功能要求：从网络下载一APK应用，显示下载速度、进度，并安装应用。
运行效果图：
工程结构图：
很简单，就一个activity，一个更新UI的线程，一个下载线程加个文件处理类
主要代码：
/**
*多线程下载，UI更新类
*@author young
* */
public class MultiThreadDownload extends Thread{
private static final String TAG = "MultiThreadDownload";
/**每一个线程需要下载的大小 */
private int blockSize;
/*** 线程数量<br> 默认为5个线程下载*/
private int threadNum = ;
/*** 文件大小 */
private int fileSize;
/** * 已经下载多少 */
private int downloadSize;
/**文件的url,线程编号，文件名称*/
private String UrlStr,ThreadNo,fileName;
/***保存的路径*/
private String savePath;
/**下载的百分比*/
private int downloadPercent = ;
/**下载的 平均速度*/
private int downloadSpeed = ;
/**下载用的时间*/
private int usedTime = ;
/**当前时间*/
private long curTime;
/**是否已经下载完成*/
private boolean completed = false;
private Handler handler ;
/**
* 下载的构造函数
* @param url 请求下载的URL
* @param handler UI更新使用
* @param savePath 保存文件的路径
*/
public MultiThreadDownload(Handler handler,String url,String savePath)
{
this.handler = handler;
this.UrlStr = url;
this.savePath = savePath;
Log.e(TAG, toString());
} @Override
public void run() { FileDownloadThread[] fds = new FileDownloadThread[threadNum];//设置线程数量
try {
URL url = new URL(UrlStr);
URLConnection conn = url.openConnection();
fileSize = conn.getContentLength(); this.fileName = FileUtil.getFileName(UrlStr);
//只创建一个文件，saveFile下载内容
File saveFile = new File(savePath+"/"+fileName);
Log.e(TAG, "文件一共："+fileSize+" savePath "+savePath+" fileName "+fileName); RandomAccessFile accessFile = new RandomAccessFile(saveFile,"rwd");
//设置本地文件的长度和下载文件相同
accessFile.setLength(fileSize);
accessFile.close();
//Handler更新UI，发送消息
sendMsg(FileUtil.startDownloadMeg);
//每块线程下载数据
blockSize = ((fileSize%threadNum)==)?(fileSize/threadNum):(fileSize/threadNum+);
Log.e(TAG, "每个线程分别下载 ："+blockSize); for (int i = ; i < threadNum; i++) {
int curThreadEndPosition = (i+)!=threadNum ? ((i+)*blockSize-) : fileSize;
FileDownloadThread fdt = new FileDownloadThread(url, saveFile, i*blockSize, curThreadEndPosition);
fdt.setName("thread"+i);
fdt.start();
fds[i]=fdt;
}
/**
* 获取数据，更新UI，直到所有下载线程都下载完成。
*/
boolean finished = false;
//开始时间，放在循环外，求解的usedTime就是总时间
long startTime = System.currentTimeMillis();
while(!finished)
{
downloadSize = ;
finished = true;
for (int i = ; i < fds.length; i++) {
downloadSize+= fds[i].getDownloadSize();
if(!fds[i].isFinished())
{
finished = false;
}
}
downloadPercent = (downloadSize*)/fileSize;
curTime = System.currentTimeMillis();
System.out.println("curTime = "+curTime+" downloadSize = "+downloadSize+" usedTime "+(int) ((curTime-startTime)/));
usedTime = (int) ((curTime-startTime)/); if(usedTime==)usedTime = ;
downloadSpeed = (downloadSize/usedTime)/;
sleep();/*1秒钟刷新一次界面*/
sendMsg(FileUtil.updateDownloadMeg);
}
Log.e(TAG, "下载完成");
completed = true;
sendMsg(FileUtil.endDownloadMeg);
} catch (Exception e) {
Log.e(TAG, "multi file error Exception "+e.getMessage());
e.printStackTrace();
}
super.run();
}
/**
* 得到文件的大小
* @return
*/
public int getFileSize()
{
return this.fileSize;
}
/**
* 得到已经下载的数量
* @return
*/
public int getDownloadSize()
{
return this.downloadSize;
}
/**
* 获取下载百分比
* @return
*/
public int getDownloadPercent(){
return this.downloadPercent;
}
/**
* 获取下载速度
* @return
*/
public int getDownloadSpeed(){
return this.downloadSpeed;
