Android实现断点多线程下载

断点多线程下载的几个关键点：①：得到要下载的文件大小后，均分给几个线程。②：使用RandomAccessFile类进行读写，可以指定开始写入的位置。③：数据库保存下载信息，下一次继续下载的时候从数据库取出数据，然后从上次下载结束的地方开始。

这里我使用了FinalDb的数据库框架，同时在内存中存储了一份所有线程的下载信息，负责时时更新和查询下载进度。我测试用的是百度云网盘，文件大小50M左右。注意，线程中指定了开始结束下载位置的网络请求成功的返回码是206，并不是200。

效果图：

线程类：线程类负责具体的下载，线程的下载信息被存储到了数据库。线程开始下载时，根据线程ID查询自己的存储信息，然后开始从指定的位置下载和写入文件。完毕后根据自己的当前下载结果设置自己当前的下载状态。时时的下载进度存储只存储到了内存，只在本次下载结束才存储到数据库。

public class DownloadThread extends Thread {

  /**
   * 数据库操作工具
   */
  private FinalDb finalDb;

  /**
   * 下载状态：未开始
   */
  public static final int STATE_READY = 1;

  /**
   * 下载状态：下载中
   */
  public static final int STATE_LOADING = 2;

  /**
   * 下载状态：下载暂停中
   */
  public static final int STATE_PAUSING = 3;

  /**
   * 下载状态：下载完成
   */
  public static final int STATE_FINISH = 4;

  /**
   * 下载状态
   */
  public int downloadState;

  /**
   * 线程ID
   */
  private int threadID;

  /**
   * 要下载的URL路径
   */
  private String url;

  /**
   * 本线程要下载的文件
   */
  public RandomAccessFile file;

  /**
   * 构造器
   */
  public DownloadThread(Context context, int threadID, String downloadUrl, RandomAccessFile randomAccessFile) {
    this.threadID = threadID;
    this.url = downloadUrl;
    this.file = randomAccessFile;
    finalDb = DBUtil.getFinalDb(context);
  }

  @Override
  public void run() {
    //数据库查询本线程下载进度
    List<ThreadDownloadInfoBean> list = finalDb.findAllByWhere(ThreadDownloadInfoBean.class, "threadID='" + threadID + "'");
    //下载信息存放到内存
    if (list.get(0) != null) {
      MapUtil.map.put(threadID, list.get(0));
    }
    //取出实体类
    ThreadDownloadInfoBean bean = MapUtil.map.get(threadID);
    Utils.Print("bean：" + bean.toString());
    InputStream is;
    HttpURLConnection conn;
    try {
      Utils.Print("线程" + threadID + "开始连接");
      conn = (HttpURLConnection) new URL(url).openConnection();
      conn.setConnectTimeout(5000);
      conn.setReadTimeout(5000);
      conn.setRequestMethod("GET");
      //设置下载开始和结束的位置
      conn.setRequestProperty("Range", "bytes=" + (bean.startDownloadPosition + bean.downloadedSize) + "-" + bean.endDownloadPosition);
      conn.connect();
      if (conn.getResponseCode() == 206) {
        //更改下载状态
        downloadState = STATE_LOADING;
        bean.downloadState = STATE_LOADING;
        Utils.Print("线程" + threadID + "连接成功");
        is = conn.getInputStream();
        // 1K的数据缓冲
        byte[] bs = new byte[1024];
        // 读取到的数据长度
        int len;
        //从指定的位置开始下载
        file.seek(bean.startDownloadPosition);
        // 循环读取，当已经下载的大小达到了指定的本线程负责的大小时跳出循环，线程之间负责的文件首尾有重合的话没有影响，因为写入的内容时相同的
        while ((len = is.read(bs)) != -1) {
          //不用在这个循环里面更新数据库
          file.write(bs, 0, len);
          //时时更新内存中的已下载大小信息
          bean.downloadedSize += len;
          //如果调用者暂停下载，则跳出结束方法
          if (downloadState == STATE_PAUSING) {
            Utils.Print("线程" + threadID + "暂停下载");
            break;
          }
        }
        is.close();
        file.close();
      } else {
        Utils.Print("线程" + threadID + "连接失败");
      }
      conn.disconnect();
      //如果这个线程已经下载完了自己负责的部分就修改下载状态
      if (bean.downloadedSize >= bean.downloadTotalSize) {
        bean.downloadState = STATE_FINISH;
      } else {
        bean.downloadState = STATE_PAUSING;
      }
      //内存中信息更新至数据库
      finalDb.update(bean, "threadID='" + bean.threadID + "'");
    } catch (IOException e) {
      Utils.Print("线程" + threadID + "IO异常");
      e.printStackTrace();
    }
  }
}

