[英]How to change the contents of JComboBox based on a condition?
我对 OOP 和学习比较陌生。 我一直在弄清楚如何才能更改窗格的内容。
我想要发生的是如果我点击一个不同的单位，两个窗格的内容将根据我选择的单位而改变。
这是我的代码的要点：
private Container c;
private JTextField t1;
private JTextField t2;
private JButton b1;
String[] choicelen = {"meter", "kilometer", "centimeter", "millimeter", "mile", "yard", "foot"};
private JComboBox clen;
String[] choicelen1 = {"meter", "kilometer", "centimeter", "millimeter", "mile", "yard", "foot"};
private JComboBox clen1;
String[] choicetem = {"celsius", "kelvin", "fahrenheit"};
String[] choicetem1 = {"celsius", "kelvin", "fahrenheit"};
String[] choicearea = {"acre", "hectare", "sq mile", "sq yard", "sq foot", "sq inch"};
String[] choicearea1 = {"acre", "hectare"};
String[] choicevol = {"liter", "milliliter", "gallon", "quart", "pint", "cup", "fluid ounce"};
String[] choicevol1 = {"liter", "milliliter", "gallon", "quart", "pint", "cup", "fluid ounce"};
String[] choicewt = {"gram", "kilogram", "milligram", "metric ton", "pound", "ounce", "carrat"};
String[] choicewt1 = {"gram", "kilogram", "milligram", "metric ton", "pound", "ounce", "carrat"};
String[] choicetime = {"second", "millisecond", "minute", "hour", "day", "week", "month", "year"};
String[] choicetime1 = {"second", "millisecond", "minute", "hour", "day", "week", "month", "year"};
String[] choices = {"Length", "Temperature", "Area", "Volume", "Weight", "Time"};
private JComboBox c3;
OP 的代码不是最小的可重现示例。
所以，我继续创建了以下 GUI。
我只对长度和温度的转换进行了编码。 我将 rest 作为 OP 的练习。
Oracle 有一个有用的教程，使用 Swing 创建 GUI 。 跳过学习 Swing 和 NetBeans IDE 部分。
当我创建 Swing GUI 时，我使用model-view-controller (MVC) 模式。 这种模式使我能够分离我的关注点并一次专注于应用程序的一部分。
model 是任何 Swing 应用程序中最重要的部分。 一个好的 model 使得编码视图和控制器变得容易得多。
JFrame和所需数量的JPanels和JDialogs 。Action或Listener 。一个 Swing 应用程序通常有多个 controller 类。
我为此应用程序创建了两个 model 类。
Measurement class 包含一个文本字符串、一个乘法器和一个加法器。
让我们采用温度转换的公式。
f = (c * 9/5) + 32
c = (f - 32) / 9/5
任何测量转换的通用公式是
to value = (from value * multiplier) + adder
因此，对于长度，我将 from 值转换为毫米，并将毫米转换为 to 值。 我对温度做了类似的事情，我将 from 值转换为 celsius，并将 celsius 转换为 to 值。
这样，我减少了进行转换所需的代码。 OP 所要做的就是在UnitConversionModel class 中插入乘法器和加法器的 rest。
UnitConversionModel class 包含一个带有String键的Map和一个List<Measurement> object。这个Map允许我轻松填充JComboBoxes并为我提供转换值。
我大致根据 OP 的图片生成了一个视图。 model 使构建视图更简单。
我编码了两个 controller 类。
ComboBoxListener class 在转换单元JComboBoxes中填写 from 转换单元和 to 转换单元。
ButtonListener class 进行单位转换。
这是完整的可运行代码。 我制作了额外的类内部类，这样我就可以将代码作为一个块发布。
import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
public class UnitConversionTool implements Runnable {
public static void main(String[] args) {
SwingUtilities.invokeLater(new UnitConversionTool());
}
private JComboBox<Measurement> fromMeasurementComboBox,
toMeasurementComboBox;
private JComboBox<String> measurementTypeComboBox;
private JTextField fromMeasurementField, toMeasurementField;
private UnitConversionModel model;
public UnitConversionTool() {
this.model = new UnitConversionModel();
}
@Override
public void run() {
JFrame frame = new JFrame("Unit Conversion Tool");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(createMainPanel(), BorderLayout.CENTER);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
private JPanel createMainPanel() {
JPanel panel = new JPanel(new GridBagLayout());
panel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
GridBagConstraints gbc = new GridBagConstraints();
gbc.anchor = GridBagConstraints.LINE_START;
gbc.fill = GridBagConstraints.NONE;
gbc.insets = new Insets(0, 5, 5, 5);
String[] measurementTypes = model.getMeasurementTypes();
gbc.gridwidth = 2;
gbc.gridx = 0;
gbc.gridy = 0;
measurementTypeComboBox = new JComboBox<>(measurementTypes);
String measurementType = measurementTypes[measurementTypes.length - 1];
measurementTypeComboBox.setSelectedItem(measurementType);
measurementTypeComboBox
