为什么这只适用于设计的 comboBox 而不是硬编码的 swing？
Why does this only work on designed comboBox and not on hardcoded swing?
新手问题：
所以这段代码在这里
public void comboItemItemStateChanged(java.awt.event.ItemEvent evt) {
ArrayList<String> arrayItem = new ArrayList<>();
Iterator<String> iter;
if(comboGroup.getSelectedItem().equals("Betta Fish")){
comboItem.removeAllItems();
arrayItem.add("Plakat");
arrayItem.add("Halfmoon");
arrayItem.add("Crown Tail");
arrayItem.add("Double Tail");
iter = arrayItem.iterator();
while(iter.hasNext()){
comboItem.addItem(iter.next());
}
}
else if(comboGroup.getSelectedItem().equals("Snails")){
comboItem.removeAllItems();
arrayItem.add("Apple Horn");
arrayItem.add("RamsHorn");
arrayItem.add("Pond Snail");
arrayItem.add("Assassin Snail");
iter = arrayItem.iterator();
while(iter.hasNext()){
comboItem.addItem(iter.next());
}
当我在 NetBeans 的 Design 选项卡的组合框上尝试它时有效。但是当我尝试将它应用到我的编码 ComboBox 时，我从 evt 收到一条消息说 Unused method parameters should be removed。我能解释一下为什么以及硬编码 comboBox 的替代方案是什么吗？
代码的用途：一个动态的 comboBox 所以无论我从 comboBox1 中选择什么都会有每个自己的列表集 comboBox2
注意：我还尝试将 comboItemItemStateChanged 更改为 itemStatChanged。
我的项目源代码：https://github.com/kontext66/GuwiPos/blob/main/GuwiPos
对不起大家的困惑，我有一个主要的class。
public class Main{
public static void main(String[] args){
new GuwiPos();
new HelpWin();
}
}
Main.java、GuwiPos.java
真的很简单。
该消息只是 NetBeans 通知您方法 comboItemItemStateChanged 的代码未引用方法参数 evt。这不是错误，甚至不是警告。你可以忽略它。当您编写代码时，NetBeans 在其编辑器中显示这些“提示”，而 NetBeans GUI 生成器生成代码。
请注意，每次选择 JComboBox 中的项目以及每次选择 de-selected 中的项目时，都会调用方法 comboItemItemStateChanged。我猜你只希望在选择一个项目时代码为 运行，因此方法的第一行 comboItemItemStateChanged 应该是
if (evt.getStateChange() == ItemEvent.SELECTED) {
然后您正在引用方法参数，“提示”将消失。
参考How to Write an Item Listener
编辑
我想您可能会从学习 GUI 设计中受益。我从来没有见过像你这样的人。我想知道您是如何得出该设计的。在任何情况下，下面的代码仅解决 comboItem 中的列表根据 comboGroup.
中的所选项目进行调整的功能
根据我的经验，通过方法 removeAllItems 和 addItem 删除和添加项目到 JComboBox 非常慢。简单地替换我在下面的代码中所做的 JComboBox 模型会更有效。对于像您这样的小列表，差异不会被注意到，但随着列表变大，差异会增加。
此外，[JComboBox] 所选项目位于方法 comboItemItemStateChanged 的 evt 参数中。
您的原始代码没有向 comboGroup 添加 项目侦听器 ，也没有 main 方法。我在下面的代码中添加了这些。请注意，项目侦听器 是通过 method reference.
