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界面跳转解决方案

www.MyException.Cn  网友分享于:2013-12-27  浏览:18次
界面跳转
要实现的功能很简单,但总是有问题,麻烦大家看看
首先,主界面:
武汉特色介绍

景点
小吃/小吃街
购物街
。。。

完后点击景点,进入子界面:
黄鹤楼
中山公园
江滩

到此我都实现了,下一步,我点击黄鹤楼,就显示一段描述黄鹤楼的文字,这个位置总报错,程序如下(其中DivPage.java单独运行是可以的,所以错误应该在Main.java):

Main.java

Java code

package wuhan; 

import javax.microedition.midlet.*; 
import javax.microedition.lcdui.*; 

public class Main extends MIDlet implements CommandListener{ 
private Display display; 
private Form form; 
private Command exit; 
private Command process; 
private ChoiceGroup characters; 
private ChoiceGroup cg; 
private int characterIndex; 
private TestCanvas canvas;

public Main() { 
    display = Display.getDisplay(this); 
    characters = new ChoiceGroup("武汉特色介绍",Choice.EXCLUSIVE); 
    characters.append("景点", null); 
    characters.append("小吃/小吃街", null); 
    characters.append("购物街", null); 
    characters.append("大型购物商场", null); 
    characters.append("大型购物超市", null); 
    characters.append("大学院校", null); 
    exit = new Command("Exit",Command.EXIT,1); 
    process = new Command("Process",Command.SCREEN,2); 
    form = new Form(""); 
    characterIndex = form.append(characters); 
    form.addCommand(exit); 
    form.addCommand(process); 
    form.setCommandListener(this); 
} 

    public void startApp(){ 
        display.setCurrent(form); 
    } 
    
    public void pauseApp(){ 
    } 

    public void destroyApp(boolean arg0){ 
    } 
    
    public void commandAction(Command command,Displayable displayable){ 
        if(command==exit){ 
            destroyApp(true); 
            notifyDestroyed(); 
        } 
        else if(command==process){
            int x=0;
            boolean picks[] = new boolean[characters.size()]; 
            characters.getSelectedFlags(picks); 
            for(;x <picks.length;x++){ 
                if(picks[x]){ 
                    cg = new ChoiceGroup("",Choice.EXCLUSIVE); 
                    switch(x){ 
                        case 0: cg.append("黄鹤楼", null); 
                                cg.append("中山公园", null); 
                                cg.append("江滩", null); 
                                break; 
                        case 1: cg.append("热干面", null); 
                                cg.append("豆皮", null); 
                                break; 
                        case 2: 
                        case 3: 
                        case 4: 
                        case 5: break; 
                        default: break; 
                    }
                    break;
                } 
          } 
          form.delete(characterIndex); 
          characterIndex = form.append(cg); 
          boolean picks2[] = new boolean[cg.size()];
          cg.getSelectedFlags(picks2);
          if(x==0){
              for(int y=0;y<picks2.length;y++){
                  if(picks2[y]){
                      switch(y){
                          case 0: canvas = new TestCanvas(new DivPage());
                                  display.setCurrent(canvas);
                                  break;
                          default: break;
                      }
                  }
              }
          }
          form.delete(characterIndex); 
        }
    } 
} 




DivPage.java

Java code

package wuhan;

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class DivPage extends MIDlet {
    private Display display;

    private TestCanvas canvas;

    public DivPage() {
        display = Display.getDisplay(this);
        canvas = new TestCanvas(this);
    }

    protected void startApp() throws MIDletStateChangeException {
        display.setCurrent(canvas);
    }

    protected void pauseApp() {

    }

    protected void destroyApp(boolean arg0) {

    }

    public void exitMIDlet() {
        destroyApp(true);
        notifyDestroyed();
    }
}

