GUI，Java Swing，标签和文本字段

Question

i recently started learning how to code in Java swing, writing it by hand. I am trying to make a GUI, for an assignment, but i am struggling to attach four labels to four text fields that are in a Grid format.

The text fields are in a panel, within a panel. So i could have the the fields next to the buttons.

I am really confused on how to go from where i am. As i want each label to go on the left hand side of each text field. So the "Train on" goes on the left hand side next to the text field "On", And the "Train Moving" label goes on the left hand side of the text field "off". And so on. I'm quite a newb at this, so any help would be greatly appreciated thank you. The code i have posted currently works.

Edit

Had to remove code for reasons

Answer 1

Every realistic example I have of a GridBagLayout is complicated. This is the simplest, real world example that I have. This dialog has a GridBagLayout inside of a BoxLayout. The button is in a JPanel using a FlowLayout

And here's the code:

package com.ggl.sudoku.solver.view;

import java.awt.Component;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class SolutionDialog {

    protected static final Insets   buttonInsets    = new Insets(10, 10, 0, 10);

    private int                     singleCount;
    private int                     guessCount;

    private long                    elapsedTime;

    private JDialog                 dialog;

    private SudokuFrame             frame;

    public SolutionDialog(SudokuFrame frame, int singleCount, int guessCount,
            long elapsedTime) {
        this.frame = frame;
        this.singleCount = singleCount;
        this.guessCount = guessCount;
        this.elapsedTime = elapsedTime;
        createPartControl();
    }

    private void createPartControl() {
        dialog = new JDialog(frame.getFrame(), "Statistics");
        dialog.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE);

        JPanel mainPanel = new JPanel();
        mainPanel.setLayout(new BoxLayout(mainPanel, BoxLayout.Y_AXIS));

        JPanel resultsPanel = new JPanel();
        resultsPanel.setLayout(new GridBagLayout());

        int gridy = 0;

        JLabel singleCountLabel = new JLabel("Cells with one possible number:");
        addComponent(resultsPanel, singleCountLabel, 0, gridy, 1, 1,
                buttonInsets, GridBagConstraints.LINE_START,
                GridBagConstraints.HORIZONTAL);

        String s = singleCount + " cells";
        JLabel singleCountString = new JLabel(s);
        addComponent(resultsPanel, singleCountString, 1, gridy++, 1, 1,
                buttonInsets, GridBagConstraints.LINE_START,
                GridBagConstraints.HORIZONTAL);

        JLabel guessCountLabel = new JLabel("Cells where the solver guessed:");
        addComponent(resultsPanel, guessCountLabel, 0, gridy, 1, 1,
                buttonInsets, GridBagConstraints.LINE_START,
                GridBagConstraints.HORIZONTAL);

        s = guessCount + " cells";
        JLabel guessCountString = new JLabel(s);
        addComponent(resultsPanel, guessCountString, 1, gridy++, 1, 1,
                buttonInsets, GridBagConstraints.LINE_START,
                GridBagConstraints.HORIZONTAL);

        JLabel elapsedTimeLabel = new JLabel("Elapsed Time:");
        addComponent(resultsPanel, elapsedTimeLabel, 0, gridy, 1, 1,
                buttonInsets, GridBagConstraints.LINE_START,
                GridBagConstraints.HORIZONTAL);

        s = elapsedTime + " milliseconds";
        JLabel elapsedTimeString = new JLabel(s);
        addComponent(resultsPanel, elapsedTimeString, 1, gridy++, 1, 1,
                buttonInsets, GridBagConstraints.LINE_START,
                GridBagConstraints.HORIZONTAL);

        mainPanel.add(resultsPanel);

        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new FlowLayout());

        JButton okButton = new JButton("OK");
        okButton.setAlignmentX(JButton.RIGHT_ALIGNMENT);
        okButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent event) {
                dialog.setVisible(false);
                dialog.dispose();
            }
        });
        buttonPanel.add(okButton);

        mainPanel.add(buttonPanel);

        dialog.add(mainPanel);
        dialog.pack();
        dialog.setBounds(getBounds());
        dialog.setVisible(true);
    }

    private void addComponent(Container container, Component component,
            int gridx, int gridy, int gridwidth, int gridheight, Insets insets,
            int anchor, int fill) {
        GridBagConstraints gbc = new GridBagConstraints(gridx, gridy,
                gridwidth, gridheight, 1.0D, 1.0D, anchor, fill, insets, 0, 0);
        container.add(component, gbc);
    }

    protected Rectangle getBounds() {
        Rectangle f = frame.getBounds();
        Rectangle d = dialog.getBounds();
        d.x = f.x + (f.width - d.width) / 2;
        d.y = f.y + (f.height - d.height) / 2;
        return d;
    }

}

In the addComponent method, I create a new GridBagConstraints for each Swing component. I do this because I don't like remembering defaults. I prefer to specify all of the constraints for each Swing component.

