我正在创建一个GUI，无法弄清楚如何在数组中存储JList用户选择。我尝试了List<<Sting>>，Object[]等... JRadioButtons其他图形用户界面很好，只有JList无效...
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Test extends JFrame {
private JTextField num3;
private JLabel label3;
private JButton button;
private JRadioButton radio2;
private JRadioButton radio3;
private ButtonGroup radioGroup;
private JList statesList;
String[] states = {"Alabama", "Alaska", "Wyoming"};
String expression;
String frequency;
// no args constructor
public Test() {
createUI();
}
private void createUI() {
Container contentPane = getContentPane();
contentPane.setLayout(null);
label3 = new JLabel();
label3.setText("Search Expression");
label3.setBounds(16, 120, 200, 21);
contentPane.add(label3);
num3 = new JTextField();
num3.setText("(any expression)");
num3.setBounds(16, 144, 150, 21);
num3.setHorizontalAlignment(JTextField.LEFT);
contentPane.add(num3);
button = new JButton("Start!");
button.setBounds(90,430,126,24);
contentPane.add(button);
button.addActionListener(
new ActionListener() {
public void actionPerformed(ActionEvent event)
{
buttonActionPerformed(event);
}
}
);
// States Selection
statesList = new JList(states);
statesList.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
statesList.setVisibleRowCount(5);
statesList.setBounds(400, 16, 100, 50);
JScrollPane statesScroll = new JScrollPane(statesList);
statesScroll.setBounds(180, 16, 135, 400);
contentPane.add(statesScroll);
// Radio Buttons
radio2 = new JRadioButton();
radio3 = new JRadioButton();
radio3.setSelected(true);
radioGroup = new ButtonGroup();
radioGroup.add(radio2);
radioGroup.add(radio3);
radio2.setText("Quarterly");
radio3.setText("Yearly");
radio2.setBounds(16,360,90,23);
radio3.setBounds(16,385,75,23);
contentPane.add(radio2);
contentPane.add(radio3);
// set the content Pane window
setTitle("Search Engine");
setSize(750,500);
setVisible(true);
}
// Getting the user's TextField and JRadioButton input
private void buttonActionPerformed(ActionEvent event) {
expression = num3.getText();
if (radio2.isSelected())
frequency = "quarterly";
else frequency = "yearly";
System.out.println(expression+","+frequency);
// The above "expression" and "frequency" work fine. But JList does not
// work. What am I doing wrong? I tried Object[] instead of List<String>...
List<String> values = statesList.getSelectedValues();
return values==null ? null : values.toArray(new String[values.size()]);
}
// main thread
public static void main(String[] args) {
Test application = new Test();
application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
答案 0 :(得分：2)
此变体迭代Object[]返回的getSelectedValues()以在控制台中显示预期值。接下来要修复的是布局。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
//public class Test extends JFrame {
public class Test {
private JTextField num3;
private JLabel label3;
private JButton button;
private JRadioButton radio2;
private JRadioButton radio3;
private ButtonGroup radioGroup;
private JList statesList;
String[] states = {"Alabama", "Alaska", "Wyoming"};
String expression;
String frequency;
// no args constructor
public Test() {
createUI();
}
private void createUI() {
JFrame f = new JFrame("Search Engine");
Container contentPane = f.getContentPane();
// This needs fixing NEXT!
contentPane.setLayout(null);
label3 = new JLabel();
label3.setText("Search Expression");
label3.setBounds(16, 120, 200, 21);
contentPane.add(label3);
num3 = new JTextField();
num3.setText("(any expression)");
num3.setBounds(16, 144, 150, 21);
num3.setHorizontalAlignment(JTextField.LEFT);
contentPane.add(num3);
button = new JButton("Start!");
button.setBounds(90,430,126,24);
contentPane.add(button);
button.addActionListener(
new ActionListener() {
public void actionPerformed(ActionEvent event) {
buttonActionPerformed(event);
}
});
// States Selection
statesList = new JList(states);
statesList.setSelectionMode(ListSelectionModel.MULTIPLE_INTERVAL_SELECTION);
statesList.setVisibleRowCount(5);
statesList.setBounds(400, 16, 100, 50);
JScrollPane statesScroll = new JScrollPane(statesList);
statesScroll.setBounds(180, 16, 135, 400);
contentPane.add(statesScroll);
// Radio Buttons
radio2 = new JRadioButton();
radio3 = new JRadioButton();
radio3.setSelected(true);
radioGroup = new ButtonGroup();
radioGroup.add(radio2);
radioGroup.add(radio3);
radio2.setText("Quarterly");
radio3.setText("Yearly");
radio2.setBounds(16,360,90,23);
radio3.setBounds(16,385,75,23);
contentPane.add(radio2);
contentPane.add(radio3);
// set the content Pane window
f.setSize(750,500);
//f.pack();
f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
f.setLocationByPlatform(true);
f.setVisible(true);
}
// Getting the user's TextField and JRadioButton input
private void buttonActionPerformed(ActionEvent event) {
expression = num3.getText();
if (radio2.isSelected())
frequency = "quarterly";
else frequency = "yearly";
System.out.println(expression+","+frequency);
Object[] values = statesList.getSelectedValues();
for (Object state : values) {
System.out.println(state);
}
}
// main thread
public static void main(String[] args) {
Runnable r = new Runnable() {
@Override
public void run() {
Test application = new Test();
}
};
// Swing GUIs should be created and updated on the EDT
// http://docs.oracle.com/javase/tutorial/uiswing/concurrency/initial.html
SwingUtilities.invokeLater(r);
}
}
contentPane.setLayout(null);这在现实世界中无效（可能将下一台PC称为“现实世界”）。使用布局管理器来实现强大的GUI。有关详细信息，请参阅Laying Out Components Within a Container，根据需要，请参阅此nested layout example以进行分组布局。答案 1 :(得分：0)
根据documentation，getSelectedValues返回一个对象数组。
Object[] values = statesList.getSelectedValues();
如果你是肯定的，他们都是字符串，你可以输入它们。
String[] values = (String[]) statesList.getSelectedValues();
编辑：试试这个：
Object[] values = statesList.getSelectedValues();
String[] strings = new String[values.length];
for(int i = 0; i < values.length; i++) {
if(values[i] instanceof String) {
strings[i] = ((String) values[i]);
}
}