Creating the User Interface for the Text Editor Application

Creating the User Interface for the Text Editor Application

The Editor.java file helps create a user interface with a menu bar and a text area for the Text Editor application. Using this interface, the end user can create, open , save, lock, edit, or format a new file or the existing file. The user interface also contains a text area where the contents of the new file or existing file are displayed to the end user.

Listing 6-1 shows the contents of the Editor.java file:

Listing 6-1: The Editor.java File

 /* Imports the java.net package class. */ import java.net.URL; /* Imports javax.swing.undo package classes. */ import javax.swing.undo.UndoManager; import javax.swing.undo.CannotUndoException; import javax.swing.undo.CannotRedoException; /* Imports javax.swing package classes. */ import javax.swing.JColorChooser; import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; import javax.swing.JTextArea; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JCheckBoxMenuItem; import javax.swing.UIManager; import javax.swing.Action; import javax.swing.KeyStroke; import javax.swing.AbstractAction; /* Imports java.awt package class. */ import java.awt.BorderLayout; /* Imports java.awt.event package classes. */ import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.ActionEvent; import java.awt.event.KeyEvent; /* Imports javax.swing.event package classes. */ import javax.swing.event.UndoableEditListener; import javax.swing.event.UndoableEditEvent; /* Class Editor - This class is the main class of the application. This class initializes  the interface and loads all components like text area and menu bar on the main window. Fields:    menu - Creates the menu bar.    file - Creates the File menu.    edit - Creates the Edit menu.    format - Creates the Format menu.    lock - Creates the Lock menu.    help - Creates the Help menu.    newfile - Creates the New menu item.    open - Creates the Open menu item.    print - Creates the Print menu item.    save - Creates the Save menu item.    saveas - Creates the Save As menu item.    exit - Creates the Open Exit item.    cut - Creates the Cut menu item.    copy - Creates the Copy menu item.    paste - Creates the Paste menu item.    find - Creates the Find menu item.    selectAll - Creates the Select All menu tem.    datetime - Creates the Date/Time menu item.    font - Creates the Open Font item.    color - Creates the Open Color item.    about - Creates the Open Help item.    area - Creates an object the JTextArea class that contains the file contents.    panel - Creates the panel menu item that contains all the AWT and swing components.    scrollpane - Creates an object of the JScrollPane class that is added to the text area.    str - Creates the String object.    wordWrap - Creates the Word Wrap menu item.    exclusiveLock - Creates the Exclusive menu item.    shareLock - Creates the Share menu item. Methods:    addWindowListener() - This method is called when end user clicks the window close button.    actionPerformed() - This method is invoked when an end user selects any command from the menu bar.    undoableEditHappened() - This method is called when an end user performs undo and redo operation.    main() - This method creates the main window of the application and displays it. */ public class Editor extends JFrame implements ActionListener, UndoableEditListener, Runnable {    /* Creates an object of the ActionPerform class. */    public ActionPerform action = new ActionPerform(this);    /* Creates an object of the UndoManager class. */    UndoManager undoManager = new UndoManager();    /* Creates an instance of the UndoAction class. */    UndoAction undoAction = new UndoAction();    /* Creates an instance of the RedoAction class. */    RedoAction redoAction = new RedoAction();    /* Declares an object of the JMenuBar class. */    JMenuBar menu;    /* Declares objects of the JMenu class. */    JMenu file;    JMenu edit;    JMenu format;    JMenu lock;    JMenu help;    /* Declares objects of the JMenuItem class. */    JMenuItem newfile;    JMenuItem open;    JMenuItem print;    JMenuItem save;    JMenuItem saveas;    JMenuItem exit;    JMenuItem cut;    JMenuItem copy;    JMenuItem paste;    JMenuItem find;    JMenuItem selectAll;    JMenuItem datetime;    JMenuItem font;    JMenuItem color;    JMenuItem about;    /* Declares an object of the JTextArea class. */    JTextArea area;    /* Declares an object of the JPanel class. */    JPanel panel;    /* Declares an object of the JScrollPane class. */    JScrollPane scrollpane;    /* Declares an object of the String class. */    String str;    /* Declares objects of the JCheckBoxMenuItem class. */    JCheckBoxMenuItem wordWrap;    JCheckBoxMenuItem exclusiveLock;    JCheckBoxMenuItem shareLock;    /* Declares objects of the Thread class. */    Thread t1;    Thread t2;    Thread t3;    int act;    /* Defines the constructor of the Editor class. */    public Editor()    {       /*        Initializes the menu bar and sets the menu bar to the frame.        */       menu = new JMenuBar();       setJMenuBar(menu);       setTitle("Text Editor");       /*        Initializes the menu and adds the menus to the menu bar.        */       file = new JMenu("File");       menu.add(file);       edit = new JMenu("Edit");       menu.add(edit);       format = new JMenu("Format");       menu.add(format);       lock = new JMenu("Locks");       menu.add(lock);       help = new JMenu("Help");       menu.add(help);       /* Sets the mnemonic to the menu. */       file.setMnemonic('f');       edit.setMnemonic('e');       lock.setMnemonic('l');       format.setMnemonic('o');       help.setMnemonic('h');       /*       Initializes the menu items.       Adds the menu item to the particular menu.       Adds the action listener with each menu item.       Sets accelerator to each menu item.       */       /* File->New */       newfile = new JMenuItem("New");       newfile.addActionListener(this);       newfile.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_N, ActionEvent.CTRL_MASK));       file.add(newfile);       /* File->Open */       open = new JMenuItem("Open...");       open.addActionListener(this);       open.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_O, ActionEvent.CTRL_MASK));       file.add(open);       /* File->Save */       save = new JMenuItem("Save");       save.addActionListener(this);       save.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S, ActionEvent.CTRL_MASK));       file.add(save);       /* File->Save As */       saveas = new JMenuItem("Save As...");       saveas.addActionListener(this);       file.add(saveas);       /* File->Print */       print = new JMenuItem("Print");       print.addActionListener(this);       print.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_P, ActionEvent.CTRL_MASK));       file.add(print);       /* File->Exit */       exit = new JMenuItem("Exit");       exit.addActionListener(this);       exit.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_F4, ActionEvent.CTRL_MASK));       file.add(exit);       /* Inserts separators at the 4th and 6th positions. */       file.insertSeparator(4);       file.insertSeparator(6);       /* Edit->Undo */       edit.add(undoAction);       /* Edit->Redo */       edit.add(redoAction);       /* Edit->Cut */       cut = new JMenuItem("Cut");       edit.add(cut);       cut.addActionListener(this);       cut.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_X, ActionEvent.CTRL_MASK));       /* Edit->Copy */       copy = new JMenuItem("Copy");       edit.add(copy);       copy.addActionListener(this);       copy.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_C, ActionEvent.CTRL_MASK));       /* Edit->Paste */       paste = new JMenuItem("Paste");       edit.add(paste);       paste.addActionListener(this);       paste.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_V, ActionEvent.CTRL_MASK));       /* Edit->Find */       find = new JMenuItem("Find");       edit.add(find);       find.addActionListener(this);       find.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_F, ActionEvent.CTRL_MASK));       /* Edit->Select All */       selectAll = new JMenuItem("Select All");       edit.add(selectAll);       selectAll.addActionListener(this);       selectAll.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_A, ActionEvent.CTRL_MASK));       /* Edit->Date/Time */       datetime = new JMenuItem("Date/Time");       edit.add(datetime);       datetime.addActionListener(this);       datetime.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_F5, ActionEvent.CTRL_MASK));       /* Inserts separators at the 2nd, 6th, and 9th positions. */       edit.insertSeparator(2);       edit.insertSeparator(6);       edit.insertSeparator(9);       /* Format->Font */       font = new JMenuItem("Font");       format.add(font);       font.addActionListener(this);       /* Format->Color */       color = new JMenuItem("Color");       format.add(color);       color.addActionListener(this);       /* Format->Word Wrap */       wordWrap = new JCheckBoxMenuItem("Word Wrap");       format.add(wordWrap);       wordWrap.addActionListener(this);       /* Lock->Exclusive Lock */       exclusiveLock = new JCheckBoxMenuItem("Exclusive Lock");       exclusiveLock.setEnabled(false);       lock.add(exclusiveLock);       exclusiveLock.addActionListener(this);       /* Lock->Share Lock */       shareLock = new JCheckBoxMenuItem("Share Lock");       shareLock.setEnabled(false);       lock.add(shareLock);       shareLock.addActionListener(this);       /* Help->Help Topics */        about = new JMenuItem("Help Topics");       help.add(about);       about.addActionListener(this);       /* Initializes the panel. */       panel = new JPanel();       /* Sets the panel layout as BorderLayout. */       panel.setLayout(new BorderLayout());       /* Adds the panel to the frame. */       getContentPane().add(panel, BorderLayout.CENTER);       /* Initializes the object of text area */        area = new JTextArea(25, 65);       /*        Adds UndoableEditListener to the area for undo and redo operations.        */       area.getDocument().addUndoableEditListener(this);       /* Sets line wrap to false. */        area.setLineWrap(false);       /* Sets word wrap style to false. */        area.setWrapStyleWord(false);       /*        Initializes the object of the Scrollpane class and adds the text area to the scroll pane.        */       scrollpane = new JScrollPane(area);       /* Adds the scroll pane to the panel. */       panel.add(scrollpane);       /* Sets default close operation to false. */        setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);       /*       addWindowListener - It contains a windowClosing() method.       