多线程断线下载
执行下载的主程序MainActivity
public class DemoActivity extends Activity implements OnClickListener { private ProgressBar pb; private Button bt; private TextView tv; private EditText et; boolean flag = true; boolean stopflag = false; private Handler handler = new Handler() { //进度条下面是-- 当前下载大小/总大小 下载速度 @Override public void handleMessage(Message msg) { pb.setProgress(total); int max = pb.getMax(); //获取进度条的上限值 if (total >= (max - 1)) { total = max; flag = false; } int result = (total * 100 / max); tv.setText("当前进度 :" + result + "%"); super.handleMessage(msg); } }; int total = 0; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); pb = (ProgressBar) this.findViewById(R.id.pb); bt = (Button) this.findViewById(R.id.bt); tv = (TextView) this.findViewById(R.id.tv_process); et = (EditText) this.findViewById(R.id.et); bt.setOnClickListener(this); } @Override public void onClick(View v) { switch (v.getId()) { case R.id.bt: // 创建一个子线程 定期的更新ui if ("开始下载".equals(bt.getText().toString())) { //原来是"开始下载" 按下去 变成"暂停" 程序暂停下载 下载标志为false bt.setText("暂停"); stopflag = false; // 开始下载 } else { bt.setText("开始下载"); stopflag = true; } new Thread() { @Override public void run() { super.run(); while (flag) { try { //每暂停一秒 更新一下下载百分数 sleep(1000); // 如果total > = 文件长度 Message msg = new Message(); handler.sendMessage(msg); } catch (InterruptedException e) { e.printStackTrace(); } } } }.start(); // 开始执行下载的操作 String path = et.getText().toString().trim(); if ("".equals(path)) { Toast.makeText(this, "路径不能为空", 1).show(); return; } try { //连接服务器 -- 获取服务器上面资源总大小,并设置进度条,启动下载 URL url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url .openConnection(); conn.setRequestMethod("GET"); conn.setConnectTimeout(5000); //设置支持的浏览器 conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)"); int code = conn.getResponseCode(); if (code == 200) { int len = conn.getContentLength(); RandomAccessFile file = new RandomAccessFile("/mnt/sdcard/" + getFilenName(path), "rwd"); // 1.设置本地文件大小跟服务器的文件大小一致 file.setLength(len); // 设置进度条的最大值 pb.setMax(len); // 2 .假设开启3 个线程 int threadnumber = 3; int blocksize = len / threadnumber; /** * 线程1 0~ blocksize 线程2 1*bolocksize ~ 2*blocksize 线程3 * 2*blocksize ~ 文件末尾 */ for (int i = 0; i < threadnumber; i++) { int startposition = i * blocksize; int endpositon = (i + 1) * blocksize; if (i == (threadnumber - 1)) { // 最后一个线程 endpositon = len; } DownLoadTask task = new DownLoadTask(i, path, startposition, endpositon); task.start(); } } } catch (Exception e) { Toast.makeText(this, "下载出现异常", 0).show(); e.printStackTrace(); } break; } } class DownLoadTask extends Thread { int threadid; String filepath; int startposition; int endpositon; public DownLoadTask(int threadid, String filepath, int startposition, int endpositon) { this.threadid = threadid; this.filepath = filepath; this.startposition = startposition; this.endpositon = endpositon; } @Override public void run() { try { //记录当前已经下载的文件 File postionfile = new File("/mnt/sdcard/" + threadid + ".txt"); URL url = new URL(filepath); HttpURLConnection conn = (HttpURLConnection) url .openConnection(); System.out.println("线程" + threadid + "正在下载 " + "开始位置 : " + startposition + "结束位置 " + endpositon); if (postionfile.exists()) { FileInputStream fis = new FileInputStream(postionfile); //此数组表示已经从服务器下载的数据量 byte[] result = StreamTool.getBytes(fis); String str = new String(result); //设置新的下载位置 if (!"".equals(str)) { int newstartposition = Integer.parseInt(str); if (newstartposition > startposition) { startposition = newstartposition; } } } // "Range", "bytes=2097152-4194303") conn.setRequestProperty("Range", "bytes=" + startposition + "-" + endpositon); conn.setRequestMethod("GET"); conn.setConnectTimeout(5000); conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)"); InputStream is = conn.getInputStream(); //执行随机读写 RandomAccessFile file = new RandomAccessFile("/mnt/sdcard/" + getFilenName(filepath), "rwd"); // 设置 数据从文件哪个位置开始写 file.seek(startposition); byte[] buffer = new byte[1024]; int len = 0; // 代表当前读到的服务器数据的位置 ,同时这个值已经存储的文件的位置 int currentPostion = startposition; // 创建一个文件对象 ,记录当前某个文件的下载位置 while ((len = is.read(buffer)) != -1) { if (stopflag) { return; } file.write(buffer, 0, len); synchronized (DemoActivity.this) { total += len; } currentPostion += len; // 需要把currentPostion 信息给持久化到存储设备 String position = currentPostion + ""; FileOutputStream fos = new FileOutputStream(postionfile); fos.write(position.getBytes()); fos.flush(); fos.close(); } file.close(); System.out.println("线程" + threadid + "下载完毕"); // 当线程下载完毕后 把文件删除掉 if (postionfile.exists()) { postionfile.delete(); } } catch (Exception e) { e.printStackTrace(); } super.run(); } } public String getFilenName(String path) { int start = path.lastIndexOf("/") + 1; return path.substring(start, path.length()); } }
使用到的工具类StreamTool
public class StreamTool { /** * 把一个inputstream里面的内容转化成一个byte[] */ public static byte[] getBytes(InputStream is) throws Exception{ ByteArrayOutputStream bos = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; int len = 0; while((len = is.read(buffer))!=-1){ bos.write(buffer, 0, len); } is.close(); bos.flush(); byte[] result = bos.toByteArray(); System.out.println(new String(result)); return result; } }
布局文件
<?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="fill_parent" android:orientation="vertical" > <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/down_load" /> <EditText android:id="@+id/et" android:layout_width="fill_parent" android:layout_height="wrap_content" android:hint="@string/hint" android:text="http://192.168.1.101:8080/youdao.exe" /> <ProgressBar android:id="@+id/pb" style="?android:attr/progressBarStyleHorizontal" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <TextView android:id="@+id/tv_process" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <Button android:id="@+id/bt" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/download" /> </LinearLayout>
