Java Swing中JList选择事件监听器ListSelectionListener用法示例

转载  2017-11-14   作者:pzy4447   我要评论

这篇文章主要介绍了Java Swing中JList选择事件监听器ListSelectionListener用法,结合具体实例形式分析了中JList选择事件监听器ListSelectionListener的功能、使用方法及相关注意事项,需要的朋友可以参考下

本文实例讲述了Java Swing中JList选择事件监听器ListSelectionListener用法。分享给大家供大家参考,具体如下:

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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 *  - Redistributions in binary form must reproduce the above copyright
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 *   documentation and/or other materials provided with the distribution.
 *
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 *   contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 */ 
package awtDemo;
/*
 * ListSelectionDemo.java requires no other files.
 */
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
@SuppressWarnings("serial")
public class ListSelectionDemo extends JPanel {
  JTextArea output;
  @SuppressWarnings("rawtypes")
 JList list; 
  JTable table;
  String newline = "\n";
  ListSelectionModel listSelectionModel;
  @SuppressWarnings({ "unchecked", "rawtypes" })
 public ListSelectionDemo() {
    super(new BorderLayout());
    String[] listData = { "one", "two", "three", "four",
               "five", "six", "seven" };
    @SuppressWarnings("unused")
 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 - www.jb51.net");
    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());
    }
  }
}

运行效果:

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