添加的
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.BorderFactory;
import javax.swing.ComboBoxModel;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.JComboBox;
import java.awt.Color;
import java.awt.EventQueue;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Vector;
import java.awt.event.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
/**
*
* @author kahbg
*/
public class GuwiPos extends JFrame implements ActionListener {
public static final Map<String, ComboBoxModel<String>> LISTS;
JButton buttonBasket;
JButton buttonHelp;
JTextField txtGroup;
JTextField txtItem;
JTextField txtQty;
JTextField txtTotal;
JTextField txtPrice;
JComboBox<String> comboGroup;
JComboBox<String> comboItem;
static {
LISTS = new HashMap<>();
Vector<String> v = new Vector<>();
v.add("Plakat");
v.add("Halfmoon");
v.add("Crown Tail");
v.add("Double Tail");
ComboBoxModel<String> model = new DefaultComboBoxModel<>(v);
LISTS.put("Betta Fish", model);
v = new Vector<>();
v.add("Apple Horn");
v.add("RamsHorn");
v.add("Pond Snail");
v.add("Assassin Snail");
model = new DefaultComboBoxModel<>(v);
LISTS.put("Snails", model);
v = new Vector<>();
v.add("Small Fine Net");
v.add("Large Fine Net");
v.add("Flaring Mirror");
v.add("Aquarium Hose");
model = new DefaultComboBoxModel<>(v);
LISTS.put("Supplies", model);
v = new Vector<>();
v.add("Tubifex");
v.add("Daphnia");
v.add("Optimum Pellets");
model = new DefaultComboBoxModel<>(v);
LISTS.put("Food", model);
}
GuwiPos() {
// ComboBox
String[] products = {"Select Item...", "Betta Fish", "Snails", "Supplies", "Food"};
comboGroup = new JComboBox<String>(products);
comboGroup.addItemListener(this::comboItemItemStateChanged);
comboGroup.setBounds(130, 35, 150, 40);
comboItem = new JComboBox<String>();
comboItem.setBounds(130, 85, 150, 40);
// TextFields
txtPrice = new JTextField();
txtPrice.setBounds(130, 135, 150, 40);
txtQty = new JTextField();
txtQty.setBounds(130, 185, 150, 40);
txtTotal = new JTextField();
txtTotal.setBounds(130, 235, 150, 40);
// txtTotalAmt = new JTextField(); to code later on
// txtPaid = new JTextField(); to code later on
// txtChange = new JTextField(); to code later on
// Labels
// Product
JLabel labelProduct = new JLabel();
labelProduct.setText("Item Group");
labelProduct.setBounds(10, 5, 100, 100);
// Item
JLabel labelItem = new JLabel();
labelItem.setText("Item");
labelItem.setBounds(10, 55, 100, 100);
// Price
JLabel labelPrice = new JLabel();
labelPrice.setText("Price");
labelPrice.setBounds(10, 105, 100, 100);
// Qty
JLabel labelQty = new JLabel();
labelQty.setText("Quantity");
labelQty.setBounds(10, 155, 100, 100);
// Total
JLabel labelTotal = new JLabel();
labelTotal.setText("Total");
labelTotal.setBounds(10, 205, 100, 100);
// Buttons
buttonBasket = new JButton();
buttonBasket.setBounds(0, 0, 300, 50);
buttonBasket.setText("Add to Basket");
buttonBasket.setFocusable(false);
buttonBasket.setBorder(BorderFactory.createEtchedBorder());
buttonBasket.addActionListener(this);
JButton buttonPay = new JButton();
buttonPay.setText("PAY");
buttonPay.setBounds(0, 50, 150, 100);
buttonPay.setFocusable(false);
buttonPay.setBorder(BorderFactory.createEtchedBorder());
buttonPay.addActionListener(e -> System.out.println("Payment Success"));
JButton buttonCancel = new JButton();
buttonCancel.setText("CANCEL");
buttonCancel.setBounds(0, 150, 150, 100);
buttonCancel.setFocusable(false);
buttonCancel.setBorder(BorderFactory.createEtchedBorder());
buttonCancel.addActionListener(e -> System.out.println("Transaction Cancelled"));
JButton buttonDiscount = new JButton();
buttonDiscount.setText("Apply Discount?");
buttonDiscount.setBounds(150, 50, 150, 50);
buttonDiscount.setFocusable(false);
buttonDiscount.setBorder(BorderFactory.createEtchedBorder());
buttonDiscount.addActionListener(e -> System.out.println("20% Discount Applied"));
JButton buttonHelp = new JButton();
buttonHelp.setText("HELP");
buttonHelp.setBounds(150, 100, 150, 100);
buttonHelp.setFocusable(false);
buttonHelp.setBorder(BorderFactory.createEtchedBorder());