.addActionListener(new ComboBoxListener(this, model));
panel.add(measurementTypeComboBox, gbc);
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.gridwidth = 1;
gbc.gridy++;
gbc.weightx = 1.0;
panel.add(new JLabel("From"), gbc);
Measurement[] measurementUnits = model
.getMeasurementList(measurementType);
gbc.gridx++;
fromMeasurementComboBox = new JComboBox<>(measurementUnits);
panel.add(fromMeasurementComboBox, gbc);
gbc.gridx++;
fromMeasurementField = new JTextField(10);
panel.add(fromMeasurementField, gbc);
gbc.gridx++;
panel.add(new JLabel("to"), gbc);
gbc.gridx++;
toMeasurementComboBox = new JComboBox<>(measurementUnits);
panel.add(toMeasurementComboBox, gbc);
gbc.gridx++;
toMeasurementField = new JTextField(10);
toMeasurementField.setEditable(false);
panel.add(toMeasurementField, gbc);
gbc.gridwidth = 6;
gbc.gridx = 0;
gbc.gridy++;
JButton button = new JButton("Convert");
button.addActionListener(new ButtonListener(this, model));
panel.add(button, gbc);
return panel;
}
public JComboBox<Measurement> getFromMeasurementComboBox() {
return fromMeasurementComboBox;
}
public JComboBox<Measurement> getToMeasurementComboBox() {
return toMeasurementComboBox;
}
public JComboBox<String> getMeasurementTypeComboBox() {
return measurementTypeComboBox;
}
public JTextField getFromMeasurementField() {
return fromMeasurementField;
}
public JTextField getToMeasurementField() {
return toMeasurementField;
}
public class ComboBoxListener implements ActionListener {
private final UnitConversionTool view;
private final UnitConversionModel model;
public ComboBoxListener(UnitConversionTool view,
UnitConversionModel model) {
this.view = view;
this.model = model;
}
@Override
public void actionPerformed(ActionEvent event) {
String selectedMeasurementType = (String) view
.getMeasurementTypeComboBox().getSelectedItem();
Measurement[] measurementUnits = model
.getMeasurementList(selectedMeasurementType);
int count = view.getFromMeasurementComboBox().getItemCount();
for (int index = count - 1; index >= 0; index--) {
view.getFromMeasurementComboBox().removeItemAt(index);
view.getToMeasurementComboBox().removeItemAt(index);
}
for (Measurement m : measurementUnits) {
view.getFromMeasurementComboBox().addItem(m);
view.getToMeasurementComboBox().addItem(m);
}
}
}
public class ButtonListener implements ActionListener {
private final UnitConversionTool view;
private final UnitConversionModel model;
public ButtonListener(UnitConversionTool view,
UnitConversionModel model) {
this.view = view;
this.model = model;
}
@Override
public void actionPerformed(ActionEvent event) {
Measurement fromMeasurement = (Measurement) view
.getFromMeasurementComboBox().getSelectedItem();
Measurement toMeasurement = (Measurement) view
.getToMeasurementComboBox().getSelectedItem();
double fromValue = Double
.valueOf(view.getFromMeasurementField().getText());
double toValue = (fromValue + fromMeasurement.getAdder())
* fromMeasurement.getMultiplier();
toValue = toValue / toMeasurement.getMultiplier()
- toMeasurement.getAdder();
String text = String.format("%.2f", toValue);
view.getToMeasurementField().setText(text);
}
}
public class UnitConversionModel {
private final Map<String, List<Measurement>> measurementMap;
private final Measurement[] lengthMeasurements = {
new Measurement("meter", 1000, 0),
new Measurement("kilometer", 1_000_000, 0),
new Measurement("centimeter", 10, 0),
new Measurement("millimeter", 1, 0),
new Measurement("mile", 1.609344e+6, 0),
new Measurement("yard", 914.4, 0),
new Measurement("foot", 304.8, 0) };
private final Measurement[] temperatureMeasurements = {
new Measurement("celsius", 1, 0),
new Measurement("kelvin", 1, -273.15),
new Measurement("fahrenheit", 5.0 / 9.0, -32) };
private final Measurement[] areaMeasurements = {
new Measurement("acre", 0, 0), new Measurement("hectare", 0, 0),