These Swing components create a JDialog, but the same principles would apply when creating a JPanel.

If you want to see how the whole Swing application fits together, read my article Sudoku Solver Swing GUI .

Here's another example that's more complicated, but it includes JTextFields.

And here's the code to create the entry panel:

package com.ggl.envelopes.view;

import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;

import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

import com.ggl.envelopes.model.Address;
import com.ggl.envelopes.model.EnvelopeModel;
import com.ggl.envelopes.model.State;

public class AddressPanel {

    private static final Insets entryInsets = 
            new Insets(0, 10, 4, 10);
    private static final Insets spaceInsets = 
            new Insets(10, 10, 4, 10);

    private Address currentAddress;

    private AddressComboBoxItemListener listener;

    private DefaultComboBoxModel<Address> addressComboBoxModel;
    private DefaultComboBoxModel<State> stateComboBoxModel;

    private EnvelopeModel model;

    private JButton updateButton;
    private JButton deleteButton;

    private JComboBox<Address> addressComboBox;
    private JComboBox<State> stateComboBox;

    private JLabel messageLabel;

    private JPanel mainPanel;

    private JTextField nameField;
    private JTextField address1Field;
    private JTextField address2Field;
    private JTextField cityField;
    private JTextField zip5Field;
    private JTextField zip4Field;

    public AddressPanel(EnvelopeModel model) {
        this.model = model;
        this.listener = new AddressComboBoxItemListener();
        this.addressComboBoxModel = 
                new DefaultComboBoxModel<Address>();
        this.stateComboBoxModel =
                new DefaultComboBoxModel<State>();
        createPartControl();
    }

    private void createPartControl() {
        mainPanel = new JPanel();
        mainPanel.setLayout(new GridBagLayout());

        int gridy = 0;

        if (model.getAddresses().size() > 0) {
            gridy = createAddressComboBox(gridy);
        }

        gridy = createAddressControl(gridy);
    }

    private int createAddressComboBox(int gridy) {
        JLabel addressesLabel = new JLabel("Addresses:");
        addressesLabel.setHorizontalAlignment(JLabel.LEFT);
        addComponent(mainPanel, addressesLabel, 0, gridy, 
                1, 1, spaceInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        buildAddressComboBoxModel();

        addressComboBox = new JComboBox<Address>(addressComboBoxModel);
        addressComboBox.addItemListener(listener);
        addComponent(mainPanel, addressComboBox, 1, gridy++, 
                4, 1, spaceInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        return gridy;
    }

    private int createAddressControl(int gridy) {
        JLabel nameLabel = new JLabel("Name:");
        nameLabel.setHorizontalAlignment(JLabel.LEFT);
        addComponent(mainPanel, nameLabel, 0, gridy, 
                1, 1, spaceInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        nameField = new JTextField(30);
        nameLabel.setLabelFor(nameField);
        addComponent(mainPanel, nameField, 1, gridy++, 
                4, 1, spaceInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        JLabel address1Label = new JLabel("Address:");
        address1Label.setHorizontalAlignment(JLabel.LEFT);
        addComponent(mainPanel, address1Label, 0, gridy, 
                1, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        address1Field = new JTextField(30);
        address1Label.setLabelFor(address1Field);
        addComponent(mainPanel, address1Field, 1, gridy++, 
                4, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        JLabel address2Label = new JLabel(" ");
        address2Label.setHorizontalAlignment(JLabel.LEFT);
        addComponent(mainPanel, address2Label, 0, gridy, 
                1, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        address2Field = new JTextField(30);
        address2Label.setLabelFor(address2Field);
        addComponent(mainPanel, address2Field, 1, gridy++, 
                4, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        JLabel dummyLabel = new JLabel(" ");
        dummyLabel.setHorizontalAlignment(JLabel.LEFT);
        addComponent(mainPanel, dummyLabel, 0, gridy, 
                1, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        cityField = new JTextField(10);
        dummyLabel.setLabelFor(cityField);
        addComponent(mainPanel, cityField, 1, gridy, 
                1, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        buildStateComboBoxModel();