JButton buttonDelete = new JButton();
buttonDelete.setText("DELETE");
buttonDelete.setBounds(150, 200, 150, 50);
buttonDelete.setFocusable(false);
buttonDelete.setBorder(BorderFactory.createEtchedBorder());
buttonDelete.addActionListener(e -> System.out.println("Item Deleted"));
// Panels
// Left contains item and price
JPanel bluePanel = new JPanel();
bluePanel.setBackground(Color.blue);
bluePanel.setBounds(0, 0, 300, 300); // x,y,width,height
bluePanel.setLayout(null);
// Right contains product basket
JPanel redPanel = new JPanel();
redPanel.setBackground(Color.red);
redPanel.setBounds(300, 0, 600, 300); // x,y,width,length
redPanel.setLayout(null);
// Bottom Left contains buttons pay,change,discount
JPanel greenPanel = new JPanel();
greenPanel.setBackground(Color.green);
greenPanel.setBounds(0, 300, 300, 450);// x,y,width,length
greenPanel.setLayout(null);
// Bottom Right contains total amount
JPanel yellowPanel = new JPanel();
yellowPanel.setBackground(Color.yellow);
yellowPanel.setBounds(0, 300, 900, 450);// x,y,width,length
yellowPanel.setLayout(null);
this.setTitle("Open Betta POS");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(null);
this.setSize(900, 590);
this.setResizable(false);
this.setVisible(true);
// ADDED AWT
bluePanel.add(txtQty);
bluePanel.add(txtTotal);
bluePanel.add(txtPrice);
bluePanel.add(comboItem);
bluePanel.add(comboGroup);
bluePanel.add(labelProduct);
bluePanel.add(labelItem);
bluePanel.add(labelPrice);
bluePanel.add(labelQty);
bluePanel.add(labelTotal);
greenPanel.add(buttonBasket);
greenPanel.add(buttonPay);
greenPanel.add(buttonCancel);
greenPanel.add(buttonDiscount);
greenPanel.add(buttonHelp);
greenPanel.add(buttonDelete);
this.add(bluePanel);
this.add(redPanel);
this.add(greenPanel);
this.add(yellowPanel);
}
@Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == buttonBasket) {
System.out.println("Added Item to Basket: " + comboGroup.getSelectedItem() + "\n"
+ comboItem.getSelectedItem());
}
}
// This is not working
public void comboItemItemStateChanged(java.awt.event.ItemEvent evt) {
if (evt.getStateChange() == ItemEvent.SELECTED) {
Object selection = evt.getItem();
ArrayList<String> arrayItem = new ArrayList<>();
Iterator<String> iter;
if (selection.equals("Betta Fish")) {
comboItem.setModel(LISTS.get("Betta Fish"));
}
else if (selection.equals("Snails")) {
comboItem.setModel(LISTS.get("Snails"));
}
else if (selection.equals("Supplies")) {
comboItem.setModel(LISTS.get("Supplies"));
}
else if (selection.equals("Food")) {
comboItem.setModel(LISTS.get("Food"));
}
else if (selection.equals("Select Item...")) {
comboItem.removeAllItems();
arrayItem.add("Select Item...");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
}
}
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new GuwiPos());
}
}
您的代码（改进版 - 减一 ActionListener）
public class SwingApp {
private static JComboBox<String> comboItem;
private static JComboBox<String> productCombo;
public static void main (String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run () {
createAndShowGUI();
}
});
}
private static void createAndShowGUI () {
JFrame frame = createMainFrame();
JPanel bluePanel = createBluePanel();
JPanel greenPanel = createGreenPanel();
JPanel redPanel = createRedPanel();
JPanel yellowPanel = createYellowPanel();
frame.add(bluePanel);
frame.add(greenPanel);
frame.add(redPanel);
frame.add(yellowPanel);
frame.setVisible(true);
}
private static JFrame createMainFrame () {
JFrame frame = new JFrame("Open Betta POS");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(null);
frame.setSize(900, 590);
frame.setResizable(false);
return frame;
}
private static JPanel createBluePanel () {
ComboSelectionListener productComboListener = new ComboSelectionListener();
JPanel panel = new JPanel(null); // Sets layout manager to null which is a bad idea!
String[] products =
{"Select Item...", "Betta Fish", "Snails", "Supplies", "Food"};
productCombo = new JComboBox<>(products);
productCombo.setBounds(130, 35, 150, 40);
productCombo.setActionCommand("selectProduct");