线程信息的封装类：负责存储每个线程的ID，开始下载的位置，结束下载的位置，已经下载的大小，下载状态等；这个类用FinalDb数据库存储到数据库，一定要写get,set方法和空参构造器

@Table(name = "ThreadInfo")
public class ThreadDownloadInfoBean {

  /**
   * id
   */
  public int id;

  /**
   * 线程ID
   */
  public int threadID;

  /**
   * 本线程时时下载开始的位置
   */
  public long startDownloadPosition;

  /**
   * 本线程时时下载结束的位置
   */
  public long endDownloadPosition;

  /**
   * 本线程负责下载的文件大小
   */
  public long downloadTotalSize;

  /**
   * 已经下载了的文件大小
   */
  public long downloadedSize;

  /**
   * 本线程的下载状态
   */
  public int downloadState;

  public ThreadDownloadInfoBean() {

  }

  public ThreadDownloadInfoBean(int downloadState, long downloadedSize, long downloadTotalSize, long endDownloadPosition, long startDownloadPosition, int threadID) {
    this.downloadState = downloadState;
    this.downloadedSize = downloadedSize;
    this.downloadTotalSize = downloadTotalSize;
    this.endDownloadPosition = endDownloadPosition;
    this.startDownloadPosition = startDownloadPosition;
    this.threadID = threadID;
  }

  public int getId() {
    return id;
  }

  public void setId(int id) {
    this.id = id;
  }

  public int getThreadID() {
    return threadID;
  }

  public void setThreadID(int threadID) {
    this.threadID = threadID;
  }

  public long getStartDownloadPosition() {
    return startDownloadPosition;
  }

  public void setStartDownloadPosition(long startDownloadPosition) {
    this.startDownloadPosition = startDownloadPosition;
  }

  public long getEndDownloadPosition() {
    return endDownloadPosition;
  }

  public void setEndDownloadPosition(long endDownloadPosition) {
    this.endDownloadPosition = endDownloadPosition;
  }

  public long getDownloadTotalSize() {
    return downloadTotalSize;
  }

  public void setDownloadTotalSize(long downloadTotalSize) {
    this.downloadTotalSize = downloadTotalSize;
  }

  public long getDownloadedSize() {
    return downloadedSize;
  }

  public void setDownloadedSize(long downloadedSize) {
    this.downloadedSize = downloadedSize;
  }

  public int getDownloadState() {
    return downloadState;
  }

  public void setDownloadState(int downloadState) {
    this.downloadState = downloadState;
  }

  @Override
  public String toString() {
    return "ThreadDownloadInfoBean{" +
        "id=" + id +
        ", threadID=" + threadID +
        ", startDownloadPosition=" + startDownloadPosition +
        ", endDownloadPosition=" + endDownloadPosition +
        ", downloadTotalSize=" + downloadTotalSize +
        ", downloadedSize=" + downloadedSize +
        ", downloadState=" + downloadState +
        '}';
  }
}

下载工具类：这个类负责得到下载文件大小，分配线程下载大小，管理下载线程

public class DownUtil {

  /**
   * 数据库操作工具
   */
  public FinalDb finalDb;

  /**
   * 下载状态：准备好
   */
  public static final int STATE_READY = 1;

  /**
   * 下载状态：下载中
   */
  public static final int STATE_LOADING = 2;

  /**
   * 下载状态：暂停中
   */
  public static final int STATE_PAUSING = 3;

  /**
   * 下载状态：下载完成
   */
  public static final int STATE_FINISH = 4;

  /**
   * 下载状态
   */
  public int downloadState;

  /**
   * context
   */
  private Context context;

  /**
   * 要下载文件的大小
   */
  public long fileSize;

  /**
   * 线程集合
   */
  private ArrayList<DownloadThread> threadList = new ArrayList<>();

  /**
   * 构造器
   */
  public DownUtil(Context context) {
    this.context = context;
    finalDb = DBUtil.getFinalDb(context);
    judgeDownState();
  }

  /**
   * 初始化时判断下载状态
   */
  public void judgeDownState() {
    //取出数据库中的下载信息，存储到内存中
    List<ThreadDownloadInfoBean> list = finalDb.findAll(ThreadDownloadInfoBean.class);
    if (list != null && list.size() == DownloadActivity.threadNum) {
      for (int i = 0; i < list.size(); i++) {
        MapUtil.map.put(i, list.get(i));
      }
    }
    //查询SP中是否存储过要下载的文件大小
    Long spFileSize = SPUtil.getInstance(context).getLong(DownloadActivity.fileName, 0L);
    long downloadedSize = getFinishedSize();
    //SP中或者数据库中没有查询到说明从没有进行过下载
    if (spFileSize == 0 || downloadedSize == 0) {
      downloadState = STATE_READY;
    } else if (downloadedSize >= spFileSize) {
      downloadState = STATE_FINISH;
    } else {
      downloadState = STATE_PAUSING;
      fileSize = spFileSize;
    }
  }

  /**
   * 点击了开始按钮
   */
  public void clickDownloadBtn() {
    if (downloadState == STATE_READY) {
      startDownload();
    } else if (downloadState == STATE_PAUSING) {
      continueDownload();
    }
  }

  /**
   * 进入应用第一次开始下载
   */
  private void startDownload() {
    //开启新线程，得到要下载的文件大小
    new Thread() {
      @Override
      public void run() {
        try {
          HttpURLConnection conn;
          conn = (HttpURLConnection) new URL(DownloadActivity.url).openConnection();
          conn.setConnectTimeout(5000);
          conn.setReadTimeout(5000);
          conn.setRequestMethod("GET");
          conn.connect();
          if (conn.getResponseCode() == 200) {
            Utils.Print("DownUtil连接成功");
            //得到要下载的文件大小
            fileSize = conn.getContentLength();
            //得到文件名后缀名
            String contentDisposition = new String(conn.getHeaderField("Content-Disposition").getBytes("ISO-8859-1"), "UTF-8");
            String fileName = "下载测试" + contentDisposition.substring(contentDisposition.lastIndexOf("."), contentDisposition.lastIndexOf("\""));
            //得到存储路径
            String sdCardPath = context.getExternalFilesDir(null).getPath();
            DownloadActivity.fileName = sdCardPath + "/" + fileName;
            SPUtil.getInstance(context).saveString(DownloadActivity.FILE_NAME, DownloadActivity.fileName);
            SPUtil.getInstance(context).saveLong(DownloadActivity.fileName, fileSize);
            /*
             * 计算一下每个线程需要分担的下载文件大小 比如 总下载量为100 一共有三个线程
             * 那么 线程1负责0-32，线程2负责33-65，线程3负责66-99和100，
             * 也就是说下载总量除以线程数如果有余数，那么最后一个线程多下载一个余数部分
             */
            //每个线程均分的大小
            long threadDownSize = fileSize / DownloadActivity.threadNum;
            //线程均分完毕剩余的大小
            long leftDownSize = fileSize % DownloadActivity.threadNum;
            //创建要写入的文件
            RandomAccessFile file = new RandomAccessFile(DownloadActivity.fileName, "rw");
            //设置文件大小
            file.setLength(fileSize);
            //关闭
            file.close();
            for (int i = 0; i < DownloadActivity.threadNum; i++) {
              Utils.Print("开启线程" + i);
              //指定每个线程开始下载的位置
              long startPosition = i * threadDownSize;
              //指定每个线程负责下载的大小，当现场是集合里面最后一个线程的时候，它要增加leftDownSize的大小
              threadDownSize = i == DownloadActivity.threadNum - 1 ? threadDownSize + leftDownSize : threadDownSize;
              //存储線程信息
              ThreadDownloadInfoBean bean = new ThreadDownloadInfoBean(DownloadThread.STATE_READY, 0, threadDownSize, startPosition + threadDownSize, startPosition, i);
              finalDb.save(bean);
              RandomAccessFile threadFile = new RandomAccessFile(DownloadActivity.fileName, "rw");
              threadList.add(new DownloadThread(context, i, DownloadActivity.url, threadFile));
              threadList.get(i).start();
            }
            downloadState = STATE_LOADING;
            downloadInfoListener.connectSuccess();
          } else {
            Utils.Print("DownUtil-连接失败");
            downloadInfoListener.connectFail();
          }
          conn.disconnect();
        } catch (IOException e) {
          Utils.Print("DownUtil-IO异常");
          downloadInfoListener.IOException();
          e.printStackTrace();
        }
      }
    }.start();
  }

