Java笔记

Posted 灌水乐园

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了Java笔记相关的知识,希望对你有一定的参考价值。

GUI:

awt和swing:

java.awt:Abstract Window ToolKit(抽象窗口工具包),需要调用本地系统方法实现功能。属于重量级控件。

javax.swing:在awt的基础上,建立的一套图形界面系统,其中提供了更多的组件,而且完全由Java实现。增强了移植性,属于轻量级控件。

创建图形化界面:

(1)创建Frame窗体;

(2)对窗体进行基本设置。如:大小、位置、布局;

(3)定义组件;

(4)将组件通过窗体的add方法添加到窗体中;

(5)让窗体显示,通过setVisible(true)。

事件监听机制的特点:

(1)事件源

(2)事件

(3)监听器

(4)事件处理

事件源:就是awt包或者swing包中的那些图形界面组件。

事件:每一个事件源都有自己特有的对应事件和共性事件。

监听器:将可以触发某一个事件的动作(不止一个)都封装到了监听器中。

以上三者,在Java中都定义好了,直接获取其对象来用就可以。我们只要对产生的动作进行处理。

 1 import java.awt.Button;
 2 import java.awt.FlowLayout;
 3 import java.awt.Frame;
 4 import java.awt.event.ActionEvent;
 5 import java.awt.event.ActionListener;
 6 import java.awt.event.WindowAdapter;
 7 import java.awt.event.WindowEvent;
 8 
 9 public class Demo{
10     //定义该图形中的所需组件的引用
11     private Frame f;
12     private Button b;
13     Demo(){
14         init();
15     }
16     public void init(){
17         f = new Frame("my frame");
18         
19         //对frame进行基本设置
20         f.setBounds(300, 200, 300, 200);
21         f.setLayout(new FlowLayout());
22         
23         b = new Button("按钮");
24         
25         //将组件添加到frame中
26         f.add(b);
27         
28         //加载一下窗体上的事件
29         myEvent();
30         
31         //显示窗体
32         f.setVisible(true);
33     }
34     private void myEvent(){
35         f.addWindowListener(new WindowAdapter(){
36             public void windowClosing(WindowEvent e){
37                 System.exit(0);
38             }
39         });
40         
41         //让按钮具备退出程序的功能
42         //此时按钮就是事件源,想要知道哪个组件具备什么样的特有监听器,需要查看该组件对象的功能,通过查阅button的描述,
43         //发现按钮支持一个特有监听addActionListener
44         b.addActionListener(new ActionListener(){
45             public void actionPerformed(ActionEvent e){
46                 System.exit(0);
47             }
48         });
49     }
50     public static void main(String[] args){
51         new Demo();
52     }
53 }

鼠标事件:

 1 import java.awt.Button;
 2 import java.awt.FlowLayout;
 3 import java.awt.Frame;
 4 import java.awt.event.MouseAdapter;
 5 import java.awt.event.MouseEvent;
 6 import java.awt.event.WindowAdapter;
 7 import java.awt.event.WindowEvent;
 8 
 9 public class Demo{
10     private Frame f;
11     private Button b;
12     Demo(){
13         init();
14     }
15     public void init(){
16         f = new Frame("my frame");
17         
18         f.setBounds(300, 200, 300, 200);
19         f.setLayout(new FlowLayout());
20         
21         b = new Button("按钮");
22         
23         f.add(b);
24         
25         myEvent();
26         
27         f.setVisible(true);
28     }
29     private void myEvent(){
30         f.addWindowListener(new WindowAdapter(){
31             public void windowClosing(WindowEvent e){
32                 System.exit(0);
33             }
34         });
35         b.addMouseListener(new MouseAdapter(){
36             public void mouseEntered(MouseEvent e){
37                 System.out.println("鼠标进入该组件");
38             }
39             
40             public void mouseClicked(MouseEvent e){
41                 if(e.getClickCount() == 2)
42                     System.out.println("双击动作");
43             }
44         });
45     }
46     public static void main(String[] args){
47         new Demo();
48     }
49 }

键盘事件:

 1 import java.awt.Button;
 2 import java.awt.FlowLayout;
 3 import java.awt.Frame;
 4 import java.awt.TextField;
 5 import java.awt.event.KeyAdapter;
 6 import java.awt.event.KeyEvent;
 7 import java.awt.event.WindowAdapter;
 8 import java.awt.event.WindowEvent;
 9 
10 public class Demo{
11     private Frame f;
12     private Button b;
13     private TextField tf;
14     Demo(){
15         init();
16     }
17     public void init(){
18         f = new Frame("my frame");
19         
20         f.setBounds(300, 200, 300, 200);
21         f.setLayout(new FlowLayout());
22         
23         tf = new TextField(20);
24         
25         b = new Button("按钮");
26         
27         f.add(b);
28         f.add(tf);
29         
30         myEvent();
31         
32         f.setVisible(true);
33     }
34     private void myEvent(){
35         f.addWindowListener(new WindowAdapter(){
36             public void windowClosing(WindowEvent e){
37                 System.exit(0);
38             }
39         });
40         
41         //添加键盘监听
42         b.addKeyListener(new KeyAdapter(){
43 //            public void keyPressed(KeyEvent e){
44 //                //按“ESC”键,程序退出
45 //                if(e.getKeyCode() == KeyEvent.VK_ESCAPE)
46 //                    System.exit(0);
47 //            }
48             
49             //Ctrl+回车键,使程序退出
50             public void keyPressed(KeyEvent e){
51                 if(e.isControlDown() && e.getKeyCode() == KeyEvent.VK_ENTER)
52                     System.exit(0);
53             }
54         });
55         
56         //设置文本框,使它只能被输入数字
57         tf.addKeyListener(new KeyAdapter(){
58             public void keyPressed(KeyEvent e){
59                 int code = e.getKeyCode();
60                 if(!(code >= KeyEvent.VK_0 && code <= KeyEvent.VK_9)){
61                     System.out.println(code + "...是非法的");
62                     e.consume();
63                 }
64             }
65         });
66     }
67     public static void main(String[] args){
68         new Demo();
69     }
70 }

例:列出指定目录内容:

 

  1 import java.awt.Button;
  2 import java.awt.Dialog;
  3 import java.awt.FlowLayout;
  4 import java.awt.Frame;
  5 import java.awt.Label;
  6 import java.awt.TextArea;
  7 import java.awt.TextField;
  8 import java.awt.event.ActionEvent;
  9 import java.awt.event.ActionListener;
 10 import java.awt.event.KeyAdapter;
 11 import java.awt.event.KeyEvent;
 12 import java.awt.event.WindowAdapter;
 13 import java.awt.event.WindowEvent;
 14 import java.io.File;
 15 
 16 public class Demo{
 17     private Frame f;
 18     private Button b;
 19     private TextField tf;
 20     private TextArea ta;
 21     private Dialog d;
 22     private Label label;
 23     private Button okBut;
 24     Demo(){
 25         init();
 26     }
 27     public void init(){
 28         f = new Frame("练习");
 29         f.setBounds(300, 100, 600, 500);
 30         f.setLayout(new FlowLayout());
 31         
 32         b = new Button("转到");
 33         
 34         tf = new TextField(60);
 35         ta = new TextArea(25, 70);
 36         
 37         //参数为true,表明必须先操作Dialog
 38         d = new Dialog(f, "提示信息-self", true);
 39         d.setBounds(400, 200, 240, 150);
 40         d.setLayout(new FlowLayout());
 41         label = new Label();
 42         okBut = new Button("确定");
 43         d.add(label);
 44         d.add(okBut);
 45         
 46         f.add(tf);
 47         f.add(b);
 48         f.add(ta);
 49         
 50         myEvent();
 51         
 52         f.setVisible(true);
 53     }
 54     public void myEvent(){
 55         f.addWindowListener(new WindowAdapter(){
 56             public void windowClosing(WindowEvent e){
 57                 System.exit(0);
 58             }
 59         });
 60         
 61         b.addActionListener(new ActionListener(){
 62             public void actionPerformed(ActionEvent e){
 63                 showDir();
 64             }
 65         });
 66         
 67         d.addWindowListener(new WindowAdapter(){
 68             public void windowClosing(WindowEvent e){
 69                 d.setVisible(false);
 70             }
 71         });
 72         
 73         okBut.addActionListener(new ActionListener(){
 74             public void actionPerformed(ActionEvent e){
 75                 d.setVisible(false);
 76             }
 77         });
 78         
 79         tf.addKeyListener(new KeyAdapter(){
 80             public void keyPressed(KeyEvent e){
 81                 if(e.getKeyCode() == KeyEvent.VK_ENTER){
 82                     showDir();
 83                 }
 84             }
 85         });
 86     }
 87     
 88     private void showDir(){
 89         String dirPath = tf.getText();
 90         File file = new File(dirPath);
 91         if(file.exists() && file.isDirectory()){
 92             tf.setText("");
 93             String[] names = file.list();
 94             for(String name : names){
 95                 ta.append(name + "\\r\\n");
 96             }
 97         }
 98         else{
 99             String info = "您输入的信息: " + dirPath + "是错误的。请重新输入!";
100             label.setText(info);
101             d.setVisible(true);
102         }
103     }
104     
105     public static void main(String[] args) {
106         new Demo();
107     }
108 }

菜单:

