JavaMe开发：也说MVC设计模式

【更新】本文将适时做出更新，所以现在不是终稿，如有不当之处，敬请指出。

【问题描述】介绍设计模式的文章和书很多，但只有使用时，才能理解设计模式的妙处。接上一篇《JavaMe连载(2)-低级界面绘图之菜单》，本文一则对UIController作出解释，一则将自己理解的MVC设计模式，结合实例，与大家交流学习。

【理论】什么是MVC？

MVC就是模型(model)、视图(view)和控制(control)。什么是模型呢？本例中，模型就是对数据使用时的封装。视图很容易理解，那就是显示内容的具体表示。控制呢？有很多人对视图和控制分不清。在本例中，控制包含视图控制器以及方法的封装。

【实例】

1、先看工程结构，如图1所示。

图1 工程结构

工程中将用户数据单独封装，作为model。供控制器和视图调用。将显示页面单独封装，作为视图。将视图控制器UIController和常用方法封装为util。UIController就是控制。

2、UML图(后续更新时补充)

先看代码，再分析工作机理

【代码清单】

MainMidlet.java

package com.token.midlet;  
 
import java.io.IOException;  
 
import javax.microedition.lcdui.*;  
import javax.microedition.midlet.MIDlet;  
import javax.microedition.midlet.MIDletStateChangeException;  
import com.token.util.UIController;  
 
public class MainMidlet extends MIDlet {  
      
    private Display display;  
    private static UIController controller;  
    public MainMidlet() {  
        // TODO Auto-generated constructor stub  
        super();  
        display=Display.getDisplay(this);  
          
    }  
 
    /* (non-Javadoc)  
     * @see javax.microedition.midlet.MIDlet#pauseApp()  
     */ 
    protected void startApp() throws MIDletStateChangeException {  
        controller=new UIController(this);  
        try {  
            controller.init();  
        } catch (IOException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }//初始化RecordStore  
    }  
 
    /* (non-Javadoc)  
     * @see javax.microedition.midlet.MIDlet#pauseApp()  
     */ 
    protected void pauseApp() {  
        this.notifyPaused();  
    }  
 
    /* (non-Javadoc)  
     * @see javax.microedition.midlet.MIDlet#destroyApp(boolean)  
     */ 
    protected void destroyApp(boolean arg0) throws MIDletStateChangeException {  
        controller=null;  
          
    }  
      
    public void setCurrent(Displayable disp){  
        display.setCurrent(disp);  
    }  
      
    public void setCurrent(Alert alert, Displayable disp){  
        display.setCurrent(alert, disp);  
    }  
    public Displayable getCurrent(){  
        return display.getCurrent();  
    }  
      
    public void exit(boolean arg0){  
        try{  
            destroyApp(arg0);  
            notifyDestroyed();  
        }catch(MIDletStateChangeException e){  
            //  
        }  
    }  
 
}  

模型(Model)

UserDataItem.java

package com.token.model;  
 
import com.token.util.StringDealMethod;  
 
public class UserDataItem {  
    private int id;  
    public String name = null;  
    public String passwd = null;  
 
    public UserDataItem(String name,String passwd)  
    {  
        this.name = name;  
        this.passwd = passwd;     
    }  
      
    public UserDataItem(int id,byte[] data){  
        this.id=id;  
        String temp=new String(data);  
        String temp_sub[] = StringDealMethod.split(temp, ",");  
        this.name = temp_sub[0];  
        this.passwd = temp_sub[1];  
    }  
      
    public int getId(){  
        return id;  
    }  
      
    public void setId(int id){  
        this.id=id;  
    }  
      
    public String getName(){  
        return name;  
    }  
      
    public void setName(String name){  
        this.name = name;  
    }  
      
    public String getPasswd(){  
        return passwd;  
    }  
      
    public void setPasswd(String passwd){  
        this.passwd = passwd;  
    }  
      
    public byte[] getBytes(){  
        String temp=null;  
          
        if(name==null||passwd==null){  
            return null;  
        }else{  
            temp=name+","+passwd;  
        }  
          
        return temp.getBytes();  
    }  
}  

控制(control)