windowClosing: It is called when the user clicks the cancel button of the Window.        It closes the main window.       Parameter: we- Represents an object of the WindowEvent class.       Return Value: NA       */       addWindowListener(new WindowAdapter()       {          public void windowClosing(WindowEvent we)          {              System.exit(0);           }        });        }       /*       undoableEditHappened() - This method is called when the user wants to perform undo/redo.       Parameters: e  Represents an object of UndoableEditEvent class that contains        the details of the undo/redo events.       Return Value: NA       */       public void undoableEditHappened(UndoableEditEvent e)       {          /*           Inserts an Edit at indexOfNextAdd and removes any old edits that were at indexOfNextAdd or later.           */           undoManager.addEdit(e.getEdit());          /* Calls the update() method to perform undo operations. */           undoAction.update();          /* Calls the update() method to perform redo operations. */           redoAction.update();       }       /*       actionPerformed() - This method is called when the end user selects any menu item from the menu bar.       Parameters: ae  Represents an object of the ActionEvent class that contains the details of the event.       Return Value: NA       */       public void actionPerformed(ActionEvent ae)       {          /*           This section is executed when the end user selects the File->New command to the menu bar.          */           if(ae.getSource() == newfile)           {             /* Calls the newFile() method. */              exclusiveLock.setEnabled(false);              shareLock.setEnabled(false);              action.newFile();           }          /*           This section is executed when the end user selects the File->Open command to the menu bar.          */           else if(ae.getSource() == open)           {             /* Calls the openFile() method. */              action.openFile();           }                    /*           This section is executed when the end user selects the File->Save command to the menu bar.          */           else if(ae.getSource() == save)           {             /* Calls the saveFile() method. */              action.saveFile();           }          /*           This section is executed when the end user selects the File->Save As command to the menu bar.          */           else if(ae.getSource() == saveas)           {             /* Calls the saveAsFile() method. */              action.saveAsFile();           }          /*           This section is executed when the end user selects the File->Print command to the menu bar.          */           else if(ae.getSource() == print)           {             /* Calls the printFile() method. */              act = 1;              t1 = new Thread(this);              t1.start();           }          /*           This section is executed when the end user selects the Edit->Exit command to the menu bar.          */           else if(ae.getSource() == exit)           {             /* Calls the exitFile() method. */              action.exitFile();           }          /*           This section is executed when the end user selects the Edit->Cut command to the menu bar.          */           else if(ae.getSource() == cut)           {             /* Calls the cutFile() method. */              action.cutFile();           }          /*           This section is executed when the end user selects the Edit->Copy command to the menu bar.          */           else if(ae.getSource() == copy)           {             /* Calls the copyFile() method. */              action.copyFile();           }          /*           This section is executed when the end user selects the Edit->Paste command to the menu bar.          */           else if(ae.getSource() == paste)           {                /* Calls the pasteFile() method. */                 action.pasteFile();           }          /*           This section is executed when the end user selects the Edit->Date/Time command to the menu bar.          */           else if(ae.getSource() == datetime)           {             /* Calls the dateTime() method. */              action.dateTime();           }          /*           This section is executed when the end user selects the Edit->Find command to the menu bar.          */           else if(ae.getSource() == find)           {             /* Calls the findFile() method. */              action.findFile();           }          /*           This section is executed when the end user selects the Edit->Select All command to the menu bar.          */           else if(ae.getSource() == selectAll)           {             /* Calls the selectAllFile() method. */              action.selectAllFile();           }          /*           This section is executed when the end user selects the Format->Font command to the menu bar.          */           else if(ae.getSource() == font)           {             /* Calls the fontFile() method. */              action.fontFile();           }          /*           This section is executed when the end user selects the Format->Color command to the menu bar.          */           else if(ae.getSource() == color)           {             /* Calls the colorFile() method. */              action.colorFile();            }          /*           This section is executed when the end user selects the Format->Word Wrap command to the menu bar.          */           else if(ae.getSource() == wordWrap)           {             /* Calls the warpFile() method. */              action.wrapFile();           }          /*           This section is executed when the end user selects the Lock->Exclusive command to the menu bar.          */           else if(ae.getSource() == exclusiveLock)           {              act = 2;              t2 = new Thread(this);              t2.start();           }          /*           This section is executed when the end user selects the Lock->Share command to the menu bar.          */           else if(ae.getSource() == shareLock)           {              act = 3;              t3 = new Thread(this);              t3.start();           }          /*           This section is executed when the end user selects the Help->Help Topics command to the menu bar.          */           else if(ae.getSource() == about)           {             /* Calls the aboutFile() method. */              action.aboutFile();            }         }        public void run()        {           if(act==1)           {              action.printFile();        }        else if(act==2)        {          /* Calls the exLockFile() method. */           action.exLockFile();        }        else if(act==3)        {          /* Calls the shLockFile() method. */           action.shLockFile();        }     }    /*    main() - This method creates the main window of the user interface and displays it.    Parameters:    args[] - Contains any command line arguments passed.    Return Value: NA    */     public static void main(String args[])     {        try        {          /*           Initializes and sets the look and feel of the application to Windows look and feel.           */          UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");        }        catch(Exception e)        {          System.out.println("Unknown Look and Feel." + e);         }       /* Creates an object of the Editor class. */        Editor ed = new Editor();       /* Sets the size of the main window. */        ed.setSize(725, 460);       /* Sets the visibility of the window to TRUE. */         ed.setVisible(true);       /* Displays the main window. */        ed.show();     }    /*    Class UndoAction - Extends the AbstractAction class to perform undo operations.    Method:    UndoAction() - Implements the default constructor of the UndoClass.    actionPerformed() - Performs the action event.    update() - Updates the change made by the end user. */     class UndoAction extends AbstractAction     {       /* Defines the default constructor. */        public UndoAction()     {        super("Undo");        setEnabled(false);     }    /*    actionPerformed() - This method is called when the end user select the Edit->Undo command from the menu bar.    Parameters: e  Represent an object of the ActionEvent class that contains details of the event.    Return Value: NA    */    public void actionPerformed(ActionEvent e)     {        try        {           undoManager.undo();        }        catch (Exception ex)        {          System.out.println("Error: " + ex);        }        update();        redoAction.update();     }    /*    update() - This method performs undo operations.     Parameters: NA    Return Value: NA    */     protected void update()     {        if(undoManager.canUndo())        {             setEnabled(true);             putValue("Undo", undoManager.getUndoPresentationName());        }        else        {          setEnabled(false);          putValue(Action.NAME, "Undo");        }     }  } /* Class UndoAction - Extends the AbstractAction class to perform redo operations. Method: RedoAction() - Implements the default constructor of UndoClass. actionPerformed() - Performs the action event. update() - Updates the changes made by the end user.  */  class RedoAction extends AbstractAction  {    /* Defines the default constructor. */     public RedoAction()     {        super("Redo");        setEnabled(false);     }       /*       actionPerformed() - This method is called when the end user selects the        Edit->Redo command from the menu bar.       Parameters: e  Represents an object of the ActionEvent class that contains        the details of the event.       Return Value: NA       */       public void actionPerformed(ActionEvent e)       {          try          {              undoManager.redo();          }           catch (Exception ex)           {             System.out.println("Error: " + ex);           }           update();           undoAction.update();        }       /*       update() - This method performs the redo operations.        Parameters: NA       Return Value: NA       */       protected void update()       {           if(undoManager.canRedo())           {                setEnabled(true);                putValue("Redo", undoManager.getRedoPresentationName());           }           else           {              setEnabled(false);             putValue(Action.NAME, "Redo");           }        }     } } 

