[英]getSelectedIndex() for JList always return -1 eventhough an item is selected
http://prntscr.com/9jhrwa “ GUI的外观”
公共类Okno1扩展了javax.swing.JFrame {
static Konto[]konto;
static DefaultListModel listModel;
static int indexKonta;
public Okno1() {
initComponents();
napolniKonto();
jScrollPane1.setVisible(false);
button_potrdiKonto.setVisible(false);
}
在这里,我用对象填充数组并将其添加到DefaultListModel,同时使用上述DefaultListModel创建一个新列表
listModel=new DefaultListModel();
list_konto.setModel(listModel);
konto=new Konto[4];
konto[0]=new Konto("10000/20000", "Test konto primer1");
konto[1]=new Konto("20000/30000", "Test konto primer2");
konto[2]=new Konto("50000/60000", "Test konto primer3");
konto[3]=new Konto("30000/50000", "Test konto primer4");
for (int i = 0; i < konto.length; i++) {
listModel.addElement(konto[i].getID()+" | "+konto[i].getOpis());
}
list_konto=new JList(listModel);
jScrollPane1.repaint();
}
在这里,我显示了按下此按钮时的jScrollPanel,还显示了如果要获取显示的JList中选定元素的索引必须按下的按钮
private void button_prikaziKontoActionPerformed(java.awt.event.ActionEvent evt) {
jScrollPane1.setVisible(true);
button_potrdiKonto.setVisible(true);
//revalidate();
//repaint();
}
在这里,我按下一个按钮,它应该使我获得所选项目的索引,但是它一直给我-1,并且是否选择了JList上的项目并不重要
private void button_potrdiKontoActionPerformed(java.awt.event.ActionEvent evt) {
//indexKonta=list_konto.getSelectedIndex();
text_opisKonta.setText(Integer.toString(list_konto.getSelectedIndex()));
}
目前尚不清楚您的代码在哪里出错。 此竞争示例可以让您单独研究问题。 还可以考虑添加ListSelectionListener
来查看效果。
myList.addListSelectionListener((ListSelectionEvent e) -> {
myLabel.setText(getSelectionIndex());
});
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.event.ListSelectionEvent;
/** @see http://stackoverflow.com/a/34497773/230513 */
public class Test extends JPanel {
private final String[] values = {"Value1", "Value2", "Value3", "Value4"};
private final JList myList = new JList(values);
private final JLabel myLabel = new JLabel();
public Test() {
myList.setSelectedIndex(values.length - 1);
myLabel.setText(getSelectionIndex());
this.add(myList);
this.add(myLabel);
this.add(new JButton(new AbstractAction("Show Selected Index") {
@Override
public void actionPerformed(ActionEvent e) {
myLabel.setText(getSelectionIndex());
}
}));
}
private String getSelectionIndex() {
return String.valueOf(myList.getSelectedIndex());
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(new Test());
f.pack();
f.setLocationByPlatform(true);
f.setVisible(true);
});
}
}
不要使用静态变量
始终测试if (list.getSelectedIndex() > -1) {
使用ListSelectionListener为JList中 ,通过总是检验if (list.getSelectedIndex() > -1) {
例如(不使用ListSelectionListener)
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JScrollPane;
public class JListAndSelection {
private JFrame frame = new JFrame();
private DefaultListModel listModel = new DefaultListModel();
private JList list = new JList(listModel);
private JScrollPane scrollPane = new JScrollPane(list);
private JLabel label = new JLabel("nothing is selected");
private JButton button1 = new JButton("print me selected value");
public JListAndSelection() {
button1.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent ae) {
if (list.getSelectedIndex() > -1) {
label.setText((String) list.getSelectedValue());
} else {
label.setText("nothing is selected");
}
}
});
listModel.addElement("10000/20000 - Test konto primer1");
listModel.addElement("20000/30000 - Test konto primer2");
listModel.addElement("50000/60000 - Test konto primer3");
listModel.addElement("30000/50000 - Test konto primer4");
list.setVisibleRowCount(5);
frame.setTitle("JFrame");
frame.add(label, BorderLayout.NORTH);
frame.add(scrollPane, BorderLayout.CENTER);
frame.add(button1, BorderLayout.SOUTH);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.pack();
frame.setLocation(150, 150);
frame.setVisible(true);
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> {
new JListAndSelection();
});
}
}
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