UIController.java

package com.token.util;  
 
import java.io.IOException;  
 
import javax.microedition.lcdui.*;  
 
import com.token.midlet.MainMidlet;  
import com.token.model.*;  
import com.token.view.*;  
//import com.token.view.components.Color;  
 
public class UIController {  
 
    private MainMidlet midlet;  
      
    private TokenDataRecord tokenRecord;  
      
    private WelcomeScreen welcomeScreen;  
    private UserRegist reg;   
    private ActiveScreen activeScreen;  
    private MainScreen mainScreen;  
    private GenPasswd gen;  
    private CheckScreen check;  
    private ViewToken viewToken;  
    private UserManage manage;  
    private ShowHelp help;  
    private UserAuth auth;  
    private PopUpTextBox textBox;  
      
    int id = 1;  
      
    public UIController(MainMidlet midlet)  
    {  
        this.midlet = midlet;  
          
        tokenRecord = new TokenDataRecord();  
    }  
      
    public void init() throws IOException{  
          
        try {  
            SplashScreen splashScreen = new SplashScreen();  
            setCurrent(splashScreen);  
            Thread.sleep(1000);  
              
            Configure.configureColor();  
            initObject();     
              
            //tokenRecord.db_deleteAllRecord();  
            if(tokenRecord.db_getRecord(1)==null)  
            {  
                //System.out.println("add");  
                ChaosMethods method = new ChaosMethods();  
                TokenDataItem tokenItem = new TokenDataItem(1,(method.ChaosInitCode()+",false").getBytes());  
                id=tokenRecord.db_addRecord(tokenItem);  
            }  
              
            //System.out.println(id);  
            TokenDataItem tokenItem1 = tokenRecord.db_getRecord(id);  
            //System.out.println(tokenItem1.token+","+tokenItem1.isActive);  
              
            if(tokenItem1.getStatus().equals("false"))  
            {  
                this.handleEvent(UIController.EventID.EVENT_NEXT_WELCOME_SCREEN,null);  
            }else 
            {  
                String flag = "0";  
                Object [] args = {flag,""};  
                this.handleEvent(UIController.EventID.EVENT_MAIN_SCREEN,args);  
            }  
        } catch (InterruptedException e) {  
            // TODO Auto-generated catch block  
            e.printStackTrace();  
        }  
          
    }  
      
    private void initObject()  
    {  
        welcomeScreen = new WelcomeScreen(this);  
        reg= new UserRegist(this);  
        activeScreen = new ActiveScreen(this);  
        ...  
        textBox = new PopUpTextBox(this,"输入文本","", 1000, TextField.ANY);  
    }  
      
    //getMethod  
    public void setCurrent(Displayable disp){  
        midlet.setCurrent(disp);  
    }  
    public void setCurrent(Alert alert, Displayable disp){  
        midlet.setCurrent(alert, disp);  
    }  
      
    //定义事件ID内部类  
    public static class EventID{  
        private EventID(){  
        }  
          
        public static final byte EVENT_EXIT = 0;//退出  
        public static final byte EVENT_NEXT_WELCOME_SCREEN = 1;//欢迎界面  
        public static final byte EVENT_NEXT_USER_REGIST_SCREEN = 2;//用户注册  
        public static final byte EVENT_USER_REGIST_EDIT = 3;//用户注册编辑  
        public static final byte EVENT_USER_REGIST_EDIT_BACK = 4;//用户注册编辑返回  
        public static final byte EVENT_NEXT_ACTIVE_SCREEN = 5;  
       //...  
    }  
      
