android 断点续传

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1.依赖

compile 'com.loopj.android:android-async-http:1.4.9'

2.main

package com.bwei.threaddownload;import android.os.Bundle;import android.os.Environment;import android.os.Handler;import android.os.Message;import android.os.SystemClock;import android.support.annotation.Nullable;import android.support.v7.app.AppCompatActivity;import android.text.TextUtils;import android.util.Log;import android.view.View;import android.widget.Button;import android.widget.ProgressBar;import android.widget.TextView;import com.loopj.android.http.HttpGet;import java.io.BufferedReader;import java.io.File;import java.io.FileReader;import java.io.FileWriter;import java.io.InputStream;import java.io.RandomAccessFile;import cz.msebera.android.httpclient.Header;import cz.msebera.android.httpclient.HttpResponse;import cz.msebera.android.httpclient.client.HttpClient;import cz.msebera.android.httpclient.client.methods.HttpHead;import cz.msebera.android.httpclient.impl.client.DefaultHttpClient;/** * 1. 类的用途  断点续传 * 2. @author forever * 3. @date 2017/11/8 16:13 */public class OtherActivity extends AppCompatActivity {    protected static final String TAG = "OtherActivity";    //下载线程的数量    private final static int threadsize = 3;    protected static final int SET_MAX = 0;    public static final int UPDATE_VIEW = 1;    private ProgressBar pb;    private Button bt_download;    private Button bt_pause;    private TextView tv_info;    //显示进度和更新进度    private Handler mHandler = new Handler(){        public void handleMessage(android.os.Message msg) {            switch (msg.what) {                case SET_MAX://设置进度条的最大值                    int filelength = msg.arg1;                    pb.setMax(filelength);                    break;                case UPDATE_VIEW://更新进度条  和 下载的比率                    int len = msg.arg1;//新下载的长度                    pb.setProgress(pb.getProgress()+len);//设置进度条的刻度                    int max = pb.getMax();//获取进度的最大值                    int progress = pb.getProgress();//获取已经下载的数据量                    //  下载：30    总：100                    int result = (progress*100)/max;                    tv_info.setText("下载:"+result+"%");                    break;                default:                    break;            }        };    };    String uri = "http://c.hiphotos.baidu.com/image/pic/item/b90e7bec54e736d1e51217c292504fc2d46269f3.jpg";    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_other);//找到控件        pb = (ProgressBar) findViewById(R.id.pb);        tv_info = (TextView) findViewById(R.id.tv_info);        bt_download = (Button) findViewById(R.id.bt_download);        bt_pause = (Button) findViewById(R.id.bt_pause);        //数据的回显        //确定下载的文件        String name = getFileName(uri);        File file = new File(Environment.getExternalStorageDirectory(), name);        if (file.exists()){//文件存在回显            //获取文件的大小            int filelength = (int) file.length();            pb.setMax(filelength);            try {                //统计原来所有的下载量                int count = 0;                //读取下载记录文件                for (int threadid = 0; threadid < threadsize; threadid++) {                    //获取原来指定线程的下载记录                    int existDownloadLength = readDownloadInfo(threadid);                    count = count + existDownloadLength;                }                //设置进度条的刻度                pb.setProgress(count);                //计算比率                int result = (count * 100) / filelength;                tv_info.setText("下载:" + result + "%");            } catch (Exception e) {                e.printStackTrace();            }        }    }    //暂停        private boolean flag = false;//是否在下载        public void pause(View v){            flag = false;            bt_download.setEnabled(true);            bt_pause.setEnabled(false);        }//下载        public void download(View v){            flag = true; //是在下载            bt_download.setEnabled(false);//一点击变成不可点击            bt_pause.setEnabled(true);//一点击变成可点击            new Thread(){//子线程                public void run() {                    try {                        //获取服务器上文件的大小                        HttpClient client = new DefaultHttpClient();                        HttpHead request = new HttpHead(uri);                        HttpResponse response = client.execute(request);                        //response  只有响应头  没有响应体                        if(response.getStatusLine().getStatusCode() == 200){                            Header[] headers = response.getHeaders("Content-Length");                            String value = headers[0].getValue();                            //文件大小                            int filelength = Integer.parseInt(value);                            Log.i(TAG, "filelength:"+filelength);                            //设置进度条的最大值                            Message msg_setmax = Message.obtain(mHandler, SET_MAX, filelength, 0);                            msg_setmax.sendToTarget();                            //处理下载记录文件                            for(int threadid=0;threadid<threadsize;threadid++){                                //对应的下载记录文件                                File file = new File(Environment.getExternalStorageDirectory(),threadid+".txt");                                //判断文件是否存在                                if(!file.exists()){                                    //创建文件                                    file.createNewFile();                                }                            }                            //在sdcard创建和服务器大小一样的文件                            String name = getFileName(uri);                            File file = new File(Environment.getExternalStorageDirectory(),name);                            //随机访问文件                            RandomAccessFile raf = new RandomAccessFile(file, "rwd");                            //设置文件的大小                            raf.setLength(filelength);                            //关闭                            raf.close();                            //计算每条线程的下载量                            int block = (filelength%threadsize == 0)?