMoved()
{
    _dataMoved = true;
    try
    {
        int rowIndex = _dataSet.getCurrentIndex();
        changeSelection(rowIndex, getSelectedColumn(), false, false);
    }
    finally
    {
        _dataMoved = false;
    }
}

重写表#changeSelection 方法：

@Override
public void changeSelection(int rowIndex, int columnIndex, boolean toggle, boolean extend)
{
    if (_dataMoved)
    {
        super.changeSelection(rowIndex, columnIndex, toggle, extend);
    }
    else
    {
        if (rowIndex != _dataSet.getCurrentIndex())
        {
            _dataSet.moveTo(rowIndex);
        }
        super.changeSelection(_dataSet.getCurrentIndex(), columnIndex, toggle, extend);
    }
}

但我没有使用这种方法，即使它比选择模型简单得多，因为 changeSelection 方法的文档说：

选择的大多数更改都是键盘或鼠标的结果 UI接收的事件通过此方法传递，以便我要被子类重写的行为。

所以我解释了

大多数更改

并非所有更改都意味着可能存在一些未通过此方法的选择更改。我是对的，还是我可以信任 changeSelection 方法？

提前谢谢。

马科斯

Answer 1

您的方法的主要缺陷是您的（导航）模型（aka：DataSet）与视图之间的硬连线双向耦合。出路就像VetoableSelectionModel：然后你可以将DataSet作为vetoablePropertyChangeListener注册到选择模型，这是松耦合，可以配置而无需对表进行子类化。

整体布线的一些代码片段：

final JTable table = new JTable(new Model());
VetoableListSelectionModel selectionModel = new VetoableListSelectionModel();
table.setSelectionModel(selectionModel);
VetoableChangeListener veto = new VetoableChangeListener() {

    @Override
    public void vetoableChange(PropertyChangeEvent evt)
            throws PropertyVetoException {
        if (2 == (Integer) evt.getNewValue()) throw new PropertyVetoException("", evt);
    }
};
selectionModel.addVetoableChangeListener(veto);
table.getSelectionModel().addListSelectionListener(
    new ListSelectionListener()
    {
        @Override
        public void valueChanged(ListSelectionEvent e)
        {
            if (!e.getValueIsAdjusting())
            {
                selectedRow.setText(
                    "Selected row: " + table.getSelectedRow());
            }
        }
    }
);

骨架选择模型（完整代码在the swingx incubator中 - 小心：未维护！）

/**
 * Quick impl of a list selection model which respects a veto before
 * changing selection state. The veto is effect in SINGLE_SELECTION mode
 * only.
 */
public class VetoableListSelectionModel extends DefaultListSelectionModel {
    private VetoableChangeSupport vetoableChangeSupport;

    /**
     * Defaults to SINGLE_SELECTION mode.
     *
     */
    public VetoableListSelectionModel() {
        super();
        setSelectionMode(SINGLE_SELECTION);
    }

    @Override
    public void setSelectionInterval(int index0, int index1) {
        if (isVetoable()) {
            try {
                fireVetoableChange(getMinSelectionIndex(), index0);
            } catch (PropertyVetoException e) {
                // vetoed - do nothing
                return;
            }
        }
        super.setSelectionInterval(index0, index1);
    }

    // similar for all methods that change the selection
    ...

    // methods to add/remove listeners and fire the event
    ...
}

在选择行之前在JTable中执行操作

1 个答案: