无法向JList添加复选框

我是编程的新手，我无法将JCheckbox添加到JList 。 没有错误但没有显示任何内容。

 JFrame f=new JFrame(); String[] labels={"a","b","c","d","e"}; JCheckBox[] ch=new JCheckBox[labels.length]; JList list=new JList(); for (int i = 0; i < labels.length; i++) { ch[i]=new JCheckBox("CheckBox"+i); list.add(ch[i]); } JScrollPane pane=new JScrollPane(list); f.add(pane); f.setVisible(true); 

Answer 1

JList渲染器可以绘制复选框，但JList不支持单元格编辑器。 相反，考虑一列JTable 。 例如 ， Boolean.class类型的列的默认渲染器和编辑器是JCheckBox 。

Answer 2

作为trashgod发布的JTable解决方案的替代方案，您还可以通过以下方式在JList中创建JCheckBoxes的外观：

1. 为JList使用自定义渲染器，将每个项目显示为JCheckBox
2. 在JList中使用自定义对象来维护它的布尔“已检查”状态
3. 将一个MouseListener添加到JList，它将设置/取消设置每个项目的已检查状态。

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 import java.awt.*; import java.awt.event.*; import javax.swing.*; import javax.swing.border.*; public class JCheckBoxListDemo implements Runnable { private JList jlist; public static void main(String args[]) { SwingUtilities.invokeLater(new JCheckBoxListDemo()); } public void run() { Object[] items = new CheckListItem[] { new CheckListItem("Apple"), new CheckListItem("Banana"), new CheckListItem("Carrot"), new CheckListItem("Date"), new CheckListItem("Eggplant"), new CheckListItem("Fig"), new CheckListItem("Guava"), }; jlist = new JList(items); jlist.setCellRenderer(new CheckBoxListRenderer()); jlist.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); jlist.setVisibleRowCount(5); jlist.addMouseListener(new MouseAdapter() { @Override public void mouseClicked(MouseEvent event) { selectItem(event.getPoint()); } }); KeyStroke keyStroke = KeyStroke.getKeyStroke(KeyEvent.VK_SPACE, 0); Object mapKey = keyStroke.toString(); jlist.getInputMap().put(keyStroke, mapKey); jlist.getActionMap().put(mapKey, new AbstractAction() { public void actionPerformed(ActionEvent event) { toggleSelectedItem(); } }); JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.getContentPane().add(new JScrollPane(jlist)); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } private void selectItem(Point point) { int index = jlist.locationToIndex(point); if (index >= 0) { CheckListItem item = (CheckListItem)jlist.getModel().getElementAt(index); item.setSelected(!item.isSelected()); jlist.repaint(jlist.getCellBounds(index, index)); } } private void toggleSelectedItem() { int index = jlist.getSelectedIndex(); if (index >= 0) { CheckListItem item = (CheckListItem)jlist.getModel().getElementAt(index); item.setSelected(!item.isSelected()); jlist.repaint(jlist.getCellBounds(index, index)); } } private class CheckListItem { private Object item; private boolean selected; public CheckListItem(Object item) { this.item = item; } @SuppressWarnings("unused") public Object getItem() { return item; } public boolean isSelected() { return selected; } public void setSelected(boolean isSelected) { this.selected = isSelected; } @Override public String toString() { return item.toString(); } } private class CheckBoxListRenderer extends JCheckBox implements ListCellRenderer { public Component getListCellRendererComponent(JList comp, Object value, int index, boolean isSelected, boolean hasFocus) { setEnabled(comp.isEnabled()); setSelected(((CheckListItem) value).isSelected()); setFont(comp.getFont()); setText(value.toString()); if (isSelected) { setBackground(comp.getSelectionBackground()); setForeground(comp.getSelectionForeground()); } else { setBackground(comp.getBackground()); setForeground(comp.getForeground()); } return this; } } } 

Answer 3

您可能正在寻找以下内容：

 import javax.swing.*; import java.awt.*; import java.awt.event.*; class CheckBo { public static void main(String[] args) { JFrame f=new JFrame(); String[]labels={"a","b","c","d","e"}; JCheckBox[]ch=new JCheckBox[labels.length]; final DefaultListModel model = new DefaultListModel(); JList list=new JList(model); list.setCellRenderer(new CheckListRenderer()); for (int i = 0; i < labels.length; i++) { //ch[i]=new JCheckBox("CheckBox"+i); model.addElement(new CheckListItem("CheckBox"+i)); } JScrollPane pane=new JScrollPane(list); list.addMouseListener(new MouseAdapter() { public void mouseClicked(MouseEvent event) { JList list = (JList) event.getSource(); // Get index of item clicked int index = list.locationToIndex(event.getPoint()); CheckListItem item = (CheckListItem) list.getModel().getElementAt(index); // Toggle selected state item.setSelected(! item.isSelected()); // Repaint cell list.repaint(list.getCellBounds(index, index)); } }); f.add(pane); f.pack(); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); f.setVisible(true); } static class CheckListItem { private String label; private boolean isSelected = false; public CheckListItem(String label) { this.label = label; } public boolean isSelected() { return isSelected; } public void setSelected(boolean isSelected) { this.isSelected = isSelected; } public String toString() { return label; } } static class CheckListRenderer extends JCheckBox implements ListCellRenderer { public Component getListCellRendererComponent(JList list, Object value, int index,boolean isSelected, boolean hasFocus) { setEnabled(list.isEnabled()); setSelected(((CheckListItem)value).isSelected()); setFont(list.getFont()); setBackground(list.getBackground()); setForeground(list.getForeground()); setText(value.toString()); return this; } } } 

以上代码的来源是这个

Answer 4

查看此链接 ，它将为您提供所需的信息。

另外，我建议使用JTable而不是JList。 Sun 在这里有很多例子。