Lecture 1: GUI (User Graphic Interface)

I. overview

1. GUI: Graphical User Interface (GUI), a graphical user interface, is a way for computers to interact with users.

2. Two ways of computer-user interaction: GUI and CLI

GUI: Graphical User Interface, Graphical User Interface, graphical user interface, to display the computer operation interface, convenient and intuitive.

CLI: Command Line User Interface, Command Line User Interface, Command Line User Interface, which is a common Dos command line operation, must remember some commands, the operation is not intuitive.

3. Java also encapsulates this interface as an object, in which the objects are placed in two packages: the java.Awt package and the javax.Swing package.

The java.Awt package: Abstract Window Toolkit, or abstract window toolkit. To call the local system method to realize the function, it is a heavyweight control.

Javaax.Swing package: A set of graphical interface system based on AWT, which provides more components and is completely implemented by java, enhances portability and is a lightweight control.

 

II. Succession Diagram

 

Container For containers, it is a special component in which other components can be added through the add method.

Container Common Subclass: Window Panel.

Common subclasses of Window s: Frame Dialog

 

3. Layout Manager

1. Layout: Component Arrangement in Containers

2. Common layout managers:

FlowLayout: Flow Layout: Flow Layout Manager. Arrange from left to right, which is the default layout manager for Panel

BorderLayout: BorderLayout, the border layout manager, is the default layout manager for Frame. If there is only one component in the form, the entire form will be covered.

3) GridLayout: Grid Layout Manager, Rule Matrix

CardLayout: Card Layout: Card Layout Manager, Tab

5) GridBayLayout: Grid Packet Layout Manager, Irregular Matrix

3. If there are many layout modes, how to create the form interface? Steps:

1) First divide the form Frame into large areas, set up its layout manager, and add panel panel Panel.

2) Add components to Panel and set the layout manager of panel.

 

4. Simple Form Creation Process

1. Create Frame Form:

Frame f = new Frame("my Frame"); // Caption can be set, that is, form name

2. Basic settings for forms: size, location, layout, etc.

f.setSize(int wight,int hight); //Form size settings

f.setLocation(int x,int y); //Form Display Position Settings, Lateral and Longitudinal Coordinates

f.setBounds(int x,int y,int wight,int hight) can also be used directly to set size and location

f.setLayout(Layout layout), with parameters specified for layout managers, such as FlowLayout

3. Define components:

For example, Button b = new Button("my Button"); and // the name of the configurable component

4. Adding components to a form through the form's add method:

f.add(b); //Add button components to forms

5. Let the form display:

f.setVisible(boolean b); // Whether the form is displayed by setting whether the parameter is true or false

Example:

1. <span style="font-size:14px;">import java.awt.*;  
2.   
3. class AwtFirstDemo   
4. {  
5.     public static void main(String[] args)   
6.     {  
7.         //Create Frame Form:  
8.         Frame f = new Frame("my Frame");//Settable title  
9.   
10.         //Basic settings for forms: size, location, layout, etc.  
11.         f.setSize(500,100);//Form Size Settings  
12.         f.setLocation(300,150);//Form Display Position Settings, Lateral and Longitudinal Coordinates  
13.   
14.        //f.setBounds(int x,int y,int wight,int hight); //You can also use this method directly to set size and location  
15.           
16.         f.setLayout(new FlowLayout());//The parameter is the specified layout manager, such as FlowLayout  
17.           
18.         //Define components:  
19.         Button b = new Button("my Button");//Name of Settable Component  
20.           
21.         //Add components to a form through the form's add method:  
22.         f.add(b);//Add the button component to the form  
23.           
24.         //Let the form display:  
25.         f.setVisible(true);//Whether the form is displayed by setting whether the parameter is true or false  
26.     }  
27. }  
28.   
29. </span>  

V. Event Monitoring Mechanism

1. Composition:

1) Event source (component): GUI components in awt or swing packages

Event: Each event source has its own unique corresponding and common events

3) Listener: Encapsulate actions that trigger an event (more than one action) into the listener.

4) Event handling: the way to deal with events after they are triggered.

