Android(安卓)使用Get方式实现断点下载(一）

public class DownloadActivity extends Activity implements OnClickListener{    private String path;    private static final int THREAD_NUM = 3;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        Button button = new Button(this);        button.setOnClickListener(this);    }    @Override    public void onClick(View v) {        download(path);    }    private void download(String path) {        try {            URL url = new URL(path);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setDoInput(true);            conn.setDoOutput(true);            conn.setRequestMethod("GET");            conn.setConnectTimeout(5000);            if (conn.getResponseCode() == 200) {                int length = conn.getContentLength();                RandomAccessFile raf = new RandomAccessFile("down.exe", "rwd");                raf.setLength(length);                raf.close();                int blocksize = length / THREAD_NUM;                for (int i = 1; i <= THREAD_NUM; i++) {                    int start = (i-1) * blocksize;                    int end = i * blocksize - 1;                    if (i == THREAD_NUM) {                        end = length;                    }                    System.out.println("线程："+i + "下载：" + start + "---->" + end);                    new DownloadThread(i, start, end, path).start();                }            }else {                System.out.println("服务器错误！");            }        } catch (Exception e) {            e.printStackTrace();        }    }    class DownloadThread extends Thread{        private int threadId;        private int start;        private int end;        private String path;        public DownloadThread(int threadId,int start,int end, String path){            this.threadId = threadId;            this.start = start;            this.end = end;            this.path = path;        }        @Override        public void run() {            try {                int tempLen=0;                //先读取临时文件                File temFile = new File(threadId+".txt");                if (temFile.exists()) {                    FileInputStream fis = new FileInputStream(temFile);                    byte[] buffer = new byte[1024];                    int len = fis.read(buffer);                    tempLen = Integer.parseInt(new String(buffer,0,len));                    start += tempLen;                }                URL url = new URL(path);                HttpURLConnection conn = (HttpURLConnection) url.openConnection();                conn.setRequestMethod("GET");                conn.setRequestProperty("Range", "bytes=" + start + "-" + end);                conn.setConnectTimeout(5000);                int total=0;                if (conn.getResponseCode() == 206) {                    InputStream inputStream = conn.getInputStream();                    RandomAccessFile raf = new RandomAccessFile("down.exe", "rwd");                    raf.seek(start);                    byte[] buffer = new byte[1024];                    int len = -1;                    while((len  = inputStream.read(buffer))!=-1){                        RandomAccessFile tempRaf = new RandomAccessFile(threadId+".txt", "rwd");                        raf.write(buffer, 0 , len);                        total+=len;                        System.out.println("线程："+threadId + "下载total:" + total);                        tempRaf.write(((tempLen + total) + "").getBytes());                        tempRaf.close();                    }                    raf.close();                }            } catch (MalformedURLException e) {                e.printStackTrace();            } catch (IOException e) {                e.printStackTrace();            }        }    }}
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