Androidx学习笔记（44）--- 多线程断点续传（Android项目）

手机版的断点续传多线程下载器

/**
* 注意：没有判断SD卡是否存在，剩余空间
*/
public class MainActivity extends ActionBarActivity {
static int ThreadCount = 3; // 下载线程的数量
static int finishedThread = 0; // 记录关闭线程的数量 用于删除临时文件
// 确定下载地址
String path = "http://192.168.1.101:8080/a/b.exe";

String fileName = null;
String fileType = null ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

//获取文件名和后缀名
File file = new File(path);
fileName = file.getName();
fileType = fileName.substring(fileName.lastIndexOf(".") ,fileName.length());
//String fileType = fileName.substring(fileName.lastIndexOf(".") +1,fileName.length());

}

public void click(View v)
{
Thread thread = new Thread()
{
public void run()
{
// 发送get请求，请求这个地址的资源
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
conn.setReadTimeout(5000);
if (conn.getResponseCode() == 200) {
// 拿到所请求资源文件的长度
int length = conn.getContentLength();
File file = new File(Environment.getExternalStorageDirectory(), fileName+fileType);
// 生成临时文件
RandomAccessFile raf = new RandomAccessFile(file, "rwd");
// 设置临时文件的大小
raf.setLength(length);
raf.close();

// 计算出每个线程应该下载多少字节
int size = length / ThreadCount;
for (int i = 0; i < ThreadCount; i++) {
// 计算线程下载的开始位置和结束位置
int startIndex = i * size;
int endIndex = (i + 1) * size - 1;
// 如果是最后一个线程，那么结束位置写死
if (i == ThreadCount - 1) {
endIndex = length - 1;
}
// System.out.println("线程" + i + "的下载区间是：" + startIndex +
// "---" + endIndex);
new DownLoadThread(startIndex, endIndex, i).start();
}
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

};
};

thread.start();
}

class DownLoadThread extends Thread {
int startIndex;
int endIndex;
int threadId;
public DownLoadThread(int startIndex, int endIndex, int threadId) {
super();
this.startIndex = startIndex;
this.endIndex = endIndex;
this.threadId = threadId;
}
@Override
public void run() {
// 再次发送http请求，下载原文件
try {
// 生成一个专门用来记录下载进度的临时文件
File progressFile = new File(Environment.getExternalStorageDirectory(),threadId + ".txt");
// 判断进度临时文件是否存在
if (progressFile.exists()) {
FileInputStream fis = new FileInputStream(progressFile);
BufferedReader br = new BufferedReader(new InputStreamReader(
fis));
// 从进度临时文件中读取出上一次下载的总进度，然后与原本的开始位置相加，得到新的开始位置
startIndex += Integer.parseInt(br.readLine());
fis.close();
}
HttpURLConnection conn;
URL url = new URL(path);
conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setConnectTimeout(5000);
conn.setReadTimeout(5000);
// 设置本次http请求所请求的数据的区间
conn.setRequestProperty("Range", "bytes=" + startIndex + "-"
+ endIndex);
// 请求部分数据，相应码是206
if (conn.getResponseCode() == 206) {
// 流里此时只有1/3原文件的数据
InputStream is = conn.getInputStream();
byte[] b = new byte[1024];
int len = 0;
int total = 0;
// 拿到临时文件的输出流
File file = new File(Environment.getExternalStorageDirectory(), fileName+fileType);
RandomAccessFile raf = new RandomAccessFile(file, "rwd");
// 把文件的写入位置移动至startIndex
raf.seek(startIndex);
while ((len = is.read(b)) != -1) {
// 每次读取流里数据之后，同步把数据写入临时文件
raf.write(b, 0, len);
total += len;
System.out.println("线程" + threadId + "下载了" + total);
RandomAccessFile progressRaf = new RandomAccessFile(
progressFile, "rwd");
// 每次读取流里数据之后，同步把当前线程下载的总进度写入进度临时文件中
progressRaf.write((total + "").getBytes());
progressRaf.close();
}
System.out
.println("线程" + threadId + "下载完毕-------------------！");
raf.close();
// 线程下载完成自加
MainActivity.finishedThread++;
// 在同步语句块中 删除所有的临时文件
synchronized ( path) {
if (MainActivity.finishedThread == MainActivity.ThreadCount) {
for (int i = 0; i < MainActivity.ThreadCount; i++) {
File f = new File(Environment.getExternalStorageDirectory(),i + ".txt");
f.delete();
}
// 线程下载数量重置
MainActivity.finishedThread = 0;
}
}
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

}