    class TestCanvas extends Canvas implements CommandListener {
        private String text = "                            武汉特色介绍"
                + "\n一、 景点"
                + "\n1、 黄鹤楼"
                + "\n        冲决巴山群峰,接纳潇湘云水,浩荡长江在三楚腹地与其最长支流汉水交汇,造就了武汉隔两江而三镇互峙的伟姿。 这里地处江汉平原东缘,鄂东南丘陵余脉起伏于平野湖沼之间,龟蛇两山相夹,江上舟辑如织黄鹤楼天造地设于斯。"
                + "\n        黄鹤楼是古典与现代熔铸、诗化与美意构筑的精品。她处在山川灵气动荡吐钠的交点,正好映和中华民族喜好登高的民风民俗、亲近自然的空间意识、崇尚宇宙的哲学观念。登黄鹤楼,不仅仅获得愉快,更能使心灵与宇宙意象互渗互融,从而使心灵净化。这大约就是黄鹤楼美的魅力经风雨而不衰,与日月共长存原因之所在。"
                + "\n        巍峨耸立于武昌蛇山的黄鹤楼,享有“天下绝景”的盛誉,与湖南岳阳楼,江西滕王阁并称为“江南三大名楼”。唐代诗人崔颢一首“昔人已乘黄鹤去,此地空余黄鹤楼。黄鹤一去不复返,白云千载空悠悠。晴川历历汉阳树,芳草萋萋鹦鹉洲。日暮乡关何处是,烟波江上使人愁。”已成为千古绝唱,更使黄鹤楼名声大噪。全楼各层布置有大型壁画、楹联、文物等。楼外铸铜黄鹤造型、胜像宝塔、牌坊、轩廊、亭阁等一批辅助建筑,将主楼烘托得更加壮丽。登楼远眺,“极目楚天舒”,不尽长江滚滚来,三镇风光尽收眼底。";

        private int sreenWidth;

        private int sreenHeight;

        private int scrollHeight;

        private int scrollY;

        private int regionY;

        private int numHeight;

        private Command exit;

        private DivPage divPage;

        public TestCanvas(DivPage divPage) {
            this.divPage = divPage;
            exit = new Command("Exit", Command.EXIT, 1);
            addCommand(exit);
            setCommandListener(this);
            try {
                this.sreenHeight = this.getHeight();
                this.sreenWidth = this.getWidth();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        protected void paint(Graphics g) {
            g.setColor(0xFFFFFF);
            g.fillRect(0, 0, this.sreenWidth, this.sreenHeight);
            Font font = g.getFont();
            g.setColor(0x00000);
            int row = drawWrapString(g, text, 0, regionY, sreenWidth - 18, font);
            if (this.numHeight == 0)
                this.numHeight = (row + 1) * font.getHeight();
            System.out.println("numHeigth=" + numHeight);
            this.scrollHeight = this.sreenHeight * this.sreenHeight / numHeight;
            this.scrollY = (-this.regionY) * this.sreenHeight / numHeight;
            g.setColor(255);
            g.fillRect(this.sreenWidth - 6, 0, 6, this.sreenHeight);
            g.setColor(0xFFFFFF);
            g.fillRect(this.sreenWidth - 5, this.scrollY, 4, this.scrollHeight);
        }

        public void keyPressed(int keyCode) {
            System.out.println(keyCode);
            System.out.println(sreenHeight);
            if (keyCode == -2) {
                if (this.sreenHeight - this.regionY >= this.numHeight)
                    return;
                this.regionY -= 30;
            } else if (keyCode == -1) {
                if (this.regionY >= 0)
                    return;
                this.regionY += 30;
            }
            this.repaint();
        }

        public void commandAction(Command command, Displayable displayable) {
            if (command == exit)
                divPage.exitMIDlet();
        }
    

        public static int drawWrapString(Graphics g, String str, int x, int y,
            int rightMargin, Font font) {
        int row = 0;
        int leftMargin = x;
        int fW = 0;
        int fH = font.getHeight();
        char c;
        for (int i = 0; i < str.length(); i++) {
            c = str.charAt(i);
            if (c == '\r')
                continue;
            fW = font.charWidth(c);

            if (c == '\n' || (x + fW) > rightMargin) {
                x = leftMargin; 
                y += fH; 
                row++;
            }

            if (c != '\n') {
                g.drawChar(c, x, y, 20);
                x += fW; 
            }

        }
        return row;
    }
}


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