        stateComboBox = new JComboBox<State>(stateComboBoxModel);
        stateComboBox.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent event) {
                if (event.getActionCommand()
                        .equals("comboBoxEdited")) {
                    String s = stateComboBox.getSelectedItem()
                            .toString();
                    State t = model.getStateByAbbreviation(s);
                    if (t != null) {
                        stateComboBox.setSelectedItem(t);
                    }
                }
            }   
        });
        stateComboBox.setEditable(true);
        addComponent(mainPanel, stateComboBox, 2, gridy, 
                1, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        zip5Field = new JTextField(6);
        addComponent(mainPanel, zip5Field, 3, gridy, 
                1, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        zip4Field = new JTextField(6);
        addComponent(mainPanel, zip4Field, 4, gridy++, 
                1, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        messageLabel = new JLabel(" ");
        messageLabel.setHorizontalAlignment(JLabel.LEFT);
        addComponent(mainPanel, messageLabel, 0, gridy++, 
                5, 1, entryInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        JPanel buttonPanel = createButtonPanel();
        addComponent(mainPanel, buttonPanel, 0, gridy++, 
                5, 1, spaceInsets, GridBagConstraints.LINE_START, 
                GridBagConstraints.HORIZONTAL);

        return gridy;
    }

    private void buildAddressComboBoxModel() {
        addressComboBoxModel.removeAllElements();
        for (Address address : model.getAddresses()) {
            addressComboBoxModel.addElement(address);
        }
    }

    private void buildStateComboBoxModel() {
        stateComboBoxModel.removeAllElements();
        for (State state : model.getStates()) {
            stateComboBoxModel.addElement(state);
        }
    }

    private JPanel createButtonPanel() {
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(1, 3, 20, 0));

        JButton addButton = new JButton("Add Address");
        addButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent event) {
                String message = checkFields();
                if (message.equals("")) {
                    Address address = createAddress();
                    model.addAddress(address);
                    if (model.getAddresses().size() == 1) {
                        mainPanel.removeAll();
                        int gridy = 0;
                        gridy = createAddressComboBox(gridy);
                        gridy = createAddressControl(gridy);
                    } else {
                        clearFields();
                        addressComboBox.removeItemListener(listener);
                        buildAddressComboBoxModel();
                        addressComboBox.addItemListener(listener);
                    }
                    messageLabel.setForeground(Color.GREEN);
                    messageLabel.setText("Address \"" + 
                            address.getName() + "\" saved");
                } else {
                    messageLabel.setForeground(Color.RED);
                    messageLabel.setText(message);
                }
            }           
        });
        addButton.setHorizontalAlignment(JButton.CENTER);
        buttonPanel.add(addButton);

        updateButton = new JButton("Change Address");
        updateButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent event) {
                String message = checkFields();
                if (message.equals("")) {
                    Address changedAddress = createAddress();
                    updateReturnSenderAddresses(
                            currentAddress, changedAddress);
                    model.updateAddress(
                            currentAddress, changedAddress);
                    clearFields();
                    addressComboBox.removeItemListener(listener);
                    buildAddressComboBoxModel();
                    addressComboBox.addItemListener(listener);
                    messageLabel.setForeground(Color.GREEN);
                    messageLabel.setText("Address \"" + 
                            currentAddress.getName() + "\" changed");
                    updateButton.setEnabled(false);
                    deleteButton.setEnabled(false);
                } else {
                    messageLabel.setForeground(Color.RED);
                    messageLabel.setText(message);
                }
            }   
        });
        updateButton.setEnabled(false);
        updateButton.setHorizontalAlignment(JButton.CENTER);
        buttonPanel.add(updateButton);

        deleteButton = new JButton("Delete Address");
        deleteButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent event) {
                deleteReturnSenderAddresses(currentAddress);
                model.removeAddress(currentAddress);
                clearFields();
                addressComboBox.removeItemListener(listener);
                buildAddressComboBoxModel();
                addressComboBox.addItemListener(listener);
                messageLabel.setForeground(Color.GREEN);
                messageLabel.setText("Address \"" + 
                        currentAddress.getName() + "\" deleted");
                updateButton.setEnabled(false);
                deleteButton.setEnabled(false);
            }   
        });
        deleteButton.setEnabled(false);
        deleteButton.setHorizontalAlignment(JButton.CENTER);
        buttonPanel.add(deleteButton);

        return buttonPanel;
    }

    private void addComponent(Container container, Component component,
            int gridx, int gridy, int gridwidth, int gridheight, 
            Insets insets, int anchor, int fill) {
        GridBagConstraints gbc = new GridBagConstraints(gridx, gridy,
                gridwidth, gridheight, 1.0D, 1.0D, anchor, 
                fill, insets, 0, 0);
        container.add(component, gbc);
    }

    private String checkFields() {
        String message = "";