productCombo.addActionListener(productComboListener);
comboItem = new JComboBox<>();
comboItem.setBounds(130, 85, 150, 40);
// TextFields
JTextField txtPrice = new JTextField();
txtPrice.setBounds(130, 135, 150, 40);
JTextField txtQty = new JTextField();
txtQty.setBounds(130, 185, 150, 40);
JTextField txtTotal = new JTextField();
txtTotal.setBounds(130, 235, 150, 40);
JLabel labelProduct = new JLabel();
labelProduct.setText("Item Group");
labelProduct.setBounds(10, 5, 100, 100);
// Item
JLabel labelItem = new JLabel();
labelItem.setText("Item");
labelItem.setBounds(10, 55, 100, 100);
// Price
JLabel labelPrice = new JLabel();
labelPrice.setText("Price");
labelPrice.setBounds(10, 105, 100, 100);
// Qty
JLabel labelQty = new JLabel();
labelQty.setText("Quantity");
labelQty.setBounds(10, 155, 100, 100);
// Total
JLabel labelTotal = new JLabel();
labelTotal.setText("Total");
labelTotal.setBounds(10, 205, 100, 100);
panel.setBackground(Color.blue);
panel.setBounds(0, 0, 300, 300); // x,y,width,height
panel.add(txtQty);
panel.add(txtTotal);
panel.add(txtPrice);
panel.add(comboItem);
panel.add(productCombo);
panel.add(labelProduct);
panel.add(labelItem);
panel.add(labelPrice);
panel.add(labelQty);
panel.add(labelTotal);
return panel;
}
private static JPanel createGreenPanel () {
JPanel panel = new JPanel(null);
panel.setBackground(Color.green);
panel.setBounds(0, 300, 300, 450);// x,y,width,length
JButton buttonBasket = new JButton();
buttonBasket.setBounds(0, 0, 300, 50);
buttonBasket.setText("Add to Basket");
buttonBasket.setFocusable(false);
buttonBasket.setBorder(BorderFactory.createEtchedBorder());
buttonBasket
.addActionListener(e -> System.out.println("Added Item to Basket: "
+ productCombo.getSelectedItem() + "\n" + comboItem.getSelectedItem()));
JButton buttonPay = new JButton();
buttonPay.setText("PAY");
buttonPay.setBounds(0, 50, 150, 100);
buttonPay.setFocusable(false);
buttonPay.setBorder(BorderFactory.createEtchedBorder());
buttonPay.addActionListener(e -> System.out.println("Payment Success"));
JButton buttonCancel = new JButton();
buttonCancel.setText("CANCEL");
buttonCancel.setBounds(0, 150, 150, 100);
buttonCancel.setFocusable(false);
buttonCancel.setBorder(BorderFactory.createEtchedBorder());
buttonCancel
.addActionListener(e -> System.out.println("Transaction Cancelled"));
JButton buttonDiscount = new JButton();
buttonDiscount.setText("Apply Discount?");
buttonDiscount.setBounds(150, 50, 150, 50);
buttonDiscount.setFocusable(false);
buttonDiscount.setBorder(BorderFactory.createEtchedBorder());
buttonDiscount
.addActionListener(e -> System.out.println("20% Discount Applied"));
JButton buttonHelp = new JButton();
buttonHelp.setText("HELP");
buttonHelp.setBounds(150, 100, 150, 100);
buttonHelp.setFocusable(false);
buttonHelp.setBorder(BorderFactory.createEtchedBorder());
JButton buttonDelete = new JButton();
buttonDelete.setText("DELETE");
buttonDelete.setBounds(150, 200, 150, 50);
buttonDelete.setFocusable(false);
buttonDelete.setBorder(BorderFactory.createEtchedBorder());
buttonDelete.addActionListener(e -> System.out.println("Item Deleted"));
panel.add(buttonBasket);
panel.add(buttonPay);
panel.add(buttonCancel);
panel.add(buttonDiscount);
panel.add(buttonHelp);
panel.add(buttonDelete);
return panel;
}
private static JPanel createRedPanel () {
JPanel panel = new JPanel(null);
panel.setBackground(Color.red);
panel.setBounds(300, 0, 600, 300); // x,y,width,length
return panel;
}
private static JPanel createYellowPanel () {
JPanel panel = new JPanel();
panel.setBackground(Color.yellow);
panel.setBounds(0, 300, 900, 450); // x,y,width,length
return panel;
}
private static class ComboSelectionListener implements ActionListener {
@Override
public void actionPerformed (ActionEvent e) {
JComboBox<String> comboGroup = (JComboBox<String>) e.getSource();
ArrayList<String> arrayItem = new ArrayList<>();
Iterator<String> iter;
if (comboGroup.getSelectedItem().equals("Betta Fish")) {
comboItem.removeAllItems();
arrayItem.add("Plakat");
arrayItem.add("Halfmoon");
arrayItem.add("Crown Tail");
