package com.zhous.download;
import com.zhous.download.api.Connection;
import com.zhous.download.api.ConnectionException;
import com.zhous.download.api.ConnectionManager;
import com.zhous.download.api.DownloadListener;
import java.io.File;
import java.util.Set;
public class FileDownloader {
String url="https://image.baidu.com/search/down?tn=download&word=download&ie=utf8&fr=detail&url=https%3A%2F%2Ftimgsa.baidu.com%2Ftimg%3Fimage%26quality%3D80%26size%3Db9999_10000%26sec%3D1490203615530%26di%3D2b1827956a01011d3634f3e04b01b15c%26imgtype%3D0%26src%3Dhttp%253A%252F%252Fimg15.3lian.com%252F2015%252Fh1%252F338%252Fd%252F157.jpg&thumburl=https%3A%2F%2Fss1.bdstatic.com%2F70cFvXSh_Q1YnxGkpoWK1HF6hhy%2Fit%2Fu%3D2613489365%2C2336631324%26fm%3D23%26gp%3D0.jpg";
private static int threadNum = 5;
private static int threadCount = 0;
int avgBytes = 0;
DownloadListener listener;
ConnectionManager cm;
File file = null;
public FileDownloader(String _url,String fileName) {
this.url = _url;
this.file = new File(fileName);
}
public void execute(){
// 在这里实现你的代码, 注意: 需要用多线程实现下载
// 这个类依赖于其他几个接口, 你需要写这几个接口的实现代码
// (1) ConnectionManager , 可以打开一个连接,通过Connection可以读取其中的一段(用startPos, endPos来指定)
// (2) DownloadListener, 由于是多线程下载, 调用这个类的客户端不知道什么时候结束,所以你需要实现当所有
// 线程都执行完以后, 调用listener的notifiedFinished方法, 这样客户端就能收到通知。
// 具体的实现思路:
// 1. 需要调用ConnectionManager的open方法打开连接, 然后通过Connection.getContentLength方法获得文件的长度
// 2. 至少启动3个线程下载, 注意每个线程需要先调用ConnectionManager的open方法
// 然后调用read方法, read方法中有读取文件的开始位置和结束位置的参数, 返回值是byte[]数组
// 3. 把byte数组写入到文件中
// 4. 所有的线程都下载完成以后, 需要调用listener的notifiedFinished方法
// 下面的代码是示例代码, 也就是说只有一个线程, 你需要改造成多线程的。
Connection conn = null;
try {
conn = cm.open(this.url);
int length = conn.getContentLength();
avgBytes = length / threadNum;
//使用5个线程去下载;
for (int i = 0; i < threadNum; i++) {
int startPos = i*avgBytes;
int endPos = startPos + avgBytes - 1;
if(i == threadNum -1) {
endPos = length;
}
Connection c = cm.open(this.url);
DownloadThread thread = new DownloadThread(c,startPos,endPos,file,this.getListener());
thread.setName("Thread"+(i+1) );
thread.start();
}
} catch (ConnectionException e) {
e.printStackTrace();
}finally{
if(conn != null){
conn.close();
}
}
}
public void setListener (DownloadListener listener){
this.listener = listener;
}
public synchronized static boolean isDownloadFinish(){
threadCount++;
return threadCount == threadNum;
}
public void setConnectionManager(ConnectionManager ucm){
this.cm = ucm;
}
public DownloadListener getListener(){
return this.listener;
}
}