Question

您好我正在尝试获取数组中复选框列表的所有选中项目索引。但显然方法是getCheckBoxListSelectedIndices（）;正在返回一个空数组

package cct.karim;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import com.jidesoft.swing.CheckBoxList;
import javax.swing.DefaultListModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.border.EtchedBorder;
import javax.swing.border.TitledBorder;

/**
 *
 * @author beastieux
 */

public class E_JCheckListBox extends JFrame implements ActionListener {
    protected JLabel loglabel;
    private CheckBoxList List; 
    public E_JCheckListBox()
    {
        super("Select RFQs to Export");

        loglabel=new JLabel("Log:                                   .");
        List=new CheckBoxList();
        CheckBoxList List = new CheckBoxList();
        JScrollPane scp=new JScrollPane();

        DefaultListModel lmdlEjemplo=new DefaultListModel();

        lmdlEjemplo.addElement("  Item 0  ");
        lmdlEjemplo.addElement("  Item 1  ");
        lmdlEjemplo.addElement("  Item 2  ");
        lmdlEjemplo.addElement("  Item 3  ");
        lmdlEjemplo.addElement("  Item 4  ");
        lmdlEjemplo.addElement("  Item 5  ");
        lmdlEjemplo.addElement("  Item 6  ");
        lmdlEjemplo.addElement("  Item 7  ");
        lmdlEjemplo.addElement("  Item 8  ");
        lmdlEjemplo.addElement("  Item 9  ");

        List.setModel(lmdlEjemplo);

        scp.add(List);
        this.add(scp);

        scp.getViewport().add(List);

        getContentPane().setLayout(new FlowLayout());
        this.setSize(300, 300);
        scp.setSize(300, 350);

        JPanel p = new JPanel();
        p.setSize(500, 500);
        p.setLayout(new BorderLayout());
        p.add(scp, BorderLayout.CENTER);
        p.add(loglabel, BorderLayout.SOUTH);
        p.setBorder(new TitledBorder(new EtchedBorder(),
        "Please select options:") );

        getContentPane().add(p);
        JButton k= new JButton("Export");
        k.addActionListener(this);

        k.setMaximumSize(new Dimension(1, 1));
        add(k);
    //  pack();
        setVisible(true);
        setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
    }

    public static void main(String args[]) {
        E_JCheckListBox obj = new E_JCheckListBox();
        obj.setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent arg0) {
        // TODO Auto-generated method stub
        int k[]=List.getCheckBoxListSelectedIndices();
        System.out.println(k[0]);
    }
}

这是我得到的例外：

Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 0 
at cct.karim.E_JCheckListBox.actionPerformed(E_JCheckListBox.java:92)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

我错过了什么，因为我不熟悉GUI编程吗？

Answer 1

问题似乎很简单。实例变量和方法变量的名称相同。 List被声明为实例变量并在ActionListner中使用，但是同样用于创建局部变量，因此本地在构造函数中具有首选项。

下面的错误代码应该正常工作。

private CheckBoxList List; 
        public E_JCheckListBox()
        {
            super("Select RFQs to Export");

            loglabel=new JLabel("Log:                                   .");
            List=new CheckBoxList();
//            CheckBoxList List = new CheckBoxList();
            JScrollPane scp=new JScrollPane();

另外，请在访问元素之前添加数组中的长度检查。在Java中，强烈检查数组索引。

获取JCheckListBox的所有选中项索引

1 个答案: