Creating a basic notepad app

Posted: February 27, 2012 in Java Posts
Tags: , , , , , , , , , ,
25

  • English: Basic Notepad
  • Notepad (software)

What do I already need to know in order to follow this tutorial?
Not a lot, actually. This stuff is a lot easier than people tend to make it look. My aim is to show you how simple it is to harness the power of Java. Just so long as you’ve got a basic grasp of the stuff, you should be able to take it in.

So what am I going to learn?
Hopefully, quite a bit! In this tutorial, I’m going to cover the basics of:

So, to get started, we need to import a few things, namely:

import javax.swing.*; // for the main JFrame design
import java.awt.*; // for the GUI stuff
import java.awt.event.*; // for the event handling
import java.util.Scanner; // for reading from a file
import java.io.*; // for writing to a file

Next, let’s go over multiple inheritance. Our notepad app is going to have the appearance of a JFrame, and the functionality of an ActionListener.

So, we’re going to extend JFrame, and implement ActionListener. Makes sense, right?

1 public class Notepad extends JFrame implements ActionListener {

w00t!

Now we’re going to set up our basic stuff. The classes that we’ll be using for the design are:

  • TextArea
  • MenuBar
  • Menu
  • MenuItem

So, let’s go over it:

The TextArea The most important bit, right?
This is the area of text that the user can write in. You’d never guess that, would you?!

So, the constructor for our TextArea is quite big~ it accepts quite a few parameters.

1 private TextArea textArea = new TextArea("", 0,0, TextArea.SCROLLBARS_VERTICAL_ONLY);

Let’s break it down.
First, we pass “” which is basically an empty string. The constructor is looking for the text to put in the TextArea initially, so you could pass “poo” and the TextArea would say poo when you launch the app.
Next, we have the size. 0,0 (Height/Width)
This might seem weird~ we’re setting it to be 0×0 pixels, so it won’t be visible, right? Wrong. The basic GUI design in Java will automatically set the TextArea to fill the window. In other words, we don’t have to worry about it.
TextArea.SCROLLBARS_VERTICAL_ONLY adds WordWrap to our application, to make it look neater. Times where you shouldn’t have WordWrap include code views (it all belongs on one line)

The MenuBar
Much simpler, the code speaks for itself:

1     private MenuBar menuBar = new MenuBar(); // first, create a MenuBar item
2 private Menu file = new Menu(); // our File menu
3 // what's going in File? let's see...
4 private MenuItem openFile = new MenuItem();  // an open option
5 private MenuItem saveFile = new MenuItem(); // a save option
6 private MenuItem close = new MenuItem(); // and a close option!

On to the constructor!
Personally, I find it easier to go along code when it’s together. So, I’ve added enough comments in to the constructor code for it to make sense:

01 public Notepad() {
02     this.setSize(500, 300); // set the initial size of the window
03     this.setTitle("Java Notepad Tutorial"); // set the title of the window
04     setDefaultCloseOperation(EXIT_ON_CLOSE); // set the default close operation (exit when it gets closed)
05     this.textArea.setFont(new Font("Century Gothic", Font.BOLD, 12)); // set a default font for the TextArea
06     // this is why we didn't have to worry about the size of the TextArea!
07     this.getContentPane().setLayout(new BorderLayout()); // the BorderLayout bit makes it fill it automatically
08     this.getContentPane().add(textArea);
09
10     // add our menu bar into the GUI
11     this.setMenuBar(this.menuBar);
12     this.menuBar.add(this.file); // we'll configure this later
13     
14     // first off, the design of the menuBar itself. Pretty simple, all we need to do
15     // is add a couple of menus, which will be populated later on
16     this.file.setLabel("File");
17     
18     // now it's time to work with the menu. I'm only going to add a basic File menu
19     // but you could add more!
20     
21     // now we can start working on the content of the menu~ this gets a little repetitive,
22     // so please bare with me!
23     
24     // time for the repetitive stuff. let's add the "Open" option
25     this.openFile.setLabel("Open"); // set the label of the menu item
26     this.openFile.addActionListener(this); // add an action listener (so we know when it's been clicked
27     this.openFile.setShortcut(new MenuShortcut(KeyEvent.VK_O, false)); // set a keyboard shortcut
28     this.file.add(this.openFile); // add it to the "File" menu
29     
30     // and the save...
31     this.saveFile.setLabel("Save");
32     this.saveFile.addActionListener(this);
33     this.saveFile.setShortcut(new MenuShortcut(KeyEvent.VK_S, false));
34     this.file.add(this.saveFile);
35     
36     // and finally, the close option
37     this.close.setLabel("Close");
38     // along with our "CTRL+F4" shortcut to close the window, we also have
39     // the default closer, as stated at the beginning of this tutorial.
40     // this means that we actually have TWO shortcuts to close:
41     // 1) the default close operation (example, Alt+F4 on Windows)
42     // 2) CTRL+F4, which we are about to define now: (this one will appear in the label)
43     this.close.setShortcut(new MenuShortcut(KeyEvent.VK_F4, false));
44     this.close.addActionListener(this);
45     this.file.add(this.close);
46 }

