为什么按下按钮后 JLabel 不再出现？

Question

我试图让按钮在 JTextField 旁边显示一个 Jlabel，但是当我按下时，JLabels 就不再出现了。

如果它引起问题，我对一些框和标签使用相同的坐标，我希望它们根据我按下的按钮出现在同一个位置。

单张图的问题：

import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class partegrafica extends JFrame{
    private static final long serialVersionUID = 1L;
    JPanel palumno,pprofe,ptutor,ptodo;
    JButton balumno,brofe,butor,avance,retroceso,guardar;
    JTextField boxname,boxdni,boxfecha,boxnrp,boxcial,boxcentrodestino,boxespecialidad,boxsalario,boxciclo;
    JLabel lavacia,lavaciaver, laname,ladni,lafecha,lanrp,lacial,laciclo,lacentrodestino,laespecialidad,lasalario,latitulo;

    public partegrafica(String[] args) {
    super("Catalogador de Humanos");

    GridBagConstraints cor = new GridBagConstraints();
    cor.anchor = GridBagConstraints.NORTHWEST;
    cor.weightx=1;
    cor.weighty=1;

setLayout(new GridBagLayout());

ptodo= new JPanel(new GridBagLayout());
setPreferredSize(new Dimension(1200, 800));
latitulo =new JLabel("Escoge perfil a introducir");
cor.gridx=0;
cor.gridy=0;
cor.gridheight=1;
cor.gridwidth=3;
ptodo.add(latitulo, cor);
balumno = new JButton("Insertar alumno");
cor.gridx=0;
cor.gridy=1;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(balumno, cor);
brofe = new JButton("Insertar Profesor");
cor.gridx=1;
cor.gridy=1;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(brofe, cor);
butor= new JButton("Insertar Tutor");
cor.gridx=2;
cor.gridy=1;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(butor, cor);
lavacia=new JLabel("                  ");
cor.gridx=3;
cor.gridy=1;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(lavacia, cor);
retroceso=new JButton("<");
cor.gridx=4;
cor.gridy=1;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(retroceso, cor);
avance=new JButton(">");
cor.gridx=5;
cor.gridy=1;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(avance, cor);
laname=new JLabel("Nombre");
cor.gridx=0;
cor.gridy=3;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(laname, cor);
boxname = new JTextField(10);
cor.gridx=1;
cor.gridy=3;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(boxname, cor);
ladni= new JLabel("DNI");
cor.gridx=0;
cor.gridy=4;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(ladni, cor);
boxdni = new JTextField(10);
cor.gridx=1;
cor.gridy=4;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(boxdni, cor);
lafecha= new JLabel("Fecha Nacimiento");
cor.gridx=0;
cor.gridy=5;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(lafecha, cor);
boxfecha= new JTextField(10);
cor.gridx=1;
cor.gridy=5;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(boxfecha, cor);
lanrp= new JLabel("NRP");
lanrp.setVisible(false);
cor.gridx=0;
cor.gridy=6;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(lanrp, cor);
boxnrp= new JTextField(10);
boxnrp.setVisible(false);
cor.gridx=1;
cor.gridy=6;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(boxnrp, cor);
lacial= new JLabel("CIAL");
lacial.setVisible(false);
cor.gridx=0;
cor.gridy=6;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(lacial, cor);
boxcial= new JTextField(10);
boxcial.setVisible(false);
cor.gridx=1;
cor.gridy=6;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(boxcial, cor);
laespecialidad= new JLabel("Especialidad (nº)");
//laespecialidad.setVisible(false);
cor.gridx=0;
cor.gridy=7;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(laespecialidad, cor);
boxespecialidad= new JTextField(10);
//boxespecialidad.setVisible(false);
cor.gridx=1;
cor.gridy=7;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(boxespecialidad, cor);
laciclo= new JLabel("Ciclo");
//laciclo.setVisible(false);
cor.gridx=0;
cor.gridy=7;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(laciclo, cor);
boxciclo=new JTextField(10);
//boxciclo.setVisible(false);
cor.gridx=1;
cor.gridy=7;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(boxciclo, cor);
lacentrodestino= new JLabel("Centro Destino");
//lacentrodestino.setVisible(false);
cor.gridx=0;
cor.gridy=8;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(lacentrodestino, cor);
boxcentrodestino= new JTextField(10);
//boxcentrodestino.setVisible(false);
cor.gridx=1;
cor.gridy=8;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(boxcentrodestino, cor);
lasalario= new JLabel("Salario:");
lasalario.setVisible(true);
cor.gridx=0;
cor.gridy=9;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(lasalario, cor);
boxsalario= new JTextField(10);
//boxsalario.setVisible(false);
cor.gridx=1;
cor.gridy=9;
cor.gridheight=1;
cor.gridwidth=1;
ptodo.add(boxsalario, cor);
guardar= new JButton("Guardar");
cor.gridx=2;
cor.gridy=3;
cor.gridheight=3;
cor.gridwidth=1;
ptodo.add(guardar, cor);

