动态简单文本编辑器Java

Question

我为我的项目修改了代码here。 我想制作一个具有动态文本区域的编辑器。每次按Enter键，都会创建一个新的文本区域。对不起，我无法用英文解释。

请看看我的代码：

import javax.swing.*; 
import javax.swing.text.*; 
import java.awt.*; 
import java.io.*; 
import java.awt.event.*; 
import java.util.Hashtable; 

public class SimpleEditor extends JFrame { 

    int count = 0; 
    private Action openAction = new SimpleEditor.OpenAction(); 
    private Action saveAction = new SimpleEditor.SaveAction(); 
    //private JTextComponent textComp; 
    private JTextComponent[] textComp2; 
    //private Hashtable actionHash = new Hashtable(); 

    public static void main(String[] args) { 
     SimpleEditor editor = new SimpleEditor(); 
     editor.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     editor.setVisible(true); 
    } 

    // Create an editor. 
    public SimpleEditor() { 
     super("Swing Editor"); 
     //textComp = createTextComponent(); 
     coba(); 
     makeActionsPretty(); 

     Container content = getContentPane(); 
     //content.add(textComp, BorderLayout.CENTER); 
     for (int i = 0; i < count; i++) { 
      content.add(textComp2[i], BorderLayout.CENTER); 
     } 
     content.add(createToolBar(), BorderLayout.NORTH); 
     setJMenuBar(createMenuBar()); 
     setSize(320, 240); 
    } 

    //coba-coba 
    protected void coba() { 
     if (count == 0) { 
      textComp2 = new JTextComponent[1]; 
      count += 1; 
     } else { 
      JTextComponent[] texttemp; 
      texttemp = new JTextComponent[count]; 
      for (int i = 0; i < count; i++) { 
       texttemp[i] = createTextComponent(); 
       texttemp[i] = textComp2[i]; 
      } 
      count += 1; 
      textComp2 = new JTextComponent[count]; 
      for (int i = 0; i < count - 1; i++) { 
       textComp2[i] = createTextComponent(); 
       textComp2[i] = texttemp[i]; 
      } 
     } 
    } 

    // Create the JTextComponent subclass. 
    protected JTextComponent createTextComponent() { 
     JTextArea ta = new JTextArea(); 
     ta.setFont(new Font("Courier New", Font.PLAIN, 12)); 
     ta.setLineWrap(true); 
     ta.addKeyListener(new java.awt.event.KeyAdapter() { 
      public void keyPressed(java.awt.event.KeyEvent ev) { 
       taKeyPressed(ev); 
      } 
     }); 
     return ta; 
    } 

    private void taKeyPressed(java.awt.event.KeyEvent ev) { 
     if (ev.getKeyCode() == 13) { 
      coba(); 
     } 
    } 

    // Add icons and friendly names to actions we care about. 
    protected void makeActionsPretty() { 
     Action a; 
     /*a = textComp.getActionMap().get(DefaultEditorKit.cutAction); 
     a.putValue(Action.SMALL_ICON, new ImageIcon("icons/cut.gif")); 
     a.putValue(Action.NAME, "Cut"); 

     a = textComp.getActionMap().get(DefaultEditorKit.copyAction); 
     a.putValue(Action.SMALL_ICON, new ImageIcon("icons/copy.gif")); 
     a.putValue(Action.NAME, "Copy"); 

     a = textComp.getActionMap().get(DefaultEditorKit.pasteAction); 
     a.putValue(Action.SMALL_ICON, new ImageIcon("icons/paste.gif")); 
     a.putValue(Action.NAME, "Paste"); 

     a = textComp.getActionMap().get(DefaultEditorKit.selectAllAction); 
     a.putValue(Action.NAME, "Select All");*/ 

     for (int i = 0; i < count; i++) { 
      a = textComp2[i].getActionMap().get(DefaultEditorKit.cutAction); 
      a.putValue(Action.SMALL_ICON, new ImageIcon("icons/cut.gif")); 
      a.putValue(Action.NAME, "Cut"); 

      a = textComp2[i].getActionMap().get(DefaultEditorKit.copyAction); 
      a.putValue(Action.SMALL_ICON, new ImageIcon("icons/copy.gif")); 
      a.putValue(Action.NAME, "Copy"); 

      a = textComp2[i].getActionMap().get(DefaultEditorKit.pasteAction); 
      a.putValue(Action.SMALL_ICON, new ImageIcon("icons/paste.gif")); 
      a.putValue(Action.NAME, "Paste"); 

      a = textComp2[i].getActionMap().get(DefaultEditorKit.selectAllAction); 
      a.putValue(Action.NAME, "Select All"); 
     } 
    } 

    // Create a simple JToolBar with some buttons. 
    protected JToolBar createToolBar() { 
     JToolBar bar = new JToolBar(); 

     // Add simple actions for opening & saving. 
     bar.add(getOpenAction()).setText(""); 
     bar.add(getSaveAction()).setText(""); 
     bar.addSeparator(); 

