>我创建了一个 JComboBox 的 ArrayList
private static ArrayList<JComboBox> comboList = new ArrayList<>();
然后将每个JComboBox
实例添加到ArrayList
private void courseUnit() {
String[] units = {"6", "5", "4", "3", "2", "1"};
int x = 520, y = 30;
for (int i = 0; i < 10; i++) {
comboUnits = new JComboBox<>(units);
comboUnits.setBounds(x, y, 100, 25);
y += 30;
comboUnits.setToolTipText("Select course unit");
comboUnits.setVisible(true);
comboUnits.addActionListener(new PaneAction());
add(comboUnits);
comboList.add(comboUnits); //comboUnits added to ArrayList
}
}
我的问题是,我如何从 ArrayList 中的每个组合框中获取选定的项,因为我尝试过这个
//this is supposed to get the selected item of the first ComboBox and assign to courseGrade[0]
public void actionPerformed(ActionEvent evt) {
String[] courseGrade = new String[10];
courseGrade[0] = (String)comboList.get(0).getSelectedItem();
并且程序没有编译。
您可以在将
JComboBox
添加到ArrayList
时附加ActionListner
private void courseUnit() {
String[] units = {"6", "5", "4", "3", "2", "1"};
int x = 520, y = 30;
for (int i = 0; i < 10; i++) {
comboUnits = new JComboBox<>(units);
comboUnits.setBounds(x, y, 100, 25);
y += 30;
comboUnits.setToolTipText("Select course unit");
comboUnits.setVisible(true);
//comboUnits.addActionListener(new PaneAction());
add(comboUnits);
//////////////// Here are the changes
comboUnits.addActionListener (new ActionListener () {
public void actionPerformed(ActionEvent e) {
String selectedItem = (String)e.getSelectedItem();
}
});
comboList.add(comboUnits); //comboUnits added to ArrayList
}
}
我终于明白了。我必须将 ArrayList 创建为静态实例变量
private static ArrayList<JComboBox> comboList;
然后在构造函数中实例化它
comboList = new ArrayList<>();
新的 courseUnit() 方法现在看起来像这样
private void courseUnit() {
String[] units = {"6", "5", "4", "3", "2", "1"};
int x = 520, y = 30;
for (int i = 0; i < 10; i++) {
comboUnits = new JComboBox<>(units);
comboUnits.setBounds(x, y, 100, 25);
comboUnits.setToolTipText("Select course unit");
y += 30;
comboUnits.setVisible(true);
add(comboUnits);
//I added ActionListener to each comboBox in the ArrayList,
//thanks to Junaid for this
comboUnits.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent evt){
ArrayList<String> courseGrade = new ArrayList<>();
JComboBox comboBox = (JComboBox) evt.getSource();
courseGrade.add((String) comboBox.getSelectedItem());
}
});
comboList.add(comboUnits);
}//end of loop
} //end of method