    //事件处理  
    public void handleEvent( int eventID, Object[] args)  
    {  
        switch (eventID)  
        {     
            case EventID.EVENT_EXIT:  
            {  
                midlet.exit(false);  
                break;  
            }  
            case EventID.EVENT_NEXT_WELCOME_SCREEN:  
            {  
                    welcomeScreen.show();  
                midlet.setCurrent(welcomeScreen);  
                break;  
            }  
            case EventID.EVENT_NEXT_USER_REGIST_SCREEN:  
            case EventID.EVENT_USER_REGIST_EDIT_BACK:  
            {  
                reg.show(args);  
                Thread thread = new Thread(reg);  
                thread.start();  
                midlet.setCurrent(reg);  
                break;  
            }  
            case EventID.EVENT_USER_REGIST_EDIT:  
            {  
                textBox.init(args);  
                midlet.setCurrent(textBox);  
                break;  
            }  
            case EventID.EVENT_NEXT_ACTIVE_SCREEN:  
            {  
                activeScreen.show(args);  
                Thread thread = new Thread(activeScreen);  
                thread.start();  
                midlet.setCurrent(activeScreen);  
                break;  
            }  
            //...  
            default:  
                break;  
        }  
    }  
}  

#p#

UserDataRecord.java

package com.token.util;  
 
import java.util.Vector;  
 
import javax.microedition.rms.RecordComparator;  
import javax.microedition.rms.RecordEnumeration;  
import javax.microedition.rms.RecordStore;  
import javax.microedition.rms.RecordStoreException;  
 
import com.token.model.*;  
 
public class UserDataRecord {  
    private static final String RECORDSTORE_NAME="USER_DB";  
    private static RecordStore info;  
      
    public UserDataRecord(){  
    }  
      
    //打开RecordStore，没有则创建  
    public void openDataBase() {  
        try {  
            info = RecordStore.openRecordStore(RECORDSTORE_NAME, true);  
        }catch (RecordStoreException ex) {              
            info =null;  
        }  
    }  
    //关闭RecordStore  
    public void closeDataBase() {  
        if (info!= null) {  
            try {  
                info.closeRecordStore();  
                info=null;  
            } catch (RecordStoreException ex) {}  
        }  
    }  
    //增加记录  
    public int db_addRecord(UserDataItem item) {  
                     
                try {  
                    this.openDataBase();  
                    byte[] data=item.getBytes();  
                    int id=info.getNextRecordID();  
                    info.addRecord(data,0,data.length);  
                    this.closeDataBase();  
                    return id;  
                } catch (RecordStoreException ex) { }  
          
        return -1;  
    }  
    //更新记录  
    public void db_updateRecord(UserDataItem item){  
 
            try {  
                this.openDataBase();        
                byte[] data=item.getBytes();  
                info.setRecord(item.getId(),data,0,data.length);  
                this.closeDataBase();  
            } catch (RecordStoreException ex) { }  
    }  
    //访问一条记录  
    public UserDataItem db_getRecord(int id){  
        UserDataItem item=null;  
 
            try {  
                this.openDataBase();  
                item = new UserDataItem(id,info.getRecord(id));  
                this.closeDataBase();  
            } catch (RecordStoreException ex) { }  
 
         return item;  
    }  
    //删除一条记录  
    public void db_deleteRecord(int id){  
            try {  
                this.openDataBase();  
                info.deleteRecord(id);  
                this.closeDataBase();  
            } catch (RecordStoreException ex) {}  
    }  
      
    //删除所有记录  
    public void db_deleteAllRecord(){  
            try {  
                RecordStore.deleteRecordStore(RECORDSTORE_NAME);  
            } catch (RecordStoreException ex) {}  
    }  
      
    //访问所有记录  
    public Vector db_getRecords(){  
        Vector items=new Vector(10,3);  
        this.openDataBase();//打开RecordStore  
        RecordEnumeration enum1=null;  
        int ind=0;  
        try{  
            UserDataItem item=null;  
            enum1=info.enumerateRecords(null,new InnerComparator(),false);  
              
            while(enum1.hasPreviousElement()){  
                ind=enum1.previousRecordId();  
                item=new UserDataItem(ind,info.getRecord(ind));  
                items.addElement(item);  
            }  
              
