Java JComboBox返回值
使用什么方法返回用户选择的选项Java JComboBox返回值,java,swing,jcombobox,java-7,Java,Swing,Jcombobox,Java 7,使用什么方法返回用户选择的选项 JPanel ageSelection = new JPanel(); JLabel age = new JLabel("Age:"); ArrayList<Integer> ageList = new ArrayList<Integer>(); for (int i = 1; i <= 100; ++i) { ageList.add(i); } DefaultComboBoxModel<Integer> m
JPanel ageSelection = new JPanel();
JLabel age = new JLabel("Age:");
ArrayList<Integer> ageList = new ArrayList<Integer>();
for (int i = 1; i <= 100; ++i) {
ageList.add(i);
}
DefaultComboBoxModel<Integer> modelAge = new DefaultComboBoxModel<Integer>();
for (Integer i : ageList) {
modelAge.addElement(i);
}
JComboBox<Integer> ageEntries = new JComboBox<Integer>();
ageEntries.setModel(modelAge);
ageEntries.addActionListener(new putInTextListener());
ageSelection.add(age);
ageSelection.add(ageEntries);
class putInTextListener implements ActionListener {
public void actionPerformed (ActionEvent event) {
ageEntries.getSelectedItem();
}
}
1此语句为空，您可能希望从当前选定的项中获取整数/对象/字符串值 2最好用于，而不是注意ItemListener激发的事件已选择/取消选择，总是两次
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ComboBoxListeners {
private JFrame f;
private JComboBox flyFromCombo;
private JComboBox flyToCombo;
private JLabel tripLabel = new JLabel();
private Object[] itemsFrom;
private Object[] itemsTo;
public ComboBoxListeners() {
itemsFrom = new Object[]{"-", "First - From", "Second - From", "Third - From"};
itemsTo = new Object[]{"-", "First - To", "Second - To", "Third - To"};
//flyFromCombo.setPrototypeDisplayValue("################################################");
flyFromCombo = new JComboBox(itemsFrom);
flyFromCombo.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
if ((e.getStateChange() == ItemEvent.SELECTED)) {
String str = flyFromCombo.getSelectedItem().toString();
String str1 = flyToCombo.getSelectedItem().toString();
setLabelText(str, str1);
}
}
});
flyToCombo = new JComboBox(itemsTo);
flyToCombo.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
if ((e.getStateChange() == ItemEvent.SELECTED)) {
String str = flyFromCombo.getSelectedItem().toString();
String str1 = flyToCombo.getSelectedItem().toString();
setLabelText(str, str1);
}
}
});
tripLabel.setPreferredSize(new Dimension(400, 30));
f = new JFrame("ComboBox ItemListeners");
f.setLayout(new GridLayout(0, 1, 15, 15));
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(flyFromCombo);
f.add(flyToCombo);
f.add(tripLabel);
f.setLocation(150, 150);
f.pack();
f.setVisible(true);
}
private void setLabelText(String str1, String str2) {
String textForLabel = "";
String helpStringFirst = str1.trim();
if (helpStringFirst != null && helpStringFirst.length() > 0) {
if (!helpStringFirst.equals("-")) {
textForLabel = "Flight No57. from : " + helpStringFirst;
} else {
textForLabel = "Flight from Un-Know : ";
}
}
String helpStringSecond = str2.trim();
if (helpStringSecond != null && helpStringSecond.length() > 0) {
if (!helpStringSecond.equals("-")) {
textForLabel = textForLabel + " --> to : " + helpStringSecond;
} else {
textForLabel += " to : Un-Know ";
}
}
final String pushTextForLabel = textForLabel;
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
tripLabel.setText(pushTextForLabel);
}
});
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
ComboBoxListeners comboBoxListeners = new ComboBoxListeners();
}
});
}
}
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.*;
public class ComboBoxListeners {
private JFrame f;
private JComboBox flyFromCombo;
private JLabel tripLabel = new JLabel();
public ComboBoxListeners() {
ArrayList<Integer> ageList = new ArrayList<Integer>();
for (int i = 1; i <= 100; ++i) {
ageList.add(i);
}
DefaultComboBoxModel modelAge = new DefaultComboBoxModel();
for (Integer i : ageList) {
modelAge.addElement(i);
}
flyFromCombo = new JComboBox(modelAge);
flyFromCombo.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
if ((e.getStateChange() == ItemEvent.SELECTED)) {
String str = flyFromCombo.getSelectedItem().toString();
tripLabel.setText("Selected Age From JComboBox is : " + str);
}
}
});
tripLabel.setPreferredSize(new Dimension(400, 30));
f = new JFrame("ComboBox ItemListeners");
f.setLayout(new GridLayout(0, 1, 15, 15));
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(flyFromCombo);
f.add(tripLabel);
f.setLocation(150, 150);
f.pack();
f.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
ComboBoxListeners comboBoxListeners = new ComboBoxListeners();
}
});
}
}
作为参考，这里是@mKorbel的一个变体，它演示了在Java7中添加到JComboBox和ComboxModel的通用参数。它还使用了Java7中提供的一个新的推理功能，这将在中进一步讨论