arrayItem.add("Double Tail");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Snails")) {
comboItem.removeAllItems();
arrayItem.add("Apple Horn");
arrayItem.add("RamsHorn");
arrayItem.add("Pond Snail");
arrayItem.add("Assassin Snail");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Supplies")) {
comboItem.removeAllItems();
arrayItem.add("Small Fine Net");
arrayItem.add("Large Fine Net");
arrayItem.add("Flaring Mirror");
arrayItem.add("Aquarium Hose");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Food")) {
comboItem.removeAllItems();
arrayItem.add("Tubifex");
arrayItem.add("Daphnia");
arrayItem.add("Optimum Pellets");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Select Item...")) {
comboItem.removeAllItems();
arrayItem.add("Select Item...");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
}
}
}
}
改进（除了解决主要问题）
- 创建了一个不是 Swing 组件的 Swing（主要）class
- 主要 class 没有实现
ActionListener
- 已使用
SwingUtilities 启动 Swing 应用程序
- 创建方法来封装涉及创建组件的细节
- 最小化变量范围
新手问题：
所以这段代码在这里
public void comboItemItemStateChanged(java.awt.event.ItemEvent evt) {
ArrayList<String> arrayItem = new ArrayList<>();
Iterator<String> iter;
if(comboGroup.getSelectedItem().equals("Betta Fish")){
comboItem.removeAllItems();
arrayItem.add("Plakat");
arrayItem.add("Halfmoon");
arrayItem.add("Crown Tail");
arrayItem.add("Double Tail");
iter = arrayItem.iterator();
while(iter.hasNext()){
comboItem.addItem(iter.next());
}
}
else if(comboGroup.getSelectedItem().equals("Snails")){
comboItem.removeAllItems();
arrayItem.add("Apple Horn");
arrayItem.add("RamsHorn");
arrayItem.add("Pond Snail");
arrayItem.add("Assassin Snail");
iter = arrayItem.iterator();
while(iter.hasNext()){
comboItem.addItem(iter.next());
}
当我在 NetBeans 的 Design 选项卡的组合框上尝试它时有效。但是当我尝试将它应用到我的编码 ComboBox 时，我从 evt 收到一条消息说 Unused method parameters should be removed。我能解释一下为什么以及硬编码 comboBox 的替代方案是什么吗？
代码的用途：一个动态的 comboBox 所以无论我从 comboBox1 中选择什么都会有每个自己的列表集 comboBox2
注意：我还尝试将 comboItemItemStateChanged 更改为 itemStatChanged。
我的项目源代码：https://github.com/kontext66/GuwiPos/blob/main/GuwiPos
对不起大家的困惑，我有一个主要的class。
public class Main{
public static void main(String[] args){
new GuwiPos();
new HelpWin();
}
}
Main.java、GuwiPos.java
真的很简单。
该消息只是 NetBeans 通知您方法 comboItemItemStateChanged 的代码未引用方法参数 evt。这不是错误，甚至不是警告。你可以忽略它。当您编写代码时，NetBeans 在其编辑器中显示这些“提示”，而 NetBeans GUI 生成器生成代码。
请注意，每次选择 JComboBox 中的项目以及每次选择 de-selected 中的项目时，都会调用方法 comboItemItemStateChanged。我猜你只希望在选择一个项目时代码为 运行，因此方法的第一行 comboItemItemStateChanged 应该是
if (evt.getStateChange() == ItemEvent.SELECTED) {
然后您正在引用方法参数，“提示”将消失。
参考How to Write an Item Listener
编辑
我想您可能会从学习 GUI 设计中受益。我从来没有见过像你这样的人。我想知道您是如何得出该设计的。在任何情况下，下面的代码仅解决 comboItem 中的列表根据 comboGroup.
根据我的经验，通过方法 removeAllItems 和 addItem 删除和添加项目到 JComboBox 非常慢。简单地替换我在下面的代码中所做的 JComboBox 模型会更有效。对于像您这样的小列表，差异不会被注意到，但随着列表变大，差异会增加。
此外，[JComboBox] 所选项目位于方法 comboItemItemStateChanged 的 evt 参数中。
您的原始代码没有向 comboGroup 添加 项目侦听器 ，也没有 main 方法。我在下面的代码中添加了这些。请注意，项目侦听器 是通过 method reference.
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.BorderFactory;
import javax.swing.ComboBoxModel;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.JComboBox;
import java.awt.Color;
import java.awt.EventQueue;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Vector;
import java.awt.event.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
/**
*
* @author kahbg
*/
public class GuwiPos extends JFrame implements ActionListener {
public static final Map<String, ComboBoxModel<String>> LISTS;
JButton buttonBasket;
JButton buttonHelp;
JTextField txtGroup;
JTextField txtItem;
JTextField txtQty;
JTextField txtTotal;
JTextField txtPrice;
JComboBox<String> comboGroup;
JComboBox<String> comboItem;
static {
LISTS = new HashMap<>();
Vector<String> v = new Vector<>();
v.add("Plakat");
v.add("Halfmoon");
v.add("Crown Tail");
v.add("Double Tail");
ComboBoxModel<String> model = new DefaultComboBoxModel<>(v);
LISTS.put("Betta Fish", model);
v = new Vector<>();
v.add("Apple Horn");
v.add("RamsHorn");
v.add("Pond Snail");
v.add("Assassin Snail");
model = new DefaultComboBoxModel<>(v);