        }catch(Exception ex){ex.printStackTrace();}  
        finally{  
                try{  
                    enum1.destroy();  
                }catch(Exception e){}  
                  
                this.closeDataBase();//关闭RecordStore  
        }//end finally  
      
        return items;  
    }  
    //一个简单的比较器  
    private class InnerComparator implements RecordComparator{  
        public int compare(byte[] rec1, byte[] rec2){  
            if(rec1.length>rec2.length)  
                return FOLLOWS;  
            else if(rec1.length<rec2.length)  
                return PRECEDES;  
            else   
                return EQUIVALENT;  
        }  
 
    }  
}  

视图(view)

WelcomeScreen.java

package com.token.view;  
 
import javax.microedition.lcdui.*;  
import javax.microedition.lcdui.game.GameCanvas;  
 
import com.token.util.UIController;  
import com.token.util.StringDealMethod;  
import com.token.view.components.*;  
 
 
public class WelcomeScreen extends GameCanvas {  
 
    private UIController controller;  
    private Graphics graphics;  
    private Font ft;  
    private String info;  
    private String info_wrap[];  
    private int width;  
    private int height;  
      
    private Menu menu;  
    private Head head;  
    private BackGroud backGroud;  
      
    public WelcomeScreen(UIController control) {  
        // TODO Auto-generated constructor stub  
        super(false);  
        controller=control;  
        setFullScreenMode(true);  
        graphics = getGraphics();  
          
        width = getWidth();  
        height = getHeight();  
          
        menu = new Menu(this);  
        head = new Head(this);  
        backGroud = new BackGroud(this);  
    }  
 
    public void show() {  
        // TODO Auto-generated method stub  
        //clearScreen();  
        backGroud.drawBackGroud(this, graphics);  
        head.drawHead(this,graphics,"");  
        menu.drawMenu(this, graphics,"下一步","退出");  
        drawBody();  
    }  
      
    public void drawBody()  
    {  
        ft = Font.getFont(Font.FACE_PROPORTIONAL,Font.STYLE_BOLD,Font.SIZE_LARGE);  
          
        info = "欢迎使用！\n" 
                +"1 MVC测试；\n" 
                +"2 自动换行测试，绘制可自动识别换行的字符串。\n";  
        info_wrap = StringDealMethod.format(info, width-10, ft);  
          
        graphics.setColor(Color.text);  
        graphics.setFont(ft);  
        for(int i=0; i<info_wrap.length; i++)  
        {  
            graphics.drawString(info_wrap[i], 5, i * ft.getHeight()+40, Graphics.TOP|Graphics.LEFT);  
        }  
    }  
      
    public void clearScreen()  
    {  
        graphics.setColor(0xff,0xff,0xff);  
        graphics.fillRect(0, 0, width, height);  
    }  
      
    protected void keyPressed(int keycode)  
    {  
        switch(keycode)  
        {  
            case KeyID.SOFT_RIGHT:  
            {  
                controller.handleEvent(UIController.EventID.EVENT_EXIT,null);  
                break;  
            }  
            case KeyID.SOFT_LEFT:  
            {  
                String editor = "regist_name";  
                Object [] args = {"registScreen",editor, null,null,null};  
                controller.handleEvent(UIController.EventID.EVENT_NEXT_USER_REGIST_SCREEN,args);  
                break;  
            }  
            default:;  
        }  
    }  
      
}  

UserRegist.java

package com.token.view;  
 
import javax.microedition.lcdui.Font;  
import javax.microedition.lcdui.Graphics;  
import javax.microedition.lcdui.game.GameCanvas;  
import com.token.model.*;  
import com.token.util.*;  
import com.token.view.components.*;  
 
public class UserRegist extends GameCanvas implements Runnable {  
 
    private UIController controller;  
    private Graphics graphics;  
      
    private Font ft;  
      
    private Menu menu;  
    private Head head;  
    private BackGroud backGroud;  
      
    private UserDataRecord userRecord;  
 
    private String title;  
      
    private TextEdit textEdit_name;  
    private TextEdit textEdit_passwd;  
    private TextEdit textEdit_passwd_re;  
    private int textEdit_name_x;  
    private int textEdit_name_y;  
    private int textEdit_passwd_x;  
    private int textEdit_passwd_y;  
    private int textEdit_passwd_re_x;  
    private int textEdit_passwd_re_y;  
    private int currentlySelectedIndex = 0;  
      
