如何动态更改 JComboBox 中的项目数

Question

private void dropDownMenu(JPanel jp1, String prodId){
    int len = storeManager.getInv().getStockAmount(prodId);
    int[] nums = new int[len];
    String[] numPossible = new String[len];

    for (int i=0; i<len; i++){
        nums[i] = i+1;
    }
    for (int i=0; i<len; i++){
        numPossible[i] = String.valueOf(nums[i]);
    }
    JComboBox<String> cb = new JComboBox<String>(numPossible);
    JButton okButton = new JButton("Add To Cart");
    okButton.addActionListener(new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            Product p1 = storeManager.getInv().getProd(prodId);
            String quan = (String) cb.getSelectedItem();
            int quantity = Integer.parseInt(quan);
            if (quantity > storeManager.getInv().getStockAmount(prodId)) {
                System.out.println("Not Enough Stock.");
            } else {
                storeManager.getCart().addToCart(p1, quantity);
                storeManager.getInv().removeStockAmount(prodId, quantity);
                //update the dropdown menu here
            }
        }
    });
    jp1.add(cb);
    jp1.add(okButton);
}

基本上我正在寻找的是，每当我从下拉菜单中 select 一个数字时，我希望菜单中的项目数量减少添加到购物车的数量。例如，如果我将 5 添加到购物车，那么我希望下拉菜单从只允许我选择 10 到 5。 Image of GUI

Answer 1

作为一个想法...与其进行所有这些从整数到字符串以及从字符串到整数的转换以填充您的组合框，为什么不只使用一个整数组合框？无论如何，您最初处理的是整数值：

JComboBox<Integer> cb = new JComboBox<>();
int len = storeManager.getInv().getStockAmount(prodId);
for (int i = 1; i <= len; i++) {
   cb.addItem(i);
}
cb.setSelectedIndex(0);

您的动作侦听器现在可能看起来像这样：

okButton.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        Product p1 = storeManager.getInv().getProd(prodId);
        int quantity = (int) cb.getSelectedItem();
        /* This 'if' statement below would be moot if the Combo-Box 
           is properly updated unless editing is allowed in the combo
           which in this case...disable that feature.     */
        if (quantity > storeManager.getInv().getStockAmount(prodId)) {
            System.out.println("Not Enough Stock.");
        } else {
            storeManager.getCart().addToCart(p1, quantity);
            len = storeManager.getInv().removeStockAmount(prodId, quantity);
            cb.removeAllItems();
            for (int i = 1; i <= len; i++) { cb.addItem(i); }
            cb.setSelectedIndex(0); 
        }
    }
});

可能更好的方法是使用 JSpinner 组件而不是组合框。在我看来，这个用例中的下拉列表总是显得有点突兀。

如何动态更改 JComboBox 中的项目数

How can I dynamically change the number of items in a JComboBox

java

user-interface

swing

jframe

jcombobox