Android文件下载功能实现代码

本文实例为大家分享了Android文件下载功能的具体代码，供大家参考，具体内容如下

1.普通单线程下载文件：

直接使用URLConnection.openStream()打开网络输入流,然后将流写入到文件中！

public static void downLoad(String path,Context context)throws Exception
{
URL url = new URL(path);
InputStream is = url.openStream();
//截取最后的文件名
String end = path.substring(path.lastIndexOf("."));
//打开手机对应的输出流,输出到文件中
OutputStream os = context.openFileOutput("Cache_"+System.currentTimeMillis()+end, Context.MODE_PRIVATE);
byte[] buffer = new byte[1024];
int len = 0;
//从输入六中读取数据,读到缓冲区中
while((len = is.read(buffer)) > 0)
{
 os.write(buffer,0,len);
}
//关闭输入输出流
is.close();
os.close();
}

2.普通多线程下载：

步骤：

• 获取网络连接

• 本地磁盘创建相同大小的空文件

• 计算每条线程需从文件哪个部分开始下载，结束

• 依次创建，启动多条线程来下载网络资源的指定部分
  

public class Downloader {
//添加@Test标记是表示该方法是Junit测试的方法,就可以直接运行该方法了
 @Test
 public void download() throws Exception
 {
  //设置URL的地址和下载后的文件名
  String filename = "meitu.exe";
  String path = "http://10.13.20.32:8080/Test/XiuXiu_Green.exe";
  URL url = new URL(path);
  HttpURLConnection conn = (HttpURLConnection) url.openConnection();
  conn.setConnectTimeout(5000);
  conn.setRequestMethod("GET");
  //获得需要下载的文件的长度(大小)
  int filelength = conn.getContentLength();
  System.out.println("要下载的文件长度"+filelength);
  //生成一个大小相同的本地文件
  RandomAccessFile file = new RandomAccessFile(filename, "rwd");
  file.setLength(filelength);
  file.close();
  conn.disconnect();
  //设置有多少条线程下载
  int threadsize = 3;
  //计算每个线程下载的量
  int threadlength = filelength ％ 3 == 0 ? filelength/3:filelength+1;
  for(int i = 0;i < threadsize;i++)
  {
   //设置每条线程从哪个位置开始下载
   int startposition = i * threadlength;
   //从文件的什么位置开始写入数据
   RandomAccessFile threadfile = new RandomAccessFile(filename, "rwd");
   threadfile.seek(startposition);
   //启动三条线程分别从startposition位置开始下载文件
   new DownLoadThread(i,startposition,threadfile,threadlength,path).start();
  }
  int quit = System.in.read();
  while('q' != quit)
  {
   Thread.sleep(2000);
  }
 }

private class DownLoadThread extends Thread {
 private int threadid;
 private int startposition;
 private RandomAccessFile threadfile;
 private int threadlength;
 private String path;
 public DownLoadThread(int threadid, int startposition,
   RandomAccessFile threadfile, int threadlength, String path) {
  this.threadid = threadid;
  this.startposition = startposition;
  this.threadfile = threadfile;
  this.threadlength = threadlength;
  this.path = path;
 }
 public DownLoadThread() {}
 @Override
 public void run() {
  try
  {
   URL url = new URL(path);
   HttpURLConnection conn = (HttpURLConnection) url.openConnection();
   conn.setConnectTimeout(5000);
   conn.setRequestMethod("GET");
   //指定从什么位置开始下载
   conn.setRequestProperty("Range", "bytes="+startposition+"-");
   //System.out.println(conn.getResponseCode());
   if(conn.getResponseCode() == 206)
   {
    InputStream is = conn.getInputStream();
    byte[] buffer = new byte[1024];
    int len = -1;
    int length = 0;
    while(length < threadlength && (len = is.read(buffer)) != -1)
    {
     threadfile.write(buffer,0,len);
     //计算累计下载的长度
     length += len;
    }
    threadfile.close();
    is.close();
    System.out.println("线程"+(threadid+1) + "已下载完成");
   }
  }catch(Exception ex){System.out.println("线程"+(threadid+1) + "下载出错"+ ex);}
 }

}
}