 

2. Instructions for Use

The first three components have been defined in java and can be used directly by capturing their objects. What we need to do is to process the generated actions.

Steps:

1) Identify the source of the event (container or component). The listener is registered on the event source by the addXXXListener() method of the event source object. This method receives subclass objects of XXXListener, or subclass objects of XXXAdapter, a subclass of XXXListener.

2) Generally expressed by anonymous inner classes. When overriding a method, the parameters of the method are generally accepted by variables of type XXXEvent.

Such as:

1. f.addWindowlistener(new WindowAdapter()  
2. {  
3.      public void windowClosing(WindowEvent e)  
4.      {  
5.           System.exit(0);//Represents closing windows  
6.      }  
7. });  

Explain:

1) When an event is triggered, it is packaged as an object and passed to the variable of the parameter in the replication method. Including event source objects. Get it through getSource() or getComponent().

2) If you use subclasses to implement the Windows Listener interface, you need to override seven of these methods. You can only use the closing action in them. Other actions are not used, but you have to rewrite all of them. Because Windows Adapter, a subclass of Windows Lister, has implemented this interface and covered all of its methods. Then just inherit the Windows Adapter and override the required methods.

3) Identify events and process them. In fact, adding any listener requires adding any event.

Example:

1. /* 
2. Requirements: Make the Closing Function of Forms Implemented 
3.       Let the button also have the function of quitting the program 
4. */  
5.   
6. import java.awt.*;  
7. import java.awt.event.*;  
8.   
9. class  AwtEventDemo  
10. {  
11.     //Define references to components required for the graphical interface  
12.     private Frame f=null;  
13.     private Button but=null;  
14.   
15.     //Initial constructor  
16.     AwtEventDemo()  
17.     {  
18.         init();  
19.     }  
20.   
21.     //Form Creation and Function Implementation  
22.     public void init()  
23.     {  
24.         //Instance component  
25.         f=new Frame("my Frame");  
26.         but=new Button("my Botton");  
27.   
28.         //Basic settings for windows  
29.         //f.setSize(500,300); // Set Size  
30.         //f.setLocation(300,200);//window initial display position  
31.         f.setBounds(350,300,300,200);//Setting Form Size and Position Together  
32.         f.setLayout(new FlowLayout());//Set to Streaming Layout  
33.   
34.         //Add the button component to the form  
35.         f.add(but);  
36.   
37.         //Load events on forms  
38.         myEvent();  
39.   
40.         //Display Form  
41.         f.setVisible(true);  
42.   
43.     }  
44.   
45.     //Registration event  
46.     private void myEvent()  
47.     {  
48.         //Closing function of form  
49.         f.addWindowListener(new WindowAdapter()  
50.         {  
51.             public void windowClosing(WindowEvent e)  
52.             {  
53.                 System.out.println("window closing");  
54.                 System.exit(0);//Close window program  
55.             }  
56.         });  
57.   
58.         //Let the button have the function of quitting the program  
59.         /* 
60.         The button is the event source. 
61.         So which listener to choose? 
62.         You learn by closing the form example that you want to know which component has what particular listeners. 
63.         You need to view the functionality of the component object. 
64.          Refer to the description of button. The Discovery button supports a unique listening addAction Listener. 
65.          */  
66.         but.addActionListener(new ActionListener()  
67.         {  
68.             public void actionPerformed(ActionEvent e)  
69.             {  
70.                 System.out.println("Button Control Window Closed");  
71.                 System.exit(0);//Close window program  
72.             }  
73.         });  
74.     }  
75.   
76.     public static void main(String[] args)   
77.     {  
78.         //Running Form Program  
79.         new AwtEventDemo();  
80.     }  
81. }  

Practice:

1. /* 
2. Common Events: Keyboard Events and Mouse Events 
3.  
4. Requirement: List the contents of the specified directory in the form 
5. */  
6. import java.awt.*;  
7. import java.awt.event.*;  
8. import java.io.*;  
9.   
10. class KeyAndMouseEvent   
11. {  
12.     //GLOBAL VARIABLES INTERFACE COMPONENT REFERENCE  
13.     private Frame f;  
14.     private Button but;  
15.     private TextField tf;  
16.     private TextArea ta;  
17.   
18.     //Constructor  
19.     KeyAndMouseEvent()  
20.     {  
21.         init();  
22.     }  
23.   
24.     //Form Creation and Function Implementation  
25.     public void init()  
26.     {  
27.         //Component instantiation  
28.         f=new Frame("my fame");  
29.         but=new Button("Jump");  
30.         tf=new TextField(50);  
31.         ta=new TextArea(30,58);  
32.   
33.         //Basic Form Settings  
34.         f.setBounds(300,150,500,500);  
35.         f.setLayout(new FlowLayout());  
36.   
37.         //add component  
38.         f.add(tf);  
39.         f.add(but);  
40.         f.add(ta);  
41.   
42.         //Form Events  
43.         myEvent();  
44.           
45.         //Form display  
46.         f.setVisible(true);  
47.     }  
48.   
49.     //Registration event  
50.     public void myEvent()  
51.     {  
52.         //Form Closing Function  
53.         f.addWindowListener(new WindowAdapter()  
54.         {  
55.             public void windowClosing(WindowEvent e)  
56.             {  
57.                 System.exit(0);  
58.             }  
59.         });  
60.   
61.         /* 
62.         //Mouse Activity Event 
63.         but.addActionListener(new ActionListener() 
64.         { 
65.             public void actionPerformed(ActionEvent e) 
66.             { 
67.                 System.out.println("The button is moving. 
68.             } 
69.         }); 
70.         */  
71.   
72.         //Mouse event  
73.         but.addMouseListener(new MouseAdapter()  
74.         {  
75.             //int count=0;  
76.             public void mouseClicked(MouseEvent e)  
77.             {  
78.             //  if(e.getClickCount()==2)  
79.             //System.out.println("double-click mouse button");  
80.   
81.             //System.out.println("mouse click button");  
82.                 //System.exit(0);  
83.   
84.                 showFile();//Display in text area  
85.             }  
86.             /* 
87.             public void mouseEntered(MouseEvent e) 
88.             { 
89.                 System.out.println("Mouse into the button range "+(+++ count) +" times "; 
90.             } 
91.             */  
92.         });  
93.   
94.         /* 
95.         //Button Keyboard Event 
96.         but.addKeyListener(new KeyAdapter() 
97.         { 
98.             public void keyPressed(KeyEvent e) 
99.             { 
100.                 //Capture and press ctrl+entry at the same time 
101.                 if(e.isControlDown()&&e.getKeyCode()==KeyEvent.VK_ENTER) 
102.                     System.out.println("Ctrl+Enter.....is Down"); 
103.                  
104.                 //System.out.println(e.getKeyText(e.getKeyCode())+"---"+e.getKeyCode());     
105.             } 
106.         }); 
107.         */  
108.   
109.         //Textbox Keyboard Events  
110.         tf.addKeyListener(new KeyAdapter()  
111.         {  
112.             public void keyPressed(KeyEvent e)  
113.             {  
114.                 /* 
115.                 //Determine whether the input character is a number? 
116.                 if(e.getKeyCode()<KeyEvent.VK_0||e.getKeyCode()>KeyEvent.VK_9) 
117.                 { 
118.                     System.out.println("The number you entered is illegal. Please multiply it. 
119.                     e.consume();//Characters that do not display input 
120.                 } 
121.                 */  
122.   
123.                 if(e.getKeyCode()==KeyEvent.VK_ENTER)  
124.                     showFile();//Display the contents of the directory into the text area  
125.             }  
126.         });  
127.     }  
128.   
129.     //List directories or files under paths  
130.     private void showFile()  
131.     {  
132.         String path=tf.getText();//Get text box content  
133.         File file=new File(path);//Encapsulating paths as file objects  
134.         //Judging whether it exists  
135.         if(file.exists())  
136.         {  
137.             ta.setText("");//Empty the content in the text area  
138.             //If it is a directory  
139.             if(file.isDirectory())  
140.             {  
141.                 String[] dir=file.list();//List the files and directories under the directory  
142.                 //ergodic  
143.                 for (String name : dir)  
144.                 {  
145.                     ta.append(name+"\r\n");//Add to the text area  
146.                 }  
147.             }  
148.             else  
149.                 ta.append(file.getName());//If it is a file, only the name of the file is displayed.  
150.         }  
151.         else  
152.             System.out.println("The path you entered does not exist. Please retransmit or go to the hospital.");  
153.     }  
154.       
155.   
156.     public static void main(String[] args)   
157.     {  
158.         //Run form  
159.         new KeyAndMouseEvent();  
160.     }  
161. }  

