在细胞选择jtable事件之前 [英] before cell select jtable event

问题描述

在即将选择单元格时是否会触发任何事件？有ListSelectionListener，但它只有在选择发生后触发的事件。我需要某种方法来取消选择事件并使用ListSelectionListener它并不容易，因为选择已经发生，我需要一些状态变量来指示选择是正常还是取消之前的选择。

Are there any event that is fired when cell is about to be selected? There is ListSelectionListener, but it has event that is fired only after selection has happened. I need some way to cancel selection event and using ListSelectionListener it is not easy as selection has already happened and I need to have some state variable that indicates if selection is normal or is cancel of a previous selection.

有没有办法关闭选择通知？然而，这不是100％好的解决方案（如果一些监听器在其本地存储中保存选择状态会有问题）这总比没有好。

Are there a way to switch off selection notifications? However this is not 100% good solution (there will be problems if some listeners saves selection state in its local storage) this is better than nothing.

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.ListSelectionModel;
import javax.swing.border.EmptyBorder;
import javax.swing.event.ListSelectionEvent;
import javax.swing.event.ListSelectionListener;
import javax.swing.table.AbstractTableModel;
import javax.swing.JTable;

public class JTableExample extends JFrame {

    /**
     * 
     */
    private static final long serialVersionUID = 6040280633406589974L;
    private JPanel contentPane;
    private JTable table;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    JTableExample frame = new JTableExample();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public JTableExample() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 450, 300);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        contentPane.setLayout(new BorderLayout(0, 0));
        setContentPane(contentPane);

        table = new JTable(new MyTableModel());
        ListSelectionModel selectionModel = table.getSelectionModel();
        selectionModel.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
        selectionModel.addListSelectionListener(new MySelectionListener());
        contentPane.add(table, BorderLayout.CENTER);
    }

    class MyTableModel extends AbstractTableModel {
        /**
         * 
         */
        private static final long serialVersionUID = -8312320171325776638L;

        public int getRowCount() {
            return 10;
        }

        public int getColumnCount() {
            return 10;
        }

        public Object getValueAt(int rowIndex, int columnIndex) {
            return rowIndex * columnIndex;
        }
    }

    class MySelectionListener implements ListSelectionListener {
        public void valueChanged(ListSelectionEvent e) {
            int selectedRow = table.getSelectedRow();
            if (selectedRow == 5) {
                System.out.println("I would like this selection never happened.");
            }
        }
    }

}

推荐答案

无论你想达到什么目标：认为mouseEvent还不够，选择可能因其他原因而改变（键盘输入，编程触发器......）。恢复监听器中未经改变的更改不是一种选择：正如您已经指出的那样，需要保留选择的副本并且可能会混淆其他监听器。

whatever the goal is that you want to achieve: thinking "mouseEvent" is not enough, selection might change for other reasons (f.i. keyboard input, programmatic trigger, ..). Reverting an unwated change in a listener is not an option: as you already noted that would require to keep a duplicate of the selection and might confuse other listeners.

唯一的方法（我认为，当然可能是其他人;-)首先是不要让它发生：实现List SelectionModel，如果满足某些条件，它不会改变选择。我最喜欢的（有偏见的:-)是 VetoableListSelectionModel 它是DefaultListSelectionModel的子类，在SingleSelectionMode中，在实际更改之前等待来自感兴趣方的否决。

The only way (that I see, could be others, of course ;-) is not to let it happen in the first place: implement a List SelectionModel which doesn't change the selection if certain conditions are met. My favourite (biased me :-) is a VetoableListSelectionModel It's a subclass of DefaultListSelectionModel which in SingleSelectionMode waits for vetoes from interested parties before actually changing.

这是一个使用它的（原始）代码片段：

Here's a (raw) code snippet using it:

    VetoableListSelectionModel vetoableSelection = new VetoableListSelectionModel();
    VetoableChangeListener navigationController = new VetoableChangeListener() {

        public void vetoableChange(PropertyChangeEvent evt)
                throws PropertyVetoException {
            // custom method that implements your condition 
            if (!canSelect((int) evt.getOldValue(), (int) evt.getNewValue()))
                throw new PropertyVetoException("uncommitted changes",
                        evt);
        }

    };
    vetoableSelection.addVetoableChangeListener(navigationController);
    myTable.setSelectionModel(vetoableSelection);

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