手机端多线程下载

文件来源于在 imooc 网站的学习视频，安装视频敲写出来的，。
由于用到了，。多线程下载，利用线程池的方式，不是全部下载逻辑自己书写的，代码简单好用，所以分享出来，参考参考

public class Download {    /**     * 创建线程池     */    private Executor threadPool = Executors.newFixedThreadPool(3);    private Handler handler;    public Download(Handler handler) {        this.handler = handler;    }    static class DownLoadRunnable implements Runnable {        private String url;        private String fileName;        private long start;        private long end;        private Handler handler;        public DownLoadRunnable(String url, String fileName, long start, long end, Handler handler) {            this.url = url;            this.fileName = fileName;            this.start = start;            this.end = end;            this.handler = handler;        }        @Override        public void run() {            try {                URL httpurl = new URL(url);                HttpURLConnection conn = (HttpURLConnection) httpurl.openConnection();                conn.setReadTimeout(5000);                conn.setRequestProperty("Range", "bytes=" + start + "-" + end);                conn.setRequestMethod("GET");                RandomAccessFile access = new RandomAccessFile(                        new File(fileName), "rwd"                );                access.seek(start);                InputStream in = conn.getInputStream();                byte[] b = new byte[1024 * 4];                int len = 0;                while ((len = in.read(b)) != -1) {                    access.write(b, 0, len);                }                if (access != null) {                    access.close();                }                if (in != null) {                    in.close();                }                Message message = new Message();                message.what = 1;                handler.sendMessage(message);            } catch (MalformedURLException e) {                e.printStackTrace();            } catch (IOException e) {                e.printStackTrace();            }        }    }    public void dowmLoadFile(String url) {        try {            URL httpurl = new URL(url);            HttpURLConnection conn = (HttpURLConnection) httpurl.openConnection();            conn.setReadTimeout(5000);            conn.setRequestMethod("GET");            int count = conn.getContentLength();            int block = count / 3;            String fileName = getFileName(url);//拿到文件名            System.out.println("=======  "+fileName+"   =======");            File parent = Environment.getExternalStorageDirectory();            System.out.println(parent.toString()+"/"+fileName+"====111=======");            File fileDownLoad = new File(parent, fileName);            /**             *             */            for (int i = 0; i < 3; i++) {                long start = i * block;                long end = (i + 1) * block - 1;                //最后一个进程，要下载一下全部的                if (i == 2) {                    end = count;                }                DownLoadRunnable runnable =                        new DownLoadRunnable(                                url, fileDownLoad.getAbsolutePath()                                , start, end,handler);                threadPool.execute(runnable);            }        } catch (ProtocolException e) {            e.printStackTrace();        } catch (MalformedURLException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    public String getFileName(String url) {        return url.substring(url.lastIndexOf("/") + 1);    }}

   private Handler handler = new Handler() {        @Override        public void handleMessage(Message msg) {            int result = msg.what;            count += result;            if (count == 3) {                textView.setText("downlaod success");                String laoding = Environment.getExternalStorageDirectory().toString() + "/70.jpg";                Drawable d = Drawable.createFromPath(laoding);                imageView.setImageDrawable(d);                System.out.println(laoding+"===2222====");            }        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        button = (Button) findViewById(R.id.button1);        textView = (TextView) findViewById(R.id.textView);        imageView = (ImageView) findViewById(R.id.imageView);        button2 = (Button) findViewById(R.id.button2);        button2.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent intent = new Intent();                intent.setClass(MainActivity.this, uploadActivity.class);                startActivity(intent);            }        });        button.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                new Thread() {                    @Override                    public void run() {                        Download load = new Download(handler);                        load.dowmLoadFile("http://img15.3lian.com/2015/f2/50/d/70.jpg");                    }                }.start();            }        });