menucanvas.java

j2me简单实例,j2me教程加源码,希望大家喜欢

package com.j2medev.chapter3;

import javax.microedition.lcdui.*;

public class MenuCanvas extends Canvas{
    
    //selected变量标记了焦点位置
    private int selected = 0;
    private int preferWidth = -1;
    private int preferHeight = -1;
    public static final int[] OPTIONS = {0,1,2,3};
    public static final String[] LABELS={"New Game","Setttings","High Scores","Exit"};
    
    public MenuCanvas() {
        selected = OPTIONS[0];
        //计算菜单选项的长度和高度值
        Font f = Font.getDefaultFont();
        for(int i = 0;i<LABELS.length;i++){
            int temp = f.stringWidth(LABELS[i]);
            if(temp > preferWidth){
                preferWidth = temp;
            }
        }
        preferWidth  = preferWidth + 2*8;
        preferHeight = f.getHeight()+2*4;
    }
    
    public void paint(Graphics g){
        //清除屏幕
        int color = g.getColor();
        g.setColor(0xFFFFFF);
        g.fillRect(0,0,getWidth(),getHeight());
        g.setColor(color);
        //计算整个菜单的高度，宽度和（x,y）
        int rectWidth = preferWidth;
        int rectHeight = preferHeight * LABELS.length;
        int x = (getWidth()-rectWidth)/2;
        int y = (getHeight()-rectHeight)/2;
        //画矩形
        g.drawRect(x,y,rectWidth,rectHeight);
        for(int i = 1;i<LABELS.length;i++){
            g.drawLine(x,y+preferHeight*i,x+rectWidth,y+preferHeight*i);
        }
        //画菜单选项，并根据selected的值判断焦点
        for(int j = 0;j<LABELS.length;j++){
            if(selected == j){
                g.setColor(0x6699cc);
                g.fillRect(x+1,y+j*preferHeight+1,rectWidth-1,preferHeight-1);
                g.setColor(color);
            }
            g.drawString(LABELS[j],x+8,y+j*preferHeight+4,Graphics.LEFT|Graphics.TOP);
        }
    }
    
    public void keyPressed(int keyCode){
        //根据用户输入更新selected的值，并重新绘制屏幕
        int action = this.getGameAction(keyCode);
        switch(action){
            case Canvas.FIRE:
                printLabel(selected);
                break;
            case Canvas.DOWN:
                selected = (selected+1)%4;
                break;
            case Canvas.UP:{
                if(--selected < 0){
                    selected+=4;
                }
                break;
            }
            default:
                break;
        }
        repaint();
        serviceRepaints();
    }
    //showNotify()在paint()之前被调用
    public void showNotify(){
        System.out.println("showNotify() is called");
    }
    private void printLabel(int selected){
        System.out.println(LABELS[selected]);
    }
    
}