    private String username;  
    private String passwd;  
    private String passwd_re;  
      
    long caretBlinkDelay = 500L;  
    long lastCaretBlink = 0;  
    private String object_name;  
    private String editor;  
    private boolean cursorBlinkOn1;  
    private boolean cursorBlinkOn2;  
    private boolean cursorBlinkOn3;  
      
    private int width;  
    private int height;  
      
    public UserRegist(UIController control)   
    {  
        super(false);  
        this.controller=control;  
        this.title = "用户注册";  
        setFullScreenMode(true);  
        graphics = getGraphics();  
          
        width = getWidth();  
        height = getHeight();  
          
        menu = new Menu(this);  
        head = new Head(this);  
        backGroud = new BackGroud(this);  
          
        userRecord = new UserDataRecord();  
          
        textEdit_name = new TextEdit(this);  
        textEdit_passwd = new TextEdit(this);  
        textEdit_passwd_re = new TextEdit(this);  
    }  
 
    public void show(Object[] args) {  
        // TODO Auto-generated method stub  
        setFullScreenMode(true);  
          
        object_name = ((String)args[0]!=null)?(String)args[0]:"";  
        editor = ((String)args[1]!=null)?(String)args[1]:"";  
        username = ((String)args[2]!=null)?(String)args[2]:"";  
        passwd = ((String)args[3]!=null)?(String)args[3]:"";  
        passwd_re = ((String)args[4]!=null)?(String)args[4]:"";  
          
        if(editor.equals("regist_name"))  
        {  
            cursorBlinkOn1 = true;  
            cursorBlinkOn2 = false;  
            cursorBlinkOn3 = false;  
            currentlySelectedIndex =0;  
        }  
        else if(editor.equals("regist_passwd"))  
        {  
            cursorBlinkOn1 = false;  
            cursorBlinkOn2 = true;  
            cursorBlinkOn3 = false;  
            currentlySelectedIndex =1;  
        }  
        else if(editor.equals("regist_passwd_re"))  
        {  
            cursorBlinkOn1 = false;  
            cursorBlinkOn2 = false;  
            cursorBlinkOn3 = true;  
            currentlySelectedIndex =2;  
        }  
          
        //System.out.println(object_name);  
        //System.out.println(editor);  
        draw();  
        redraw();  
    }  
 
    public void draw()  
    {  
        //clearScreen();  
        backGroud.drawBackGroud(this, graphics);  
        head.drawHead(this,graphics,this.title);  
        menu.drawMenu(this,graphics,"下一步","退出");  
        drawBody();  
    }  
 
    private void redraw()  
    {  
        switch(currentlySelectedIndex)  
        {  
            case 0:  
            {  
                cursorBlinkOn2 = false;  
                cursorBlinkOn3 = false;  
                editor = "regist_name";  
                break;  
            }  
            case 1:  
            {  
                cursorBlinkOn1 = false;  
                cursorBlinkOn3 = false;  
                editor = "regist_passwd";  
                break;  
            }  
            case 2:  
            {  
                cursorBlinkOn1 = false;  
                cursorBlinkOn2 = false;  
                editor = "regist_passwd_re";  
                break;  
            }  
            default:;  
        }  
          
        textEdit_name.drawTextBox(this, graphics, username, textEdit_name_x, textEdit_name_y, cursorBlinkOn1);  
        textEdit_passwd.drawTextBox(this, graphics, passwd, textEdit_passwd_x, textEdit_passwd_y, cursorBlinkOn2);  
        textEdit_passwd.drawTextBox(this, graphics, passwd_re, textEdit_passwd_re_x, textEdit_passwd_re_y, cursorBlinkOn3);  
        textEdit_name.flushGraphics();  
    }  
 
    public void drawBody()  
    {  
        int margin =5;  
        ft = Font.getFont(Font.FACE_PROPORTIONAL,Font.STYLE_BOLD,Font.SIZE_LARGE);  
          