balumno.addActionListener(new AAlumno());
brofe.addActionListener(new AProfe());
butor.addActionListener(new ATutor());
avance.addActionListener(new Avanzar());
retroceso.addActionListener(new Retroceso());
guardar.addActionListener(new Guardar());

add(ptodo, cor);

ptodo.setVisible(true);
pack();
}

    public class AAlumno implements ActionListener{
        public void actionPerformed(ActionEvent e){

        lacial.setVisible(true);
        boxcial.setVisible(true);
        laciclo.setVisible(true);
        boxciclo.setVisible(true);

        lanrp.setVisible(false);
        boxnrp.setVisible(false);
        laespecialidad.setVisible(false);
        boxespecialidad.setVisible(false);
        lacentrodestino.setVisible(false);
        boxcentrodestino.setVisible(false);
        lasalario.setVisible(false);
        boxsalario.setVisible(false);

        lanrp.setText("");
        boxnrp.setText("");
        laespecialidad.setText("");
        boxespecialidad.setText("");
        lacentrodestino.setText("");
        boxcentrodestino.setText("");
        lasalario.setText("");
        boxsalario.setText("");
        lacial.setText("");
        boxcial.setText("");
        laciclo.setText("");
        boxciclo.setText("");
        validate();

        }
    }
    public class AProfe implements ActionListener{
        public void actionPerformed(ActionEvent e){

        lacial.setVisible(false);
        boxcial.setVisible(false);
        laciclo.setVisible(false);
        boxciclo.setVisible(false);

        lanrp.setVisible(true);
        boxnrp.setVisible(true);
        laespecialidad.setVisible(true);
        boxespecialidad.setVisible(true);
        lacentrodestino.setVisible(true);
        boxcentrodestino.setVisible(true);
        lasalario.setVisible(true);
        boxsalario.setVisible(true);
        lacial.setText("");
        boxcial.setText("");
        laciclo.setText("");
        boxciclo.setText("");
        lanrp.setText("");
        boxnrp.setText("");
        laespecialidad.setText("");
        boxespecialidad.setText("");
        lacentrodestino.setText("");
        boxcentrodestino.setText("");
        lasalario.setText("");
        boxsalario.setText("");
        validate();
        }
    }
    public class ATutor implements ActionListener{
        public void actionPerformed(ActionEvent e){

        }
    }
    public class Avanzar implements ActionListener{
        public void actionPerformed(ActionEvent e){

        }
    }
    public class Retroceso implements ActionListener{
        public void actionPerformed(ActionEvent e){

        }
    }
    public class Guardar implements ActionListener{
        public void actionPerformed(ActionEvent e){

        }
    }
        }

Answer 1

我的主要建议是使用 JPanel 交换 JPanel“视图”，但如果您绝对需要使用上述代码，则不要交换 JLabels，而是交换它们显示的 文本使用setText(...) 方法。并且不要让 JLabel 可见或不可见，如果要使其不可见，则不要通过 setText("") 向它们提供任何文本。

CardLayout 教程可以在这里找到：CardLayout tutorial。

以 CardLayout 为例：

import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.util.HashMap;
import java.util.Map;

import javax.swing.*;

