JavaSE 基于AWT的记事本实现

{功能描述}
NoteBook 类是一个记事本的基本类，该类的对象具有记事本的基本功能，包括：
打开文件、保存文件以及文本的复制、粘贴、删除等。
该程序主要包括为窗口添加菜单栏、在菜单栏中添加菜单以及为菜单栏添加菜单项，并且为每一个菜单项添加相应的监听器完成相应的操作。另外，还包括文件内容的读取和保存。

{相关代码}

package sup.orange.learn;



import java.awt.*;

import java.awt.datatransfer.Clipboard;

import java.awt.datatransfer.DataFlavor;

import java.awt.datatransfer.StringSelection;

import java.awt.datatransfer.Transferable;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.event.WindowAdapter;

import java.awt.event.WindowEvent;

import java.io.File;

import java.io.FileReader;

import java.io.FileWriter;

import java.io.IOException;



/**

 * Created by re-x on 11/3/14.

 */

public class NoteBook extends Frame implements ActionListener{

    MenuBar menuBar = new MenuBar();



    TextArea textArea = new TextArea();



    // file menu

    Menu fileMenu = new Menu("File");

    MenuItem newItem = new MenuItem("New");

    MenuItem openItem = new MenuItem("Open");

    MenuItem saveItem = new MenuItem("Save");

    MenuItem saveAsItem = new MenuItem("Save As");

    MenuItem exitItem = new MenuItem("Exit");



    // edit menu

    Menu editMenu = new Menu("Edit");

    MenuItem selectItem = new MenuItem("Select All");

    MenuItem copyItem = new MenuItem("Copy");

    MenuItem cutItem = new MenuItem("Cut");

    MenuItem pasteItem = new MenuItem("Paste");



    String fileName = "NoName.txt";

    Toolkit toolkit = Toolkit.getDefaultToolkit();

    Clipboard clipboard = toolkit.getSystemClipboard();





    // create and init open file dialog && save file dialog

    private FileDialog openFileDialog = new FileDialog(this, "Open File", FileDialog.LOAD);

    private FileDialog saveAsFileDialog = new FileDialog(this, "Save As", FileDialog.SAVE);



    public NoteBook() {

        setTitle("NotePad");

        setFont(new Font("Times New Roman", Font.PLAIN, 12));

        setBackground(Color.gray);

        setSize(600, 400);



        fileMenu.add(newItem);

        fileMenu.add(openItem);

        fileMenu.addSeparator();

        fileMenu.add(saveItem);

        fileMenu.add(saveAsItem);

        fileMenu.addSeparator();

        fileMenu.add(exitItem);



        editMenu.add(selectItem);

        editMenu.addSeparator();

        editMenu.add(copyItem);

        editMenu.add(cutItem);

        editMenu.add(pasteItem);



        menuBar.add(fileMenu);

        menuBar.add(editMenu);



        setMenuBar(menuBar);

        add(textArea);



        addWindowListener(new WindowAdapter() {

            @Override

            public void windowClosing(WindowEvent e) {

                super.windowClosing(e);

                dispose();

                System.exit(0);

            }

        });



        newItem.addActionListener(this);

        openItem.addActionListener(this);

        saveItem.addActionListener(this);

        saveAsItem.addActionListener(this);

        exitItem.addActionListener(this);



        selectItem.addActionListener(this);

        copyItem.addActionListener(this);

        cutItem.addActionListener(this);

        pasteItem.addActionListener(this);



    }



    public static void main(String[] args) {

        Frame frame = new NoteBook();

        Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); // get screen size

        Dimension frameSize = frame.getSize();  // get frame size



        if (frameSize.height > screenSize.height) {

            frameSize.height = screenSize.height;

        }

        if (frameSize.width > screenSize.width) {

            frameSize.width = screenSize.width;

        }



        frame.setLocation((screenSize.width-frameSize.width)/2, (screenSize.height-frameSize.height)/2);

        frame.setVisible(true);

    }



    public void actionPerformed(ActionEvent e) {

        Object eventSource = e.getSource();



        // judge which menuItem is the source

        if (eventSource == newItem) {

            textArea.setText("");

        }

        else if (eventSource == openItem) {

            openFileDialog.setVisible(true);

            fileName = openFileDialog.getDirectory()+openFileDialog.getFile();

            if (fileName != null) {

                readFile(fileName);

            }

        }

        else if (eventSource == saveItem) {

            if (fileName != null) {

                writeFile(fileName);

            }

        }

        else if (eventSource == saveAsItem) {

            saveAsFileDialog.setVisible(true);

            fileName = saveAsFileDialog.getDirectory()+saveAsFileDialog.getFile();

            if (fileName != null) {

                writeFile(fileName);

            }

        }

        else if (eventSource == selectItem) {

            textArea.selectAll();

        }

        else if (eventSource == copyItem) {

            String text = textArea.getSelectedText();

            StringSelection selection = new StringSelection(text);

            clipboard.setContents(selection, null);

        }

        else if (eventSource == cutItem) {

            String text = textArea.getSelectedText();

            StringSelection selection = new StringSelection(text);

            clipboard.setContents(selection, null);

            textArea.replaceRange("", textArea.getSelectionStart(), textArea.getSelectionEnd());

        }

        else if (eventSource == pasteItem) {

            Transferable contents = clipboard.getContents(this);

            if (contents == null) {

                return;

            }

            String text = "";

            try {

                text = (String)contents.getTransferData(DataFlavor.stringFlavor);

            }

            catch (Exception ex) {

                ex.printStackTrace();

            }



            textArea.replaceRange(text, textArea.getSelectionStart(), textArea.getSelectionEnd());

        }

        else if (eventSource == exitItem) {

            System.exit(0);

        }

    }



    public void readFile(String fileName) {

        try {

            File file = new File(fileName);

            FileReader readIn = new FileReader(file);

            int size = (int)file.length();

            int charsRead = 0;

            char [] content = new char[size];



            while (readIn.ready()) {

                charsRead += readIn.read(content, charsRead, size-charsRead);

            }

            readIn.close();

            textArea.setText(new String(content, 0, charsRead));

        }

        catch (IOException e) {

            e.printStackTrace();

        }

    }



    public void writeFile(String fileName) {

        try {

            File file = new File(fileName);

            FileWriter writeOut = new FileWriter(file);

            writeOut.write(textArea.getText());

            writeOut.close();

        }

        catch (IOException e) {

            e.printStackTrace();

        }

    }

}