Android实现简单断点续传和下载到本地功能

概述本文实例为大家分享了Android实现断点续传和下载的具体代码，供大家参考，具体内容如下

本文实例为大家分享了AndroID实现断点续传和下载的具体代码，供大家参考，具体内容如下

效果展示

导入依赖与权限

依赖

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

权限

 <uses-permission androID:name="androID.permission.INTERNET"></uses-permission>  <uses-permission androID:name="androID.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>  <uses-permission androID:name="androID.permission.READ_EXTERNAL_STORAGE"></uses-permission>

主MainActivity（布局）

<?xml version="1.0" enCoding="utf-8"?><relativeLayout xmlns:androID="http://schemas.androID.com/apk/res/androID"  xmlns:tools="http://schemas.androID.com/tools"  androID:ID="@+ID/activity_main"  androID:layout_wIDth="match_parent"  androID:layout_height="match_parent"  androID:paddingBottom="@dimen/activity_vertical_margin"  androID:paddingleft="@dimen/activity_horizontal_margin"  androID:paddingRight="@dimen/activity_horizontal_margin"  androID:paddingtop="@dimen/activity_vertical_margin"  tools:context="com.lv.mama.test004.MainActivity">  <Progressbar        androID:layout_wIDth="match_parent"    androID:layout_height="20dp"    androID:layout_margintop="15dp"    androID:ID="@+ID/pb"    androID:layout_alignParenttop="true"    androID:layout_alignParentleft="true"    androID:layout_alignParentStart="true"    />  <TextVIEw    androID:text="TextVIEw"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_below="@+ID/pb"    androID:layout_alignParentleft="true"    androID:layout_alignParentStart="true"    androID:layout_marginleft="20dp"    androID:layout_marginStart="20dp"    androID:layout_margintop="13dp"    androID:ID="@+ID/tv_info" />  <button    androID:text="暂停"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_margintop="17dp"    androID:ID="@+ID/bt_pause"    androID:onClick="pause"    androID:layout_below="@+ID/tv_info"    androID:layout_alignParentleft="true"    androID:layout_alignParentStart="true"    androID:layout_marginleft="11dp"    androID:layout_marginStart="11dp" />  <button    androID:text="开始"    androID:layout_wIDth="wrap_content"    androID:layout_height="wrap_content"    androID:layout_marginRight="24dp"    androID:layout_marginEnd="24dp"    androID:ID="@+ID/bt_download"    androID:onClick="download"    androID:layout_alignBaseline="@+ID/bt_pause"    androID:layout_alignBottom="@+ID/bt_pause"    androID:layout_alignParentRight="true"    androID:layout_alignParentEnd="true" /></relativeLayout>

主MainActivity

public class MainActivity 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(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentVIEw(R.layout.activity_main);    //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,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 *** 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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