        State state = null;
        try {
            state = (State) stateComboBox.getSelectedItem();
        } catch (ClassCastException e) {
            message = "State abbreviation is invalid";
            return message;
        }

        if (state == null) {
            message = "State abbreviation is null";
            return message;
        }

        String abbreviation = state.getAbbreviation();

        boolean n = nameField.getText().trim().isEmpty();
        boolean a = address1Field.getText().trim().isEmpty();
        boolean c = cityField.getText().trim().isEmpty();
        boolean s = abbreviation.trim().isEmpty();
        boolean z = zip5Field.getText().trim().isEmpty();

        if (n || a || c || s || z) {
            message = "One or more required fields are empty";
            return message;
        }

//      boolean x = stateField.getText().trim().length() > 2;
        boolean g = isNumeric(zip5Field.getText().trim());

//      if (x) {
//          message = "State is more than 2 characters";
//          return message;
//      }

        if (!g) {
            message = "Zip 5 is not numeric";
            return message;
        }

        if (zip4Field.getText().trim().isEmpty()) {
            return message;
        } else {
            if (isNumeric(zip4Field.getText().trim())) {
                return message;
            } else {
                message = "Zip 4 is not numeric";
                return message;
            }
        }
    }

    private boolean isNumeric(String s) {
        try {
            Integer.valueOf(s);
            return true;
        } catch (NumberFormatException e) {
            return false;
        }
    }

    private Integer setZip(String s) {
        return (s.isEmpty()) ? null : Integer.valueOf(s);
    }

    private Address createAddress() {
        String abbreviation = 
                ((State) stateComboBox.getSelectedItem())
                .getAbbreviation();

        return new Address(
                nameField.getText().trim(),
                address1Field.getText().trim(),
                address2Field.getText().trim(),
                cityField.getText().trim(),
                abbreviation.toUpperCase(),
                setZip(zip5Field.getText().trim()),
                setZip(zip4Field.getText().trim())
                );
    }

    private void clearFields() {
        nameField.setText("");
        address1Field.setText("");
        address2Field.setText("");
        cityField.setText("");
        stateComboBox.setSelectedIndex(0);
        zip5Field.setText("");
        zip4Field.setText("");
    }

    private void setFields(Address address) {
        nameField.setText(address.getName());
        address1Field.setText(address.getAddressLine1());
        address2Field.setText(address.getAddressLine2());
        cityField.setText(address.getCity());
        stateComboBox.setSelectedItem(
                model.getStateByAbbreviation(address.getState()));
        zip5Field.setText(String.format("%05d", address.getZip5()));
        zip4Field.setText(displayZip4(address.getZip4()));
    }

    private String displayZip4(Integer value) {
        return (value == null) ? "" : String.format("%04d", value);
    }

    private void updateReturnSenderAddresses(Address oldAddress,
            Address newAddress) {
        if (oldAddress.equals(model.getReturnAddress())) {
            model.setReturnAddress(newAddress);
        }
        if (oldAddress.equals(model.getSenderAddress())) {
            model.setSenderAddress(newAddress);
        }
    }

    private void deleteReturnSenderAddresses(Address address) {
        if (address.equals(model.getReturnAddress())) {
            model.clearReturnAddress();
        }
        if (address.equals(model.getSenderAddress())) {
            model.clearSenderAddress();
        }
    }

    public void refresh() {
        messageLabel.setText(" ");
    }

    public JPanel getMainPanel() {
        return mainPanel;
    }

    public class AddressComboBoxItemListener implements ItemListener {
        @Override
        public void itemStateChanged(ItemEvent event) {
            currentAddress = (Address) 
                    addressComboBox.getSelectedItem();
            setFields(currentAddress);
            updateButton.setEnabled(true);
            deleteButton.setEnabled(true);
        }

    }

}

I used the same addComponent method to add the Swing components to the main JPanel. You can see how I dealt with the JTextFields.