viewcanvas.java

j2me简单实例,j2me教程加源码,希望大家喜欢

package com.j2medev.chapter3;

import java.io.IOException;
import javax.microedition.lcdui.*;

public class ViewCanvas extends Canvas implements CommandListener{
    
    //用作图标的图片与标题
    private Image[] menus = new Image[9];
    private String[] titles = new String[]{"Login","Picture","Audio","Camera",
        "WAP","Article","Help","Config","About"};
    //标志焦点的位置，与titles的标签对应
    private int focus = 0;
    //一系列的变量，用于计算相对位置适应不同的屏幕
    private int canvasWidth = -1;
    private int canvasHeight = -1;
    private int margin = 1;//间距
    private int maxHeight = -1;
    private int imgHeight = -1;//图标高度
    private int imgWidth = -1;//图标宽度
    private Command exitCommand = new Command("Exit",Command.EXIT,1);
    
    public ViewCanvas() {
        addCommand(exitCommand);
        setCommandListener(this);
        //初始化图片数组，将原始图片分割为Image[]
        try{
            Image src = Image.createImage("/menus.png");
            for(int i = 0;i<menus.length;i++){
                menus[i] = Image.createImage(28,28);
                Graphics g = menus[i].getGraphics();
                g.translate(-28*i,0);
                g.drawImage(src,0,0,Graphics.LEFT|Graphics.TOP);
            }
            src = null;//可以被回收
        }catch(IOException ex){
            ex.printStackTrace();
        }
        imgWidth = menus[0].getWidth();
        imgHeight = menus[0].getHeight();
        //默认字体的高度
        int fontHeight = Font.getDefaultFont().getHeight();
        canvasWidth = getWidth();
        canvasHeight = getHeight();
        maxHeight = margin+imgHeight+fontHeight;//图片+标题的高度
    }
    
    public void paint(Graphics g){
        //清除屏幕
        int color = g.getColor();
        g.setColor(0xFFFFFF);
        g.fillRect(0,0,canvasWidth,canvasHeight);
        g.setColor(color);
        //计算每个单元格的高度和宽度
        int cellWidth = canvasWidth/3;
        int cellHeight = canvasHeight/3;
        //绘制
        for(int i = 0;i<menus.length;i++){
            //绘制图标
            g.drawImage(menus[i],cellWidth*(i%3)+(cellWidth-imgWidth)/2,cellHeight*(i/3)+(cellHeight-maxHeight)/2,Graphics.LEFT|Graphics.TOP);
            int _length = Font.getDefaultFont().stringWidth(titles[i]);
            //绘制标题
            g.drawString(titles[i],cellWidth*(i%3)+(cellWidth-_length)/2,cellHeight*(i/3)+(cellHeight-maxHeight)/2+imgHeight+margin,Graphics.LEFT|Graphics.TOP);
            //绘制焦点
            if(i == focus){
                g.drawRect(cellWidth*(i%3),cellHeight*(i/3),cellWidth-margin,cellHeight-margin);
            }
        }
    }
    
    public void keyPressed(int keyCode){
        //将键码转换为game action
        int action = getGameAction(keyCode);
        switch(action){
            //响应用户的确认事件
            case FIRE:{
                System.out.println(titles[focus]);
                Alert alert = new Alert("you select",titles[focus],menus[focus],AlertType.INFO);
                alert.setTimeout(2000);
                IconViewMIDlet.setCurrent(alert);
                break;
            }
            //根据用户按下的方向键计算focus的变化
            case UP:{
                focus = focus - 3;
                if(focus<0){
                    focus = focus + 9;
                }
                break;
            }case DOWN:{
                focus = focus + 3;
                if(focus >= 9){
                    focus = focus - 9;
                }
                break;
            }
            case LEFT:{
                if(focus <= 0){
                    focus = 8;
                }else{
                    focus = (--focus)%9;
                }
                break;
            }case RIGHT:{
                focus = (++focus)%9;
                break;
            }
        }
        repaint();
        serviceRepaints();
    }
    public void commandAction(Command cmd,Displayable displayable){
        if(cmd == exitCommand){
            IconViewMIDlet.exitMIDlet();
        }
    }
}