        String info = "用户名：\n";  
        String info_wrap1[] = StringDealMethod.format(info, width-10, ft);  
          
        graphics.setFont(ft);  
        graphics.setColor(Color.text);  
        for(int i=0; i<info_wrap1.length; i++)  
        {  
            graphics.drawString(info_wrap1[i],5, (i) * ft.getHeight()+40, Graphics.TOP|Graphics.LEFT);  
        }  
          
        textEdit_name_x = 5;  
        textEdit_name_y = info_wrap1.length * ft.getHeight()+40;  
        textEdit_name.drawTextBox(this, graphics, username, textEdit_name_x, textEdit_name_y, cursorBlinkOn1);  
          
        info = "用户密码：\n";  
        String info_wrap2[] = StringDealMethod.format(info, width-10, ft);  
      
        graphics.setFont(ft);  
        graphics.setColor(Color.text);  
        for(int i=0; i<info_wrap2.length; i++)  
        {  
            graphics.drawString(info_wrap2[i],5, (i+info_wrap1.length) * ft.getHeight()+textEdit_name.height+margin+40, Graphics.TOP|Graphics.LEFT);  
        }  
          
        textEdit_passwd_x = 5;  
        textEdit_passwd_y = (info_wrap1.length+info_wrap2.length) * ft.getHeight()+textEdit_name.height+margin+40;  
        textEdit_passwd.drawTextBox(this, graphics, passwd, textEdit_passwd_x, textEdit_passwd_y, cursorBlinkOn2);  
      
        info = "密码确认：\n";  
        String info_wrap3[] = StringDealMethod.format(info, width-10, ft);  
      
        graphics.setFont(ft);  
        graphics.setColor(Color.text);  
        for(int i=0; i<info_wrap3.length; i++)  
        {  
            graphics.drawString(info_wrap3[i],5, (i+info_wrap1.length+info_wrap2.length) * ft.getHeight()+textEdit_name.height+textEdit_passwd.height+2*margin+40, Graphics.TOP|Graphics.LEFT);  
        }  
          
        textEdit_passwd_re_x = 5;  
        textEdit_passwd_re_y = (info_wrap1.length+info_wrap2.length+info_wrap3.length) * ft.getHeight()+textEdit_name.height+textEdit_passwd.height+2*margin+40;  
        textEdit_passwd_re.drawTextBox(this, graphics, passwd_re, textEdit_passwd_re_x, textEdit_passwd_re_y, cursorBlinkOn3);  
      
          
    }  
 
    public void clearScreen()  
    {  
        graphics.setColor(0xff,0xff,0xff);  
        graphics.fillRect(0, 0, width, height);  
    }  
 
    public void checkTimeStamp()  
    {  
        long currentTime = System.currentTimeMillis();  
        //System.out.println("1");  
        if(lastCaretBlink + caretBlinkDelay < currentTime)  
        {  
            //System.out.println("2");  
            if(editor.equals("regist_name"))  
            {  
                cursorBlinkOn1 =! cursorBlinkOn1;  
                cursorBlinkOn2 = false;  
                cursorBlinkOn3 = false;  
            }  
            else if(editor.equals("regist_passwd"))  
            {  
                cursorBlinkOn1 = false;  
                cursorBlinkOn2 =! cursorBlinkOn2;  
                cursorBlinkOn3 = false;  
            }  
            else if(editor.equals("regist_passwd_re"))  
            {  
                cursorBlinkOn1 = false;  
                cursorBlinkOn2 = false;  
                cursorBlinkOn3 =! cursorBlinkOn3;  
            }  
            lastCaretBlink = currentTime;  
        }  
    }  
 
    public void run()  
    {  
        //System.out.println("run");  
        while(true)  
        {  
            checkTimeStamp();  
              
            redraw();  
            try   
            {  
                synchronized(this)  
                {  
                    //System.out.println("3");  
                    wait(50L);  
                }             
            }  
            catch(Exception e)  
            {  
                e.printStackTrace();  
            }  
              
