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;  }}