See? That wasn’t so bad now, was it? I told you this stuff is easy~ it’s just a little repetitive at times.

Listening for Events
Remember how I said earlier that we implement ActionListener? Well, now it’s time to learn about events. Because we’re implementing ActionListener, we can have a function called ActionPerformed() which will listen for events for us. Neat, huh? Again, I’ve added plenty of comments so you can see what’s happening along the way.
NOTE: This section will also cover the basics of file I/O, and the use of JFileChooser

01 public void actionPerformed (ActionEvent e) {
02     // if the source of the event was our "close" option
03     if (e.getSource() == this.close)
04         this.dispose(); // dispose all resources and close the application
05     
06     // if the source was the "open" option
07     else if (e.getSource() == this.openFile) {
08         JFileChooser open = new JFileChooser(); // open up a file chooser (a dialog for the user to browse files to open)
09         int option = open.showOpenDialog(this); // get the option that the user selected (approve or cancel)
10         // NOTE: because we are OPENing a file, we call showOpenDialog~
11         // if the user clicked OK, we have "APPROVE_OPTION"
12         // so we want to open the file
13         if (option == JFileChooser.APPROVE_OPTION) {
14             this.textArea.setText(""); // clear the TextArea before applying the file contents
15             try {
16                 // create a scanner to read the file (getSelectedFile().getPath() will get the path to the file)
17                 Scanner scan = new Scanner(new FileReader(open.getSelectedFile().getPath()));
18                 while (scan.hasNext()) // while there's still something to read
19                     this.textArea.append(scan.nextLine() + "\n"); // append the line to the TextArea
20             } catch (Exception ex) { // catch any exceptions, and...
21                 // ...write to the debug console
22                 System.out.println(ex.getMessage());
23             }
24         }
25     }
26     
27     // and lastly, if the source of the event was the "save" option
28     else if (e.getSource() == this.saveFile) {
29         JFileChooser save = new JFileChooser(); // again, open a file chooser
30         int option = save.showSaveDialog(this); // similar to the open file, only this time we call
31         // showSaveDialog instead of showOpenDialog
32         // if the user clicked OK (and not cancel)
33         if (option == JFileChooser.APPROVE_OPTION) {
34             try {
35                 // create a buffered writer to write to a file
36                 BufferedWriter out = new BufferedWriter(new FileWriter(save.getSelectedFile().getPath()));
37                 out.write(this.textArea.getText()); // write the contents of the TextArea to the file
38                 out.close(); // close the file stream
39             } catch (Exception ex) { // again, catch any exceptions and...
40                 // ...write to the debug console
41                 System.out.println(ex.getMessage());
42             }
43         }
44     }
45 }

Oh, and don’t forget to close off the class! }

So, you should now have a basic Notepad app!

As with all my other tutorials, I’ll post the complete code, in case you got lost along the way:

THE FINAL PRODUCT!

