我需要显示带有名为Item的自定义JPanel组件的JList。这些组件具有唯一的标识name。它们可以动态添加到JList中，也可以更新(如果已经存在)。我尝试以下实现，但它只会生成一个空的JList。请指教。

class Item extends JPanel {

JLabel name = new JLabel(" ");

JLabel col1 = new JLabel(" ");

JLabel col2 = new JLabel(" ");

Item(){

setMinimumSize(new Dimension(100, 20));

setLayout(new BorderLayout());

add(name, BorderLayout.WEST);

add(col1, BorderLayout.CENTER);

add(col2, BorderLayout.EAST);

}

}

public class Test_List extends JFrame {

private final JList list = new JList(new Item[0]);

HashMap map = new HashMap();

Test_List(){

setTitle("Test JList");

setLayout(new BorderLayout());

add(new JScrollPane(list), BorderLayout.CENTER);

pack();

}

public void update_item(String name, String s1, String s2){

Item item = map.get(name);

if (item == null){ // add new

item = new Item();

item.name.setText(name);

map.put(name, item);

list.add(item);

}

item.col1.setText(s1);

item.col2.setText(s2);

}

public static void main(String s[]) {

final Test_List frame = new Test_List();

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

SwingUtilities.invokeLater(new Runnable() {

@Override

public void run() {

frame.setVisible(true);

}

});

frame.update_item("A", "a", "aa"); // add new item

frame.update_item("B", "b", "bb"); // add new item

frame.update_item("A", "aa", "a"); // update existing item

}

}

参考方案

模型负责对数据建模，因为它永远不应该包含UI特定的信息，因为模型不关心显示方式，它负责转换数据，因此可以确认是否符合视图/模型协定ListModel合同。

首先看一下Writing a Custom Cell Renderer

import java.awt.BorderLayout;

import java.awt.Color;

import java.awt.Component;

import java.awt.Dimension;

import java.awt.EventQueue;

import javax.swing.DefaultListModel;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JList;

import javax.swing.JPanel;

import javax.swing.JScrollPane;

import javax.swing.ListCellRenderer;

import javax.swing.UIManager;

import javax.swing.UnsupportedLookAndFeelException;

import javax.swing.border.Border;

import javax.swing.border.EmptyBorder;

public class TestListCellRenderer {

public static void main(String[] args) {

new TestListCellRenderer();

}

public TestListCellRenderer() {

EventQueue.invokeLater(new Runnable() {

@Override

public void run() {

try {

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {

ex.printStackTrace();

}

DefaultListModel model = new DefaultListModel();

model.addElement(new Item("A", "a", "aa"));

model.addElement(new Item("B", "b", "bb"));

model.addElement(new Item("C", "c", "cc"));

model.addElement(new Item("D", "d", "dd"));

JList list = new JList(model);

list.setCellRenderer(new ItemCellRenderer());

JFrame frame = new JFrame("Testing");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.add(new JScrollPane(list));

frame.pack();

frame.setLocationRelativeTo(null);

frame.setVisible(true);

}

});

}

public static class Item {

private String name;

private String col1;

private String col2;

public Item(String name, String col1, String col2) {

this.name = name;

this.col1 = col1;

this.col2 = col2;

}

public String getCol1() {

return col1;

}

public String getCol2() {

return col2;

}

public String getName() {

return name;

}

}

public static class ItemCellRenderer extends JPanel implements ListCellRenderer{

private static final Border SAFE_NO_FOCUS_BORDER = new EmptyBorder(1, 1, 1, 1);

private static final Border DEFAULT_NO_FOCUS_BORDER = new EmptyBorder(1, 1, 1, 1);

protected static Border noFocusBorder = DEFAULT_NO_FOCUS_BORDER;

JLabel name = new JLabel(" ");

JLabel col1 = new JLabel(" ");

JLabel col2 = new JLabel(" ");

public ItemCellRenderer() {

setLayout(new BorderLayout());

add(name, BorderLayout.WEST);

add(col1, BorderLayout.CENTER);

add(col2, BorderLayout.EAST);

}

@Override

public Dimension getMinimumSize() {

return new Dimension(100, 20);

}

@Override

public Dimension getPreferredSize() {

return getMinimumSize();

}

protected Border getNoFocusBorder() {

Border border = UIManager.getBorder("List.cellNoFocusBorder");

if (System.getSecurityManager() != null) {

if (border != null) return border;

return SAFE_NO_FOCUS_BORDER;

} else {

if (border != null &&

(noFocusBorder == null ||

noFocusBorder == DEFAULT_NO_FOCUS_BORDER)) {

return border;

}

return noFocusBorder;

}

}

@Override

public Component getListCellRendererComponent(JList extends Item> list, Item value, int index, boolean isSelected, boolean cellHasFocus) {

setComponentOrientation(list.getComponentOrientation());

Color bg = null;

Color fg = null;

JList.DropLocation dropLocation = list.getDropLocation();

if (dropLocation != null

&& !dropLocation.isInsert()

&& dropLocation.getIndex() == index) {

bg = UIManager.getColor("List.dropCellBackground");

fg = UIManager.getColor("List.dropCellForeground");

isSelected = true;

}

if (isSelected) {

setBackground(bg == null ? list.getSelectionBackground() : bg);

setForeground(fg == null ? list.getSelectionForeground() : fg);

} else {

setBackground(list.getBackground());

setForeground(list.getForeground());

}

name.setText(value.getName());

col1.setText(value.getCol1());

col2.setText(value.getCol2());

name.setForeground(getForeground());

col1.setForeground(getForeground());

col2.setForeground(getForeground());

setEnabled(list.isEnabled());

name.setFont(list.getFont());

col1.setFont(list.getFont());

col2.setFont(list.getFont());

Border border = null;

if (cellHasFocus) {

if (isSelected) {

border = UIManager.getBorder("List.focusSelectedCellHighlightBorder");

}

if (border == null) {

border = UIManager.getBorder("List.focusCellHighlightBorder");

}

} else {

border = getNoFocusBorder();

}

setBorder(border);

return this;

}

}

}

说了这么多，我认为使用JTable会更好，请参见How to Use Tables

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