  /**
   * 继续下载
   */
  private void continueDownload() {
    List<ThreadDownloadInfoBean> list = finalDb.findAll(ThreadDownloadInfoBean.class);
    for (int i = 0; i < DownloadActivity.threadNum; i++) {
      //当前线程已经下载完了就不再开启
      if (list.get(i).downloadState != DownloadThread.STATE_FINISH) {
        Utils.Print("重新开启线程" + i);
        RandomAccessFile threadFile = null;
        try {
          threadFile = new RandomAccessFile(DownloadActivity.fileName, "rw");
        } catch (FileNotFoundException e) {
          e.printStackTrace();
        }
        DownloadThread downloadThread = new DownloadThread(context, i, DownloadActivity.url, threadFile);
        threadList.add(downloadThread);
        downloadThread.start();
      }
    }
    downloadState = STATE_LOADING;
    downloadInfoListener.connectSuccess();
  }

  /**
   * 点击了暂停的按钮
   */
  public void clickPauseBtn() {
    if (downloadState == STATE_LOADING) {
      stopDownload();
    }
  }

  /**
   * 暂停下载
   */
  private void stopDownload() {
    for (int i = 0; i < threadList.size(); i++) {
      if (threadList.get(i).downloadState == DownloadThread.STATE_LOADING) {
        threadList.get(i).downloadState = DownloadThread.STATE_PAUSING;
      }
    }
    downloadState = STATE_PAUSING;
    threadList.clear();
  }

  /**
   * 返回此刻所有线程完成的下载大小
   */
  public long getFinishedSize() {
    long totalSize = 0;
    for (int i = 0; i < DownloadActivity.threadNum; i++) {
      ThreadDownloadInfoBean bean = MapUtil.map.get(i);
      if (bean != null) {
        //如果该线程已经下载的部分大于分配给它的部分多余部分不予计算
        long addSize = bean.downloadedSize > bean.downloadTotalSize ? bean.downloadTotalSize : bean.downloadedSize;
        totalSize += addSize;
      }
    }
    return totalSize;
  }

  /**
   * 下载信息监听器
   */
  private DownloadInfoListener downloadInfoListener;

  /**
   * 下载信息监听器
   */
  public interface DownloadInfoListener {

    void connectSuccess();

    void connectFail();

    void IOException();
  }

  /**
   * 设置下载信息监听器
   */
  public void setDownloadInfoListener(DownloadInfoListener downloadInfoListener) {
    this.downloadInfoListener = downloadInfoListener;
  }

}

页面Activity：负责展示下载进度等信息，提供操作页面

public class DownloadActivity extends BaseActivity {

  /**
   * 下载地址输入框
   */
  private EditText et_download_url;

  /**
   * 确定输入地址的按钮
   */
  private Button btn_download_geturl;

  /**
   * 进度条
   */
  private NumberProgressView np_download;

  /**
   * 开始下载的按钮
   */
  private Button btn_download_start;

  /**
   * 暂停下载的按钮
   */
  private Button btn_download_pause;

  /**
   * 取消下载的按钮
   */
  private Button btn_download_cancel;

  /**
   * 文件信息显示
   */
  private TextView tv_download_file_info;

  /**
   * 下载速度显示
   */
  private TextView tv_download_speed;

  /**
   * 显示下载信息
   */
  private TextView tv_download_speed_info;

  /**
   * 每隔一段时间刷新下载进度显示
   */
  private final static int WHAT_INCREACE = 1;

  /**
   * 得到了文件名称
   */
  private final static int WHAT_GET_FILENAME = 2;