(filelength/threadsize):(filelength/threadsize+1);                            //开启三条线程执行下载                            for(int threadid=0;threadid<threadsize;threadid++){                                new DownloadThread(threadid, uri, file, block).start();                            }                        }                    } catch (Exception e) {                        e.printStackTrace();                    }                };            }.start();        }        //线程下载类        private class DownloadThread extends Thread{            private int threadid;//线程的id            private String uri;//下载的地址            private File file;//下载文件            private int block;//下载的块            private int start;            private int end;            public DownloadThread(int threadid, String uri, File file, int block) {                super();                this.threadid = threadid;                this.uri = uri;                this.file = file;                this.block = block;                //计算下载的开始位置和结束位置                start = threadid * block;                end = (threadid + 1)*block -1;                try {                    //读取该条线程原来的下载记录                    int existDownloadLength = readDownloadInfo(threadid);                    //修改下载的开始位置   从新下载                    start = start + existDownloadLength;                } catch (Exception e) {                    e.printStackTrace();                }            }            //下载   状态码：200是普通的下载      206是分段下载        Range:范围            @Override            public void run() {                super.run();                try {                    RandomAccessFile raf = new RandomAccessFile(file, "rwd");                    //跳转到起始位置                    raf.seek(start);                    //分段下载                    HttpClient client = new DefaultHttpClient();                    HttpGet request = new HttpGet(uri);                    request.addHeader("Range", "bytes:"+start+"-"+end);//添加请求头                    HttpResponse response = client.execute(request);                    if(response.getStatusLine().getStatusCode() == 200){                        InputStream inputStream = response.getEntity().getContent();                        //把流写入到文件                        byte[] buffer = new byte[1024];                        int len = 0;                        while((len = inputStream.read(buffer)) != -1){                            //如果暂停下载  点击暂停 false 就直接return 点击下载true接着下载                            if(!flag){                                return;//标准线程结束                            }                            //写数据                            raf.write(buffer, 0, len);                            //读取原来下载的数据量 这里读取是为了更新下载记录                            int existDownloadLength = readDownloadInfo(threadid);//原来下载的数据量                            //计算最新的下载                            int newDownloadLength = existDownloadLength + len;                            //更新下载记录 从新记录最新下载位置                            updateDownloadInfo(threadid, newDownloadLength);                            //更新进度条的显示   下载的百分比                            Message update_msg = Message.obtain(mHandler, UPDATE_VIEW, len, 0);                            update_msg.sendToTarget();                            //模拟  看到进度条动的效果                            SystemClock.sleep(50);                        }                        inputStream.close();                        raf.close();                        Log.i(TAG, "第"+threadid+"条线程下载完成");                    }                } catch (Exception e) {                    e.printStackTrace();                }            }        }        /**         * 读取指定线程的下载数据量         * @param threadid  线程的id         * @return         * @throws Exception         */        public int readDownloadInfo(int threadid) throws Exception{            //下载记录文件            File file = new File(Environment.getExternalStorageDirectory(),threadid+".txt");            BufferedReader br = new BufferedReader(new FileReader(file));            //读取一行数据            String content = br.readLine();            int downlength = 0;            //如果该文件第一次创建去执行读取操作  文件里面的内容是 null            if(!TextUtils.isEmpty(content)){                downlength = Integer.parseInt(content);            }            //关闭流            br.close();            return downlength;        }        /**         * 更新下载记录         * @param threadid         * @param newDownloadLength         */        public void updateDownloadInfo(int threadid,int newDownloadLength) throws Exception{            //下载记录文件            File file = new File(Environment.getExternalStorageDirectory(),threadid+".txt");            FileWriter fw = new FileWriter(file);            fw.write(newDownloadLength+"");            fw.close();        }        /**         * 获取文件的名称         * @param uri         * @return         */        private String getFileName(String uri){            return uri.substring(uri.lastIndexOf("/")+1);        }}

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