001 import javax.swing.*;
002 import java.awt.*;
003 import java.awt.event.*;
004 import java.util.Scanner;
005 import java.io.*;
006
007 public class Notepad extends JFrame implements ActionListener {
008     private TextArea textArea = new TextArea("", 0,0, TextArea.SCROLLBARS_VERTICAL_ONLY);
009     private MenuBar menuBar = new MenuBar(); // first, create a MenuBar item
010     private Menu file = new Menu(); // our File menu
011     // what's going in File? let's see...
012     private MenuItem openFile = new MenuItem();  // an open option
013     private MenuItem saveFile = new MenuItem(); // a save option
014     private MenuItem close = new MenuItem(); // and a close option!
015     
016     public Notepad() {
017         this.setSize(500, 300); // set the initial size of the window
018         this.setTitle("Java Notepad Tutorial"); // set the title of the window
019         setDefaultCloseOperation(EXIT_ON_CLOSE); // set the default close operation (exit when it gets closed)
020         this.textArea.setFont(new Font("Century Gothic", Font.BOLD, 12)); // set a default font for the TextArea
021         // this is why we didn't have to worry about the size of the TextArea!
022         this.getContentPane().setLayout(new BorderLayout()); // the BorderLayout bit makes it fill it automatically
023         this.getContentPane().add(textArea);
024
025         // add our menu bar into the GUI
026         this.setMenuBar(this.menuBar);
027         this.menuBar.add(this.file); // we'll configure this later
028         
029         // first off, the design of the menuBar itself. Pretty simple, all we need to do
030         // is add a couple of menus, which will be populated later on
031         this.file.setLabel("File");
032         
033         // now it's time to work with the menu. I'm only going to add a basic File menu
034         // but you could add more!
035         
036         // now we can start working on the content of the menu~ this gets a little repetitive,
037         // so please bare with me!
038         
039         // time for the repetitive stuff. let's add the "Open" option
040         this.openFile.setLabel("Open"); // set the label of the menu item
041         this.openFile.addActionListener(this); // add an action listener (so we know when it's been clicked
042         this.openFile.setShortcut(new MenuShortcut(KeyEvent.VK_O, false)); // set a keyboard shortcut
043         this.file.add(this.openFile); // add it to the "File" menu
044         
045         // and the save...
046         this.saveFile.setLabel("Save");
047         this.saveFile.addActionListener(this);
048         this.saveFile.setShortcut(new MenuShortcut(KeyEvent.VK_S, false));
049         this.file.add(this.saveFile);
050         
051         // and finally, the close option
052         this.close.setLabel("Close");
053         // along with our "CTRL+F4" shortcut to close the window, we also have
054         // the default closer, as stated at the beginning of this tutorial.
055         // this means that we actually have TWO shortcuts to close:
056         // 1) the default close operation (example, Alt+F4 on Windows)
057         // 2) CTRL+F4, which we are about to define now: (this one will appear in the label)
058         this.close.setShortcut(new MenuShortcut(KeyEvent.VK_F4, false));
059         this.close.addActionListener(this);
060         this.file.add(this.close);
061     }
062     
063     public void actionPerformed (ActionEvent e) {
064         // if the source of the event was our "close" option
065         if (e.getSource() == this.close)
066             this.dispose(); // dispose all resources and close the application
067         
068         // if the source was the "open" option
069         else if (e.getSource() == this.openFile) {
070             JFileChooser open = new JFileChooser(); // open up a file chooser (a dialog for the user to browse files to open)
071             int option = open.showOpenDialog(this); // get the option that the user selected (approve or cancel)
072             // NOTE: because we are OPENing a file, we call showOpenDialog~
073             // if the user clicked OK, we have "APPROVE_OPTION"
074             // so we want to open the file
075             if (option == JFileChooser.APPROVE_OPTION) {
076                 this.textArea.setText(""); // clear the TextArea before applying the file contents
077                 try {
078                     // create a scanner to read the file (getSelectedFile().getPath() will get the path to the file)
079                     Scanner scan = new Scanner(new FileReader(open.getSelectedFile().getPath()));
080                     while (scan.hasNext()) // while there's still something to read
081                         this.textArea.append(scan.nextLine() + "\n"); // append the line to the TextArea
082                 } catch (Exception ex) { // catch any exceptions, and...
083                     // ...write to the debug console
084                     System.out.println(ex.getMessage());
085                 }
086             }
087         }
088         
089         // and lastly, if the source of the event was the "save" option
090         else if (e.getSource() == this.saveFile) {
091             JFileChooser save = new JFileChooser(); // again, open a file chooser
092             int option = save.showSaveDialog(this); // similar to the open file, only this time we call
093             // showSaveDialog instead of showOpenDialog
094             // if the user clicked OK (and not cancel)
095             if (option == JFileChooser.APPROVE_OPTION) {
096                 try {
097                     // create a buffered writer to write to a file
098                     BufferedWriter out = new BufferedWriter(new FileWriter(save.getSelectedFile().getPath()));
099                     out.write(this.textArea.getText()); // write the contents of the TextArea to the file
100                     out.close(); // close the file stream
101                 } catch (Exception ex) { // again, catch any exceptions and...
102                     // ...write to the debug console
103                     System.out.println(ex.getMessage());
104                 }
105             }
106         }
107     }
108     // the main method, for actually creating our notepad and setting it to visible.
109     public static void main(String args[]) {
110         Notepad app = new Notepad();
111         app.setVisible(true);
112 }
113 }

Happy coding!

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