 

Lecture 2: Application

Dialog

When a dialog box needs to be generated: This object needs to be created when it is invoked. For example, when misoperation occurs, a dialog box prompting error information is needed to create the object at this time.

Example:

Enhanced functionality for listing examples of specified directory content.

1. /* 
2. List the contents in the specified directory, and give an error message when the input path is incorrect. 
3. */  
4.   
5. import java.io.*;  
6. import java.awt.*;  
7. import java.awt.event.*;  
8.   
9. class MyWindowDemo   
10. {  
11.     //Define required component references  
12.     private Frame f;  
13.     private Button but,bok;  
14.     private TextField tf;  
15.     private TextArea ta;  
16.     private Dialog d;  
17.     private Label lab;  
18.   
19.     //Constructor  
20.     MyWindowDemo()  
21.     {  
22.         init();  
23.     }  
24.   
25.     //Forms are basically set to function implementation  
26.     public void init()  
27.     {  
28.         //Component instantiation  
29.         f=new Frame("My Window");  
30.         but=new Button("Jump");  
31.         tf=new TextField(50);  
32.         ta=new TextArea(30,60);  
33.   
34.         //Basic setup  
35.         f.setBounds(300,150,500,500);  
36.         f.setLayout(new FlowLayout());  
37.   
38.         //add component  
39.         f.add(tf);  
40.         f.add(but);  
41.         f.add(ta);  
42.   
43.         //Form Events  
44.         myEvent();  
45.   
46.         //Form display  
47.         f.setVisible(true);  
48.     }  
49.   
50.     //Registration event  
51.     public void myEvent()  
52.     {  
53.         //Form Closing Function  
54.         f.addWindowListener(new WindowAdapter()  
55.         {  
56.             public void windowClosing(WindowEvent e)  
57.             {  
58.                 System.exit(0);  
59.             }  
60.         });  
61.   
62.         //"Jump" Button Event  
63.         but.addActionListener(new ActionListener()  
64.         {  
65.             public void actionPerformed(ActionEvent e)  
66.             {  
67.                 showFile();//List the contents of the directory in the text area  
68.             }  
69.         });  
70.   
71.           
72.   
73.         //Textbox Keyboard Events  
74.         tf.addKeyListener(new KeyAdapter()  
75.         {  
76.             public void keyPressed(KeyEvent e)  
77.             {  
78.                 //If the keyboard presses the Enter key, the contents of the directory are displayed in the text area.  
79.                 if(e.getKeyCode()==KeyEvent.VK_ENTER)  
80.                     showFile();  
81.             }  
82.         });  
83.     }  
84.   
85.     //Method of Content Display in Text Area  
86.         private void showFile()  
87.         {  
88.             String path=tf.getText();//Get the path of the input  
89.             File dir=new File(path);//Encapsulating paths into objects  
90.             //Determine whether the input path exists and whether it is a folder?  
91.             if (dir.exists()&&dir.isDirectory())  
92.             {  
93.                 ta.setText("");//Empty the content in the text area - ------------------------------------------------------------------------------------------------------  
94.                   
95.                 String names[]=dir.list();//List the contents of the directory  
96.                 //ergodic  
97.                 for (String name : names )  
98.                 {  
99.                     ta.append(name+"\r\n");//Add to text area  
100.                 }  
101.             }  
102.             else  
103.             {  
104.                 //Dialog Basic Settings  
105.                 d=new Dialog(f,"Error prompt",true);  
106.                 d.setBounds(400,200,280,150);  
107.                 d.setLayout(new FlowLayout());  
108.   
109.                 bok=new Button("Determine");  
110.                 lab=new Label();  
111.   
112.                 //Add buttons and text  
113.                 d.add(bok);  
114.                 d.add(lab);  
115.   
116.   
117.                 //Dialog box closes event  
118.                 d.addWindowListener(new WindowAdapter()  
119.                 {  
120.                     public void windowClosing(WindowEvent e)  
121.                     {  
122.                         d.setVisible(false);//Exit dialog box  
123.                     }  
124.                 });  
125.   
126.                 //OK button event  
127.                 bok.addActionListener(new ActionListener()  
128.                 {  
129.                     public void actionPerformed(ActionEvent e)  
130.                     {  
131.                         d.setVisible(false);//Press the confirmation key to exit the dialog box  
132.                     }  
133.                 });  
134.   
135.   
136.                 String info="The path you entered:"+path+"It's wrong. Please try again!";  
137.   
138.                 lab.setText(info);//Setting label text content  
139.                 d.setVisible(true);//display a dialog box  
140.             }  
141.         }  
142.   
143.     public static void main(String[] args)   
144.     {  
145.         //Run form  
146.         new MyWindowDemo();  
147.     }  
148. }  