        }  
    }  
 
    protected void keyPressed(int keyCode)  
    {  
        switch(keyCode)  
        {  
            case KeyID.SOFT_RIGHT:  
            {  
                controller.handleEvent(UIController.EventID.EVENT_EXIT,null);  
                break;  
            }  
            case KeyID.SOFT_LEFT:  
            {  
                if(username!="" && passwd!=""&&passwd_re!="")  
                {  
                    if(passwd.equals(passwd_re))  
                    {  
                          
                          
                        userRecord.db_deleteAllRecord();  
                        if(userRecord.db_getRecord(1)==null)  
                        {  
                            UserDataItem userItem = new UserDataItem(1,(username+","+passwd).getBytes());  
                            userRecord.db_addRecord(userItem);  
                            userItem = null;  
                            System.gc();  
                        }  
                          
                        String update = "start";  
                        Object [] args = {"activeScreen", null, update};  
                        controller.handleEvent(UIController.EventID.EVENT_NEXT_ACTIVE_SCREEN,args);  
                    }  
                }  
                break;  
            }  
            case KeyID.KEY_EDIT:  
            case KEY_NUM0:  
            case KEY_NUM1:  
            case KEY_NUM2:  
            case KEY_NUM3:  
            case KEY_NUM4:  
            case KEY_NUM5:  
            case KEY_NUM6:  
            case KEY_NUM7:  
            case KEY_NUM8:  
            case KEY_NUM9:  
            {  
                //System.out.println(editor);  
                Object[] args = {object_name,editor,username,passwd,passwd_re};  
                controller.handleEvent(UIController.EventID.EVENT_USER_REGIST_EDIT,args);  
                break;  
            }  
            default:;  
        }  
              
        keyCode = getGameAction(keyCode);  
        switch(keyCode)  
        {  
            case UP:  
            case LEFT:  
            {  
                currentlySelectedIndex--;  
                if(currentlySelectedIndex<0)  
                {  
                    currentlySelectedIndex=0;  
                }  
                else 
                {  
                    redraw();  
                }  
                break;  
            }  
            case DOWN:  
            case RIGHT:  
            {  
                currentlySelectedIndex++;  
                if(currentlySelectedIndex>2)  
                {  
                    currentlySelectedIndex=2;  
                }  
                else 
                {  
                    redraw();  
                }  
                  
                break;  
            }  
        }  
    }  
 
}  
 

*TextEdit是利用GameCanvas绘制的自定义文本编辑框。后续文章将给出具体实现。

#p#

【分析】

1 在MainMidlet调用控制器UIController，并向UIController传递midlet作为参数。

controller=new UIController(<span style="color:#ff0000;">this</span>);  
try {  
    controller.init();  
    } catch (IOException e) {  
    // TODO Auto-generated catch block  
    e.printStackTrace();  
    }// 

2 控制器的实现是通过一个事件的机制实现的， 在UIController中，先建立一个事件ID的内部类。

public static class EventID{  
        private EventID(){  
        }  
          
        public static final byte EVENT_EXIT = 0;//退出  
        public static final byte EVENT_NEXT_WELCOME_SCREEN = 1;//欢迎界面  
        public static final byte EVENT_NEXT_USER_REGIST_SCREEN = 2;//用户注册  
        public static final byte EVENT_USER_REGIST_EDIT = 3;//用户注册编辑  
        public static final byte EVENT_USER_REGIST_EDIT_BACK = 4;//用户注册编辑返回  
        public static final byte EVENT_NEXT_ACTIVE_SCREEN = 5;  
       //...  
    } 

3 一次性初始化所有界面，分配内存，调用时，只是执行视图类的show方法。为什么不将初始话放在调用时进行呢？主要是因为视图类有多次重用，如果每一次调用都new(初始化，分配内存)一次，手机有限的内存很快会被用光，这是会出现一些程序自动退出的问题。

private void initObject()  
{  
    welcomeScreen = new WelcomeScreen(this);  
    reg= new UserRegist(this);  
    activeScreen = new ActiveScreen(this);  
    ...  
    textBox = new PopUpTextBox(this,"输入文本","", 1000, TextField.ANY);  
} 

