学步园

本例由三个类组成：TestMidlet.java  TestCanvas.java ParseCode.java 简单的展示如何在J2ME里实现分页效果

以下代码可以直接运行
入口类：TestMidlet.java

import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class TestMidlet extends MIDlet ...{
    private static TestMidlet _instance = null;

    private Display _display = null;

    public TestMidlet() ...{
        _instance = this;
        _display = Display.getDisplay(this);
    }

    protected void destroyApp(boolean arg0) throws MIDletStateChangeException ...{
    }

    protected void pauseApp() ...{
    }

    protected void startApp() throws MIDletStateChangeException ...{ // 启动程序
        forward(new TestCanvas());
    }

    public static TestMidlet getInstance() ...{
        return _instance;
    }
    
    public static void forward(Displayable next)...{
        _instance._display.setCurrent(next);
    }

}

主屏幕：TestCanvas.java

import java.util.Vector;

import javax.microedition.lcdui.Alert;
import javax.microedition.lcdui.AlertType;
import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;

public class TestCanvas extends Canvas implements Runnable...{
    static Vector v = null;                                // 菜单项
    static final Font _LowFont = Font.getFont(Font.FACE_MONOSPACE,
            Font.STYLE_PLAIN, Font.SIZE_MEDIUM);         // 字体类型
    static final int _LowColor = 0x000000FF;             // 未选中颜色
    private static int lowFont_Height;
    static final int _HightColor = 0x000000FF;             // 选中颜色
    static final int _HightBGColor = 0x00CCCCCC;         // 背景颜色

    static int width;
    static int height; 
    static int startHeight;                             // 菜单在屏幕的起始高度
    static int menuIndex;                                 // 业务类型菜单选中项的序号
    static final int spacing = _LowFont.getHeight() / 2;// 计算两行字之间的空白距离

    private static String title = null;
    private static int twidth;
    private static int tleft_start;
    public static String curMenuText = null;             // 当前的名字
    public static String curMenuType = null;            // 当前的武力
    public static String menuType = null;                 // 武力
    public static String menuText = null;                 // 名字
    private static ParseCode pc = null;                    

    Thread menuThread;
    private static int numPerPage;                        // 每页显示的内容数量
    private static int totalPage;                        // 总页数
    private static int curPage;                            // 当前的页数
    private static int curItem = 0;                        // 当前页面显示的最前一条记录位置
    private static int curMax;                            // 当前页面显示的最后一条记录位置
    private static boolean hasInit;                        // 是否初始化了

    public TestCanvas() ...{
        if(!hasInit)...{
            width = getWidth();
            height = getHeight();

            pc = new ParseCode();
            String test = "98|赵云#98|马超#99|张飞#98|关羽#97|许褚#" +
                    "96|夏候惇#91|夏候渊#98|典韦#97|黄忠#100|吕布#" +
                    "97|太史慈#96|甘宁#95|孙策#72|周瑜#93|姜维#";
            v = pc.parseString(test);

            curPage = 1;

            title = "请选择武将";
            twidth = _LowFont.stringWidth(title);
            tleft_start = (width - twidth) / 2;
            lowFont_Height = _LowFont.getHeight();

            startHeight = lowFont_Height;
            numPerPage = (height - startHeight - spacing)/(lowFont_Height );
            if(numPerPage < v.size())...{
                totalPage = v.size() / numPerPage;
                if(v.size() % numPerPage != 0) totalPage++;
            }
            else...{
                numPerPage = v.size();
                totalPage = 1;
            }

            hasInit = true;
        }

        menuIndex = 0;

        menuThread = new Thread(this);
        menuThread.start();
    }

    public void run() ...{
        while (true) ...{
            repaint();
        }
    }

    protected void paint(Graphics g) ...{
        g.setColor(0x00FFFFFF);
        g.fillRect(0, 0, width, height);

        if(numPerPage * curPage > v.size())
            curMax = v.size();
        else
            curMax = numPerPage * curPage;
        curItem = numPerPage * (curPage - 1);

        for(int i = curItem; i < curMax; i++)...{
            int tmpHeight = startHeight + (i - curItem) * lowFont_Height + spacing;    
            String str = (String)v.elementAt(i);

            int pos = str.indexOf("|");
            if(pos != -1)...{
                menuType = str.substring(0, pos);
                menuText = str.substring(pos+1, str.length());
            }else...{
                menuType = null;
                menuText = str;
            }
            int tmpWidth = (width - _LowFont.stringWidth(menuText)) / 2;
            if ((i - curItem) == menuIndex) ...{
                curMenuType = menuType;
                curMenuText = menuText;
                g.setColor(_HightColor);
                g.fillRect(tmpWidth, tmpHeight, _LowFont.stringWidth(curMenuText),
                        lowFont_Height);
                g.setFont(_LowFont);
                g.setColor(_HightBGColor);
                g.drawString(curMenuText, tmpWidth, tmpHeight, 20);

            } else