  /**
   * downUtil连接失败
   */
  private final static int WHAI_CONNECT_FAIL = 3;

  /**
   * downUtilIO异常
   */
  private final static int WHAT_IO_EXCEPTION = 4;

  /**
   * 下载工具
   */
  private DownUtil downUtil;

  /**
   * 需要开启的线程数量
   */
  public static final int threadNum = 5;

  /**
   * 存放文件路径名称的SP键名
   */
  public static final String FILE_NAME = "fileName";

  /**
   * 要下载的文件的url地址
   */
  public static String url = "";

  /**
   * 文件下载路径和文件名称
   */
  public static String fileName;

  /**
   * 上次统计已经完成下载的文件大小
   */
  private long lastFinishedSize;

  private Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
      switch (msg.what) {
        case WHAT_INCREACE:
          updateView();
          break;
        case WHAT_GET_FILENAME:
          tv_download_file_info.setText("下载路径：" + fileName);
          break;
        case WHAI_CONNECT_FAIL:
          tv_download_file_info.setText("连接失败");
          break;
        case WHAT_IO_EXCEPTION:
          tv_download_file_info.setText("IO异常");
          break;
      }
    }
  };

  /**
   * 更新视图
   */
  private void updateView() {
    //当前已经完成下载的文件大小
    long currentFinishedSize = downUtil.getFinishedSize();
    //要显示的下载信息的文字
    StringBuilder downloadInfo = new StringBuilder();
    tv_download_speed.setText("当前下载速度：" + formateSize(currentFinishedSize - lastFinishedSize) + "/s");
    //本次统计比上次统计增加了，更新视图,本次统计较上次统计没有变化，不做视图更新
    if (currentFinishedSize > lastFinishedSize) {
      lastFinishedSize = currentFinishedSize;
      downloadInfo.append("下载进度：" + formateSize(currentFinishedSize) + "/" + formateSize(downUtil.fileSize) + "\n");
      for (int i = 0; i < threadNum; i++) {
        ThreadDownloadInfoBean bean = MapUtil.map.get(i);
        if (bean.downloadTotalSize != 0) {
          downloadInfo.append("线程" + i + "下载进度:" + bean.downloadedSize * 100 / bean.downloadTotalSize + "%  " + formateSize(bean.downloadedSize) + "/" + formateSize(bean.downloadTotalSize) + "\n");
        }
      }
      np_download.setProgress((int) (currentFinishedSize * 100 / downUtil.fileSize));
      tv_download_speed_info.setText(downloadInfo);
      //下载完成后
      if (currentFinishedSize >= downUtil.fileSize) {
        tv_download_speed.setText("下载完毕");
        handler.removeMessages(WHAT_INCREACE);
        return;
      }
    }
    handler.sendEmptyMessageDelayed(WHAT_INCREACE, 1000);
  }

  /**
   * 返回子类要显示的布局 R.layout......
   */
  @Override
  protected int childView() {
    return R.layout.activity_download;
  }

  /**
   * 强制子类实现该抽象方法，初始化各自的View
   */
  @Override
  protected void findChildView() {
    et_download_url = (EditText) findViewById(R.id.et_download_url);
    btn_download_geturl = (Button) findViewById(R.id.btn_download_geturl);
    np_download = (NumberProgressView) findViewById(R.id.np_download);
    btn_download_start = (Button) findViewById(R.id.btn_download_start);
    btn_download_pause = (Button) findViewById(R.id.btn_download_pause);
    btn_download_cancel = (Button) findViewById(R.id.btn_download_cancel);
    tv_download_file_info = (TextView) findViewById(R.id.tv_download_file_info);
    tv_download_speed = (TextView) findViewById(R.id.tv_download_speed);
    tv_download_speed_info = (TextView) findViewById(R.id.tv_download_speed_info);
  }