@SuppressWarnings("serial")
public class SwapViews extends JPanel {
    public static final String ALUMNO = "Insertar Alumno";
    public static final String PROFESSOR = "Insertar Profesor";
    public static final String[] ALUMNO_TEXTS = { "Nombre", "DNI", "Fecha Nacimiento", "CIAL",
            "Ciclo" };
    public static final String[] PROFESOR_TEXTS = { "Nombre", "DNI", "Fecha Nacimiento", "NRP",
            "Especialidad (nº)", "Centro Destino", "Salario:", };
    private static final int EB_GAP = 2;
    private CardLayout cardLayout = new CardLayout();
    private JPanel cardHolderPanel = new JPanel(cardLayout);
    private DataEntryPanel alumnoPanel = new DataEntryPanel(ALUMNO, ALUMNO_TEXTS);
    private DataEntryPanel profesorPanel = new DataEntryPanel(PROFESSOR, PROFESOR_TEXTS);

    public SwapViews() {
        JPanel alumnoWrapperPanel = new JPanel(new BorderLayout());
        alumnoWrapperPanel.add(alumnoPanel, BorderLayout.PAGE_START);

        JPanel profesorWrapperPanel = new JPanel(new BorderLayout());
        profesorWrapperPanel.add(profesorPanel, BorderLayout.PAGE_START);

        cardHolderPanel.add(alumnoWrapperPanel, ALUMNO);
        cardHolderPanel.add(profesorWrapperPanel, PROFESSOR);

        JPanel buttonPanel = new JPanel();
        buttonPanel.add(new JButton(new ShowCardAction(ALUMNO, KeyEvent.VK_A)));
        buttonPanel.add(new JButton(new ShowCardAction(PROFESSOR, KeyEvent.VK_P)));

        setBorder(BorderFactory.createEmptyBorder(EB_GAP, EB_GAP, EB_GAP, EB_GAP));
        setLayout(new BorderLayout());
        add(cardHolderPanel, BorderLayout.CENTER);
        add(buttonPanel, BorderLayout.PAGE_END);
    }

    private class ShowCardAction extends AbstractAction {
        public ShowCardAction(String name, int mnemonic) {
            super(name);
            putValue(MNEMONIC_KEY, mnemonic);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            cardLayout.show(cardHolderPanel, getValue(NAME).toString());
        }
    }

    private static void createAndShowGui() {
        SwapViews mainPanel = new SwapViews();

        JFrame frame = new JFrame("SwapViews");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}

@SuppressWarnings("serial")
class DataEntryPanel extends JPanel {
    private static final int COLUMNS = 10;
    private static final Insets WEST_INSETS = new Insets(4, 4, 4, 4);
    private static final Insets EAST_INSETS = new Insets(4, 10, 4, 4);
    private String[] labels;
    private Map<String, JTextField> fieldMap = new HashMap<>();

    public DataEntryPanel(String title, String[] labels) {
        super(new GridBagLayout());
        setBorder(BorderFactory.createTitledBorder(title));
        this.labels = labels;
        for (int i = 0; i < labels.length; i++) {
            String text = labels[i];
            JLabel label = new JLabel(text);
            JTextField textField = new JTextField(COLUMNS);
            fieldMap.put(text, textField);

            add(label, getGbc(0, i));
            add(textField, getGbc(1, i));
        }
    }

    public String[] getLabels() {
        return labels;
    }

    public static GridBagConstraints getGbc(int x, int y) {
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.gridx = x;
        gbc.gridy = y;
        gbc.anchor = x == 0 ? GridBagConstraints.WEST : GridBagConstraints.EAST;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        gbc.weightx = 1.0;
        gbc.weighty = 1.0;
        gbc.insets = x == 0 ? WEST_INSETS : EAST_INSETS;
        return gbc;
    }

    public String getLabelText(String key) {
        return fieldMap.get(key).getText();
    }

}

您的代码可能无法正常工作，因为您在同一个 GridBagLayout 位置添加了多个组件。再次保留一组可重复使用的 JLabel 会更好。

根据我的评论，您还将一些 JLabel 的文本设置为您不希望这样做的“可见”。仔细检查您的 ActionListeners 以了解我的意思。

Answer 2

我找到了标签消失的原因。我将所有标签设置为按钮内没有文本。仅此而已。一个愚蠢的错误。