 

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In the above code, the main() method creates an instance of the Editor class. This class generates the main window of the Text Editor, as shown in Figure 6-2:

Figure 6-2: The Text Editor User Interface

When an end user clicks a menu item from the menu bar, the Text Editor invokes the actionPerformed() method. This method acts as an event listener and activates an appropriate class or method, based on the selected menu item. The menu options in the Text Editor application are:

• File Menu: Contains the following menu items:
  
  

  • New: Calls a newFile() method to create a new text file.

  • Open: Calls an openFile() method to open an existing text file.

  • Save: Calls a saveFile() method to save an existing text file.

  • Save As: Calls a saveAsFile() method to save a newly created text file.

  • Print: Calls the printFile() method to display the Print dialog box, based on the value assigned to the act variable.

  • Exit: Calls an exitFile() method to close the Text Editor application.

  
  

• Edit Menu: Contains the following menu items:
  
  

  • Undo: Calls an undo() method to undo the last operation performed on the file.

  • Redo: Calls a redo() method to redo the last undo operation performed on the file.

  • Cut: Calls a cutFile() method to cut a selected text from the text file.

  • Copy: Calls a copyFile() method to copy a selected text from the text file.

  • Paste: Calls a pasteFile() method to paste the cut or copied text at a specific position.

  • Find: Calls a findFile() method to find a specific word in the file.

  • Select All: Calls a selectAllFile() method to select all the contents of the file.

  • Date/Time: Calls a dateTime() method to insert the current date and time in the text file.

  
  

• Format Menu: Contains the following menu items:
  
  

  • Font: Calls a fontFile() method to display the Font dialog box.

  • Color: Calls a colorFile() method to display the Color dialog box.

  • Word Wrap: Calls a wrapFile() method to wrap the text style in the text area.

  
  

• Locks Menu: Contains the following menu items:
  
  

  • Exclusive Lock: Calls the exLockFile() method based on the value assigned to the act variable. The exLockFile() method locks the file with an exclusive lock.

  • Share Lock: Calls the shLockFile() method based on the value assigned to the act variable. The shLockFile() method locks the file with the share lock.

  
  

• Help Menu: Contains one menu item, Help Topics. This menu item calls an aboutFile() method to display the Help dialog box.

The Editor.java file creates objects of the UndoManager, UndoAction, and RedoAction classes, which perform the undo and redo operations on the file. The UndoAction and RedoAction classes contain protected update() methods that enable or disable the Undo and Redo menu items of the Edit menu, respectively.