新来java和我无法看到为什么我的动作侦听器不工作的jcombobox。我想我已经跟着网上的其他例子getSelectedItem,但没有发生。 仅供参考,我的项目是一个单位转换器(使用MVC ..喜欢,但这不是我的优先事项)。 任何援助非常感谢。 谢谢,西蒙。JComboBox getSelectedItem
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class UnitConverterView extends JFrame{
//variables and components
private static final long serialVersionUID = -4673040337179571462L;
private JComboBox<String> unitCategory;
private JTextField fromValue = new JTextField(7);
private JComboBox<String> convertFrom;
private JLabel equalsLabel = new JLabel(" = ");
private JTextField toValue = new JTextField(7);
private JComboBox<String> convertTo;
//constructor
UnitConverterView(){
//set up the view and components
JPanel unitPanel = new JPanel();
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(600,300);
String[] categories = {"Length","Weight","Speed","Temperature"};
unitCategory = new JComboBox<>(categories);
String[] tofromValues = {" "};
convertFrom = new JComboBox<>(tofromValues);
convertTo = new JComboBox<>(tofromValues);
unitPanel.add(unitCategory);
unitPanel.add(fromValue);
unitPanel.add(convertFrom);
unitPanel.add(equalsLabel);
unitPanel.add(toValue);
unitPanel.add(convertTo);
this.add(unitPanel);
}
//get value to convert from
public int getMeasurement() {
return Integer.parseInt(fromValue.getText());
}
//listen for unitCategory to be selected
void addUnitCategoryListener(ActionListener listenForUnitCategory) {
unitCategory.addActionListener(listenForUnitCategory);
}
class UnitCatListener implements ActionListener {
public void actionPerformed(ActionEvent e) {
/*String unitSelected = (String) unitCategory.getSelectedItem();
if (e.getSource() == unitCategory) {
String unitName = (String) unitCategory.getSelectedItem();
System.out.println("UnitName = " + unitName);
changeText(unitName);
}*/
JComboBox cb = (JComboBox)e.getSource();
String unitName = (String) cb.getSelectedItem();
System.out.println("UnitName = " + unitName);
}
void changeText(String name) {
toValue.setText(name);
}
}
}
据我可以告诉你,永远不要添加监听器。你需要调用'unitCategory.addActionListener(new UnitCatListener())'。 – WillShackleford
感谢您的协助。 –