  /**
   * 强制子类实现该抽象方法，初始化各自数据
   */
  @Override
  protected void initChildData() {
    downUtil = new DownUtil(this);
    lastFinishedSize = downUtil.getFinishedSize();
    StringBuilder downloadInfo = new StringBuilder();
    fileName = SPUtil.getInstance(this).getString(FILE_NAME, null);
    if (fileName != null) {
      downloadInfo.append("下载路径：" + fileName);
      if (downUtil.downloadState == DownUtil.STATE_FINISH) {
        np_download.setProgress(100);
      } else if (downUtil.downloadState == DownUtil.STATE_PAUSING) {
        np_download.setProgress((int) (downUtil.getFinishedSize() * 100 / downUtil.fileSize));
      }
      tv_download_file_info.setText(downloadInfo);
    }
  }

  /**
   * 强制子类实现该抽象方法，设置自己的监听器
   */
  @Override
  protected View[] setChildListener() {
    downUtil.setDownloadInfoListener(new DownUtil.DownloadInfoListener() {

      @Override
      public void connectSuccess() {
        //不能在此更新，需要到主线程刷新UI
        handler.sendEmptyMessage(WHAT_GET_FILENAME);
        handler.sendEmptyMessage(WHAT_INCREACE);
      }

      @Override
      public void connectFail() {
        handler.sendEmptyMessage(WHAI_CONNECT_FAIL);
      }

      @Override
      public void IOException() {
        handler.sendEmptyMessage(WHAT_IO_EXCEPTION);
      }
    });
    return new View[]{btn_download_start, btn_download_pause, btn_download_geturl, btn_download_cancel};
  }

  /**
   * 子类在这个方法里面实现自己View的点击监听事件的相应
   *
   * @param v 父类传递到子类的点击的View
   */
  @Override
  protected void clickChildView(View v) {
    switch (v.getId()) {

      case R.id.btn_download_start:
        downUtil.clickDownloadBtn();
        break;

      case R.id.btn_download_pause:
        downUtil.clickPauseBtn();
        handler.removeMessages(WHAT_INCREACE);
        break;

      case R.id.btn_download_cancel:
        //停止发送消息
        handler.removeMessages(WHAT_INCREACE);
        //暂停下载
        downUtil.clickPauseBtn();
        //重置状态
        downUtil.downloadState = DownUtil.STATE_READY;
        //统计下载的大小归零
        lastFinishedSize = 0;
        //重置文本信息
        tv_download_speed.setText("");
        tv_download_file_info.setText("");
        tv_download_speed_info.setText("");
        //进度条归零
        np_download.setProgress(0);
        //清空内存数据
        MapUtil.map.clear();
        //sp清理
        SPUtil.getInstance(this).removeAll();
        //清空数据库
        downUtil.finalDb.deleteAll(ThreadDownloadInfoBean.class);
        //删除文件
        if (fileName != null) {
          File file = new File(fileName);
          if (file.exists()) {
            boolean delete = file.delete();
            if (delete) {
              Utils.ToastS(this, "删除" + fileName + "成功");
            } else {
              Utils.ToastS(this, "删除失败");
            }
          } else {
            Utils.ToastS(this, "文件不存在");
          }
        } else {
          Utils.ToastS(this, "文件不存在");
        }
        break;

      case R.id.btn_download_geturl:
        String editTextUrl = et_download_url.getText().toString();
        if (editTextUrl.trim().equals("")) {
          Utils.ToastS(this, "请输入地址");
        } else {
          url = editTextUrl;
        }
        break;
    }
  }

  @Override
  protected void onDestroy() {
    handler.removeCallbacksAndMessages(null);
    downUtil.clickPauseBtn();
    super.onDestroy();
  }

  /**
   * 格式化数据大小
   */
  private String formateSize(long size) {
    return Formatter.formatFileSize(this, size);
  }

}

布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical"
  tools:context="com.example.testdemo.activity.DownloadActivity">

  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">

    <EditText
      android:id="@+id/et_download_url"
      android:layout_width="0dp"
      android:layout_height="wrap_content"
      android:layout_weight="1"
      android:hint="输入下载地址"/>

    <Button
      android:id="@+id/btn_download_geturl"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="确定"/>

  </LinearLayout>

  <com.example.testdemo.view.NumberProgressView
    android:id="@+id/np_download"
    android:layout_width="match_parent"
    android:layout_height="100dp">
  </com.example.testdemo.view.NumberProgressView>

  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal">

    <Button
      android:id="@+id/btn_download_start"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="开始下载"/>

