Android编程开发实现多线程断点续传下载器实例

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  >
  <LinearLayout
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    >
    <!--进度条样式默认为圆形进度条，水平进度条需要配置style属性，
    ?android:attr/progressBarStyleHorizontal -->
    <ProgressBar
      android:layout_width="fill_parent"
      android:layout_height="20dp"
      style="?android:attr/progressBarStyleHorizontal"
      />
    <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_gravity="center"
      android:text="0%"
      />
  </LinearLayout>
  <Button
    android:layout_width="40dp"
    android:layout_height="40dp"
    android:onClick="pause"
    android:text="||"
    />
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:id="@+id/root"
  >
  <TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="请输入下载路径"
    />
  <LinearLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_marginBottom="30dp"
    >
    <EditText
      android:id="@+id/path"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:singleLine="true"
      android:layout_weight="1"
      />
    <Button
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="下载"
      android:onClick="download"
      />
  </LinearLayout>
</LinearLayout>

public class MainActivity extends Activity {
  private LayoutInflater inflater;
  private LinearLayout rootLinearLayout;
  private EditText pathEditText;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    //动态生成新View，获取系统服务LayoutInflater，用来生成新的View
    inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
    rootLinearLayout = (LinearLayout) findViewById(R.id.root);
    pathEditText = (EditText) findViewById(R.id.path);
    // 窗体创建之后, 查询数据库是否有未完成任务, 如果有, 创建进度条等组件, 继续下载
    List<String> list = new InfoDao(this).queryUndone();
    for (String path : list)
      createDownload(path);
  }
  /**
   * 下载按钮
   * @param view
   */
  public void download(View view) {
    String path = "http://192.168.1.199:8080/14_Web/" + pathEditText.getText().toString();
    createDownload(path);
  }
  /**
   * 动态生成新View
   * 初始化表单数据
   * @param path
   */
  private void createDownload(String path) {
    //获取系统服务LayoutInflater，用来生成新的View
    LayoutInflater inflater = (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE);
    LinearLayout linearLayout = (LinearLayout) inflater.inflate(R.layout.download, null);
    LinearLayout childLinearLayout = (LinearLayout) linearLayout.getChildAt(0);
    ProgressBar progressBar = (ProgressBar) childLinearLayout.getChildAt(0);
    TextView textView = (TextView) childLinearLayout.getChildAt(1);
    Button button = (Button) linearLayout.getChildAt(1);
    try {
      button.setOnClickListener(new MyListener(progressBar, textView, path));
      //调用当前页面中某个容器的addView，将新创建的View添加进来
      rootLinearLayout.addView(linearLayout);
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
  private final class MyListener implements OnClickListener {
    private ProgressBar progressBar;
    private TextView textView;
    private int fileLen;
    private Downloader downloader;
    private String name;
    /**
     * 执行下载
     * @param progressBar //进度条
     * @param textView //百分比
     * @param path //下载文件路径
     */
    public MyListener(ProgressBar progressBar, TextView textView, String path) {
      this.progressBar = progressBar;
      this.textView = textView;
      name = path.substring(path.lastIndexOf("/") + 1);
      downloader = new Downloader(getApplicationContext(), handler);
      try {
        downloader.download(path, 3);
      } catch (Exception e) {
        e.printStackTrace();
        Toast.makeText(getApplicationContext(), "下载过程中出现异常", 0).show();
        throw new RuntimeException(e);
      }
    }
    //Handler传输数据
    private Handler handler = new Handler() {
      @Override
      public void handleMessage(Message msg) {
        switch (msg.what) {
          case 0:
            //获取文件的大小
            fileLen = msg.getData().getInt("fileLen");
            //设置进度条最大刻度：setMax()
            progressBar.setMax(fileLen);
            break;
          case 1:
            //获取当前下载的总量
            int done = msg.getData().getInt("done");
            //当前进度的百分比
            textView.setText(name + "\t" + done * 100 / fileLen + "%");
            //进度条设置当前进度：setProgress()
            progressBar.setProgress(done);
            if (done == fileLen) {
              Toast.makeText(getApplicationContext(), name + " 下载完成", 0).show();
              //下载完成后退出进度条
              rootLinearLayout.removeView((View) progressBar.getParent().getParent());
            }
            break;
        }
      }
    };
    /**
     * 暂停和继续下载
     */
    public void onClick(View v) {
      Button pauseButton = (Button) v;
      if ("||".equals(pauseButton.getText())) {
        downloader.pause();
        pauseButton.setText("▶");
      } else {
        downloader.resume();
        pauseButton.setText("||");
      }
    }
  }
}