Menu: Menu

1. Menu Inheritance

       

2, explain

Menu: Menu, inherit MenuItem; there are icons in the right triangle, Menu and MenuItem can be added.

2) MenuBar: Menu bar, you can add menus and menu items. Generally, first create the menu bar, then create the menu.

Menu Item: Menu item, also known as menu item, has no right triangle icon and is the final menu item.

4) Menu event processing is the same as component, adding activity listener to event source of type MenuItem and Menu, and processing related events.

5) Add the menu to the Frame through the setMenuBar() method.

Example:

1. import java.awt.*;  
2. import java.awt.event.*;  
3.   
4. class MyMenuDemo   
5. {  
6.     //Define component references  
7.     private Frame f;  
8.     private MenuBar mb;  
9.     private Menu m,subMenu;  
10.     private MenuItem closeItem,subItem;  
11.     //Constructor  
12.     MyMenuDemo()  
13.     {  
14.         init();  
15.     }  
16. //Form Setting and Function Realization  
17.     public void init()  
18.     {  
19.         //Form settings  
20. f = new Frame("my window");  
21.         f.setBounds(300,100,500,600);  
22.         f.setLayout(new FlowLayout());  
23.       
24.         mb = new MenuBar();//Create menu bar  
25.         m = new Menu("file");//create menu  
26.         subMenu = new Menu("Submenu");//Submenu under menu  
27.   
28.         subItem = new MenuItem("subentry");//Submenu contains menu items  
29.         closeItem = new MenuItem("Sign out");//Menu contains entries  
30.           
31. //Menu Add Menu Components  
32.         subMenu.add(subItem);  
33.         m.add(subMenu);  
34.         m.add(closeItem);  
35.         mb.add(m);  
36.         //Form Add Menu Component  
37.         f.setMenuBar(mb);  
38.         //Events on Forms  
39.         myEvent();  
40.         //Form display  
41.         f.setVisible(true);  
42.     }  
43.     private void myEvent()  
44.     {  
45.         //Close menu with close events  
46.         closeItem.addActionListener(new ActionListener()  
47.         {  
48.             public void actionPerformed(ActionEvent e)  
49.             {  
50.                 System.exit(0);  
51.             }  
52.         });  
53.         //Form Closing Function  
54.         f.addWindowListener(new WindowAdapter()  
55.         {  
56.             public void windowClosing(WindowEvent e)  
57.             {  
58.                 System.exit(0);   
59.             }  
60.         });  
61.     }  
62.       
63.     public static void main(String[] args)   
64.     {  
65.         new MyMenuDemo();  
66.     }  
67. }  

 

3. Double-click execution of jar package

Since it is a graphical interface, you need to run the program in the form of a graphical interface, not on the Dos command line, so how to execute the program by double-clicking the program? This requires packing the class file of the program.