LISTS.put("Snails", model);
v = new Vector<>();
v.add("Small Fine Net");
v.add("Large Fine Net");
v.add("Flaring Mirror");
v.add("Aquarium Hose");
model = new DefaultComboBoxModel<>(v);
LISTS.put("Supplies", model);
v = new Vector<>();
v.add("Tubifex");
v.add("Daphnia");
v.add("Optimum Pellets");
model = new DefaultComboBoxModel<>(v);
LISTS.put("Food", model);
}
GuwiPos() {
// ComboBox
String[] products = {"Select Item...", "Betta Fish", "Snails", "Supplies", "Food"};
comboGroup = new JComboBox<String>(products);
comboGroup.addItemListener(this::comboItemItemStateChanged);
comboGroup.setBounds(130, 35, 150, 40);
comboItem = new JComboBox<String>();
comboItem.setBounds(130, 85, 150, 40);
// TextFields
txtPrice = new JTextField();
txtPrice.setBounds(130, 135, 150, 40);
txtQty = new JTextField();
txtQty.setBounds(130, 185, 150, 40);
txtTotal = new JTextField();
txtTotal.setBounds(130, 235, 150, 40);
// txtTotalAmt = new JTextField(); to code later on
// txtPaid = new JTextField(); to code later on
// txtChange = new JTextField(); to code later on
// Labels
// Product
JLabel labelProduct = new JLabel();
labelProduct.setText("Item Group");
labelProduct.setBounds(10, 5, 100, 100);
// Item
JLabel labelItem = new JLabel();
labelItem.setText("Item");
labelItem.setBounds(10, 55, 100, 100);
// Price
JLabel labelPrice = new JLabel();
labelPrice.setText("Price");
labelPrice.setBounds(10, 105, 100, 100);
// Qty
JLabel labelQty = new JLabel();
labelQty.setText("Quantity");
labelQty.setBounds(10, 155, 100, 100);
// Total
JLabel labelTotal = new JLabel();
labelTotal.setText("Total");
labelTotal.setBounds(10, 205, 100, 100);
// Buttons
buttonBasket = new JButton();
buttonBasket.setBounds(0, 0, 300, 50);
buttonBasket.setText("Add to Basket");
buttonBasket.setFocusable(false);
buttonBasket.setBorder(BorderFactory.createEtchedBorder());
buttonBasket.addActionListener(this);
JButton buttonPay = new JButton();
buttonPay.setText("PAY");
buttonPay.setBounds(0, 50, 150, 100);
buttonPay.setFocusable(false);
buttonPay.setBorder(BorderFactory.createEtchedBorder());
buttonPay.addActionListener(e -> System.out.println("Payment Success"));
JButton buttonCancel = new JButton();
buttonCancel.setText("CANCEL");
buttonCancel.setBounds(0, 150, 150, 100);
buttonCancel.setFocusable(false);
buttonCancel.setBorder(BorderFactory.createEtchedBorder());
buttonCancel.addActionListener(e -> System.out.println("Transaction Cancelled"));
JButton buttonDiscount = new JButton();
buttonDiscount.setText("Apply Discount?");
buttonDiscount.setBounds(150, 50, 150, 50);
buttonDiscount.setFocusable(false);
buttonDiscount.setBorder(BorderFactory.createEtchedBorder());
buttonDiscount.addActionListener(e -> System.out.println("20% Discount Applied"));
JButton buttonHelp = new JButton();
buttonHelp.setText("HELP");
buttonHelp.setBounds(150, 100, 150, 100);
buttonHelp.setFocusable(false);
buttonHelp.setBorder(BorderFactory.createEtchedBorder());
JButton buttonDelete = new JButton();
buttonDelete.setText("DELETE");
buttonDelete.setBounds(150, 200, 150, 50);
buttonDelete.setFocusable(false);
buttonDelete.setBorder(BorderFactory.createEtchedBorder());
buttonDelete.addActionListener(e -> System.out.println("Item Deleted"));
// Panels
// Left contains item and price
JPanel bluePanel = new JPanel();
bluePanel.setBackground(Color.blue);
bluePanel.setBounds(0, 0, 300, 300); // x,y,width,height
bluePanel.setLayout(null);
// Right contains product basket
JPanel redPanel = new JPanel();
redPanel.setBackground(Color.red);
redPanel.setBounds(300, 0, 600, 300); // x,y,width,length
redPanel.setLayout(null);
// Bottom Left contains buttons pay,change,discount
JPanel greenPanel = new JPanel();
greenPanel.setBackground(Color.green);
greenPanel.setBounds(0, 300, 300, 450);// x,y,width,length
greenPanel.setLayout(null);
// Bottom Right contains total amount
JPanel yellowPanel = new JPanel();
yellowPanel.setBackground(Color.yellow);
yellowPanel.setBounds(0, 300, 900, 450);// x,y,width,length
yellowPanel.setLayout(null);
this.setTitle("Open Betta POS");
