Swing-JList选择事件监听器ListSelectionListener-入门

当JList中的元素被选中时，选择事件将被触发。对于JTable也是一样，你可以把它看做是多个并列的JList。那么，如果程序需要对该事件做出响应，需要以下步骤：

(1)创建一个实现了 ListSelectionListener的监听器；

(2)使用JList或selectionModel的addListSelectionListener添加监听器；

(3)在监听器的valueChanged方法添加响应代码。

在响应代码中需要注意的是getValueIsAdjusting值的判断。测试表明，每当我们进行选择时，valueChanged方法都会被激活多次，其中，在最后的鼠标操作中，getValueIsAdjusting值为false，而在一系列中间操作中，该值均为true。比如说，用鼠标连续划过一串元素时，会有一系列getValueIsAdjusting为true的valueChanged方法激活，且最后一次为false。而我们对选择事件的判定一般是以最后接触为准，因此这里对getValueIsAdjusting值进行一个判断。

常用方法如下：

getLeadSelectionIndex()

返回当前选中的元素的index。

getMinSelectionIndex()

返回选中的多个元素中index的最小值，如果选择为空在返回-1。

getMaxSelectionIndex()

原理同上。

isSelectedIndex(int index)

判断指定index是否被选中。

clearSelection()

清除选中。

getSelectedIndex()

返回被选中的所有元素中最小的index。

getSelectedIndices()

返回一个整型数组，包含被选中的所有index。

getSelectedValue()

返回被选中的，index最小的元素值。

getSelectedValues()

返回一个object数组，包含被选中的所有元素对象。

getSelectedValuesList()

返回一个objectList，包含被选中的所有元素对象。

 

下面的demo来自于ListSelectionDemo.java

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package Swing;

/*
 * ListSelectionDemo.java requires no other files.
 */

import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;

import java.util.*;
import java.awt.*;
import java.awt.event.*;

public class ListSelectionDemo extends JPanel {
    JTextArea output;
    JList list; 
    JTable table;
    String newline = "\n";
    ListSelectionModel listSelectionModel;

    public ListSelectionDemo() {
        super(new BorderLayout());

        String[] listData = { "one", "two", "three", "four",
                              "five", "six", "seven" };
        String[] columnNames = { "French", "Spanish", "Italian" };
        list = new JList(listData);

        listSelectionModel = list.getSelectionModel();
        listSelectionModel.addListSelectionListener(
                new SharedListSelectionHandler());
        JScrollPane listPane = new JScrollPane(list);

        JPanel controlPane = new JPanel();
        String[] modes = { "SINGLE_SELECTION",
                           "SINGLE_INTERVAL_SELECTION",
                           "MULTIPLE_INTERVAL_SELECTION" };

        final JComboBox comboBox = new JComboBox(modes);
        comboBox.setSelectedIndex(2);
        comboBox.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String newMode = (String)comboBox.getSelectedItem();
                if (newMode.equals("SINGLE_SELECTION")) {
                    listSelectionModel.setSelectionMode(
                        ListSelectionModel.SINGLE_SELECTION);
                } else if (newMode.equals("SINGLE_INTERVAL_SELECTION")) {
                    listSelectionModel.setSelectionMode(
                        ListSelectionModel.SINGLE_INTERVAL_SELECTION);
                } else {
                    listSelectionModel.setSelectionMode(
                        ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
                }
                output.append("----------"
                              + "Mode: " + newMode
                              + "----------" + newline);
            }
        });
        controlPane.add(new JLabel("Selection mode:"));
        controlPane.add(comboBox);

        //Build output area.
        output = new JTextArea(1, 10);
        output.setEditable(false);
        JScrollPane outputPane = new JScrollPane(output,
                         ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,
                         ScrollPaneConstants.HORIZONTAL_SCROLLBAR_AS_NEEDED);

        //Do the layout.
        JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT);
        add(splitPane, BorderLayout.CENTER);

        JPanel topHalf = new JPanel();
        topHalf.setLayout(new BoxLayout(topHalf, BoxLayout.LINE_AXIS));
        JPanel listContainer = new JPanel(new GridLayout(1,1));
        listContainer.setBorder(BorderFactory.createTitledBorder(
                                                "List"));
        listContainer.add(listPane);
        
    topHalf.setBorder(BorderFactory.createEmptyBorder(5,5,0,5));
        topHalf.add(listContainer);
        //topHalf.add(tableContainer);

        topHalf.setMinimumSize(new Dimension(100, 50));
        topHalf.setPreferredSize(new Dimension(100, 110));
        splitPane.add(topHalf);

        JPanel bottomHalf = new JPanel(new BorderLayout());
        bottomHalf.add(controlPane, BorderLayout.PAGE_START);
        bottomHalf.add(outputPane, BorderLayout.CENTER);
        //XXX: next line needed if bottomHalf is a scroll pane:
        //bottomHalf.setMinimumSize(new Dimension(400, 50));
        bottomHalf.setPreferredSize(new Dimension(450, 135));
        splitPane.add(bottomHalf);
    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        JFrame frame = new JFrame("ListSelectionDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        ListSelectionDemo demo = new ListSelectionDemo();
        demo.setOpaque(true);
        frame.setContentPane(demo);

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }

    class SharedListSelectionHandler implements ListSelectionListener {
        public void valueChanged(ListSelectionEvent e) { 
            ListSelectionModel lsm = (ListSelectionModel)e.getSource();
            //System.out.printf("LeadSelectionIndex is %s%n",lsm.getLeadSelectionIndex());
            output.append("LeadSelectionIndex is " + lsm.getLeadSelectionIndex() + "\n");
            
            int firstIndex = e.getFirstIndex();
            int lastIndex = e.getLastIndex();
            boolean isAdjusting = e.getValueIsAdjusting(); 
            output.append("Event for indexes "
                          + firstIndex + " - " + lastIndex
                          + "; isAdjusting is " + isAdjusting
                          + "; selected indexes:");

            if (lsm.isSelectionEmpty()) {
                output.append(" <none>");
            } else {
                // Find out which indexes are selected.
                int minIndex = lsm.getMinSelectionIndex();
                int maxIndex = lsm.getMaxSelectionIndex();
                for (int i = minIndex; i <= maxIndex; i++) {
                    if (lsm.isSelectedIndex(i)) {
                        output.append(" " + i);
                    }
                }
            }
            output.append(newline);
            output.setCaretPosition(output.getDocument().getLength());
        }
    }
}