以下代码在左侧显示列表，在右侧显示内容。因此，当选择列表中的项目时，它应该在右侧显示一些内容（这使用拆分窗格）。问题是，当选择某个项目时它不会显示，而是在您单击分隔符时显示它。我想知道以下代码有什么问题，它不会自动显示内容时选择列表中的项目。提前谢谢。
下面显示了我遇到麻烦的部分代码：
public class FrequentQuestions implements ActionListener{
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
frame = new MyInternalFrame("Frequently Asked Questions");
String [] options = {"How to open/save images", "formats", "info"};
JList list = new JList(options);
panelQuestions.add(list);
list.addListSelectionListener(new ListSelectionListener(){
@Override
public void valueChanged(ListSelectionEvent e) {
// TODO Auto-generated method stub
if(e.getValueIsAdjusting())
return;
//String [] options2 = {"hello","bye"};
//JList list2 = new JList(options2);
JList list = (JList) e.getSource();
if (list.isSelectionEmpty()) {
System.out.println("list selection is empty!");
}
else{
int index = ((JList)e.getSource()).getSelectedIndex();
if(index == 0){
readFile();
}
else if(index == 1){
System.out.println("2nd item selected");
}
else{
System.out.println("3rd item selected");
}
}
}
});
scroll = new JScrollPane(panelAnswers,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
pane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, panelQuestions, scroll);
pane.setAutoscrolls(true);
pane.setOpaque(true);
panelQuestions.setMinimumSize(new Dimension(200,50));
panelQuestions.setBackground(new Color(0,0,0,0));
panelAnswers.setMinimumSize(new Dimension(100,30));
pane.setOneTouchExpandable(true);
pane.setDividerLocation(250);
frame.add(pane);
frame.setVisible(true);
desk.add(frame);
try {
frame.setSelected(true);
} catch (java.beans.PropertyVetoException e1) {
}
}
}
这是完整的代码（它可能无法编译，因为我有文本文件，我不知道这是否有用）：
public class FrequentQuestions implements ActionListener{
private int openFrameCount;
private JDesktopPane desk;
private JTextArea Tarea;
private JScrollPane scroll;
private BufferedReader in ;
JPanel panelQuestions = new JPanel();
JPanel panelAnswers = new JPanel();
JTextArea text = new JTextArea();
//private FrequentQuestions quest;
JSplitPane pane ;
MyInternalFrame frame;
public FrequentQuestions(JDesktopPane desktop) {
// TODO Auto-generated constructor stub
desk = desktop;
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
frame = new MyInternalFrame("Frequently Asked Questions");
String [] options = {"How to open/save images", "formats", "Information"};
JList list = new JList(options);
//panelQuestions.add(list);
list.addListSelectionListener(new ListSelectionListener(){
@Override
public void valueChanged(ListSelectionEvent e) {
// TODO Auto-generated method stub
if(e.getValueIsAdjusting() == false)
return;
String [] options2 = {"hello","bye"};
JList list2 = new JList(options2);
JList list = (JList) e.getSource();
if (list.isSelectionEmpty()) {
System.out.println("list selection is empty!");
}
else{
int index = ((JList)e.getSource()).getSelectedIndex();
if(index == 0){
readFile();
System.out.println("I am outputting!");
}
else if(index == 1){
readFormatFile();
System.out.println("2nd item selected");
}
else{
System.out.println("3rd item selected");
}
}
}
});
JScrollPane scroll1 = new JScrollPane(list,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
scroll = new JScrollPane(panelAnswers,JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
pane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, scroll1, scroll);
pane.setAutoscrolls(true);
pane.setOpaque(true);
panelQuestions.setMinimumSize(new Dimension(259,50));
panelQuestions.setBackground(new Color(0,0,0,0));
panelAnswers.setMinimumSize(new Dimension(340,30));
pane.setOneTouchExpandable(true);
pane.setDividerLocation(290);
frame.add(pane);
frame.setVisible(true);
desk.add(frame);
try {
frame.setSelected(true);
} catch (java.beans.PropertyVetoException e1) {
}
}
private class MyInternalFrame extends JInternalFrame {
static final int xPosition = 30, yPosition = 30;
public MyInternalFrame(String title) {
super(title, true,true, true, true);
setSize(600,500);
// Set the window's location.
setLocation(xPosition * openFrameCount, yPosition * openFrameCount);
}
}
public void readFile(){
panelAnswers.removeAll();
try {
in = new BufferedReader(new FileReader("openSave.txt"));
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
String line;
String file = "";
try {
while((line = in.readLine()) != null)
{
System.out.println(line);
file += line;
file +="\n";
}
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
in.close();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
JTextArea Tarea = new JTextArea();
//System.out.println(file);
Tarea.setText(file);
Font f = new Font("TimesNewRoman", Font.ROMAN_BASELINE, 12);
Tarea.setFont(f);
Tarea.setBackground(new Color(0,0,0,0));
Tarea.setEditable(false);
panelAnswers.add(Tarea);
}
public void readFormatFile(){
panelAnswers.removeAll();
try {
in = new BufferedReader(new FileReader("format.txt"));
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
String line;
String file = "";
try {
while((line = in.readLine()) != null)
{
System.out.println(line);
file += line;
file +="\n";
}
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
in.close();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
JTextArea Tarea = new JTextArea();
//System.out.println(file);
Tarea.setText(file);
Font f = new Font("TimesNewRoman", Font.ROMAN_BASELINE, 12);
Tarea.setFont(f);
Tarea.setBackground(new Color(0,0,0,0));
Tarea.setEditable(false);
panelAnswers.add(Tarea);
}
}
答案 0 :(得分：0)
这是一个有效的ListSelectionListener：
public class FrequentQuestions extends JFrame {
final JLabel label = new JLabel("TEXT");
public FrequentQuestions() {
JList<String> list = new JList<String>(new String[]{"A", "B"});
list.addListSelectionListener(new ListSelectionListener() {
public void valueChanged(ListSelectionEvent e) {
if (e.getValueIsAdjusting())
return;
JList<String> list = (JList<String>) e.getSource();
label.setText(list.getSelectedValue());
}
});
JSplitPane split = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, list, label);
add(split);
setLocationRelativeTo(null);
setDefaultCloseOperation(EXIT_ON_CLOSE);
pack();
setVisible(true);
}
public static void main(String[] args) {
new FrequentQuestions();
}
}