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(null);
this.setSize(900, 590);
this.setResizable(false);
this.setVisible(true);
// ADDED AWT
bluePanel.add(txtQty);
bluePanel.add(txtTotal);
bluePanel.add(txtPrice);
bluePanel.add(comboItem);
bluePanel.add(comboGroup);
bluePanel.add(labelProduct);
bluePanel.add(labelItem);
bluePanel.add(labelPrice);
bluePanel.add(labelQty);
bluePanel.add(labelTotal);
greenPanel.add(buttonBasket);
greenPanel.add(buttonPay);
greenPanel.add(buttonCancel);
greenPanel.add(buttonDiscount);
greenPanel.add(buttonHelp);
greenPanel.add(buttonDelete);
this.add(bluePanel);
this.add(redPanel);
this.add(greenPanel);
this.add(yellowPanel);
}
@Override
public void actionPerformed(ActionEvent e) {
if (e.getSource() == buttonBasket) {
System.out.println("Added Item to Basket: " + comboGroup.getSelectedItem() + "\n"
+ comboItem.getSelectedItem());
}
}
// This is not working
public void comboItemItemStateChanged(java.awt.event.ItemEvent evt) {
if (evt.getStateChange() == ItemEvent.SELECTED) {
Object selection = evt.getItem();
ArrayList<String> arrayItem = new ArrayList<>();
Iterator<String> iter;
if (selection.equals("Betta Fish")) {
comboItem.setModel(LISTS.get("Betta Fish"));
}
else if (selection.equals("Snails")) {
comboItem.setModel(LISTS.get("Snails"));
}
else if (selection.equals("Supplies")) {
comboItem.setModel(LISTS.get("Supplies"));
}
else if (selection.equals("Food")) {
comboItem.setModel(LISTS.get("Food"));
}
else if (selection.equals("Select Item...")) {
comboItem.removeAllItems();
arrayItem.add("Select Item...");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
}
}
}
public static void main(String[] args) {
EventQueue.invokeLater(() -> new GuwiPos());
}
}
您的代码（改进版 - 减一 ActionListener）
public class SwingApp {
private static JComboBox<String> comboItem;
private static JComboBox<String> productCombo;
public static void main (String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run () {
createAndShowGUI();
}
});
}
private static void createAndShowGUI () {
JFrame frame = createMainFrame();
JPanel bluePanel = createBluePanel();
JPanel greenPanel = createGreenPanel();
JPanel redPanel = createRedPanel();
JPanel yellowPanel = createYellowPanel();
frame.add(bluePanel);
frame.add(greenPanel);
frame.add(redPanel);
frame.add(yellowPanel);
frame.setVisible(true);
}
private static JFrame createMainFrame () {
JFrame frame = new JFrame("Open Betta POS");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(null);
frame.setSize(900, 590);
frame.setResizable(false);
return frame;
}
private static JPanel createBluePanel () {
ComboSelectionListener productComboListener = new ComboSelectionListener();
JPanel panel = new JPanel(null); // Sets layout manager to null which is a bad idea!
String[] products =
{"Select Item...", "Betta Fish", "Snails", "Supplies", "Food"};
productCombo = new JComboBox<>(products);
productCombo.setBounds(130, 35, 150, 40);
productCombo.setActionCommand("selectProduct");
productCombo.addActionListener(productComboListener);
comboItem = new JComboBox<>();
comboItem.setBounds(130, 85, 150, 40);
// TextFields
JTextField txtPrice = new JTextField();
txtPrice.setBounds(130, 135, 150, 40);
JTextField txtQty = new JTextField();
txtQty.setBounds(130, 185, 150, 40);
JTextField txtTotal = new JTextField();
txtTotal.setBounds(130, 235, 150, 40);
JLabel labelProduct = new JLabel();
labelProduct.setText("Item Group");
labelProduct.setBounds(10, 5, 100, 100);
// Item
JLabel labelItem = new JLabel();
labelItem.setText("Item");
labelItem.setBounds(10, 55, 100, 100);
// Price
JLabel labelPrice = new JLabel();
labelPrice.setText("Price");
labelPrice.setBounds(10, 105, 100, 100);
// Qty
JLabel labelQty = new JLabel();
labelQty.setText("Quantity");
labelQty.setBounds(10, 155, 100, 100);
// Total
JLabel labelTotal = new JLabel();
labelTotal.setText("Total");
labelTotal.setBounds(10, 205, 100, 100);
panel.setBackground(Color.blue);
panel.setBounds(0, 0, 300, 300); // x,y,width,height
panel.add(txtQty);
panel.add(txtTotal);
panel.add(txtPrice);