}
/**
* 修改默认线程数
* @param threadNum
*/
public void setThreadNum(int threadNum){
this.threadNum = threadNum;
}
/**
* 分块下载完成的标志
* @return
*/
public boolean isCompleted(){
return this.completed;
}
@Override
public String toString() {
return "MultiThreadDownload [threadNum=" + threadNum + ", fileSize="
+ fileSize + ", UrlStr=" + UrlStr + ", ThreadNo=" + ThreadNo
+ ", savePath=" + savePath + "]";
} /**
* 发送消息，用户提示
* */
private void sendMsg(int what)
{
Message msg = new Message();
msg.what = what;
handler.sendMessage(msg);
}
下载类：
public class FileDownloadThread extends Thread{
private static final String TAG = "FileDownloadThread";
/**缓冲区 */
private static final int BUFF_SIZE = ;
/**需要下载的URL*/
private URL url;
/**缓存的FIle*/
private File file;
/**开始位置*/
private int startPosition;
/**结束位置*/
private int endPosition;
/**当前位置*/
private int curPosition;
/**完成*/
private boolean finished = false;
/**已经下载多少*/
private int downloadSize = ;
/***
* 分块文件下载，可以创建多线程模式
* @param url 下载的URL
* @param file 下载的文件
* @param startPosition 开始位置
* @param endPosition 结束位置
*/
public FileDownloadThread(URL url, File file, int startPosition,
int endPosition) {
this.url = url;
this.file = file;
this.startPosition = startPosition;
this.curPosition = startPosition;
this.endPosition = endPosition;
Log.e(TAG, toString());
}
@Override
public void run() {
BufferedInputStream bis = null;
RandomAccessFile rAccessFile = null;
byte[] buf = new byte[BUFF_SIZE];
URLConnection conn = null;
try {
conn = url.openConnection();
conn.setConnectTimeout();//设置超时
conn.setReadTimeout();
conn.setAllowUserInteraction(true);
System.out.println(this.getName()+" startPosition "+startPosition+" endPosition "+endPosition);
conn.setRequestProperty("Range", "bytes="+(startPosition)+"-"+endPosition); //取剩余未下载的
rAccessFile = new RandomAccessFile(file,"rwd");//读写
//设置从什么位置开始写入数据
rAccessFile.seek(startPosition);
bis = new BufferedInputStream(conn.getInputStream(), BUFF_SIZE);
while(curPosition<endPosition) //当前位置小于结束位置 继续下载
{
int len = bis.read(buf,,BUFF_SIZE);
if(len==-) //下载完成
{
break;
}
rAccessFile.write(buf,,len);
curPosition = curPosition +len;
if(curPosition > endPosition)
{ //如果下载多了，则减去多余部分
System.out.println(" curPosition > endPosition !!!!");
int extraLen = curPosition-endPosition;
downloadSize += (len-extraLen+);
}else{
downloadSize+=len;
}
}
this.finished = true; //当前阶段下载完成
Log.e(TAG, "当前"+this.getName()+"下载完成");
} catch (Exception e) {
Log.e(TAG, "download error Exception "+e.getMessage());
e.printStackTrace();
}finally{
//关闭流
FileUtil.closeInputStream(bis);
try {
rAccessFile.close();
} catch (IOException e) {
// TODO Auto-generated catch block
Log.e("AccessFile", "AccessFile IOException "+e.getMessage());
}
}
super.run();
}
/**
* 是否完成当前段下载完成
* @return
*/
public boolean isFinished() {
return finished;
}
/**
* 已经下载多少
* @return
*/
public int getDownloadSize() {
return downloadSize;
}
@Override
public String toString() {
return "FileDownloadThread [url=" + url + ", file=" + file
+ ", startPosition=" + startPosition + ", endPosition="
+ endPosition + ", curPosition=" + curPosition + ", finished="
+ finished + ", downloadSize=" + downloadSize + "]";
}
这里面多线程下载是分段下载，创建保存一个文件，子线程分别通过RandomAccessFile类进行写入操作。