     // Add cut/copy/paste buttons. 
       /*bar.add(textComp.getActionMap().get(DefaultEditorKit.cutAction)).setText(""); 
     bar.add(textComp.getActionMap().get(
     DefaultEditorKit.copyAction)).setText(""); 
     bar.add(textComp.getActionMap().get(
     DefaultEditorKit.pasteAction)).setText("");*/ 

     for (int i = 0; i < count; i++) { 
      bar.add(textComp2[i].getActionMap().get(DefaultEditorKit.cutAction)).setText(""); 
      bar.add(textComp2[i].getActionMap().get(
       DefaultEditorKit.copyAction)).setText(""); 
      bar.add(textComp2[i].getActionMap().get(
       DefaultEditorKit.pasteAction)).setText(""); 
     } 
     return bar; 
    } 

    // Create a JMenuBar with file & edit menus. 
    protected JMenuBar createMenuBar() { 
     JMenuBar menubar = new JMenuBar(); 
     JMenu file = new JMenu("File"); 
     JMenu edit = new JMenu("Edit"); 
     menubar.add(file); 
     menubar.add(edit); 

     file.add(getOpenAction()); 
     file.add(getSaveAction()); 
     file.add(new SimpleEditor.ExitAction()); 
     /* edit.add(textComp.getActionMap().get(DefaultEditorKit.cutAction)); 
     edit.add(textComp.getActionMap().get(DefaultEditorKit.copyAction)); 
     edit.add(textComp.getActionMap().get(DefaultEditorKit.pasteAction)); 
     edit.add(textComp.getActionMap().get(DefaultEditorKit.selectAllAction));*/ 

     for (int i = 0; i < count; i++) { 
      edit.add(textComp2[i].getActionMap().get(DefaultEditorKit.cutAction)); 
      edit.add(textComp2[i].getActionMap().get(DefaultEditorKit.copyAction)); 
      edit.add(textComp2[i].getActionMap().get(DefaultEditorKit.pasteAction)); 
      edit.add(textComp2[i].getActionMap().get(DefaultEditorKit.selectAllAction)); 
     } 
     return menubar; 
    } 

    // Subclass can override to use a different open action. 
    protected Action getOpenAction() { 
     return openAction; 
    } 

    // Subclass can override to use a different save action. 
    protected Action getSaveAction() { 
     return saveAction; 
    } 

    //protected JTextComponent getTextComponent() { return textComp; } 
    // ********** ACTION INNER CLASSES ********** // 
    // A very simple exit action 
    public class ExitAction extends AbstractAction { 

     public ExitAction() { 
      super("Exit"); 
     } 

     public void actionPerformed(ActionEvent ev) { 
      System.exit(0); 
     } 
    } 

    // An action that opens an existing file 
    class OpenAction extends AbstractAction { 

     public OpenAction() { 
      super("Open", new ImageIcon("icons/open.gif")); 
     } 

     // Query user for a filename and attempt to open and read the file into the 
     // text component. 
     public void actionPerformed(ActionEvent ev) { 
      JFileChooser chooser = new JFileChooser(); 
      if (chooser.showOpenDialog(SimpleEditor.this) 
       != JFileChooser.APPROVE_OPTION) { 
       return; 
      } 
      File file = chooser.getSelectedFile(); 
      if (file == null) { 
       return; 
      } 

      FileReader reader = null; 
      try { 
       reader = new FileReader(file); 
       //textComp.read(reader, null); 
       for (int i = 0; i < count; i++) { 
        textComp2[i].read(reader, null); 
       } 
      } catch (IOException ex) { 
       JOptionPane.showMessageDialog(SimpleEditor.this, 
        "File Not Found", "ERROR", JOptionPane.ERROR_MESSAGE); 
      } finally { 
       if (reader != null) { 
        try { 
         reader.close(); 
        } catch (IOException x) { 
        } 
       } 
      } 
     } 
    } 

    // An action that saves the document to a file 
    class SaveAction extends AbstractAction { 

     public SaveAction() { 
      super("Save", new ImageIcon("icons/save.gif")); 
     } 

     // Query user for a filename and attempt to open and write the text 
     // component’s content to the file. 
     public void actionPerformed(ActionEvent ev) { 
      JFileChooser chooser = new JFileChooser(); 
      if (chooser.showSaveDialog(SimpleEditor.this) 
       != JFileChooser.APPROVE_OPTION) { 
       return; 
      } 
      File file = chooser.getSelectedFile(); 
      if (file == null) { 
       return; 
      } 

      FileWriter writer = null; 
      try { 
       writer = new FileWriter(file); 
       //textComp.write(writer); 
       for (int i = 0; i < count; i++) { 
        textComp2[i].write(writer); 
       } 
      } catch (IOException ex) { 
       JOptionPane.showMessageDialog(SimpleEditor.this, 
        "File Not Saved", "ERROR", JOptionPane.ERROR_MESSAGE); 
      } finally { 
       if (writer != null) { 
        try { 
         writer.close(); 
        } catch (IOException x) { 
        } 
       } 
      } 
     } 
    } 
} 

但是，我的代码有一些错误是这样的：

Exception in thread "main" java.lang.NullPointerException 
- at SimpleEditor.makeActionsPretty(SimpleEditor.java:101) 
- at SimpleEditor.<init>(SimpleEditor.java:29) 
- at SimpleEditor.main(SimpleEditor.java:19) 

任何人可以帮助我尽快？

Answer 1

阵列JTextComponent[]具有在不同的时间不同的尺寸，但在阵列默认null一个对象，直到下一次更改：

textComp2[i] = new JTextField("Hello");