formidlet.java

《j2me开发精解〉（詹健飞）CD-rom附带源码。用netbeans

package com.j2medev.chapter4;

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

public class ForMIDlet extends MIDlet implements CommandListener{
    
    private Display display = null;
    private List list = null;
    private RecordStore rs = null;
    public static final Command exitCommand = new Command("退出",Command.EXIT,1);
    public static final Command deleteCommand = new Command("删除",Command.OK,2);
    
    public void startApp() {
        initMIDlet();
    }
    
    private void initMIDlet(){
        if(display == null)
            display = Display.getDisplay(this);
        openDatabase();
        //从RecordStore读取记录数据
        String[] record = getRecord();
        if(record != null){
            list = new List("记录集合",List.IMPLICIT, record,null);
            list.setSelectCommand(deleteCommand);
            list.addCommand(exitCommand);
            list.setCommandListener(this);
            display.setCurrent(list);
        }else{
            displayError();
        }
    }
    //如果不能正确读取RecordStore中的数据则显示错误信息
    private void displayError(){
        Form form = new Form("结果");
        form.append("读取数据记录出错");
        display.setCurrent(form);
    }
    //使用for循环的方式读取RecordStore中的记录，注意这种方式不应该被采用。
    private String[] getRecord(){
        String[] record = null;
        try{
            int length = rs.getNumRecords();
            record = new String[length];
            for(int i = 1;i<=length;i++){
                byte[] data = rs.getRecord(i);
                //recordId的初始值为1，数组索引从0开始。
                record[i-1] = new String(data);
            }
            
        }catch(RecordStoreException e){
            record = null;
            e.printStackTrace();
        }
        return record;
    }
    //初始化RecordStore数据
    private void openDatabase(){
        try{
            rs = RecordStore.openRecordStore("forloop1",true);
            if(rs.getNumRecords() <= 0){
                for(int i = 1;i<6;i++){
                    String s = "记录"+i;
                    byte[] data = s.getBytes();
                    rs.addRecord(data, 0,data.length);
                }
            }
        }catch(RecordStoreException e){
            e.printStackTrace();
        }
    }
    
    public void pauseApp() {
    }
    
    public void destroyApp(boolean unconditional) {
    }
    
    public void commandAction(Command cmd,Displayable displayable){
        if(cmd == exitCommand){
            destroyApp(false);
            notifyDestroyed();
        }else if(cmd == deleteCommand){
            //删除记录并重新设置List
            int index = list.getSelectedIndex();
            try{
                rs.deleteRecord(index+1);
            }catch(RecordStoreException e){
                e.printStackTrace();
            }
            String[] record = getRecord();
            if(record == null){
                displayError();
            }else{
                list.deleteAll();
                for(int i = 0;i<record.length;i++){
                    list.append(record[i],null);
                }
                display.setCurrent(list);
            }
        }
    }
}