4 控制器对视图的处理采用状态机实现

public void handleEvent( int eventID, Object[] args)  
   {  
    switch (eventID)  
       {     
        case EventID.EVENT_EXIT:  
        {  
            midlet.exit(false);  
            break;  
        }  
        case EventID.EVENT_NEXT_WELCOME_SCREEN:  
        {  
                welcomeScreen.show();  
            midlet.setCurrent(welcomeScreen);  
            break;  
        }  
        case EventID.EVENT_NEXT_USER_REGIST_SCREEN:  
        case EventID.EVENT_USER_REGIST_EDIT_BACK:  
        {  
            reg.show(args);  
            Thread thread = new Thread(reg);  
            thread.start();  
            midlet.setCurrent(reg);  
            break;  
        }  
        case EventID.EVENT_USER_REGIST_EDIT:  
        {  
            textBox.init(args);  
            midlet.setCurrent(textBox);  
            break;  
        }  
        case EventID.EVENT_NEXT_ACTIVE_SCREEN:  
        {  
            activeScreen.show(args);  
            Thread thread = new Thread(activeScreen);  
            thread.start();  
            midlet.setCurrent(activeScreen);  
            break;  
        }  
        //...  
            default:  
                break;  
       }  
   }  
 

5 视图类初始化时，需要将控制器作为参数初始化，以对事件做出判断。如WelcomeScreen.java中先做出如下声明：

private UIController controller; 

再在构造函数中，传递控制器

public WelcomeScreen(UIController control) {  
        // TODO Auto-generated constructor stub  
        super(false);  
        controller=control; 

6 视图切换事件响应采用如下方式，在keyPressed中，对按键事件进行判断，然后调用UIController的handEvent方法。

protected void keyPressed(int keycode)  
    {  
        switch(keycode)  
        {  
            case KeyID.SOFT_RIGHT:  
            {  
                controller.handleEvent(UIController.EventID.EVENT_EXIT,null);  
                break;  
            }  
            case KeyID.SOFT_LEFT:  
            {  
                String editor = "regist_name";  
                Object [] args = {"registScreen",editor, null,null,null};  
                controller.handleEvent(UIController.EventID.EVENT_NEXT_USER_REGIST_SCREEN,args);  
                break;  
            }  
            default:;  
        }  
    }  
      
} 

7 控制器可以通过handEvent的args传递参数，如

String update = "start";  
Object [] args = {"activeScreen", null, update};  
controller.handleEvent(UIController.EventID.EVENT_NEXT_ACTIVE_SCREEN,args); 

UserRegist传递了一个update变量给下一个视图。

8 在看一下模型，在UserDataItem中存储的是用户注册的信息。利用UserDataRecord类对记录进行操作。

在视图类中，通过以下方式调用：

先声明

private UserDataRecord userRecord; 

构建对象

userRecord = new UserDataRecord(); 

使用对象

userRecord.db_deleteAllRecord();  
                        if(userRecord.db_getRecord(1)==null)  
                        {  
                            UserDataItem userItem = new UserDataItem(1,(username+","+passwd).getBytes());  
                            userRecord.db_addRecord(userItem);  
                            userItem = null;  
                            System.gc();  
                        }  
                         

9 包com.token.view.components是对视图类中使用的自定义控件的封装

综述，这样就实现了模型、视图、控制的分离。

【参考文献】

(1) 万辉，王军[M]. 基于Eclipse环境的J2ME应用程序开发，清华大学出版社

(2) http://blog.csdn.net/cjjky/article/category/807008

原文链接：http://blog.csdn.net/tandesir/article/details/7538817

【系列文章】

1. JavaMe开发：低级界面绘图之点阵字
2. JavaMe开发：低级界面绘图之菜单
3. JavaMe开发：也说MVC设计模式
4. JavaMe开发：绘制可自动换行文本
5. JavaMe开发：绘制文本框TextEdit
6. JavaM开发：自适应滚动显示