panel.add(comboItem);
panel.add(productCombo);
panel.add(labelProduct);
panel.add(labelItem);
panel.add(labelPrice);
panel.add(labelQty);
panel.add(labelTotal);
return panel;
}
private static JPanel createGreenPanel () {
JPanel panel = new JPanel(null);
panel.setBackground(Color.green);
panel.setBounds(0, 300, 300, 450);// x,y,width,length
JButton buttonBasket = new JButton();
buttonBasket.setBounds(0, 0, 300, 50);
buttonBasket.setText("Add to Basket");
buttonBasket.setFocusable(false);
buttonBasket.setBorder(BorderFactory.createEtchedBorder());
buttonBasket
.addActionListener(e -> System.out.println("Added Item to Basket: "
+ productCombo.getSelectedItem() + "\n" + comboItem.getSelectedItem()));
JButton buttonPay = new JButton();
buttonPay.setText("PAY");
buttonPay.setBounds(0, 50, 150, 100);
buttonPay.setFocusable(false);
buttonPay.setBorder(BorderFactory.createEtchedBorder());
buttonPay.addActionListener(e -> System.out.println("Payment Success"));
JButton buttonCancel = new JButton();
buttonCancel.setText("CANCEL");
buttonCancel.setBounds(0, 150, 150, 100);
buttonCancel.setFocusable(false);
buttonCancel.setBorder(BorderFactory.createEtchedBorder());
buttonCancel
.addActionListener(e -> System.out.println("Transaction Cancelled"));
JButton buttonDiscount = new JButton();
buttonDiscount.setText("Apply Discount?");
buttonDiscount.setBounds(150, 50, 150, 50);
buttonDiscount.setFocusable(false);
buttonDiscount.setBorder(BorderFactory.createEtchedBorder());
buttonDiscount
.addActionListener(e -> System.out.println("20% Discount Applied"));
JButton buttonHelp = new JButton();
buttonHelp.setText("HELP");
buttonHelp.setBounds(150, 100, 150, 100);
buttonHelp.setFocusable(false);
buttonHelp.setBorder(BorderFactory.createEtchedBorder());
JButton buttonDelete = new JButton();
buttonDelete.setText("DELETE");
buttonDelete.setBounds(150, 200, 150, 50);
buttonDelete.setFocusable(false);
buttonDelete.setBorder(BorderFactory.createEtchedBorder());
buttonDelete.addActionListener(e -> System.out.println("Item Deleted"));
panel.add(buttonBasket);
panel.add(buttonPay);
panel.add(buttonCancel);
panel.add(buttonDiscount);
panel.add(buttonHelp);
panel.add(buttonDelete);
return panel;
}
private static JPanel createRedPanel () {
JPanel panel = new JPanel(null);
panel.setBackground(Color.red);
panel.setBounds(300, 0, 600, 300); // x,y,width,length
return panel;
}
private static JPanel createYellowPanel () {
JPanel panel = new JPanel();
panel.setBackground(Color.yellow);
panel.setBounds(0, 300, 900, 450); // x,y,width,length
return panel;
}
private static class ComboSelectionListener implements ActionListener {
@Override
public void actionPerformed (ActionEvent e) {
JComboBox<String> comboGroup = (JComboBox<String>) e.getSource();
ArrayList<String> arrayItem = new ArrayList<>();
Iterator<String> iter;
if (comboGroup.getSelectedItem().equals("Betta Fish")) {
comboItem.removeAllItems();
arrayItem.add("Plakat");
arrayItem.add("Halfmoon");
arrayItem.add("Crown Tail");
arrayItem.add("Double Tail");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Snails")) {
comboItem.removeAllItems();
arrayItem.add("Apple Horn");
arrayItem.add("RamsHorn");
arrayItem.add("Pond Snail");
arrayItem.add("Assassin Snail");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Supplies")) {
comboItem.removeAllItems();
arrayItem.add("Small Fine Net");
arrayItem.add("Large Fine Net");
arrayItem.add("Flaring Mirror");
arrayItem.add("Aquarium Hose");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Food")) {
comboItem.removeAllItems();
arrayItem.add("Tubifex");
arrayItem.add("Daphnia");
arrayItem.add("Optimum Pellets");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
} else if (comboGroup.getSelectedItem().equals("Select Item...")) {
comboItem.removeAllItems();
arrayItem.add("Select Item...");
iter = arrayItem.iterator();
while (iter.hasNext()) {
comboItem.addItem(iter.next());
}
}
}
}
}
改进（除了解决主要问题）
- 创建了一个不是 Swing 组件的 Swing（主要）class
- 主要 class 没有实现
ActionListener - 已使用
SwingUtilities启动 Swing 应用程序 - 创建方法来封装涉及创建组件的细节
- 最小化变量范围