我仍然得到一个错误…我编辑了它，但仍然无法工作。问题可能出在放入JComboBox的内容上吗？从哪个选项中可以得到一个异常，有一些选项，如天空中的星星，请参见我的编辑。错误来自于ageEntries.getSelectedItem；该行的目的是获取用户选择的内容，并将其像文本文件一样放置在其他位置。我编辑的代码是另一次尝试，但也失败了。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class ComboBoxListeners {
private JFrame f;
private JComboBox flyFromCombo;
private JComboBox flyToCombo;
private JLabel tripLabel = new JLabel();
private Object[] itemsFrom;
private Object[] itemsTo;
public ComboBoxListeners() {
itemsFrom = new Object[]{"-", "First - From", "Second - From", "Third - From"};
itemsTo = new Object[]{"-", "First - To", "Second - To", "Third - To"};
//flyFromCombo.setPrototypeDisplayValue("################################################");
flyFromCombo = new JComboBox(itemsFrom);
flyFromCombo.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
if ((e.getStateChange() == ItemEvent.SELECTED)) {
String str = flyFromCombo.getSelectedItem().toString();
String str1 = flyToCombo.getSelectedItem().toString();
setLabelText(str, str1);
}
}
});
flyToCombo = new JComboBox(itemsTo);
flyToCombo.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
if ((e.getStateChange() == ItemEvent.SELECTED)) {
String str = flyFromCombo.getSelectedItem().toString();
String str1 = flyToCombo.getSelectedItem().toString();
setLabelText(str, str1);
}
}
});
tripLabel.setPreferredSize(new Dimension(400, 30));
f = new JFrame("ComboBox ItemListeners");
f.setLayout(new GridLayout(0, 1, 15, 15));
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(flyFromCombo);
f.add(flyToCombo);
f.add(tripLabel);
f.setLocation(150, 150);
f.pack();
f.setVisible(true);
}
private void setLabelText(String str1, String str2) {
String textForLabel = "";
String helpStringFirst = str1.trim();
if (helpStringFirst != null && helpStringFirst.length() > 0) {
if (!helpStringFirst.equals("-")) {
textForLabel = "Flight No57. from : " + helpStringFirst;
} else {
textForLabel = "Flight from Un-Know : ";
}
}
String helpStringSecond = str2.trim();
if (helpStringSecond != null && helpStringSecond.length() > 0) {
if (!helpStringSecond.equals("-")) {
textForLabel = textForLabel + " --> to : " + helpStringSecond;
} else {
textForLabel += " to : Un-Know ";
}
}
final String pushTextForLabel = textForLabel;
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
tripLabel.setText(pushTextForLabel);
}
});
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
ComboBoxListeners comboBoxListeners = new ComboBoxListeners();
}
});
}
}
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.*;
public class ComboBoxListeners {
private JFrame f;
private JComboBox flyFromCombo;
private JLabel tripLabel = new JLabel();
public ComboBoxListeners() {
ArrayList<Integer> ageList = new ArrayList<Integer>();
for (int i = 1; i <= 100; ++i) {
ageList.add(i);
}
DefaultComboBoxModel modelAge = new DefaultComboBoxModel();
for (Integer i : ageList) {
modelAge.addElement(i);
}
flyFromCombo = new JComboBox(modelAge);
flyFromCombo.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
if ((e.getStateChange() == ItemEvent.SELECTED)) {
String str = flyFromCombo.getSelectedItem().toString();
tripLabel.setText("Selected Age From JComboBox is : " + str);
}
}
});
tripLabel.setPreferredSize(new Dimension(400, 30));
f = new JFrame("ComboBox ItemListeners");
f.setLayout(new GridLayout(0, 1, 15, 15));
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(flyFromCombo);
f.add(tripLabel);
f.setLocation(150, 150);
f.pack();
f.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
ComboBoxListeners comboBoxListeners = new ComboBoxListeners();
}
});
}
}
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/** @see https://stackoverflow.com/a/9440487/230513 */
public class ComboBoxListener {
private JFrame f = new JFrame("ComboBox ItemListener");
private JPanel panel = new JPanel();
private JComboBox<Integer> combo;
private JLabel label = new JLabel("Please select a number from above.");
public ComboBoxListener() {
DefaultComboBoxModel<Integer> model = new DefaultComboBoxModel<>();
for (int i = 1; i <= 100; ++i) {
model.addElement(i);
}
combo = new JComboBox<>(model);
combo.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
if ((e.getStateChange() == ItemEvent.SELECTED)) {
Integer result = (Integer) combo.getSelectedItem();
label.setText(result.toString());
}
}
});
f = new JFrame("ComboBox ItemListener");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel.setLayout(new GridLayout(0, 1, 5, 5));
panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
panel.add(combo);
panel.add(label);
f.add(panel);
f.setLocationByPlatform(true);
f.pack();
f.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
ComboBoxListener cbl = new ComboBoxListener();
}
});
}
}