Java笔记（八）

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。

 import java.awt.Button;
 import java.awt.FlowLayout;
 import java.awt.Frame;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;

 public class Demo{
     //定义该图形中的所需组件的引用
     private Frame f;
     private Button b;
     Demo(){
         init();
     }
     public void init(){
         f = new Frame("my frame");

         //对frame进行基本设置
         f.setBounds(300, 200, 300, 200);
         f.setLayout(new FlowLayout());

         b = new Button("按钮");

         //将组件添加到frame中
         f.add(b);

         //加载一下窗体上的事件
         myEvent();

         //显示窗体
         f.setVisible(true);
     }
     private void myEvent(){
         f.addWindowListener(new WindowAdapter(){
             public void windowClosing(WindowEvent e){
                 System.exit(0);
             }
         });

         //让按钮具备退出程序的功能
         //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，
         //发现按钮支持一个特有监听addActionListener
         b.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 System.exit(0);
             }
         });
     }
     public static void main(String[] args){
         new Demo();
     }
 }

鼠标事件：

 import java.awt.Button;
 import java.awt.FlowLayout;
 import java.awt.Frame;
 import java.awt.event.MouseAdapter;
 import java.awt.event.MouseEvent;
 import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;

 public class Demo{
     private Frame f;
     private Button b;
     Demo(){
         init();
     }
     public void init(){
         f = new Frame("my frame");

         f.setBounds(300, 200, 300, 200);
         f.setLayout(new FlowLayout());

         b = new Button("按钮");

         f.add(b);

         myEvent();

         f.setVisible(true);
     }
     private void myEvent(){
         f.addWindowListener(new WindowAdapter(){
             public void windowClosing(WindowEvent e){
                 System.exit(0);
             }
         });
         b.addMouseListener(new MouseAdapter(){
             public void mouseEntered(MouseEvent e){
                 System.out.println("鼠标进入该组件");
             }

             public void mouseClicked(MouseEvent e){
                 if(e.getClickCount() == 2)
                     System.out.println("双击动作");
             }
         });
     }
     public static void main(String[] args){
         new Demo();
     }
 }

键盘事件：

 import java.awt.Button;
 import java.awt.FlowLayout;
 import java.awt.Frame;
 import java.awt.TextField;
 import java.awt.event.KeyAdapter;
 import java.awt.event.KeyEvent;
 import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;

 public class Demo{
     private Frame f;
     private Button b;
     private TextField tf;
     Demo(){
         init();
     }
     public void init(){
         f = new Frame("my frame");

         f.setBounds(300, 200, 300, 200);
         f.setLayout(new FlowLayout());

         tf = new TextField(20);

         b = new Button("按钮");

         f.add(b);
         f.add(tf);

         myEvent();

         f.setVisible(true);
     }
     private void myEvent(){
         f.addWindowListener(new WindowAdapter(){
             public void windowClosing(WindowEvent e){
                 System.exit(0);
             }
         });

         //添加键盘监听
         b.addKeyListener(new KeyAdapter(){
 //            public void keyPressed(KeyEvent e){
 //                //按“ESC”键，程序退出
 //                if(e.getKeyCode() == KeyEvent.VK_ESCAPE)
 //                    System.exit(0);
 //            }

             //Ctrl+回车键，使程序退出
             public void keyPressed(KeyEvent e){
                 if(e.isControlDown() && e.getKeyCode() == KeyEvent.VK_ENTER)
                     System.exit(0);
             }
         });

         //设置文本框，使它只能被输入数字
         tf.addKeyListener(new KeyAdapter(){
             public void keyPressed(KeyEvent e){
                 int code = e.getKeyCode();
                 if(!(code >= KeyEvent.VK_0 && code <= KeyEvent.VK_9)){
                     System.out.println(code + "...是非法的");
                     e.consume();
                 }
             }
         });
     }
     public static void main(String[] args){
         new Demo();
     }
 }

例：列出指定目录内容：

 import java.awt.Button;
 import java.awt.Dialog;
 import java.awt.FlowLayout;
 import java.awt.Frame;
 import java.awt.Label;
 import java.awt.TextArea;
 import java.awt.TextField;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import java.awt.event.KeyAdapter;
 import java.awt.event.KeyEvent;
 import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;
 import java.io.File;

 public class Demo{
     private Frame f;
     private Button b;
     private TextField tf;
     private TextArea ta;
     private Dialog d;
     private Label label;
     private Button okBut;
     Demo(){
         init();
     }
     public void init(){
         f = new Frame("练习");
         f.setBounds(300, 100, 600, 500);
         f.setLayout(new FlowLayout());

         b = new Button("转到");

         tf = new TextField(60);
         ta = new TextArea(25, 70);

