使用javax.swing，我创建了一个显示列表的窗口。
此列表有两个按钮，允许删除或添加列表中显示的商店项目。商店商品存储在文件中。
我想在单击这些按钮时使用该列表，列表会通过列出其指定目录中的所有文件来更新自身（我需要这个方法而不是直接使用model.remove（）直接修改列表。）
但是，当我执行model = new DefaultListModel()时，列表根本不会自行更新。
下面是显示商店项目列表的面板代码。
public class ShopWindowPanel extends JPanel
{
private UserInterface window;
private JList<String> jList;
private DefaultListModel<String> model;
private JButton addButton;
private JButton deleteButton;
private ArrayList<ShopItem> arrayList;
private JScrollPane jScrollPane;
/**
* Constructor method.
* @param window The window linked to the shop window panel. It is used for error pop-ups.
*/
public ShopWindowPanel(UserInterface window) {
this.window = window;
initializePanel();
}
/**
* This method initializes the panel.
*/
public void initializePanel()
{
initializeButtons();
initializeScrollPane();
add(jScrollPane);
//setting up the layout of the panel
GroupLayout gl = new GroupLayout(this);
this.setLayout(gl);
gl.setAutoCreateContainerGaps(true);
gl.setAutoCreateGaps(true);
gl.setHorizontalGroup(gl.createParallelGroup(CENTER)
.addComponent(jScrollPane)
.addGroup(gl.createParallelGroup()
.addComponent(addButton)
.addComponent(deleteButton)
));
gl.setVerticalGroup(gl.createSequentialGroup()
.addComponent(jScrollPane)
.addGroup(gl.createSequentialGroup()
.addComponent(addButton)
.addComponent(deleteButton)
));
gl.linkSize(addButton, deleteButton);
window.pack();
}
/**
* This method initializes the buttons.
*/
public void initializeButtons() {
addButton = new JButton("Add");
deleteButton = new JButton("Delete");
addButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
String text = JOptionPane.showInputDialog("Add a new item and its price in pound (item name, price");
try
{
String[] itemDetails = text.split(", ");
ShopItem shopItemToAdd = new ShopItem();
shopItemToAdd.setName(itemDetails[0]);
shopItemToAdd.setPrice(Integer.parseInt(itemDetails[1]));
shopItemToAdd.save(); //create a new file
initializeScrollPane(); //supposed to update the scroll pane
}
catch(Exception exception)
{
JOptionPane.showMessageDialog(window.getContentPane(), "An error has happened!" + exception.getClass() + ": " + exception.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
}
}
});
deleteButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent event) {
ListSelectionModel selmodel = jList.getSelectionModel();
int index = selmodel.getMinSelectionIndex();
if (index >= 0) {
arrayList.get(index).delete(); //delete the file
initializeScrollPane(); //supposed to update the scroll pane
}
}
});
}
/**
* This method initializes the list of the items.
*/
public void initializeScrollPane() {
//listing all shop items
model = new DefaultListModel<String>();
File shopItemFileFolder = new File(ShopItem.shopItemsFolder);
File[] shopItemsFiles = shopItemFileFolder.listFiles();
arrayList = new ArrayList<ShopItem>();
for(int i = 0; i<shopItemsFiles.length; i++)
{
try
{
ShopItem currentlyProcessedShopItem = new ShopItem();
currentlyProcessedShopItem.load(shopItemsFiles[i].getName());
model.addElement(currentlyProcessedShopItem.getName() + ": £" + (float) currentlyProcessedShopItem.getPrice()/100);
arrayList.add(currentlyProcessedShopItem);
}
catch(Exception e)
{
System.err.println("A problem has happened with an item.");
}
}
jList = new JList<>(model);
jList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
jScrollPane = new JScrollPane(jList);
}
}
答案 0 :(得分：1)
创建一个单独的方法，它不仅仅生成ListModel ...
public ListModel<String> initializeListModel() {
//listing all shop items
model = new DefaultListModel<String>();
File shopItemFileFolder = new File(ShopItem.shopItemsFolder);
File[] shopItemsFiles = shopItemFileFolder.listFiles();
arrayList = new ArrayList<ShopItem>();
for (int i = 0; i < shopItemsFiles.length; i++) {
try {
ShopItem currentlyProcessedShopItem = new ShopItem();
currentlyProcessedShopItem.load(shopItemsFiles[i].getName());
model.addElement(currentlyProcessedShopItem.getName() + ": £" + (float) currentlyProcessedShopItem.getPrice() / 100);
arrayList.add(currentlyProcessedShopItem);
} catch (Exception e) {
System.err.println("A problem has happened with an item.");
}
}
return model;
}
public void initializeScrollPane() {
jList = new JList<>(model);
jList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
jScrollPane = new JScrollPane(jList);
}
然后在按钮的ActionListener中，调用此方法并将结果应用到JList ...
addButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
String text = JOptionPane.showInputDialog("Add a new item and its price in pound (item name, price");
try {
String[] itemDetails = text.split(", ");
shopItemToAdd.setName(itemDetails[0]);
shopItemToAdd.setPrice(Integer.parseInt(itemDetails[1]));
shopItemToAdd.save(); //create a new file
jList.setModel(initializeListModel());
} catch (Exception exception) {
JOptionPane.showMessageDialog(ShopWindowPanel.this, "An error has happened!" + exception.getClass() + ": " + exception.getMessage(), "Error", JOptionPane.ERROR_MESSAGE);
}
}
});
deleteButton.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent event) {
ListSelectionModel selmodel = jList.getSelectionModel();
int index = selmodel.getMinSelectionIndex();
if (index >= 0) {
jList.setModel(initializeListModel());
}
}
});
答案 1 :(得分：0)
看起来要更新滚动条，我们必须跟踪模型字段，而不是重新初始化它。因此，我们必须使用相同的模型对象及其方法。一种解决方案可能是：
/**
* This method initializes the list of the items.
*/
public void initializeModel() {
try
{
model.removeAllElements();
}
catch(NullPointerException exception)
{
//putting store items in the field model
model = new DefaultListModel<String>();
}
try
{
ShopWindow.update();
}
catch(Exception e)
{
JOptionPane.showMessageDialog(window, "Problem updating the list of shop items!", "Error", JOptionPane.ERROR_MESSAGE);
System.exit(0);
}
for(int i = 0; i<ShopWindow.getList().size(); i++)
{
try
{
model.addElement(ShopWindow.getItem(i).getName() + ": £" + (float) ShopWindow.getItem(i).getPrice()/100);
}
catch(Exception e)
{
System.err.println("A problem has happened with an item.");
}
}
}
/**
* Initialize the scroll pane.
*/
public void initializeScrollPane()
{
initializeModel();
jList = new JList<String>(model);
jList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
jScrollPane = new JScrollPane(jList);
}