new Measurement("sq mile", 0, 0),
new Measurement("sq yard", 0, 0),
new Measurement("sq foot", 0, 0),
new Measurement("sq inch", 0, 0) };
private final Measurement[] volumeMeasurements = {
new Measurement("liter", 0, 0),
new Measurement("milliliter", 0, 0),
new Measurement("gallon", 0, 0), new Measurement("quart", 0, 0),
new Measurement("pint", 0, 0), new Measurement("cup", 0, 0),
new Measurement("fluid ounce", 0, 0) };
private final Measurement[] weightMeasurements = {
new Measurement("gram", 0, 0),
new Measurement("kilogram", 0, 0),
new Measurement("milligram", 0, 0),
new Measurement("metric ton", 0, 0),
new Measurement("pound", 0, 0), new Measurement("ounce", 0, 0),
new Measurement("carat", 0, 0) };
private final Measurement[] timeMeasurements = {
new Measurement("second", 0, 0),
new Measurement("millisecond", 0, 0),
new Measurement("minute", 0, 0), new Measurement("hour", 0, 0),
new Measurement("day", 0, 0), new Measurement("week", 0, 0),
new Measurement("month", 0, 0), new Measurement("year", 0, 0) };
private final String[] measurementTypes = { "Length", "Temperature",
"Area", "Volume", "Weight", "Time" };
private final Measurement[][] measurements = { lengthMeasurements,
temperatureMeasurements, areaMeasurements, volumeMeasurements,
weightMeasurements, timeMeasurements };
public UnitConversionModel() {
this.measurementMap = new LinkedHashMap<>();
for (int index = 0; index < measurementTypes.length; index++) {
String s = measurementTypes[index];
Measurement[] measurementUnits = measurements[index];
List<Measurement> measurementList = new ArrayList<>();
for (Measurement m : measurementUnits) {
measurementList.add(m);
}
measurementMap.put(s, measurementList);
}
}
public String[] getMeasurementTypes() {
return measurementTypes;
}
public Measurement[] getMeasurementList(String measurement) {
List<Measurement> measurementList = measurementMap.get(measurement);
return measurementList
.toArray(new Measurement[measurementList.size()]);
}
}
public class Measurement {
private final double adder, multiplier;
private final String text;
public Measurement(String text, double multiplier, double adder) {
this.text = text;
this.multiplier = multiplier;
this.adder = adder;
}
public double getAdder() {
return adder;
}
public double getMultiplier() {
return multiplier;
}
@Override
public String toString() {
return text;
}
}
}
我通过添加从类似帖子中找到的这段代码来让它工作：
c3 = new JComboBox<>(choices);
c.add(c3);
choose = new JComboBox<>(choicelen);
c.add(choose);
choose1 = new JComboBox<>(choicelen1);
c.add(choose1);
c3.addActionListener(new Listener());
class Listener implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
if (c3.getSelectedItem().equals("Length")) {
choose.setModel(new JComboBox<>(choicelen).getModel());
choose1.setModel(new JComboBox<>(choicelen1).getModel());
}
else if (c3.getSelectedItem().equals("Temperature")) {
choose.setModel(new JComboBox<>(choicetem).getModel());
choose1.setModel(new JComboBox<>(choicetem1).getModel());
}
else if (c3.getSelectedItem().equals("Area")) {
choose.setModel(new JComboBox<>(choicearea).getModel());
choose1.setModel(new JComboBox<>(choicearea1).getModel());
}
else if (c3.getSelectedItem().equals("Volume")) {
choose.setModel(new JComboBox<>(choicevol).getModel());
choose1.setModel(new JComboBox<>(choicevol1).getModel());
}
else if (c3.getSelectedItem().equals("Weight")) {
choose.setModel(new JComboBox<>(choicewt).getModel());
choose1.setModel(new JComboBox<>(choicewt1).getModel());
}
else if (c3.getSelectedItem().equals("Time")) {
choose.setModel(new JComboBox<>(choicetime).getModel());
choose1.setModel(new JComboBox<>(choicetime1).getModel());
}
}
}
感谢你们！
基于另一个JComboBox内容的动态JComboBox内容
[英]Dynamic JComboBox content based on the contents of another JComboBox
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