java - JTextField 在 Eclipse 中一切看起来都正常，但无法编译

Question

有人可以告诉我这段代码有什么问题吗？我需要它弹出一个框架并用某个字段填充框架，一个名称字段和一个输入字段，并在网格底部显示一个按钮。欢迎任何帮助，谢谢!!

    import java.awt.*;
    import javax.swing.*;

    public class FrameDemo 
    //To create the gui and show it.
    {   
    public static void createAndShowGUI()
    {
        //create and set up the window.
        JFrame frame = new JFrame("RungeKutta");
        GridLayout first = new GridLayout(1,14);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create, name and Populate TextField   
        JTextField PL = new JTextField("Pendulum Length", 20);
        //Set TextField to Uneditable. Each will have Empty Field Below For Variables   
        PL.setEditable(false);  
        //Set Textfield for user entered dat
        JTextField PLv = new JTextField();
        //Allow handler for user input on Empty Textfield?

        JTextField AD = new JTextField("Angular Displacement", 20);
        AD.setEditable(false);
            JTextField ADv = new JTextField();

        JTextField AV = new JTextField("Angular Velocity", 20);
        AV.setEditable(false);
        JTextField Avv = new JTextField();

        JTextField TS= new JTextField("Time Steps", 20);
        TS.setEditable(false);
        JTextField TSv = new JTextField();

        JTextField MT = new JTextField("Max Time", 20);
        MT.setEditable(false);
        JTextField MTv = new JTextField();

        JTextField V = new JTextField("Viscosity (0-1)", 20);
        V.setEditable(false);
        JTextField Vv = new JTextField();

        //Create Button to Restart
    JButton BNewGraph = new JButton("Draw New Graph"); //Button to restart entire drawing process
        JLabel emptyLabel = new JLabel("");
    emptyLabel.setPreferredSize(new Dimension(600,500));
    frame.getContentPane().add(PL, first);
    frame.getContentPane().add(PLv, first);
    frame.getContentPane().add(AD, first);
    frame.getContentPane().add(ADv, first);
    frame.getContentPane().add(AV, first);
    frame.getContentPane().add(Avv, first);
    frame.getContentPane().add(TS, first);
    frame.getContentPane().add(TSv, first);
    frame.getContentPane().add(MT, first);
    frame.getContentPane().add(MTv, first);
    frame.getContentPane().add(V, first);
    frame.getContentPane().add(Vv, first);
    frame.getContentPane().add(BNewGraph, first);
    //display the window
    frame.pack();
    frame.setVisible(true);
    }

    public static void main(String[] args)
    {
        //add job to event scheduler
        //create and show GUI
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
            }
    }

Answer 1

这不是您使用 GridLayout 的方式:

frame.getContentPane().add(PL, first);

相反，您可以使用布局管理器设置容器的布局:

frame.getContentPane().setLayout(first);

然后将组件添加到容器中:

frame.getContentPane().add(PL);
frame.getContentPane().add(PLv);
frame.getContentPane().add(AD);
frame.getContentPane().add(ADv);
frame.getContentPane().add(AV);
frame.getContentPane().add(Avv);
frame.getContentPane().add(TS);
frame.getContentPane().add(TSv);
frame.getContentPane().add(MT);
frame.getContentPane().add(MTv);
// and so on for all the components.

您需要阅读有关如何使用 GridLayout 的教程，您可以在此处找到:GridLayout Tutorial .

顺便说一句，请注意:

frame.getContentPane().add(PL);

可以缩短为:

frame.add(PL);

您还需要研究和学习 Java 命名约定:类名以大写字母开头，所有方法和变量以小写字母开头。还要避免像 pl 或 plv，或 ad 或 adv 这样的变量名，而是使用稍微长一点且有意义的名称，这些名称使您的代码具有 self 注释作用。因此，考虑使用 angularDisplacementField 作为 JTextfield 的名称而不是 AD。

---

我自己，我会使用 GridBagLayout 并做类似的事情:

import java.awt.BorderLayout;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import javax.swing.*;

public class GuiDemo extends JPanel {

   // or better -- use an enum for this
   public static final String[] FIELD_LABELS = {
      "Pendulum Length", "Angular Displacement", "Angular Velocity",
      "Time Steps", "Max Time", "Viscocity (0-1)"
   };
   private static final int TEXT_FIELD_COLUMNS = 10;
   private static final int GAP = 3;
   private static final Insets RIGHT_GAP_INSETS = new Insets(GAP, GAP, GAP, 3 * GAP);
   private static final Insets BALANCED_INSETS = new Insets(GAP, GAP, GAP, GAP);
   private Map<String, JTextField> labelFieldMap = new HashMap<>();

   public GuiDemo() {
      JPanel labelFieldPanel = new JPanel(new GridBagLayout());
      int row = 0;

      // to make sure that no focusAccelerator is re-used
      Set<Character> focusAccelSet = new HashSet<>();
      for (String fieldLabelLText : FIELD_LABELS) {
         JLabel fieldLabel = new JLabel(fieldLabelLText);
         JTextField textField = new JTextField(TEXT_FIELD_COLUMNS);
         labelFieldPanel.add(fieldLabel, getGbc(row, 0));
         labelFieldPanel.add(textField, getGbc(row, 1));
         labelFieldMap.put(fieldLabelLText, textField);

         for (char c : fieldLabelLText.toCharArray()) {
            if (!focusAccelSet.contains(c)) {
               textField.setFocusAccelerator(c);
               fieldLabel.setDisplayedMnemonic(c);
               focusAccelSet.add(c);
               break;
            }
         }

         row++;
      }
      JButton button = new JButton(new DrawGraphAction("Draw New Graph"));

      labelFieldPanel.add(button, getGbc(row, 0, 2, 1));

      setLayout(new BorderLayout(GAP, GAP));
      add(labelFieldPanel, BorderLayout.CENTER);
   }

   private class DrawGraphAction extends AbstractAction {
      public DrawGraphAction(String name) {
         super(name);
         int mnemonic = (int) name.charAt(0);
         putValue(MNEMONIC_KEY, mnemonic);
      }

      @Override
      public void actionPerformed(ActionEvent e) {
         // TODO calculation method

      }
   }

   public static GridBagConstraints getGbc(int row, int column) {
      GridBagConstraints gbc = new GridBagConstraints();
      gbc.gridx = column;
      gbc.gridy = row;
      gbc.gridwidth = 1;
      gbc.gridheight = 1;
      gbc.fill = GridBagConstraints.HORIZONTAL;
      if (column == 0) {
         gbc.anchor = GridBagConstraints.LINE_START;
         gbc.fill = GridBagConstraints.BOTH;
         gbc.insets = RIGHT_GAP_INSETS;
      } else {
         gbc.anchor = GridBagConstraints.LINE_END;
         gbc.fill = GridBagConstraints.HORIZONTAL;
         gbc.insets = BALANCED_INSETS;
      }

      return gbc;
   }

   public static GridBagConstraints getGbc(int row, int column, int width, int height) {
      GridBagConstraints gbc = getGbc(row, column);
      gbc.gridwidth = width;
      gbc.gridheight = height;
      gbc.insets = BALANCED_INSETS;
      gbc.fill = GridBagConstraints.BOTH;
      return gbc;
   }

   private static void createAndShowGui() {
      JFrame frame = new JFrame("Gui Demo");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(new GuiDemo());
      frame.pack();
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}