Android学习笔记(二十)

文件下载

DownLoaderTest

Java代码

package junit.test;

import java.io.File;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import org.junit.Test;

public class DownLoaderTest {

    @Test
    public void download() throws Exception {
        String urlpath = "%202010.10.exe";
        URL url = new URL(urlpath);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");
        conn.setReadTimeout(6 * 1000);
        // 线程数
        int threadsize = 3;
        // 获取文件大小
        int filesize = conn.getContentLength();
        // 每条线程下载的数量
        int block = filesize / 3 + 1;
        conn.disconnect();
        File file = new File("Firefox.exe");
        RandomAccessFile randfile = new RandomAccessFile(file, "rw");
        randfile.setLength(filesize);// 设置文件的大小
        randfile.close();
        for (int i = 0; i < threadsize; i++) {
            int startposition = i * block;// 从网路文件的什么位置开始下载
            RandomAccessFile threadfile = new RandomAccessFile(file, "rw");
            threadfile.seek(startposition);// 从文件的什么位置开始写入
            new DownloadThread(i, url, startposition, threadfile, block)
                    .start();
        }
        byte[] quit = new byte[1];
        System.in.read(quit);
        while (!('q' == quit[0])) {
            Thread.sleep(3 * 1000);
        }
    }

    private class DownloadThread extends Thread {
        private int threadid;
        private URL url;
        private int startposition;
        private RandomAccessFile threadfile;
        private int block;

        public DownloadThread(int threadid, URL url, int startposition,
                RandomAccessFile threadfile, int block) {
            this.threadid = threadid;
            this.url = url;
            this.startposition = startposition;
            this.threadfile = threadfile;
            this.block = block;
        }

        @Override
        public void run() {
            try {
                HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                conn.setRequestProperty("Range", "bytes=" + startposition
                                + "-");
                conn.setRequestMethod("GET");
                conn.setReadTimeout(6 * 1000);
                InputStream inputStream = conn.getInputStream();
                byte[] buffer = new byte[1024];
                int len = -1;
                int readfilesize = 0;
                while (readfilesize < block
                        && ((len = inputStream.read(buffer)) != -1)) {
                    threadfile.write(buffer, 0, len);
                    readfilesize += len;// 累计下载的文件大小
                }
                threadfile.close();
                conn.disconnect();
                System.out.println((this.threadid + 1) + "线程下载完成");
            } catch (Exception e) {
                e.printStackTrace();
            }
            super.run();
        }
    }
}