基于组合框选项显示JLabel
如何根据组合框选项显示JLabel。当我运行代码时，所有的JLabel都会立即显示出来。
combo1.addActionListener(this);
panel.add(combo1);
panel.add(img1);
panel.add(img2);
panel.add(img3);
frame.add(panel);
img1.setText("<html> Image : <a href="">Image1/</a></html>");
img2.setText("<html> Image : <a href="">Image2/</a></html>");
img3.setText("<html> Image : <a href="">Image3/</a></html>");
img1.setCursor(new Cursor(Cursor.HAND_CURSOR));
img2.setCursor(new Cursor(Cursor.HAND_CURSOR));
img3.setCursor(new Cursor(Cursor.HAND_CURSOR));
我使用MouseListener检查哪个标签被传递给goWebsite()函数，然后根据该标签添加一个超链接。
private void goWebsite(final JLabel website) {
website.addMouseListener(new MouseAdapter() {
@Override
public void mouseClicked(MouseEvent e) {
if(website == img1){
try {
Desktop.getDesktop().browse(new URI("http://2.bp.blogspot.com/_2dxp9ORKKAM/TBZpViy7O1I/AAAAAAAABGY/zitq3ZLA8K4/s1600/red.png"));
} catch (URISyntaxException | IOException ex) {
//It looks like there's a problem
}
}
if(website == img2){
try {
Desktop.getDesktop().browse(new URI("http://www.pratikbagaria.com/wp-content/uploads/2011/04/BlueGreenPink.jpg"));
} catch (URISyntaxException | IOException ex) {
//It looks like there's a problem
}
}
if(website == img3){
try {
Desktop.getDesktop().browse(new URI("http://i.imgur.com/9OPnZNk.png"));
} catch (URISyntaxException | IOException ex) {
//It looks like there's a problem
}
}
if(website == img4){
try {
Desktop.getDesktop().browse(new URI("http://www.solidbackgrounds.com/images/three/2048x2048/2048x2048-fluorescent-orange-fluorescent-pink-fluorescent-yellow-three-color-background.jpg"));
} catch (URISyntaxException | IOException ex) {
//It looks like there's a problem
}
}
操作执行检查用户从组合框中选择了哪个选项，然后将正确的img JLabel传递给goWebsite()函数。
@Override
public void actionPerformed(ActionEvent e)
{
String color1 = (String)combo1.getSelectedItem();
// Possibly check if either color is 'null' here
if (color1.equals("red") )
{
goWebsite(img1);
}
if (color1.equals("blue") )
{
goWebsite(img2);
}
if (color1.equals("green") )
{
goWebsite(img3);
}
}
解决方案
尝试将ItemListener添加到JComboBox，在调用itemStateChanged时，检查ItemEvent#getStateChanged是否等于ItemEvent.SELECTED。
选中组合框中选定的内容(或使用ItemEvent#ItemSelected)，然后使用所需信息更新单个JLabel或使用JLabel#setVisible(true)使与所选项目关联的当前标签可见，但也确保隐藏其他标签
例如...
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class ComboBoxUpdate {
public static void main(String[] args) {
new ComboBoxUpdate();
}
public ComboBoxUpdate() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private JComboBox comboBox;
private JLabel option1;
private JLabel option2;
private JLabel option3;
public TestPane() {
comboBox = new JComboBox(new String[]{"Choice 1", "Choice 2", "Choice 3"});
option1 = new JLabel("Bananas");
option2 = new JLabel("Appels");
option3 = new JLabel("Grapes");
option1.setVisible(false);
option2.setVisible(false);
option3.setVisible(false);
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = GridBagConstraints.REMAINDER;
add(comboBox, gbc);
add(option1, gbc);
add(option2, gbc);
add(option3, gbc);
comboBox.addItemListener(new ItemListener() {
@Override
public void itemStateChanged(ItemEvent e) {
switch (e.getStateChange()) {
case ItemEvent.SELECTED:
Object value = comboBox.getSelectedItem();
option1.setVisible(false);
option2.setVisible(false);
option3.setVisible(false);
if ("Choice 1".equals(value)) {
option1.setVisible(true);
} else if ("Choice 2".equals(value)) {
option2.setVisible(true);
} else if ("Choice 3".equals(value)) {
option3.setVisible(true);
}
break;
}
}
});
comboBox.setSelectedItem(null);
}
}
}
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