         //参数为true，表明必须先操作Dialog
         d = new Dialog(f, "提示信息-self", true);
         d.setBounds(400, 200, 240, 150);
         d.setLayout(new FlowLayout());
         label = new Label();
         okBut = new Button("确定");
         d.add(label);
         d.add(okBut);

         f.add(tf);
         f.add(b);
         f.add(ta);

         myEvent();

         f.setVisible(true);
     }
     public void myEvent(){
         f.addWindowListener(new WindowAdapter(){
             public void windowClosing(WindowEvent e){
                 System.exit(0);
             }
         });

         b.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 showDir();
             }
         });

         d.addWindowListener(new WindowAdapter(){
             public void windowClosing(WindowEvent e){
                 d.setVisible(false);
             }
         });

         okBut.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 d.setVisible(false);
             }
         });

         tf.addKeyListener(new KeyAdapter(){
             public void keyPressed(KeyEvent e){
                 if(e.getKeyCode() == KeyEvent.VK_ENTER){
                     showDir();
                 }
             }
         });
     }

     private void showDir(){
         String dirPath = tf.getText();
         File file = new File(dirPath);
         if(file.exists() && file.isDirectory()){
             tf.setText("");
             String[] names = file.list();
             for(String name : names){
                 ta.append(name + "\r\n");
             }
         }
         else{
             String info = "您输入的信息: " + dirPath + "是错误的。请重新输入！";
             label.setText(info);
             d.setVisible(true);
         }
     }

     public static void main(String[] args) {
         new Demo();
     }
 }

菜单：

 import java.awt.FlowLayout;
 import java.awt.Frame;
 import java.awt.Menu;
 import java.awt.MenuBar;
 import java.awt.MenuItem;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;

 public class Demo{
     private Frame f;
     private MenuBar mb;
     private Menu m, subMenu;
     private MenuItem closeItem, subItem;

     Demo(){
         init();
     }

     public void init(){
         f = new Frame("my window");
         f.setBounds(300, 100, 500, 600);
         f.setLayout(new FlowLayout());

         mb = new MenuBar();

         m = new Menu("文件");
         subMenu = new Menu("子菜单");
         closeItem = new MenuItem("退出");
         subItem = new MenuItem("子条目");

         subMenu.add(subItem);
         m.add(subMenu);
         m.add(closeItem);
         mb.add(m);
         f.setMenuBar(mb);

         myEvent();

         f.setVisible(true);
     }

     public void myEvent(){
         f.addWindowListener(new WindowAdapter(){
             public void windowClosing(WindowEvent e){
                 System.exit(0);
             }
         });

         closeItem.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 System.exit(0);
             }
         });

     }

     public static void main(String[] args) {
         new Demo();
     }
 }

如图：

打开保存文件：

 import java.awt.FileDialog;
 import java.awt.Frame;
 import java.awt.Menu;
 import java.awt.MenuBar;
 import java.awt.MenuItem;
 import java.awt.TextArea;
 import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
 import java.awt.event.WindowAdapter;
 import java.awt.event.WindowEvent;
 import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.File;
 import java.io.FileReader;
 import java.io.FileWriter;
 import java.io.IOException;

 public class Demo{
     private Frame f;
     private Menu fileMenu;
     private MenuItem openItem, saveItem, closeItem;
     private MenuBar bar;
     private FileDialog openD, saveD;
     private TextArea ta;
     private File file;
     Demo(){
         init();
     }

     public void init(){
         f = new Frame("练习");
         f.setBounds(300, 100, 650, 600);

         bar = new MenuBar();
         ta = new TextArea();
         openItem = new MenuItem("打开");
         saveItem = new MenuItem("保存");
         closeItem = new MenuItem("退出");
         fileMenu = new Menu("文件");

         fileMenu.add(openItem);
         fileMenu.add(saveItem);
         fileMenu.add(closeItem);
         bar.add(fileMenu);
         f.setMenuBar(bar);
         f.add(ta);

         openD = new FileDialog(f, "打开文件", FileDialog.LOAD);
         saveD = new FileDialog(f, "保存文件", FileDialog.SAVE);

         myEvent();

         f.setVisible(true);
     }

     public void myEvent(){
         //窗口关闭
         f.addWindowListener(new WindowAdapter(){
             public void windowClosing(WindowEvent e){
                 System.exit(0);
             }
         });

         //点击“退出”条目，退出程序
         closeItem.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 System.exit(0);
             }
         });

         //打开选中的文件，显示在TextArea中
         openItem.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 openD.setVisible(true);
                 String dirPath = openD.getDirectory();
                 String fileName = openD.getFile();
                 if(dirPath == null || fileName == null)
                     return;
                 ta.setText("");
                 file = new File(dirPath, fileName);
                 try{
                     BufferedReader bufr = new BufferedReader(new FileReader(file));
                     String line = null;
                     while((line = bufr.readLine()) != null){
                         ta.append(line + "\r\n");
                     }
                 }catch(IOException ex){
                     throw new RuntimeException("读取失败！");
                 }

             }
         });

         //保存文件
         saveItem.addActionListener(new ActionListener(){
             public void actionPerformed(ActionEvent e){
                 if(file == null){
                     saveD.setVisible(true);
                     String dirPath = openD.getDirectory();
                     String fileName = openD.getFile();
                     if(dirPath == null || fileName == null)
                         return;
                     file = new File(dirPath, fileName);
                 }
                 try{
                     BufferedWriter bufw = new BufferedWriter(new FileWriter(file));
                     String s = ta.getText();
                     bufw.write(s);
                     bufw.flush();
                     bufw.close();
                 }catch(IOException ex){
                     throw new RuntimeException("保存失败！");
                 }
             }
         });

     }

     public static void main(String[] args) {
         new Demo();
     }
 }