The steps are as follows:

1. First, import a package in a java file, and then create a package if not, such as package mymenu.

2. Generating packages: By compiling Java c-d:myclass MyMenu.java, all. class files are generated under the MyClass folder on the C disk.

3. Create a new file in this directory, such as 1.txt or any other file with any extension, and then edit it in a fixed format: "Main-Class: mymenu.MenuDemo", which only writes the contents in quotation marks. You need to have a space after the colon and return to the car at the end of the file.

Compile: jar-cvfm my.jar 1.txt mymenu. If you want to add other information, you can compile jar directly and get the corresponding command.

5. Double-click at this time to execute.

Explain:

1) In a fixed format:

(a) If there are no spaces: IO exceptions are reported at compilation time, indicating invalid header fields. This shows that 1.txt is read by IO stream.

b. If there is no carriage return, the information of loading the main class will not be added to the list. MF, that is to say, the name of the main class of the attribute of the configuration list will not be loaded into the list, and it will not be executed.

2) The jar file must be registered in the system before it can run. The registration method is as follows:

A. For XP systems:

Open any dialog box, click the Tool button in the menu bar, and select the folder option

b. Select the new - > extension, set the extension to jar, and confirm

c. Select Advanced, change the icon, and then click New, named open.

d. In executable applications, click browse, add the entire file path of bin under jdk, and add - jar after the path.

For win7 system:

a. Change the way you open it: Right-click the.jar file, click the way you open it, and select the javaw.exe application in bin under jdk as the default program.

b. Modify the registry of the associated program: Open the registry (win+r), find the registry path HKEY_CLASSES_ROOT Aplications javaw.exe shell open command, right-click the string value, and add-jar to the original path, such as: Program Files Java j6 bin javaw.exe - jar "%1". Note that there should be spaces on both sides of the jar. Save.

c. Double-click to execute the jar program, and if it still can't execute, download the latest version of jdk.

Example:

1. /* 
2. Exercise: Complete a simple notebook program with Menu components. 
3. Requirements: File menu, file opening, saving and exiting functions. Change the written program to double-click executable program. 
4. */  
5.   
6. package mymenu;  
7. import java.awt.*;  
8. import java.awt.event.*;  
9. import java.io.*;  
10.   
11. class MyMenuText  
12. {  
13.     //Define component references  
14.     private Frame f;  
15.     private TextArea ta;  
16.     private MenuBar mb;  
17.     private Menu fileMe;  
18.     private MenuItem openMi,saveMi,otherSaveMi,closeMi;  
19.   
20.     private FileDialog openDia,saveDia;  
21.   
22.     private File file;  
23.   
24.     //Constructor  
25.     MyMenuText()  
26.     {  
27.         init();  
28.     }  
29.   
30.     //Function realization  
31.     private void init()  
32.     {  
33.         //Component instantiation  
34.         f=new Frame("MyText");  
35.         ta=new TextArea();  
36.           
37.         mb=new MenuBar();  
38.         fileMe=new Menu("file");  
39.         openMi=new MenuItem("open");  
40.         saveMi=new MenuItem("Preservation");  
41.         otherSaveMi=new MenuItem("Save as");  
42.         closeMi=new MenuItem("Sign out");  
43.   
44.         openDia=new FileDialog(f,"Select the open file",FileDialog.LOAD);  
45.         saveDia=new FileDialog(f,"Where to save",FileDialog.SAVE);  
46.   
47.         //Basic setup  
48.         f.setBounds(300,150,600,500);  
49.   
50.         //add component  
51.         f.add(ta);  
52.         f.setMenuBar(mb);  
53.   
54.         mb.add(fileMe);  
55.         fileMe.add(openMi);  
56.         fileMe.add(saveMi);  
57.         fileMe.add(otherSaveMi);  
58.         fileMe.add(closeMi);  
59.   
60.         //Events in Forms  
61.         myEvent();  
62.   
63.         //Form display  
64.         f.setVisible(true);  
65.     }  
66.   
67.     private void myEvent()  
68.     {  
69.         //Form Closing Function  
70.         f.addWindowListener(new WindowAdapter()  
71.         {  
72.             public void windowClosing(WindowEvent e)  
73.             {  
74.                 System.exit(0);  
75.             }  
76.         });  
77.   
78.         //Open event  
79.         openMi.addActionListener(new ActionListener()  
80.         {  
81.             public void actionPerformed(ActionEvent e)  
82.             {  
83.                 //Display File Dialogue Window  
84.                 openDia.setVisible(true);//------------------  
85.                 String dir=openDia.getDirectory();//Get directory  
86.                 String fileName=openDia.getFile();//Get the filename  
87.                   
88.                 if(dir==null||fileName==null)//Processing for opening a file dialog box but not doing anything  
89.                     return;  
90.           
91.                 file=new File(dir,fileName);//File object  
92.                 try  
93.                 {  
94.                     ta.setText("");//Every time a file is opened, the contents of the text area are emptied  
95.                     //Read stream with buffer technology  
96.                     BufferedReader br=new BufferedReader(new FileReader(file));  
97.                     String line=null;//Read a row  
98.                     while ((line=br.readLine())!=null)  
99.                     {  
100.                         //Add to text area  
101.                         ta.append(line+"\r\n");  
102.                     }  
103.                     br.close();//Shut off flow  
104.                 }  
105.                 catch (IOException ie)  
106.                 {  
107.                     throw new RuntimeException("Failed to open file");  
108.                 }  
109.             }  
110.         });  
111.   
112.         //Save events  
113.         saveMi.addActionListener(new ActionListener()  
114.         {  
115.             public void actionPerformed(ActionEvent e)  
116.             {  
117.                 //If it is saved for the first time, the file dialog box is displayed  
118.                 if(file==null)//-------------  
119.                 {  
120.                     //Display File Dialog Box  
121.                     saveDia.setVisible(true);//----------------------  
122.                     String dir=saveDia.getDirectory();  
123.                     String filename=saveDia.getFile();  
124.                       
125.                     if(dir==null||filename==null)//--------------------  
126.                         return;  
127.   
128.                     file=new File(dir,filename);  
129.                       
130.                 }  
131.                 save();//Method of saving files  
132.             }  
133.         });  
134.           
135.         //Save as an event  
136.         otherSaveMi.addActionListener(new ActionListener()  
137.         {  
138.             public void actionPerformed(ActionEvent e)  
139.             {  
140.                 //Does the file dialog display whether it is saved for the first time or not?  
141.                 saveDia.setVisible(true);//----------------------  
142.                 String dir=saveDia.getDirectory();  
143.                 String filename=saveDia.getFile();  
144.   
145.                 if(dir==null||filename==null)//--------------------  
146.                     return;  
147.   
148.                 file=new File(dir,filename);  
149.   
150.                 save();//Method of saving files  
151.                 //When saved, the default file dialog box location is where the file is opened  
152.                 openDia.setFile(file.getName());  
153.             }  
154.         });  
155.   
156.         //Exit event  
157.         closeMi.addActionListener(new ActionListener()  
158.         {  
159.             public void actionPerformed(ActionEvent e)  
160.             {  
161.                 System.exit(0);  
162.             }  
163.         });  
164.     }  
165.       
166.     //Save file  
167.     private void save()  
168.     {             
169.         try  
170.         {  
171.             //Write stream with buffer  
172.             BufferedWriter bw=new BufferedWriter(new FileWriter(file));  
173.             //Get the content in the text area  
174.             String text=ta.getText();  
175.             bw.write(text);//Write to a file  
176.             bw.close();//Shut off flow  
177.   
178.         }  
179.         catch (IOException ie)  
180.         {  
181.             throw new RuntimeException("File save failed");  
182.         }  
183.     }  
184.   
185.     public static void main(String[] args)   
186.     {  
187.         //Program operation  
188.         new MyMenuText();  
189.     }  
190. }