    <Button
      android:id="@+id/btn_download_pause"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="暂停下载"/>

    <Button
      android:id="@+id/btn_download_cancel"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="取消下载"/>

  </LinearLayout>

  <TextView
    android:id="@+id/tv_download_file_info"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>

  <TextView
    android:id="@+id/tv_download_speed"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>

  <TextView
    android:id="@+id/tv_download_speed_info"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>

</LinearLayout>

下载Activity的父类

public abstract class BaseActivity extends Activity {

  /**
   * 点击监听器,子类也可以使用
   */
  protected BaseOnClickListener onClickListener = new BaseOnClickListener();

  /**
   * 在onCreate方法里面，找到视图，初始化数据，设置点击监听器
   */
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(childView());
    findView();
    initData();
    setListener();
  }

  /**
   * 返回子类要显示的布局 R.layout......
   */
  protected abstract int childView();

  /**
   * 找到需要的视图---网址：https://www.buzzingandroid.com/tools/android-layout-finder/
   */
  private void findView() {
    findChildView();
  }

  /**
   * 初始化数据
   */
  private void initData() {
    // 初始化子类的数据
    initChildData();
  }

  /**
   * 对需要设置监听 的视图设置监听
   */
  private void setListener() {
    // 子类实现setChildListene()方法，返回一个View数组，里面包含所有需要设置点击监听的View,然后进行For循环，对里面所有View设置监听器
    if (setChildListener() == null || setChildListener().length == 0) {
      return;
    }
    View[] viewArray = setChildListener();
    for (View view : viewArray) {
      view.setOnClickListener(onClickListener);
    }
  }

  /**
   * 自定义的点击监听类
   */
  protected class BaseOnClickListener implements View.OnClickListener {
    @Override
    public void onClick(View v) {
      clickChildView(v);
    }
  }

  /**
   * 强制子类实现该抽象方法，初始化各自的View
   */
  protected abstract void findChildView();

  /**
   * 强制子类实现该抽象方法，初始化各自数据
   */
  protected abstract void initChildData();

  /**
   * 强制子类实现该抽象方法，设置自己的监听器
   */
  protected abstract View[] setChildListener();

  /**
   * 子类在这个方法里面实现自己View的点击监听事件的相应
   *
   * @param v 父类传递到子类的点击的View
   */

  protected abstract void clickChildView(View v);

}

得到数据库的操作类

public class DBUtil {

  public static FinalDb getFinalDb(final Context context) {

    FinalDb finalDb = FinalDb.create(context, "REMUXING.db", false, 1, new FinalDb.DbUpdateListener() {
      @Override
      public void onUpgrade(SQLiteDatabase db, int oldVirsion, int newVirsion) {

      }
    });
    return finalDb;
  }
}

内存中存储下载信息的类

public class MapUtil {
  public static HashMap<Integer, ThreadDownloadInfoBean> map = new HashMap<>();
}

SP存储的工具类

public enum SPUtil {

  SPUTIL;

  public static final String NOTIFICATIONBAR_HEIGHT = "notificationbar_height";

  private static SharedPreferences sp;

  public static SPUtil getInstance(Context context) {

    if (sp == null) {
      sp = context.getSharedPreferences("REMUXING", Context.MODE_PRIVATE);
    }
    return SPUTIL;
  }

  public void saveLong(String key, Long value) {
    sp.edit().putLong(key, value).apply();
  }

  public Long getLong(String key, Long defValue) {
    return sp.getLong(key, defValue);
  }

  public void saveString(String key, String value) {
    sp.edit().putString(key, value).apply();
  }

  public String getString(String key, String defValue) {
    return sp.getString(key, defValue);
  }

  public void removeAll() {
    sp.edit().clear().apply();
  }

}

工具类

public class Utils {

  /**
   * 打印
   */
  public static void Print(String message) {
    Log.e("TAG", "-----   " + message + "   ------") ;
  }

  /**
   * 短吐司
   */
  public static void ToastS(Context context, String message) {
    Toast.makeText(context, message, Toast.LENGTH_SHORT).show();
  }
}

进度条：这个可以忽略，用安卓原生的，代码看我的另一篇博客：Android自定义View实现水平带数字百分比进度条

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。