 1 import java.awt.FlowLayout;
 2 import java.awt.Frame;
 3 import java.awt.Menu;
 4 import java.awt.MenuBar;
 5 import java.awt.MenuItem;
 6 import java.awt.event.ActionEvent;
 7 import java.awt.event.ActionListener;
 8 import java.awt.event.WindowAdapter;
 9 import java.awt.event.WindowEvent;
10 
11 public class Demo{
12     private Frame f;
13     private MenuBar mb;
14     private Menu m, subMenu;
15     private MenuItem closeItem, subItem;
16     
17     Demo(){
18         init();
19     }
20     
21     public void init(){
22         f = new Frame("my window");
23         f.setBounds(300, 100, 500, 600);
24         f.setLayout(new FlowLayout());
25         
26         mb = new MenuBar();
27         
28         m = new Menu("文件");
29         subMenu = new Menu("子菜单");
30         closeItem = new MenuItem("退出");
31         subItem = new MenuItem("子条目");
32         
33         subMenu.add(subItem);
34         m.add(subMenu);
35         m.add(closeItem);
36         mb.add(m);
37         f.setMenuBar(mb);
38         
39         myEvent();
40         
41         f.setVisible(true);
42     }
43     
44     public void myEvent(){
45         f.addWindowListener(new WindowAdapter(){
46             public void windowClosing(WindowEvent e){
47                 System.exit(0);
48             }
49         });
50         
51         closeItem.addActionListener(new ActionListener(){
52             public void actionPerformed(ActionEvent e){
53                 System.exit(0);
54             }
55         });
56         
57     }
58     
59     public static void main(String[] args) {
60         new Demo();
61     }
62 }

如图:

打开保存文件:

  1 import java.awt.FileDialog;
  2 import java.awt.Frame;
  3 import java.awt.Menu;
  4 import java.awt.MenuBar;
  5 import java.awt.MenuItem;
  6 import java.awt.TextArea;
  7 import java.awt.event.ActionEvent;
  8 import java.awt.event.ActionListener;
  9 import java.awt.event.WindowAdapter;
 10 import java.awt.event.WindowEvent;
 11 import java.io.BufferedReader;
 12 import java.io.BufferedWriter;
 13 import java.io.File;
 14 import java.io.FileReader;
 15 import java.io.FileWriter;
 16 import java.io.IOException;
 17 
 18 public class Demo{
 19     private Frame f;
 20     private Menu fileMenu;
 21     private MenuItem openItem, saveItem, closeItem;
 22     private MenuBar bar;
 23     private FileDialog openD, saveD;
 24     private TextArea ta;
 25     private File file;
 26     Demo(){
 27         init();
 28     }
 29     
 30     public void init(){
 31         f = new Frame("练习");
 32         f.setBounds(300, 100, 650, 600);
 33         
 34         bar = new MenuBar();
 35         ta = new TextArea();
 36         openItem = new MenuItem("打开");
 37         saveItem = new MenuItem("保存");
 38         closeItem = new MenuItem("退出");
 39         fileMenu = new Menu("文件");
 40         
 41         fileMenu.add(openItem);
 42         fileMenu.add(saveItem);
 43         fileMenu.add(closeItem);
 44         bar.add(fileMenu);
 45         f.setMenuBar(bar);
 46         f.add(ta);
 47         
 48         openD = new FileDialog(f, "打开文件", FileDialog.LOAD);
 49         saveD = new FileDialog(f, "保存文件", FileDialog.SAVE);
 50         
 51         myEvent();
 52         
 53         f.setVisible(true);
 54     }
 55     
 56     public void myEvent(){
 57         //窗口关闭
 58         f.addWindowListener(new WindowAdapter(){
 59             public void windowClosing(WindowEvent e){
 60                 System.exit(0);
 61             }
 62         });
 63         
 64         //点击“退出”条目,退出程序
 65         closeItem.addActionListener(new ActionListener(){
 66             public void actionPerformed(ActionEvent e){
 67                 System.exit(0);
 68             }
 69         });
 70         
 71         //打开选中的文件,显示在TextArea中
 72         openItem.addActionListener(new ActionListener(){
 73             public void actionPerformed(ActionEvent e){
 74                 openD.setVisible(true);
 75                 String dirPath = openD.getDirectory();
 76                 String fileName = openD.getFile();
 77                 if(dirPath == null || fileName == null)
 78                     return;
 79                 ta.setText("");
 80                 file = new File(dirPath, fileName);
 81                 try{
 82                     BufferedReader bufr = new BufferedReader(new FileReader(file));
 83                     String line = null;
 84                     while((line = bufr.readLine()) != JSP 学习笔记

JSP笔记

JSP学习笔记:JSP语法和指令

java代码在片段活动中不起作用

java 代码片段【JAVA】

# Java 常用代码片段