学步园

1.首先要明白它的实质：抛开网络通道，其实我们可以把它理解为 多线程断点复制。

所以，在写多线程断点上传程序时，建议大家先写个 本地电脑的多线程断点复制

 已下是个下载示例

package com.android.service;import java.util.HashMap;
import java.util.Map;

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

public class FileService {
    private DBOpenHelper openHelper;

    public FileService(Context context) {
        openHelper = new DBOpenHelper(context);
    }
   
    /**
     * 获取每条线程已经下载的文件长度
     * @param path
     * @return
     */
    public Map<Integer, Integer> getData(String path){
        SQLiteDatabase db = openHelper.getReadableDatabase();
        Cursor cursor = db.rawQuery("select threadid, downlength from filedownlog where downpath=?", new String[]{path});
        Map<Integer, Integer> data = new HashMap<Integer, Integer>();
       
        while(cursor.moveToNext()){
            data.put(cursor.getInt(0), cursor.getInt(1));
        }
       
        cursor.close();
        db.close();
        return data;
    }
   
    /**
     * 保存每条线程已经下载的文件长度
     * @param path
     * @param map
     */
    public void save(String path,  Map<Integer, Integer> map){//int threadid, int position
        SQLiteDatabase db = openHelper.getWritableDatabase();
        db.beginTransaction();
       
        try{
            for(Map.Entry<Integer, Integer> entry : map.entrySet()){
                db.execSQL("insert into filedownlog(downpath, threadid, downlength) values(?,?,?)",
                        new Object[]{path, entry.getKey(), entry.getValue()});
            }
            db.setTransactionSuccessful();
        }finally{
            db.endTransaction();
        }
       
        db.close();
    }
   
    /**
     * 实时更新每条线程已经下载的文件长度
     * @param path
     * @param map
     */
    public void update(String path, Map<Integer, Integer> map){
        SQLiteDatabase db = openHelper.getWritableDatabase();
        db.beginTransaction();
       
        try{
            for(Map.Entry<Integer, Integer> entry : map.entrySet()){
                db.execSQL("update filedownlog set downlength=? where downpath=? and threadid=?",
                        new Object[]{entry.getValue(), path, entry.getKey()});
            }
           
            db.setTransactionSuccessful();
        }finally{
            db.endTransaction();
        }
       
        db.close();
    }
   
    /**
     * 当文件下载完成后，删除对应的下载记录
     * @param path
     */
    public void delete(String path){
        SQLiteDatabase db = openHelper.getWritableDatabase();
        db.execSQL("delete from filedownlog where downpath=?", new Object[]{path});
        db.close();
    }