我正在尝试使用JList和按钮创建表单 我想要做的是从JList中选择一个项目,然后按下按钮以执行取决于选择的操作。但是,只要单击该按钮,JList就会失去焦点,选择消失,使按钮无法确定在JList中选择了哪个元素。
有解决方案吗? 在此先感谢:)
答案 0 :(得分:1)
我看不到Oracle JList教程
查看ListSelectionListener
可能会仔细阅读SelectionModes
你能描述什么是你的目标
代码示例
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class ListDemo extends JPanel implements ListSelectionListener {
private JList list;
private DefaultListModel listModel;
private static final String hireString = "Hire";
private static final String fireString = "Fire";
private JButton fireButton;
private JTextField employeeName;
public ListDemo() {
super(new BorderLayout());
listModel = new DefaultListModel();
listModel.addElement("Jane Doe");
listModel.addElement("John Smith");
listModel.addElement("Kathy Green");
list = new JList(listModel);
list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
list.setSelectedIndex(0);
list.addListSelectionListener(this);
list.setVisibleRowCount(5);
JScrollPane listScrollPane = new JScrollPane(list);
JButton hireButton = new JButton(hireString);
HireListener hireListener = new HireListener(hireButton);
hireButton.setActionCommand(hireString);
hireButton.addActionListener(hireListener);
hireButton.setEnabled(false);
fireButton = new JButton(fireString);
fireButton.setActionCommand(fireString);
fireButton.addActionListener(new FireListener());
employeeName = new JTextField(10);
employeeName.addActionListener(hireListener);
employeeName.getDocument().addDocumentListener(hireListener);
String name = listModel.getElementAt(list.getSelectedIndex()).toString();
JPanel buttonPane = new JPanel();
buttonPane.setLayout(new BoxLayout(buttonPane, BoxLayout.LINE_AXIS));
buttonPane.add(fireButton);
buttonPane.add(Box.createHorizontalStrut(5));
buttonPane.add(new JSeparator(SwingConstants.VERTICAL));
buttonPane.add(Box.createHorizontalStrut(5));
buttonPane.add(employeeName);
buttonPane.add(hireButton);
buttonPane.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
add(listScrollPane, BorderLayout.CENTER);
add(buttonPane, BorderLayout.PAGE_END);
}
class FireListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
int index = list.getSelectedIndex();
listModel.remove(index);
int size = listModel.getSize();
if (size == 0) { //Nobody's left, disable firing.
fireButton.setEnabled(false);
} else { //Select an index.
if (index == listModel.getSize()) {
index--;
}
list.setSelectedIndex(index);
list.ensureIndexIsVisible(index);
}
}
}
class HireListener implements ActionListener, DocumentListener {
private boolean alreadyEnabled = false;
private JButton button;
public HireListener(JButton button) {
this.button = button;
}
public void actionPerformed(ActionEvent e) {
String name = employeeName.getText();
if (name.equals("") || alreadyInList(name)) {
Toolkit.getDefaultToolkit().beep();
employeeName.requestFocusInWindow();
employeeName.selectAll();
return;
}
int index = list.getSelectedIndex(); //get selected index
if (index == -1) { //no selection, so insert at beginning
index = 0;
} else { //add after the selected item
index++;
}
listModel.insertElementAt(employeeName.getText(), index);
//listModel.addElement(employeeName.getText());
employeeName.requestFocusInWindow();
employeeName.setText("");
list.setSelectedIndex(index);
list.ensureIndexIsVisible(index);
}
protected boolean alreadyInList(String name) {
return listModel.contains(name);
}
public void insertUpdate(DocumentEvent e) {
enableButton();
}
public void removeUpdate(DocumentEvent e) {
handleEmptyTextField(e);
}
public void changedUpdate(DocumentEvent e) {
if (!handleEmptyTextField(e)) {
enableButton();
}
}
private void enableButton() {
if (!alreadyEnabled) {
button.setEnabled(true);
}
}
private boolean handleEmptyTextField(DocumentEvent e) {
if (e.getDocument().getLength() <= 0) {
button.setEnabled(false);
alreadyEnabled = false;
return true;
}
return false;
}
}
public void valueChanged(ListSelectionEvent e) {
if (e.getValueIsAdjusting() == false) {
if (list.getSelectedIndex() == -1) {
fireButton.setEnabled(false);
} else {
fireButton.setEnabled(true);
}
}
}
private static void createAndShowGUI() {
JFrame frame = new JFrame("ListDemo");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComponent newContentPane = new ListDemo();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane);
frame.pack();
frame.setVisible(true);
}
public static void main(String[] args) {
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}
答案 1 :(得分:0)
只需拥有一个每次进行选择时更新的字段。您可以通过在JList上添加一个侦听器来完成此操作。
private class selectListener extends MouseAdapter {
public void mouseClicked(MouseEvent e) {
if (SwingUtilities.isLeftMouseButton(e)) {
currentSelected = list.getSelectedIndex();
}
}
}
然后在按下按钮时使用该字段。