我有一个类，它定义了一个带有两个JList的图形界面。对于每个JList，我想关联一个方法public void valueChanged(ListSelectionEvent s)但我无法做到（显然）。那么我该如何解决呢？
这是我的代码：
public class Inbox implements ListSelectionListener {
public static void main(String[] args) {
Inbox inbox = new Inbox();
}
JFrame frame = new JFrame();
JPanel panel = new JPanel();
JPanel titlePanel = new JPanel();
JPanel centerPanel = new JPanel();
JPanel listPanel = new JPanel();
JPanel listRicPanel = new JPanel();
JPanel listInvPanel = new JPanel();
JPanel messPanel = new JPanel();
JPanel buttonPanel = new JPanel();
GridBagConstraints c;
JButton indietro = new JButton("Indietro");
JButton ok = new JButton("Ok");
String ricevuti[] = {"1", "2", "3", "4", "5", "6", "7", "8", "9"};
JList ricList = new JList(ricevuti);
String inviati[] = {"A", "B", "C", "D", "E"};
JList invList = new JList(inviati);
Inbox() {
frame.setTitle("Inbox"); //nome della finestra (frame)
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(panel);
frame.setVisible(true);
panel.setLayout(new BorderLayout());
centerPanel.setLayout(new BorderLayout());
listPanel.setLayout(new GridLayout(2, 0));
panel.add(titlePanel, BorderLayout.NORTH);
panel.add(buttonPanel, BorderLayout.SOUTH);
panel.add(centerPanel, BorderLayout.CENTER);
buttonPanel.add(indietro);
buttonPanel.add(ok);
centerPanel.add(listPanel, BorderLayout.WEST);
centerPanel.add(messPanel, BorderLayout.CENTER);
listPanel.add(listRicPanel);
listPanel.add(listInvPanel);
/** ScrollPane containing the first list **/
ricList.setVisibleRowCount(10);
ricList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
listRicPanel.add(new JScrollPane(ricList));
ricList.addListSelectionListener(this);
/** ScrollPane containing the second list **/
invList.setVisibleRowCount(10);
invList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
listInvPanel.add(new JScrollPane(invList));
invList.addListSelectionListener(this);
frame.pack();
}
/**
* First listener.
*/
public void valueChanged(ListSelectionEvent e) {
String str = (String) ricList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
/**
* Second listener.
*/
public void valueChanged(ListSelectionEvent e) {
String str = (String) invList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
}
我希望该计划能够将不同的听众组合到不同的scroolPane，就像我那样做？
非常感谢！
答案 0 :(得分：2)
它必须是一个方法，但您可以使用e.getSource（）方法获取触发事件的JList实例。然后就可以像这样使用它了
public void valueChanged(ListSelectionEvent e) {
String str = (String) ((JList)e.getSource()).getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
当然必须将侦听器添加到两个列表实例
答案 1 :(得分：1)
确定事件的来源并根据结果分支您的逻辑......
public void valueChanged(ListSelectionEvent e) {
if (e.getSource() == ricList) {
//...
else if (e.getSource() == invList) {
//...
}
}
这假定您要为每个源执行不同的逻辑。如果您有多个可能的来源，这可能会变得有点麻烦......
而不是＆＃34;实施＆＃34; ListSelectionListener在班级......
定义一个完全外部的类来完成你想要的特定工作......
public class MyListSelectionListener implements ListSelectionListener {
public void valueChanged(ListSelectionEvent s) {
// Custom job here...
}
}
根据您的需要，这可能是好事和坏事......有一个问题是您可能需要为课程提供额外的背景，以便它能够执行它的操作，因为事件对象可能无法单独提供足够的上下文
创建执行特定工作的内部类，特别是对于他们已在其中定义的类...
public class Inbox {
//...
Inbox() {
//...
ricList.addListSelectionListener(new RicListSelectionListener());
//...
invList.addListSelectionListener(new InvListSelectionListener());
}
//...
public class RicListSelectionListener implements ListSelectionListener {
public void valueChanged(ListSelectionEvent s) {
String str = (String) ricList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
}
public class InvListSelectionListener implements ListSelectionListener {
public void valueChanged(ListSelectionEvent s) {
String str = (String) invList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
}
}
关于这一点的好处是类可以访问父类中的所有实例变量和方法，并且整洁，并且在您需要时很容易找到...
请查看Inner Class Example了解详情
使用匿名类。这些有点像内部类，除了它们在行中定义...
public class Inbox {
//...
Inbox() {
//...
ricList.addListSelectionListener(new ListSelectionListener {
public void valueChanged(ListSelectionEvent s) {
String str = (String) ricList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
});
//...
invList.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent s) {
String str = (String) invList.getSelectedValue();
if(str.equals("Alex"))
System.out.println("Alex");
else if(str.equals("John"))
System.out.println("John");
else
System.out.println("Other name");
}
});
}
}
如果代码太长而且应该谨慎使用这些代码会使代码变得混乱，但这对于将现有功能整合在一起非常有用。
请查看Anonymous Classes了解详情