public class Downloader {
  private int done;
  private InfoDao dao;
  private int fileLen;
  private Handler handler;
  private boolean isPause;
  public Downloader(Context context, Handler handler) {
    dao = new InfoDao(context);
    this.handler = handler;
  }
  /**
   * 多线程下载
   * @param path 下载路径
   * @param thCount 需要开启多少个线程
   * @throws Exception
   */
  public void download(String path, int thCount) throws Exception {
    URL url = new URL(path);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    //设置超时时间
    conn.setConnectTimeout(3000);
    if (conn.getResponseCode() == 200) {
      fileLen = conn.getContentLength();
      String name = path.substring(path.lastIndexOf("/") + 1);
      File file = new File(Environment.getExternalStorageDirectory(), name);
      RandomAccessFile raf = new RandomAccessFile(file, "rws");
      raf.setLength(fileLen);
      raf.close();
      //Handler发送消息，主线程接收消息，获取数据的长度
      Message msg = new Message();
      msg.what = 0;
      msg.getData().putInt("fileLen", fileLen);
      handler.sendMessage(msg);
      //计算每个线程下载的字节数
      int partLen = (fileLen + thCount - 1) / thCount;
      for (int i = 0; i < thCount; i++)
        new DownloadThread(url, file, partLen, i).start();
    } else {
      throw new IllegalArgumentException("404 path: " + path);
    }
  }
  private final class DownloadThread extends Thread {
    private URL url;
    private File file;
    private int partLen;
    private int id;
    public DownloadThread(URL url, File file, int partLen, int id) {
      this.url = url;
      this.file = file;
      this.partLen = partLen;
      this.id = id;
    }
    /**
     * 写入操作
     */
    public void run() {
      // 判断上次是否有未完成任务
      Info info = dao.query(url.toString(), id);
      if (info != null) {
        // 如果有, 读取当前线程已下载量
        done += info.getDone();
      } else {
        // 如果没有, 则创建一个新记录存入
        info = new Info(url.toString(), id, 0);
        dao.insert(info);
      }
      int start = id * partLen + info.getDone(); // 开始位置 += 已下载量
      int end = (id + 1) * partLen - 1;
      try {
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setReadTimeout(3000);
        //获取指定位置的数据，Range范围如果超出服务器上数据范围, 会以服务器数据末尾为准
        conn.setRequestProperty("Range", "bytes=" + start + "-" + end);
        RandomAccessFile raf = new RandomAccessFile(file, "rws");
        raf.seek(start);
        //开始读写数据
        InputStream in = conn.getInputStream();
        byte[] buf = new byte[1024 * 10];
        int len;
        while ((len = in.read(buf)) != -1) {
          if (isPause) {
            //使用线程锁锁定该线程
            synchronized (dao) {
              try {
                dao.wait();
              } catch (InterruptedException e) {
                e.printStackTrace();
              }
            }
          }
          raf.write(buf, 0, len);
          done += len;
          info.setDone(info.getDone() + len);
          // 记录每个线程已下载的数据量
          dao.update(info);
          //新线程中用Handler发送消息，主线程接收消息
          Message msg = new Message();
          msg.what = 1;
          msg.getData().putInt("done", done);
          handler.sendMessage(msg);
        }
        in.close();
        raf.close();
        // 删除下载记录
        dao.deleteAll(info.getPath(), fileLen);
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }
  //暂停下载
  public void pause() {
    isPause = true;
  }
  //继续下载
  public void resume() {
    isPause = false;
    //恢复所有线程
    synchronized (dao) {
      dao.notifyAll();
    }
  }
}

public class DBOpenHelper extends SQLiteOpenHelper {
  public DBOpenHelper(Context context) {
    super(context, "download.db", null, 1);
  }
  @Override
  public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE info(path VARCHAR(1024), thid INTEGER, done INTEGER, PRIMARY KEY(path, thid))");
  }
  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
  }
}

public class InfoDao {
  private DBOpenHelper helper;
  public InfoDao(Context context) {
    helper = new DBOpenHelper(context);
  }
  public void insert(Info info) {
    SQLiteDatabase db = helper.getWritableDatabase();
    db.execSQL("INSERT INTO info(path, thid, done) VALUES(?, ?, ?)", new Object[] { info.getPath(), info.getThid(), info.getDone() });
  }
  public void delete(String path, int thid) {
    SQLiteDatabase db = helper.getWritableDatabase();
    db.execSQL("DELETE FROM info WHERE path=? AND thid=?", new Object[] { path, thid });
  }
  public void update(Info info) {
    SQLiteDatabase db = helper.getWritableDatabase();
    db.execSQL("UPDATE info SET done=? WHERE path=? AND thid=?", new Object[] { info.getDone(), info.getPath(), info.getThid() });
  }
  public Info query(String path, int thid) {
    SQLiteDatabase db = helper.getWritableDatabase();
    Cursor c = db.rawQuery("SELECT path, thid, done FROM info WHERE path=? AND thid=?", new String[] { path, String.valueOf(thid) });
    Info info = null;
    if (c.moveToNext())
      info = new Info(c.getString(0), c.getInt(1), c.getInt(2));
    c.close();
    return info;
  }
  public void deleteAll(String path, int len) {
    SQLiteDatabase db = helper.getWritableDatabase();
    Cursor c = db.rawQuery("SELECT SUM(done) FROM info WHERE path=?", new String[] { path });
    if (c.moveToNext()) {
      int result = c.getInt(0);
      if (result == len)
        db.execSQL("DELETE FROM info WHERE path=? ", new Object[] { path });
    }
  }
  public List<String> queryUndone() {
    SQLiteDatabase db = helper.getWritableDatabase();
    Cursor c = db.rawQuery("SELECT DISTINCT path FROM info", null);
    List<String> pathList = new ArrayList<String>();
    while (c.moveToNext())
      pathList.add(c.getString(0));
    c.close();
    return pathList;
  }
}